A realistic renormalizable supersymmetric E₆ model
Bajc, Borut; Susič, Vasja
2014-01-01
A complete realistic model based on the supersymmetric version of E₆ is presented. It consists of three copies of matter 27, and a Higgs sector made of 2×(27+27⁻)+351´+351´⁻ representations. An analytic solution to the equations of motion is found which spontaneously breaks the gauge group into the Standard Model. The light fermion mass matrices are written down explicitly as non-linear functions of three Yukawa matrices. This contribution is based on Ref. [1].
Neutrino mass and proton lifetime in a realistic supersymmetric SO(10) model
NASA Astrophysics Data System (ADS)
Severson, Matthew
This work presents a complete analysis of fermion fitting and proton decay in a supersymmetric SO(10) model previously suggested by Dutta, Mimura, and Mohapatra. A key question in any grand unified theory is whether it satisfies the stringent experimental lower limits on the partial lifetimes of the proton. In more generic models, substantial fine-tuning is required among GUT-scale parameters to satisfy the limits. In the proposed model, the 10, 1¯2¯6¯, and 20 Yukawa couplings contributing to fermion masses have restricted textures intended to give favorable results for proton lifetime, while still giving rise to a realistic fermion sector, without the need for fine-tuning, even for large beta, and for either type-I or type-II dominance in the neutrino mass matrix. In this thesis, I investigate the above hypothesis at a strict numerical level of scrutiny; I obtain a valid fit for the entire fermion sector for both types of seesaw dominance, including theta13 in good agreement with the most recent data. For the case with type-II seesaw, I find that, using the Yukawa couplings fixed by the successful fermion sector fit, proton partial lifetime limits are readily satisfied for all but one of the pertinent decay modes for nearly arbitrary values of the triplet-Higgs mixing parameters, with the K+v¯ mode requiring a minor ∂(10--1) cancellation in order to satisfy its limit. I also find a maximum partial lifetime for that mode of τ( K+v¯) ˜ 1036,years. For the type-I seesaw case, I find that K+ v¯ decay mode is satisfied for any values of the triplet mixing parameters giving no major enhancement, and all other modes are easily satisfied for arbitrary mixing values; I also find a maximum partial lifetime for K+v¯ of nearly 1036years, which is largely sub-dominant to gauge boson decay channels.
Bosonic condensates in realistic supersymmetric GUT cosmic strings
Allys, Erwan
2016-04-01
We study the realistic structure of F-term Nambu-Goto cosmic strings forming in a general supersymmetric Grand Unified Theory implementation, assuming standard hybrid inflation. Examining the symmetry breaking of the unification gauge group down to the Standard Model, we discuss the minimal field content necessary to describe abelian cosmic strings appearing at the end of inflation. We find that several fields will condense in most theories, questioning the plausible occurrence of associated currents (bosonic and fermionic). We perturbatively evaluate the modification of their energy per unit length due to the condensates. We provide a criterion for comparing the usual abelian Higgs approximation used in cosmology to realistic situations.
Bagger, J.A.
1984-09-01
We begin to construct the most general supersymmetric Lagrangians in one, two and four dimensions. We find that the matter couplings have a natural interpretation in the language of the nonlinear sigma model.
Non-tachyonic semi-realistic non-supersymmetric heterotic-string vacua
NASA Astrophysics Data System (ADS)
Ashfaque, Johar M.; Athanasopoulos, Panos; Faraggi, Alon E.; Sonmez, Hasan
2016-04-01
The heterotic-string models in the free fermionic formulation gave rise to some of the most realistic-string models to date, which possess N=1 spacetime supersymmetry. Lack of evidence for supersymmetry at the LHC instigated recent interest in non-supersymmetric heterotic-string vacua. We explore what may be learned in this context from the quasi-realistic free fermionic models. We show that constructions with a low number of families give rise to proliferation of a priori tachyon producing sectors, compared to the non-realistic examples, which typically may contain only one such sector. The reason being that in the realistic cases the internal six dimensional space is fragmented into smaller units. We present one example of a quasi-realistic, non-supersymmetric, non-tachyonic, heterotic-string vacuum and compare the structure of its massless spectrum to the corresponding supersymmetric vacuum. While in some sectors supersymmetry is broken explicitly, i.e. the bosonic and fermionic sectors produce massless and massive states, other sectors, and in particular those leading to the chiral families, continue to exhibit Fermi-Bose degeneracy. In these sectors the massless spectrum, as compared to the supersymmetric cases, will only differ in some local or global U(1) charges. We discuss the conditions for obtaining n_b=n_f at the massless level in these models. Our example model contains an anomalous U(1) symmetry, which generates a tadpole diagram at one-loop order in string perturbation theory. We speculate that this tadpole diagram may cancel the corresponding diagram generated by the one-loop non-vanishing vacuum energy and that in this respect the supersymmetric and non-supersymmetric vacua should be regarded on an equal footing. Finally we discuss vacua that contain two supersymmetry generating sectors.
Is realistic neuronal modeling realistic?
Almog, Mara; Korngreen, Alon
2016-11-01
Scientific models are abstractions that aim to explain natural phenomena. A successful model shows how a complex phenomenon arises from relatively simple principles while preserving major physical or biological rules and predicting novel experiments. A model should not be a facsimile of reality; it is an aid for understanding it. Contrary to this basic premise, with the 21st century has come a surge in computational efforts to model biological processes in great detail. Here we discuss the oxymoronic, realistic modeling of single neurons. This rapidly advancing field is driven by the discovery that some neurons don't merely sum their inputs and fire if the sum exceeds some threshold. Thus researchers have asked what are the computational abilities of single neurons and attempted to give answers using realistic models. We briefly review the state of the art of compartmental modeling highlighting recent progress and intrinsic flaws. We then attempt to address two fundamental questions. Practically, can we realistically model single neurons? Philosophically, should we realistically model single neurons? We use layer 5 neocortical pyramidal neurons as a test case to examine these issues. We subject three publically available models of layer 5 pyramidal neurons to three simple computational challenges. Based on their performance and a partial survey of published models, we conclude that current compartmental models are ad hoc, unrealistic models functioning poorly once they are stretched beyond the specific problems for which they were designed. We then attempt to plot possible paths for generating realistic single neuron models. Copyright © 2016 the American Physiological Society.
The Supersymmetric Standard Model
NASA Astrophysics Data System (ADS)
Fayet, Pierre
2016-10-01
The Standard Model may be included within a supersymmetric theory, postulating new sparticles that differ by half-a-unit of spin from their standard model partners, and by a new quantum number called R-parity. The lightest one, usually a neutralino, is expected to be stable and a possible candidate for dark matter. The electroweak breaking requires two doublets, leading to several charged and neutral Brout-Englert-Higgs bosons. This also leads to gauge/Higgs unification by providing extra spin-0 partners for the spin-1 W± and Z. It offers the possibility to view, up to a mixing angle, the new 125 GeV boson as the spin-0 partner of the Z under two supersymmetry transformations, i.e. as a Z that would be deprived of its spin. Supersymmetry then relates two existing particles of different spins, in spite of their different gauge symmetry properties, through supersymmetry transformations acting on physical fields in a non-polynomial way. We also discuss how the compactification of extra dimensions, relying on R-parity and other discrete symmetries, may determine both the supersymmetrybreaking and grand-unification scales.
Supersymmetric orientifolds of Gepner models
NASA Astrophysics Data System (ADS)
Blumenhagen, Ralph
2003-11-01
Supersymmetric orientifolds of four dimensional Gepner Models are constructed in a systematic way. For all levels of the Gepner model being odd the generic expression for both the A-type and the B-type Klein bottle amplitude is derived. The appearing massless tadpoles are canceled by introducing appropriate boundary states of Recknagel/Schomerus(RS). After determining the Möbius strip amplitude we extract general expressions for the tadpole cancellation conditions. We discuss the issue of chirality for such supersymmetric orientifold models and finally present a couple of examples in detail.
Supersymmetric Ruijsenaars-Schneider Model
NASA Astrophysics Data System (ADS)
Blondeau-Fournier, O.; Desrosiers, P.; Mathieu, P.
2015-03-01
An integrable supersymmetric generalization of the trigonometric Ruijsenaars-Schneider model is presented whose symmetry algebra includes the super Poincaré algebra. Moreover, its Hamiltonian is shown to be diagonalized by the recently introduced Macdonald superpolynomials. Somewhat surprisingly, the consistency of the scalar product forces the discreteness of the Hilbert space.
Supersymmetric chiral models: Geometrical aspects
NASA Astrophysics Data System (ADS)
Perelomov, A. M.
1989-03-01
We consider classical supersymmetric chiral models of field theory and focus our attention on the geometrical aspects of such theories. A characteristic feature of such models is that the interaction is not introduced by adding the interaction Lagrangian to the free field Lagrangian, but has a purely geometrical origin and is related to the inner curvature of the target manifold. In many aspects these models are analogous to gauge theories and, as became clear recently, they are also important for superstring theory, which nowadays is the most probable candidate for a truly unified theory of all interactions including gravitation.
Quadrality for supersymmetric matrix models
NASA Astrophysics Data System (ADS)
Franco, Sebastián; Lee, Sangmin; Seong, Rak-Kyeong; Vafa, Cumrun
2017-07-01
We introduce a new duality for N = 1 supersymmetric gauged matrix models. This 0 d duality is an order 4 symmetry, namely an equivalence between four different theories, hence we call it Quadrality. Our proposal is motivated by mirror symmetry, but is not restricted to theories with a D-brane realization and holds for general N = 1 matrix models. We present various checks of the proposal, including the matching of: global symmetries, anomalies, deformations and the chiral ring. We also consider quivers and the corresponding quadrality networks. Finally, we initiate the study of matrix models that arise on the worldvolume of D(-1)-branes probing toric Calabi-Yau 5-folds.
Chiral Supersymmetric Gepner Model Orientifolds
NASA Astrophysics Data System (ADS)
Blumenhagen, Ralph; Weigand, Timo
2004-02-01
We explicitly construct A-type orientifolds of supersymmetric Gepner models. In order to reduce the tadpole cancellation conditions to a treatable number we explicitly work out the generic form of the one-loop Klein bottle, annulus and Möbius strip amplitudes for simple current extensions of Gepner models. Equipped with these formulas, we discuss two examples in detail to provide evidence that in this setting certain features of the MSSM like unitary gauge groups with large enough rank, chirality and family replication can be achieved.
A Maximally Supersymmetric Kondo Model
Harrison, Sarah; Kachru, Shamit; Torroba, Gonzalo; /Stanford U., Phys. Dept. /SLAC
2012-02-17
We study the maximally supersymmetric Kondo model obtained by adding a fermionic impurity to N = 4 supersymmetric Yang-Mills theory. While the original Kondo problem describes a defect interacting with a free Fermi liquid of itinerant electrons, here the ambient theory is an interacting CFT, and this introduces qualitatively new features into the system. The model arises in string theory by considering the intersection of a stack of M D5-branes with a stack of N D3-branes, at a point in the D3 worldvolume. We analyze the theory holographically, and propose a dictionary between the Kondo problem and antisymmetric Wilson loops in N = 4 SYM. We perform an explicit calculation of the D5 fluctuations in the D3 geometry and determine the spectrum of defect operators. This establishes the stability of the Kondo fixed point together with its basic thermodynamic properties. Known supergravity solutions for Wilson loops allow us to go beyond the probe approximation: the D5s disappear and are replaced by three-form flux piercing a new topologically non-trivial S3 in the corrected geometry. This describes the Kondo model in terms of a geometric transition. A dual matrix model reflects the basic properties of the corrected gravity solution in its eigenvalue distribution.
A maximally supersymmetric Kondo model
NASA Astrophysics Data System (ADS)
Harrison, Sarah; Kachru, Shamit; Torroba, Gonzalo
2012-10-01
We study the maximally supersymmetric Kondo model obtained by adding a fermionic impurity to N=4 supersymmetric Yang-Mills theory. While the original Kondo problem describes a defect interacting with a free Fermi liquid of itinerant electrons, here the ambient theory is an interacting CFT, and this introduces qualitatively new features into the system. The model arises in string theory by considering the intersection of a stack of M D5-branes with a stack of N D3-branes, at a point in the D3 worldvolume. We analyze the theory holographically, and propose a dictionary between the Kondo problem and antisymmetric Wilson loops in N=4 SYM. We perform an explicit calculation of the D5 fluctuations in the D3 geometry and determine the spectrum of defect operators. This establishes the stability of the Kondo fixed point together with its basic thermodynamic properties. Known supergravity solutions for Wilson loops allow us to go beyond the probe approximation: the D5s disappear and are replaced by three-form flux piercing a new topologically non-trivial S3 in the corrected geometry. This describes the Kondo model in terms of a geometric transition. A dual matrix model reflects the basic properties of the corrected gravity solution in its eigenvalue distribution.
Realistic inflation models and primordial gravity waves
NASA Astrophysics Data System (ADS)
Rehman, Mansoor Ur
We investigate both supersymmetric and non-supersymmetric realistic models of inflation. In non-supersymmetric models, inflation is successfully realized by employing both Coleman Weinberg and Higgs potentials in GUTs such as SU(5) and SO(10). The quantum smearing of tree level predictions is discussed in the Higgs inflation. These quantum corrections can arise from the inflaton couplings to other particles such as GUT scalars. As a result of including these corrections, a reduction in the tensor-to-scalar ratio r, a canonical measure of gravity waves produced during inflation, is observed. In a simple phi4 chaotic model, we reconsider a non-minimal (xi > 0) gravitationalcoupling of inflaton φ arising from the interaction xi R phi2, where R is the Ricci scalar. In estimating bounds on various inflationaryparameters we also include quantum corrections. We emphasize that while working with high precision observations such as the current Planck satellite experiment we cannot ignore these radiative and gravitational corrections in analyzing the predictions of various inflationary models. In supersymmetric hybrid inflation with minimal Kahler potential, the soft SUSY breaking terms are shown to play an important role in realizing inflation consistent with the latest WMAP data. The SUSY hybrid models which we consider here predict exceedingly small values of r. However, to obtain observable gravity waves the non-minimal Kahler potential turns out to be a necessary ingredient. A realistic model of flipped SU(5) model, which benefits from the absence of topological defects, is considered in the standard SUSY hybrid inflation. We also present a discussion of shifted hybrid inflation in a realistic model of SUSY SU(5) GUT.
The Minimal Supersymmetric Fat Higgs Model
Harnik, Roni; Kribs, Graham D.; Larson, Daniel T.; Murayama, Hitoshi
2003-11-26
We present a calculable supersymmetric theory of a composite"fat'" Higgs boson. Electroweak symmetry is broken dynamically through a new gauge interaction that becomes strong at an intermediate scale. The Higgs mass can easily be 200-450 GeV along with the superpartner masses, solving the supersymmetric little hierarchy problem. We explicitly verify that the model is consistent with precision electroweak data without fine-tuning. Gauge coupling unification can be maintained despite the inherently strong dynamics involved in electroweak symmetry breaking. Supersymmetrizing the Standard Model therefore does not imply a light Higgs mass, contrary to the lore in the literature. The Higgs sector of the minimal Fat Higgs model has a mass spectrum that is distinctly different from the Minimal Supersymmetric Standard Model.
Less minimal supersymmetric standard model
de Gouvea, Andre; Friedland, Alexander; Murayama, Hitoshi
1998-03-28
Most of the phenomenological studies of supersymmetry have been carried out using the so-called minimal supergravity scenario, where one assumes a universal scalar mass, gaugino mass, and trilinear coupling at M{sub GUT}. Even though this is a useful simplifying assumption for phenomenological analyses, it is rather too restrictive to accommodate a large variety of phenomenological possibilities. It predicts, among other things, that the lightest supersymmetric particle (LSP) is an almost pure B-ino, and that the {mu}-parameter is larger than the masses of the SU(2){sub L} and U(1){sub Y} gauginos. We extend the minimal supergravity framework by introducing one extra parameter: the Fayet'Iliopoulos D-term for the hypercharge U(1), D{sub Y}. Allowing for this extra parameter, we find a much more diverse phenomenology, where the LSP is {tilde {nu}}{sub {tau}}, {tilde {tau}} or a neutralino with a large higgsino content. We discuss the relevance of the different possibilities to collider signatures. The same type of extension can be done to models with the gauge mediation of supersymmetry breaking. We argue that it is not wise to impose cosmological constraints on the parameter space.
Supersymmetric cosmological FRW model and dark energy
Rosales, J. J.; Tkach, V. I.
2010-11-15
In this work we consider a flat cosmological model with a set of fluids in the framework of supersymmetric cosmology. The obtained supersymmetric algebra allowed us to take quantum solutions. It is shown that only in the case of a cosmological constant do we have a condition between the density of dark energy {rho}{sub {Lambda}} and density energy of matter {rho}{sub M}, {rho}{sub {Lambda}>}2{rho}{sub M}.
Non-supersymmetric orientifolds of Gepner models
NASA Astrophysics Data System (ADS)
Gato-Rivera, B.; Schellekens, A. N.
2009-01-01
Starting from a previously collected set of tachyon-free closed strings, we search for N = 2 minimal model orientifold spectra which contain the standard model and are free of tachyons and tadpoles at lowest order. For each class of tachyon-free closed strings - bulk supersymmetry, automorphism invariants or Klein bottle projection - we do indeed find non-supersymmetric and tachyon free chiral brane configurations that contain the standard model. However, a tadpole-cancelling hidden sector could only be found in the case of bulk supersymmetry. Although about half of the examples we have found make use of branes that break the bulk space-time supersymmetry, the resulting massless open string spectra are nevertheless supersymmetric in all cases. Dropping the requirement that the standard model be contained in the spectrum, we find chiral tachyon and tadpole-free solutions in all three cases, although in the case of bulk supersymmetry all massless spectra are supersymmetric. In the other two cases we find truly non-supersymmetric spectra, but a large fraction of them are nevertheless partly or fully supersymmetric at the massless level.
Supersymmetric SYK model and random matrix theory
NASA Astrophysics Data System (ADS)
Li, Tianlin; Liu, Junyu; Xin, Yuan; Zhou, Yehao
2017-06-01
In this paper, we investigate the effect of supersymmetry on the symmetry classification of random matrix theory ensembles. We mainly consider the random matrix behaviors in the N=1 supersymmetric generalization of Sachdev-Ye-Kitaev (SYK) model, a toy model for two-dimensional quantum black hole with supersymmetric constraint. Some analytical arguments and numerical results are given to show that the statistics of the supersymmetric SYK model could be interpreted as random matrix theory ensembles, with a different eight-fold classification from the original SYK model and some new features. The time-dependent evolution of the spectral form factor is also investigated, where predictions from random matrix theory are governing the late time behavior of the chaotic hamiltonian with supersymmetry.
A supersymmetric SYK-like tensor model
Peng, Cheng; Spradlin, Marcus; Volovich, Anastasia
2017-05-11
We consider a supersymmetric SYK-like model without quenched disorder that is built by coupling two kinds of fermionic Ν = 1 tensor-valued superfields, ''quarks'' and ''mesons''. We prove that the model has a well-defined large-N limit in which the (s)quark 2-point functions are dominated by mesonic ''melon'' diagrams. We sum these diagrams to obtain the Schwinger-Dyson equations and show that in the IR, the solution agrees with that of the supersymmetric SYK model.
Supersymmetric defect models and mirror symmetry
Hook, Anson; Kachru, Shamit; Torroba, Gonzalo
2013-11-01
We study supersymmetric field theories in three space-time dimensions doped by various configurations of electric charges or magnetic fluxes. These are supersymmetric avatars of impurity models. In the presence of additional sources such configurations are shown to preserve half of the supersymmetries. Mirror symmetry relates the two sets of configurations. We discuss the implications for impurity models in 3d NN = 4 QED with a single charged hypermultiplet (and its mirror, the theory of a free hypermultiplet) as well as 3d NN = 2 QED with one flavor and its dual, a supersymmetric Wilson-Fisher fixed point. Mirror symmetry allows us to find backreacted solutions for arbitrary arrays of defects in the IR limit of NN = 4 QED. Our analysis, complemented with appropriate string theory brane constructions, sheds light on various aspects of mirror symmetry, the map between particles and vortices and the emergence of ground state entropy in QED at finite density.
Quantum Supersymmetric Models in the Causal Approach
NASA Astrophysics Data System (ADS)
Grigore, Dan-Radu
2007-04-01
We consider the massless supersymmetric vector multiplet in a purely quantum framework. First order gauge invariance determines uniquely the interaction Lagrangian as in the case of Yang-Mills models. Going to the second order of perturbation theory produces an anomaly which cannot be eliminated. We make the analysis of the model working only with the component fields.
Supersymmetric Model Builing (and Sweet Spot Supersymmetry)
Ibe, Masahiro; Kitano, Ryuichiro; /Los Alamos
2008-01-08
It has been more than twenty years since theorists started discussing supersymmetric model building/phenomenology. We review mechanisms of supersymmetry breaking/mediation and problems in each scenario. We propose a simple model to address those problems and discuss its phenomenology.
Constraints from unrealistic vacua in the supersymmetric standard model with neutrino mass operators
Kanehata, Yoshimi; Kobayashi, Tatsuo; Konishi, Yasufumi; Shimomura, Takashi
2010-10-01
We analyze a scalar potential of the minimal supersymmetric standard model (MSSM) with neutrino mass operators along unbounded-from-below and color and/or charged breaking directions. We show necessary conditions to avoid the potential minima which can be deeper than the realistic vacuum. These conditions would constrain more strongly than conditions in the MSSM without taking into account neutrino mass operators and can improve the predictive power of supersymmetric models with neutrino mass operators.
Supersymmetric {sigma}-models in 2-dimensions
Zumino, B. |
1997-02-01
The author gives a brief introduction to supersymmetric {sigma}-models in two space-time dimensions. The topics he covers are: the bosonic {sigma}-model; supersymmetry in two dimensions; complex manifolds; the Kaehler and hyper-Kaehler case; and chiral supersymmetries. The lesson to be learned from the lecture is that the number of supersymmetries is intimately related to the geometric structure of the target space manifold: more geometric structure corresponds to more supersymmetries.
Utilitarian supersymmetric gauge model of particle interactions
NASA Astrophysics Data System (ADS)
Ma, Ernest
2010-05-01
A remarkabale U(1) gauge extension of the supersymmetric standard model was proposed 8 years ago. It is anomaly free, has no μ term, and conserves baryon and lepton numbers automatically. The phenomenology of a specific version of this model is discussed. In particular, leptoquarks are predicted, with couplings to the heavy singlet neutrinos, the scalar partners of which may be components of dark matter. The Majorana neutrino mass matrix itself may have two zero subdeterminants.
Constraining supersymmetric SO(10) models through cosmology
NASA Astrophysics Data System (ADS)
Jeannerot, Rachel; Davis, Anne-Christine
1995-12-01
We study the impact of the symmetry-breaking patterns from supersymmetric SO(10) down to the standard model on the standard big-bang cosmology through the formation of topological defects. None of the models is consistent with the standard cosmology without invoking any mechanism to solve the monopole problem. For this purpose, we use a hybrid false vacuum inflationary scenario. Only two symmetry-breaking patterns are consistent with these topological considerations and with the actual data on the proton lifetime.
Supersymmetric model with Dirac neutrino masses
Marshall, Gardner; McCaskey, Mathew; Sher, Marc
2010-03-01
New models have recently been proposed in which a second Higgs doublet couples only to the lepton doublets and right-handed neutrinos, yielding Dirac neutrino masses. The vacuum value of this second 'nu-Higgs' doublet is made very small by means of a very softly-broken Z{sub 2} or U(1) symmetry. The latter is technically natural and avoids fine-tuning and very light scalars. We consider a supersymmetric version of this model, in which two additional doublets are added to the minimal supersymmetric standard model (MSSM). If kinematically allowed, the decay of the heavy MSSM scalar into charged nu-Higgs scalars will yield dilepton events which can be separated from the W-pair background. In addition, the nu-Higgsinos can lead to very dramatic tetralepton, pentalepton, and hexalepton events which have negligible background and can be detected at the LHC and the Tevatron.
Topological solitons in the supersymmetric Skyrme model
NASA Astrophysics Data System (ADS)
Gudnason, Sven Bjarke; Nitta, Muneto; Sasaki, Shin
2017-01-01
A supersymmetric extension of the Skyrme model was obtained recently, which consists of only the Skyrme term in the Nambu-Goldstone (pion) sector complemented by the same number of quasi-Nambu-Goldstone bosons. Scherk-Schwarz dimensional reduction yields a kinetic term in three or lower dimensions and a potential term in two dimensions, preserving supersymmetry. Euclidean solitons (instantons) are constructed in the supersymmetric Skyrme model. In four dimensions, the soliton is an instanton first found by Speight. Scherk-Schwarz dimensional reduction is then performed once to get a 3-dimensional theory in which a 3d Skyrmion-instanton is found and then once more to get a 2d theory in which a 2d vortex-instanton is obtained. Although the last one is a global vortex it has finite action in contrast to conventional theory. All of them are non-BPS states breaking all supersymmetries.
Supersymmetric Calogero models by gauging
Fedoruk, Sergey; Ivanov, Evgeny; Lechtenfeld, Olaf
2009-05-15
New superconformal extensions of d=1 Calogero-type systems are obtained by gauging the U(n) isometry of matrix superfield models. We consider the cases of N=1, N=2, and N=4 as one-dimensional supersymmetries. The bosonic core of the N=1 and N=2 models is the standard conformal A{sub n-1} Calogero system, whereas the N=4 model is an extension of the U(2)-spin Calogero system.
Beyond the supersymmetric standard model
Hall, L.J.
1988-02-01
The possibility of baryon number violation at the weak scale and an alternative primordial nucleosynthesis scheme arising from the decay of gravitations are discussed. The minimal low energy supergravity model is defined and a few of its features are described. Renormalization group scaling and flavor physics are mentioned.
Stochastic model for supersymmetric particle branching process
NASA Astrophysics Data System (ADS)
Zhang, Yuanyuan; Chan, Aik Hui; Oh, Choo Hiap
2017-01-01
We develop a stochastic branching model to describe the jet evolution of supersymmetric (SUSY) particles. This model is a modified two-phase branching process, or more precisely, a two-phase simple birth process plus Poisson process. Both pure SUSY partons initiated jets and SUSY plus ordinary partons initiated jets scenarios are considered. The stochastic branching equations are established and the Multiplicity Distributions (MDs) are derived for these two scenarios. We also fit the distribution of the general case (SUSY plus ordinary partons initiated jets) with experimental data. The fitting shows the SUSY particles have not participated in branching at current collision energy yet.
Supersymmetric chameleons and ultralocal models
NASA Astrophysics Data System (ADS)
Brax, Philippe; Rizzo, Luca Alberto; Valageas, Patrick
2016-07-01
Super-chameleon models where all types of matter belong to three secluded sectors, i.e. the dark, supersymmetry breaking and matter sectors, are shown to be dynamically equivalent to ultralocal models of modified gravity. In the dark sector, comprising both dark matter and dark energy, the interaction range between the dark energy field and dark matter is constrained to be extremely short, i.e. shorter than the inverse gravitino mass set by supersymmetry breaking. This realizes an extreme version of chameleon screening of the dark energy interaction. On the other hand, the baryonic matter sector decouples from the dark energy in a Damour-Polyakov way. These two mechanisms preclude the existence of any modification of gravity locally in the Solar System due to the presence of the super-chameleon field. On larger scales, the super-chameleon can have effects on the growth of structure and the number of dark matter halos. It can also affect the dynamics of galaxies where the fifth-force interaction that it induces can have the same order of magnitude as Newton's interaction.
Supersymmetric Sachdev-Ye-Kitaev models
NASA Astrophysics Data System (ADS)
Fu, Wenbo; Gaiotto, Davide; Maldacena, Juan; Sachdev, Subir
2017-01-01
We discuss a supersymmetric generalization of the Sachdev-Ye-Kitaev (SYK) model. These are quantum mechanical models involving N Majorana fermions. The supercharge is given by a polynomial expression in terms of the Majorana fermions with random coefficients. The Hamiltonian is the square of the supercharge. The N =1 model with a single supercharge has unbroken supersymmetry at large N , but nonperturbatively spontaneously broken supersymmetry in the exact theory. We analyze the model by looking at the large N equation, and also by performing numerical computations for small values of N . We also compute the large N spectrum of "singlet" operators, where we find a structure qualitatively similar to the ordinary SYK model. We also discuss an N =2 version. In this case, the model preserves supersymmetry in the exact theory and we can compute a suitably weighted Witten index to count the number of ground states, which agrees with the large N computation of the entropy. In both cases, we discuss the supersymmetric generalizations of the Schwarzian action which give the dominant effects at low energies.
Higgs boson masses in supersymmetric models
Berger, M.S.
1991-04-01
Imposing supersymmetry on a Higgs potential constrains the parameters that define the potential. In supersymmetric extensions to the stranded model containing only Higgs SU(2){sub L} doublets there exist Higgs boson mass sum rules and bounds on the Higgs masses at tree level. The prescription for renormalizing these sum rules is derived. An explicit calculation is performed in the minimal supersymmetric extension to the standard model (MSSM). In this model at tree level the mass sum rule is M{sub H}{sup 2} + M{sub h}{sup 2} = M{sub A}{sup 2} + M{sub Z}{sup 2}. The results indicate that large corrections to the sum rules may arise from heavy matter fields, e.g. a heavy top quark. Squarks significantly heavier than their fermionic partners contribute large contributions when mixing occurs in the squark sector. These large corrections result from squark-Higgs couplings that become large in this limit. Contributions to individual Higgs boson masses that are quadratic in the squark masses cancel in the sum rule. Thus the naturalness constraint on Higgs boson masses is hidden in the combination of Higgs boson masses that comprise the sum rule. 39 refs., 13 figs.
On supermatrix models, Poisson geometry, and noncommutative supersymmetric gauge theories
Klimčík, Ctirad
2015-12-15
We construct a new supermatrix model which represents a manifestly supersymmetric noncommutative regularisation of the UOSp(2|1) supersymmetric Schwinger model on the supersphere. Our construction is much simpler than those already existing in the literature and it was found by using Poisson geometry in a substantial way.
Bootstrapping the Three Dimensional Supersymmetric Ising Model.
Bobev, Nikolay; El-Showk, Sheer; Mazáč, Dalimil; Paulos, Miguel F
2015-07-31
We implement the conformal bootstrap program for three dimensional conformal field theories with N=2 supersymmetry and find universal constraints on the spectrum of operator dimensions in these theories. By studying the bounds on the dimension of the first scalar appearing in the operator product expansion of a chiral and an antichiral primary, we find a kink at the expected location of the critical three dimensional N=2 Wess-Zumino model, which can be thought of as a supersymmetric analog of the critical Ising model. Focusing on this kink, we determine, to high accuracy, the low-lying spectrum of operator dimensions of the theory, as well as the stress-tensor two-point function. We find that the latter is in an excellent agreement with an exact computation.
Realistic models of paracrystalline silicon
NASA Astrophysics Data System (ADS)
Nakhmanson, S. M.; Voyles, P. M.; Mousseau, Normand; Barkema, G. T.; Drabold, D. A.
2001-06-01
We present a procedure for the preparation of physically realistic models of paracrystalline silicon based on a modification of the bond-switching method of Wooten, Winer, and Weaire. The models contain randomly oriented c-Si grains embedded in a disordered matrix. Our technique creates interfaces between the crystalline and disordered phases of Si with an extremely low concentration of coordination defects. The resulting models possess structural and vibrational properties comparable with those of good continuous random network models of amorphous silicon and display realistic optical properties, correctly reproducing the electronic band gap of amorphous silicon. The largest of our models also shows the best agreement of any atomistic model structure that we tested with fluctuation microscopy experiments, indicating that this model has a degree of medium-range order closest to that of the real material.
A tool box for implementing supersymmetric models
NASA Astrophysics Data System (ADS)
Staub, Florian; Ohl, Thorsten; Porod, Werner; Speckner, Christian
2012-10-01
We present a framework for performing a comprehensive analysis of a large class of supersymmetric models, including spectrum calculation, dark matter studies and collider phenomenology. To this end, the respective model is defined in an easy and straightforward way using the Mathematica package SARAH. SARAH then generates model files for CalcHep which can be used with micrOMEGAs as well as model files for WHIZARD and O'Mega. In addition, Fortran source code for SPheno is created which facilitates the determination of the particle spectrum using two-loop renormalization group equations and one-loop corrections to the masses. As an additional feature, the generated SPheno code can write out input files suitable for use with HiggsBounds to apply bounds coming from the Higgs searches to the model. Combining all programs provides a closed chain from model building to phenomenology. Program summary Program title: SUSY Phenomenology toolbox. Catalog identifier: AEMN_v1_0. Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMN_v1_0.html. Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland. Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html. No. of lines in distributed program, including test data, etc.: 140206. No. of bytes in distributed program, including test data, etc.: 1319681. Distribution format: tar.gz. Programming language: Autoconf, Mathematica. Computer: PC running Linux, Mac. Operating system: Linux, Mac OS. Classification: 11.6. Nature of problem: Comprehensive studies of supersymmetric models beyond the MSSM is considerably complicated by the number of different tasks that have to be accomplished, including the calculation of the mass spectrum and the implementation of the model into tools for performing collider studies, calculating the dark matter density and checking the compatibility with existing collider bounds (in particular, from the Higgs searches). Solution method: The
Radiative neutralino production in low energy supersymmetric models
Basu, Rahul; Sharma, Chandradew; Pandita, P. N.
2008-06-01
We study the production of the lightest neutralinos in the radiative process e{sup +}e{sup -}{yields}{chi}-tilde{sub 1}{sup 0}{chi}-tilde{sub 1}{sup 0}{gamma} in low energy supersymmetric models for the International Linear Collider energies. This includes the minimal supersymmetric standard model as well as its extension with an additional chiral Higgs singlet superfield, the nonminimal supersymmetric standard model. We compare and contrast the dependence of the signal cross section on the parameters of the neutralino sector of the minimal and nonminimal supersymmetric standard model. We also consider the background to this process coming from the standard model process e{sup +}e{sup -}{yields}{nu}{nu}{gamma}, as well as from the radiative production of the scalar partners of the neutrinos (sneutrinos) e{sup +}e{sup -}{yields}{nu}-tilde{nu}-tilde*{gamma}, which can be a background to the radiative neutralino production when the sneutrinos decay invisibly. In low energy supersymmetric models radiative production of the lightest neutralinos may be the only channel to study supersymmetric partners of the standard model particles at the first stage of a linear collider, since heavier neutralinos, charginos, and sleptons may be too heavy to be pair produced at a e{sup +}e{sup -} machine with {radical}(s)=500 GeV.
Particle physics and cosmology in supersymmetric models
NASA Astrophysics Data System (ADS)
Morrissey, David Edgar
The Standard Model (SM) of particle physics provides an excellent description of the elementary particle interactions observed in particle collider experiments, but the model does less well when it is applied to cosmology. Recent measurements of the Universe over very large distances indicate the existence of non-luminous dark matter and an excess of baryons over anti-baryons. The SM is unable to account for either of these results, implying that an extension of the SM description is needed. One such extension is supersymmetry. Within the minimal supersymmetric version of the SM, the MSSM, the lightest superpartner particle can make up the dark matter, and the baryon asymmetry can be generated by the mechanism of electroweak baryogenesis (EWBG). In this work, we examine these issues together in order to find out whether the MSSM can account for both of them simultaneously. We find that the MSSM can explain both the baryon asymmetry and the dark matter, but only over a very constrained region of the model parameter space. The strongest constraints on this scenario come from the lower bound on the Higgs boson mass, and the upper bound on the electric dipole moment of the electron. Moreover, upcoming experiments will probe the remaining allowed parameter space in the near future. Some of these constraints may be relaxed by going beyond the MSSM. With this in mind, we also investigate the nMSSM, a minimal singlet extension of the MSSM. We find that this model can also explain both the dark matter and the baryon asymmetry.
A simple and realistic model of supersymmetry breaking
NASA Astrophysics Data System (ADS)
Nomura, Yasunori; Papucci, Michele
2008-03-01
We present a simple and realistic model of supersymmetry breaking. In addition to the minimal supersymmetric standard model, we only introduce a hidden sector gauge group SU (5) and three fields X, F and Fbar. Supersymmetry is broken at a local minimum of the potential, and its effects are transmitted to the supersymmetric standard model sector through both standard model gauge loops and local operators suppressed by the cutoff scale, which is taken to be the unification scale. The form of the local operators is controlled by a U (1) symmetry. The generated supersymmetry breaking and μ parameters are comparable in size, and no flavor or CP violating terms arise. The spectrum of the first two generation superparticles is that of minimal gauge mediation with the number of messengers Nmess = 5 and the messenger scale 1011 GeV ≲Mmess ≲1013 GeV. The spectrum of the Higgs bosons and third generation superparticles, however, can deviate from it. The lightest supersymmetric particle is the gravitino with a mass of order (1- 10) GeV.
Supersymmetric lepton flavor violation in low-scale seesaw models
NASA Astrophysics Data System (ADS)
Ilakovac, Amon; Pilaftsis, Apostolos
2009-11-01
We study a new supersymmetric mechanism for lepton flavor violation in μ and τ decays and μ→e conversion in nuclei, within a minimal extension of the minimal supersymmetric standard model with low-mass heavy singlet neutrinos and sneutrinos. We find that the decays μ→eγ, τ→eγ and τ→μγ are forbidden in the supersymmetric limit of the theory, whereas other processes, such as μ→eee, μ→e conversion, τ→eee and τ→eμμ, are allowed and can be dramatically enhanced several orders of magnitude above the observable level by potentially large neutrino Yukawa coupling effects. The profound implications of supersymmetric lepton flavor violation for present and future experiments are discussed.
Challenging the minimal supersymmetric SU(5) model
Bajc, Borut; Lavignac, Stéphane; Mede, Timon
2014-06-24
We review the main constraints on the parameter space of the minimal renormalizable supersymmetric SU(5) grand unified theory. They consist of the Higgs mass, proton decay, electroweak symmetry breaking and fermion masses. Superpartner masses are constrained both from below and from above, giving hope for confirming or definitely ruling out the theory in the future. This contribution is based on Ref. [1].
Lepton flavor violating higgs decays in supersymmetric models
NASA Astrophysics Data System (ADS)
Ün, Cem Salih; Hammad, Ahmed; Khalil, Shaaban
2017-02-01
The ATLAS and CMS collaborations reported the first signal of Lepton Flavor Violating (LFV) Higgs decay into τ and µ leptons. Standard Model forbids such processes at the renormalizable level because of lepton flavor symmetry. On the other hand, many extensions of the Standard Model do not exhibit such a symmetry and the models beyond the Standard Model (BSM) yield such processes. Hence, any signal for LFV processes can be interpreted as a direct probe for the BSM models. In this work, we consider LFV Higgs boson decays in a class of supersymmetric models including minimal supersymmetric extension of the SM (MSSM), Supersymmetric Type I Seesaw, and U(1)B-L extended MSSM supplied with the inverse seesaw mechanism for non-zero neutrino masses.
Ellis, John; Olive, Keith A.; Savage, Christopher; Spanos, Vassilis C.
2010-04-15
We evaluate the neutrino fluxes to be expected from neutralino lightest supersymmetric particle (LSP) annihilations inside the Sun, within the minimal supersymmetric extension of the standard model with supersymmetry-breaking scalar and gaugino masses constrained to be universal at the grand unified theory scale [the constrained minimal supersymmetric standard model (CMSSM)]. We find that there are large regions of typical CMSSM (m{sub 1/2},m{sub 0}) planes where the LSP density inside the Sun is not in equilibrium, so that the annihilation rate may be far below the capture rate. We show that neutrino fluxes are dependent on the solar model at the 20% level, and adopt the AGSS09 model of Serenelli et al. for our detailed studies. We find that there are large regions of the CMSSM (m{sub 1/2},m{sub 0}) planes where the capture rate is not dominated by spin-dependent LSP-proton scattering, e.g., at large m{sub 1/2} along the CMSSM coannihilation strip. We calculate neutrino fluxes above various threshold energies for points along the coannihilation/rapid-annihilation and focus-point strips where the CMSSM yields the correct cosmological relic density for tan{beta}=10 and 55 for {mu}>0, exploring their sensitivities to uncertainties in the spin-dependent and -independent scattering matrix elements. We also present detailed neutrino spectra for four benchmark models that illustrate generic possibilities within the CMSSM. Scanning the cosmologically favored parts of the parameter space of the CMSSM, we find that the IceCube/DeepCore detector can probe at best only parts of this parameter space, notably the focus-point region and possibly also at the low-mass tip of the coannihilation strip.
Generalized Kähler Geometry from Supersymmetric Sigma Models
NASA Astrophysics Data System (ADS)
Bredthauer, Andreas; Lindström, Ulf; Persson, Jonas; Zabzine, Maxim
2006-09-01
We give a physical derivation of generalized Kähler geometry. Starting from a supersymmetric nonlinear sigma model, we rederive and explain the results of Gualtieri (Generalized complex geometry, DPhil thesis, Oxford University, 2004) regarding the equivalence between generalized Kähler geometry and the bi-hermitean geometry of Gates et al. (Nucl Phys B248:157, 1984). When cast in the language of supersymmetric sigma models, this relation maps precisely to that between the Lagrangian and the Hamiltonian formalisms. We also discuss topological twist in this context.
Shell-model study on event rates of lightest supersymmetric particles scattering off 83Kr and 125Te
NASA Astrophysics Data System (ADS)
Pirinen, P.; Srivastava, P. C.; Suhonen, J.; Kortelainen, M.
2016-05-01
We investigate the elastic and inelastic scattering of lightest supersymmetric particle (LSP) dark matter off two possible target nuclei, 83Kr and 125Te. For the nuclear-structure calculations, we employ the nuclear shell model using recently generated realistic interactions. We have condensed the nuclear-physics contribution to a set of nuclear-structure factors that are independent of the adopted supersymmetric (SUSY) model. Total event rates are then easily calculated by combining the nuclear-structure factors with SUSY parameters of choice. In particular, 125Te shows promise as a detector material with both the elastic and inelastic channels yielding an appreciable nuclear response.
Automatically [ital R]-conserving supersymmetric SO(10) models and mixed light Higgs doublets
Lee, D.; Mohapatra, R.N. )
1995-02-01
In automatic [ital R]-parity-conserving supersymmetric (SUSY) SO(10) models, the simplest way to accommodate realistic fermion masses is to demand that the light Higgs doublets are linear combinations of the [l brace]10[r brace] and [l brace]12[bar 6][r brace] grand unified Higgs representations. We study the realization of this mixed light Higgs property consistent with doublet-triplet splitting in a minimal [ital R]-conserving SUSY SO(10) model. We then discuss predictions for neutrino masses and mixings in this model as well as its implications for proton decay.
Collective field theory of a singular supersymmetric matrix model
de Mello Koch, R.; Rodrigues, J.P.
1995-05-15
The supersymmetric collective field theory with the potential {ital v}{prime}({ital x})={omega}{ital x}{minus}{eta}/{ital x} is studied. Consistency with supersymmetry enforces a two band solution. A supersymmetric classical configuration is found, and interpreted in terms of the density of zeroes of certain Laguerre polynomials. The spectrum of the model is then studied and is seen to correspond to a massless scalar and a Majorana fermion. The {ital x} space eigenfunctions are constructed and expressed in terms of Chebyshev polynomials. Higher order interactions are also discussed.
False Vacuum in the Supersymmetric Mass Varying Neutrino Model
Tanimoto, Morimitsu
2009-04-17
We discuss the vacuum structure of the scalar potential in a supersymmetric Mass Varying Neutrinos model. The observed dark energy density is identified with the false vacuum energy and the dark energy scale of order (10{sup -3} eV){sup 4} is understood by gravitationally suppressed supersymmetry breaking scale, F(TeV{sup 2})/M{sub pl}.
R-invariant new inflation model versus supersymmetric standard model
Ibe, M.; Shinbara, Y.
2008-02-01
We revisit the implications of the R-invariant new inflation model to the supersymmetric standard model in light of recent discussion of gravitino production processes by the decay of the inflaton and the supersymmetry breaking field. We show that the models with supergravity mediation do not work well together with the R-invariant new inflation model, where the gravitino abundance produced by the decay of the inflaton and the supersymmetry breaking field significantly exceeds the bounds from cosmological observations without fine-tuning. We also show that the models with gauge mediation can go together with the R-invariant new inflation model, where the dark matter abundance and the baryon asymmetry of the universe are consistently explained without severe fine-tuning.
Supersymmetric models with higher dimensional operators
NASA Astrophysics Data System (ADS)
Antoniadis, I.; Dudas, E.; Ghilencea, D. M.
2008-03-01
In 4D renormalisable theories, integrating out massive states generates in the low energy effective action higher dimensional operators (derivative or otherwise). Using a superfield language it is shown that a 4D N=1 supersymmetric theory with higher derivative operators in either the Kahler or the superpotential part of the Lagrangian and with an otherwise arbitrary superpotential, is equivalent to a 4D N=1 theory of second order (i.e. without higher derivatives) with additional superfields and renormalised interactions. We provide examples where a free theory with trivial supersymmetry breaking provided by a linear superpotential becomes, in the presence of higher derivatives terms and in the second order version, a non-trivial interactive one with spontaneous supersymmetry breaking. The couplings of the equivalent theory acquire a threshold correction through their dependence on the scale of the higher dimensional operator(s). The scalar potential in the second order theory is not necessarily positive definite, and one can in principle have a vanishing potential with broken supersymmetry. We provide an application to MSSM and argue that at tree-level and for a mass scale associated to a higher derivative term in the TeV range, the Higgs mass can be lifted above the current experimental limits.
Discrimination of supersymmetric grand unified models in gaugino mediation
Okada, Nobuchika; Hieu Minh Tran
2011-03-01
We consider supersymmetric grand unified theory (GUT) with the gaugino mediated supersymmetry breaking and investigate a possibility to discriminate different GUT models in terms of predicted sparticle mass spectra. Taking two example GUT models, the minimal SU(5) and simple SO(10) models, and imposing a variety of theoretical and experimental constraints, we calculate sparticle masses. Fixing parameters of each model so as to result in the same mass of neutralino as the lightest supersymmetric particle (LSP), giving the observed dark matter relic density, we find sizable mass differences in the left-handed slepton and right-handed down-type squark sectors in two models, which can be a probe to discriminate the GUT models realized at the GUT scale far beyond the reach of collider experiments.
Higher-rank supersymmetric models and topological conformal field theory
NASA Astrophysics Data System (ADS)
Kawai, Toshiya; Uchino, Taku; Yang, Sung-Kil
1993-03-01
In the first part of this paper we investigate the operator aspect of a higher-rank supersymmetric model which is introduced as a Lie theoretic extension of the N = 2 minimal model with the simplest case su(2) corresponding to the N = 2 minimal model. In particular we identify the analogs of chirality conditions and chiral ring. In the second part we construct a class of topological conformal field theories starting with this higher-rank supersymmetric model. We show the BRST-exactness of the twisted stress-energy tensor, find out physical observables and discuss how to make their correlation functions. It is emphasized that in the case of su(2) the topological field theory constructed in this paper is distinct from the one obtained by twisting the N = 2 minimal model through the usual procedure.
Extended Jackiw-Pi model and its supersymmetrization
NASA Astrophysics Data System (ADS)
Nishino, Hitoshi; Rajpoot, Subhash
2015-07-01
We present an extended version of the so-called Jackiw-Pi (JP) model in three dimensions, and perform its supersymmetrization. Our field content has three multiplets: (i) Yang-Mills vector multiplet (AIμ ,λI), (ii) Parity-odd extra vector multiplet (BIμ ,χI), and (iii) Scalar multiplet (CI ,ρI ;fI). The bosonic fields in these multiplets are the same as the original JP-model, except for the auxiliary field fI which is new, while the fermions λI, χI and ρI are their super-partners. The basic difference from the original JP-model is the presence of the kinetic term for CI with its modified field-strength HIμ ≡DμCI + mBIμ. The inclusion of the CI-kinetic term is to comply with the recently-developed tensor hierarchy formulation for supersymmetrization.
Neutrino masses in the left right supersymmetric model
NASA Astrophysics Data System (ADS)
Frank, M.
2002-08-01
We show that in a left-right supersymmetric model with a Higgs structure that supports the see-saw mechanism, the neutrinos get additional contributions to their masses at one loop level. The mechanism responsible is analogous to the Grossman-Haber see-saw mechanism, but the additional mass terms are proportional to the mass difference of the right-handed sneutrinos. We show that the data on both the solar and the atmospheric neutrinos can be accommodated by either two almost degenerate right-handed sneutrinos, or two heavy sneutrino with different, but still relatively small, mass splittings. We discuss the implications of this result for the masses and mixings of the heavy sneutrinos, and the soft-breaking parameters of the left-right supersymmetric model.
Development of a realistic human airway model.
Lizal, Frantisek; Elcner, Jakub; Hopke, Philip K; Jedelsky, Jan; Jicha, Miroslav
2012-03-01
Numerous models of human lungs with various levels of idealization have been reported in the literature; consequently, results acquired using these models are difficult to compare to in vivo measurements. We have developed a set of model components based on realistic geometries, which permits the analysis of the effects of subsequent model simplification. A realistic digital upper airway geometry except for the lack of an oral cavity has been created which proved suitable both for computational fluid dynamics (CFD) simulations and for the fabrication of physical models. Subsequently, an oral cavity was added to the tracheobronchial geometry. The airway geometry including the oral cavity was adjusted to enable fabrication of a semi-realistic model. Five physical models were created based on these three digital geometries. Two optically transparent models, one with and one without the oral cavity, were constructed for flow velocity measurements, two realistic segmented models, one with and one without the oral cavity, were constructed for particle deposition measurements, and a semi-realistic model with glass cylindrical airways was developed for optical measurements of flow velocity and in situ particle size measurements. One-dimensional phase doppler anemometry measurements were made and compared to the CFD calculations for this model and good agreement was obtained.
Comments on HKT supersymmetric sigma models and their Hamiltonian reduction
NASA Astrophysics Data System (ADS)
Fedoruk, Sergey; Smilga, Andrei
2015-05-01
Using complex notation, we present new simple expressions for two pairs of complex supercharges in HKT (‘hyper-Kähler with torsion’) supersymmetric sigma models. The second pair of supercharges depends on the holomorphic antisymmetric ‘hypercomplex structure’ tensor {{I}jk} which plays the same role for the HKT models as the complex structure tensor for the Kähler models. When the Hamiltonian and supercharges commute with the momenta conjugate to the imaginary parts of the complex coordinates, one can perform a Hamiltonian reduction. The models thus obtained represent a special class of quasicomplex sigma models introduced recently by Ivanov and Smilga (2013 SIGMA 9 069)
False vacuum in the supersymmetric mass varying neutrinos model
Takahashi, Ryo; Tanimoto, Morimitsu
2008-02-15
We present detailed analyses of the vacuum structure of the scalar potential in a supersymmetric mass varying neutrinos model. The observed dark energy density is identified with false vacuum energy and the dark energy scale of order (10{sup -3} eV){sup 4} is understood by the gravitationally suppressed supersymmetry breaking scale, F(TeV){sup 2}/M{sub Pl}, in the model. The vacuum expectation values of sneutrinos should be tiny in order that the model works. Some decay processes of superparticles into an acceleron and sterile neutrino are also discussed in the model.
No-scale supersymmetric standard model
NASA Astrophysics Data System (ADS)
Ellis, John; Lahanas, A. B.; Nanopoulos, D. V.; Tamvakis, K.
1984-01-01
We propose a class of supergravity models coupled to matter in which the scales of supersymmetry breaking and of weak gauge symmetry breaking are both fixed by dimensional transmutation, not put in by hand. The models have a flat potential with zero cosmological constant before the evaluation of weak radiative corrections which determine m3/2, mW = exp [-O(1)/αt]mp:αt = O(α). These models are consistent with all particle physi cs and cosmological constraints for top quark masses in the range 30 GeV < mt < 100 GeV.
Strong coupling phase transitions in supersymmetric grand unified models
NASA Astrophysics Data System (ADS)
Reiss, David B.
1985-08-01
The determination of the temperature at which a grand unified model becomes strongly coupled should be based upon a physical quantity such as the screening lenght rather than the ad hoc condition that the opening becomes O(1). I use a recent calculation of this screening length (the inverse electric mass) to discuss some aspects of strong coupling behavior in the cosmology of supersymmetric grand unified models. Significant effects may occur in a variety of cases. An interesting possibilit is that there may be a pair of confining and deconfining phase transitions at a temperature as low as the supersymmetry breaking scale (O(TeV)). I present illustrative examples for these effects.
E6 inspired supersymmetric models with exact custodial symmetry
NASA Astrophysics Data System (ADS)
Nevzorov, Roman
2013-01-01
The breakdown of E6 gauge symmetry at high energies may lead to supersymmetric models based on the standard model gauge group together with extra U(1)ψ and U(1)χ gauge symmetries. To ensure anomaly cancellation the particle content of these E6 inspired models involves extra exotic states that generically give rise to nondiagonal flavor transitions and rapid proton decay. We argue that a single discrete Z˜2H symmetry can be used to forbid tree-level flavor changing transitions, as well as the most dangerous baryon and lepton number violating operators. We present 5D and 6D orbifold grand unified theory constructions that lead to the E6 inspired supersymmetric models of this type. The breakdown of U(1)ψ and U(1)χ gauge symmetries that preserves E6 matter parity assignment guarantees that ordinary quarks and leptons and their superpartners, as well as the exotic states which originate from 27 representations of E6, survive to low energies. These E6 inspired models contain two dark matter candidates and must also include additional TeV scale vectorlike lepton or vectorlike down-type quark states to render the lightest exotic quark unstable. We examine gauge coupling unification in these models and discuss their implications for collider phenomenology and cosmology.
𝒩 = 4 supersymmetric quantum mechanical model: Novel symmetries
NASA Astrophysics Data System (ADS)
Krishna, S.
2017-04-01
We discuss a set of novel discrete symmetry transformations of the 𝒩 = 4 supersymmetric quantum mechanical model of a charged particle moving on a sphere in the background of Dirac magnetic monopole. The usual five continuous symmetries (and their conserved Noether charges) and two discrete symmetries together provide the physical realizations of the de Rham cohomological operators of differential geometry. We have also exploited the supervariable approach to derive the nilpotent 𝒩 = 4 SUSY transformations and provided the geometrical interpretation in the language of translational generators along the Grassmannian directions 𝜃α and 𝜃¯α onto (1, 4)-dimensional supermanifold.
Vacuum fluctuations in a supersymmetric model in FRW spacetime
Bilic, Neven
2011-05-15
We study a noninteracting supersymmetric model in an expanding FRW spacetime. A soft supersymmetry breaking induces a nonzero contribution to the vacuum energy density. A short distance cutoff of the order of Planck length provides a scale for the vacuum energy density comparable with the observed cosmological constant. Assuming the presence of a dark energy substance in addition to the vacuum fluctuations of the field, an effective equation of state is derived in a self-consistent approach. The effective equation of state is sensitive to the choice of the cutoff but no fine-tuning is needed.
Electroweak baryogenesis in the exceptional supersymmetric standard model
Chao, Wei
2015-08-28
We study electroweak baryogenesis in the E{sub 6} inspired exceptional supersymmetric standard model (E{sub 6}SSM). The relaxation coefficients driven by singlinos and the new gaugino as well as the transport equation of the Higgs supermultiplet number density in the E{sub 6}SSM are calculated. Our numerical simulation shows that both CP-violating source terms from singlinos and the new gaugino can solely give rise to a correct baryon asymmetry of the Universe via the electroweak baryogenesis mechanism.
A review of Higgs mass calculations in supersymmetric models
NASA Astrophysics Data System (ADS)
Draper, Patrick; Rzehak, Heidi
2016-03-01
The discovery of the Higgs boson is both a milestone achievement for the Standard Model and an exciting probe of new physics beyond the SM. One of the most important properties of the Higgs is its mass, a number that has proven to be highly constraining for models of new physics, particularly those related to the electroweak hierarchy problem. Perhaps the most extensively studied examples are supersymmetric models, which, while capable of producing a 125 GeV Higgs boson with SM-like properties, do so in non-generic parts of their parameter spaces. We review the computation of the Higgs mass in the Minimal Supersymmetric Standard Model, in particular the large radiative corrections required to lift mh to 125 GeV and their calculation via Feynman-diagrammatic and effective field theory techniques. This review is intended as an entry point for readers new to the field, and as a summary of the current status, including the existing analytic calculations and publicly-available computer codes.
Dark matter candidates in the constrained exceptional supersymmetric standard model
NASA Astrophysics Data System (ADS)
Athron, P.; Thomas, A. W.; Underwood, S. J.; White, M. J.
2017-02-01
The exceptional supersymmetric standard model is a low energy alternative to the minimal supersymmetric standard model (MSSM) with an extra U (1 ) gauge symmetry and three generations of matter filling complete 27-plet representations of E6. This provides both new D and F term contributions that raise the Higgs mass at tree level, and a compelling solution to the μ -problem of the MSSM by forbidding such a term with the extra U (1 ) symmetry. Instead, an effective μ -term is generated from the vacuum expectation value of an SM singlet which breaks the extra U (1 ) symmetry at low energies, giving rise to a massive Z'. We explore the phenomenology of the constrained version of this model in substantially more detail than has been carried out previously, performing a ten dimensional scan that reveals a large volume of viable parameter space. We classify the different mechanisms for generating the measured relic density of dark matter found in the scan, including the identification of a new mechanism involving mixed bino/inert-Higgsino dark matter. We show which mechanisms can evade the latest direct detection limits from the LUX 2016 experiment. Finally we present benchmarks consistent with all the experimental constraints and which could be discovered with the XENON1T experiment.
Supersymmetric nonlinear O(3) sigma model on the lattice
NASA Astrophysics Data System (ADS)
Flore, Raphael; Körner, Daniel; Wipf, Andreas; Wozar, Christian
2012-11-01
A supersymmetric extension of the nonlinear O(3) sigma model in two spacetime dimensions is investigated by means of Monte Carlo simulations. We argue that it is impossible to construct a lattice action that implements both the O(3) symmetry as well as at least one supersymmetry exactly at finite lattice spacing. It is shown by explicit calculations that previously proposed discretizations fail to reproduce the exact symmetries of the target manifold in the continuum limit. We provide an alternative lattice action with exact O(3) symmetry and compare two approaches based on different derivative operators. Using the nonlocal SLAC derivative for the quenched model on moderately sized lattices we extract the value σ(2 , u 0) = 1 .2604(13) for the step scaling function at u 0 = 1 .0595, to be compared with the exact value 1 .261210. For the supersymmetric model with SLAC derivative the discrete chiral symmetry is maintained but we encounter strong sign fluctuations, rendering large lattice simulations ineffective. By applying the Wilson prescription, supersymmetry and chiral symmetry are broken explicitly at finite lattice spacing, though there is clear evidence that both are restored in the continuum limit by fine tuning of a single mass parameter.
Novel symmetries in N=2 supersymmetric quantum mechanical models
Malik, R.P.; Khare, Avinash
2013-07-15
We demonstrate the existence of a novel set of discrete symmetries in the context of the N=2 supersymmetric (SUSY) quantum mechanical model with a potential function f(x) that is a generalization of the potential of the 1D SUSY harmonic oscillator. We perform the same exercise for the motion of a charged particle in the X–Y plane under the influence of a magnetic field in the Z-direction. We derive the underlying algebra of the existing continuous symmetry transformations (and corresponding conserved charges) and establish its relevance to the algebraic structures of the de Rham cohomological operators of differential geometry. We show that the discrete symmetry transformations of our present general theories correspond to the Hodge duality operation. Ultimately, we conjecture that any arbitrary N=2 SUSY quantum mechanical system can be shown to be a tractable model for the Hodge theory. -- Highlights: •Discrete symmetries of two completely different kinds of N=2 supersymmetric quantum mechanical models have been discussed. •The discrete symmetries provide physical realizations of Hodge duality. •The continuous symmetries provide the physical realizations of de Rham cohomological operators. •Our work sheds a new light on the meaning of the above abstract operators.
Constant curvature surfaces of the supersymmetric ℂP{sup N−1} sigma model
Delisle, L.; Hussin, V.; Yurduşen, İ.; Zakrzewski, W. J.
2015-02-15
Constant curvature surfaces are constructed from the finite action solutions of the supersymmetric ℂP{sup N−1} sigma model. It is shown that there is a unique holomorphic solution which leads to constant curvature surfaces: the generalized Veronese curve. We give a general criterion to construct non-holomorphic solutions of the model. We extend our analysis to general supersymmetric Grassmannian models.
Realistic molecular model of kerogen's nanostructure
NASA Astrophysics Data System (ADS)
Bousige, Colin; Ghimbeu, Camélia Matei; Vix-Guterl, Cathie; Pomerantz, Andrew E.; Suleimenova, Assiya; Vaughan, Gavin; Garbarino, Gaston; Feygenson, Mikhail; Wildgruber, Christoph; Ulm, Franz-Josef; Pellenq, Roland J.-M.; Coasne, Benoit
2016-05-01
Despite kerogen's importance as the organic backbone for hydrocarbon production from source rocks such as gas shale, the interplay between kerogen's chemistry, morphology and mechanics remains unexplored. As the environmental impact of shale gas rises, identifying functional relations between its geochemical, transport, elastic and fracture properties from realistic molecular models of kerogens becomes all the more important. Here, by using a hybrid experimental-simulation method, we propose a panel of realistic molecular models of mature and immature kerogens that provide a detailed picture of kerogen's nanostructure without considering the presence of clays and other minerals in shales. We probe the models' strengths and limitations, and show that they predict essential features amenable to experimental validation, including pore distribution, vibrational density of states and stiffness. We also show that kerogen's maturation, which manifests itself as an increase in the sp2/sp3 hybridization ratio, entails a crossover from plastic-to-brittle rupture mechanisms.
Realistic molecular model of kerogen's nanostructure.
Bousige, Colin; Ghimbeu, Camélia Matei; Vix-Guterl, Cathie; Pomerantz, Andrew E; Suleimenova, Assiya; Vaughan, Gavin; Garbarino, Gaston; Feygenson, Mikhail; Wildgruber, Christoph; Ulm, Franz-Josef; Pellenq, Roland J-M; Coasne, Benoit
2016-05-01
Despite kerogen's importance as the organic backbone for hydrocarbon production from source rocks such as gas shale, the interplay between kerogen's chemistry, morphology and mechanics remains unexplored. As the environmental impact of shale gas rises, identifying functional relations between its geochemical, transport, elastic and fracture properties from realistic molecular models of kerogens becomes all the more important. Here, by using a hybrid experimental-simulation method, we propose a panel of realistic molecular models of mature and immature kerogens that provide a detailed picture of kerogen's nanostructure without considering the presence of clays and other minerals in shales. We probe the models' strengths and limitations, and show that they predict essential features amenable to experimental validation, including pore distribution, vibrational density of states and stiffness. We also show that kerogen's maturation, which manifests itself as an increase in the sp(2)/sp(3) hybridization ratio, entails a crossover from plastic-to-brittle rupture mechanisms.
Higgs sector of the supersymmetric reduced 331 model
NASA Astrophysics Data System (ADS)
Ferreira, J. G., Jr.; Pires, C. A. de S.; da Silva, P. S. Rodrigues; Sampieri, A.
2013-11-01
A supersymmetric version of the recently proposed reduced minimal 331 model is considered and its Higgs sector is investigated. We focus on the mass spectrum of the lightest scalars of the model. We show that the Higgs mass of 125 GeV requires substantial radiative corrections. However, stops may develop small mixing and must have a mass around TeV. Moreover, some soft supersymmetry breaking terms may lie at the electroweak scale, which alleviates some tension concerning the fine-tuning of the related parameters. The lightest doubly charged scalar may have a mass of around a few hundreds of GeV, which can be probed at the LHC, while the remaining scalars of the model have masses at the TeV scale.
Maintaining Realistic Uncertainty in Model and Forecast
1999-09-30
Maintaining Realistic Uncertainty in Model and Forecast Leonard Smith Pembroke College Oxford University St Aldates Oxford OX1 3LB England phone... Oxford University ,Pembroke College,St Aldates,Oxford OX1 3LB England, 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S...in my group. REFERENCES Clarke, L. (1999) Rogue Thermocouple Detection. MSc Thesis, Mathematical Institute, Oxford University . Hansen J. and L. A
Maintaining Realistic Uncertainty in Model and Forecast
2000-09-30
Maintaining Realistic Uncertainty in Model and Forecast Leonard Smith Pembroke College Oxford University St. Aldates Oxford OX1 1DW United Kingdom...5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Pembroke College, Oxford University ,,St...evaluation: l-shadowing, probabilistic prediction and weather forecasting. D.Phil Thesis, Oxford University . Lorenz, E. (1995) Predictability-a Partially
NASA Astrophysics Data System (ADS)
Das, Debottam; Ellwanger, Ulrich; Teixeira, Ana M.
2012-03-01
The code NMSDECAY allows to compute widths and branching ratios of sparticle decays in the Next-to-Minimal Supersymmetric Standard Model. It is based on a generalization of SDECAY, to include the extended Higgs and neutralino sectors of the NMSSM. Slepton 3-body decays, possibly relevant in the case of a singlino-like lightest supersymmetric particle, have been added. NMSDECAY will be part of the NMSSMTools package, which computes Higgs, sparticle masses and Higgs decays in the NMSSM. Program summaryProgram title: NMSDECAY Catalogue identifier: AELC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AELC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 188 177 No. of bytes in distributed program, including test data, etc.: 1 896 478 Distribution format: tar.gz Programming language: FORTRAN77 Computer: All supporting g77, gfortran, ifort Operating system: All supporting g77, gfortran, ifort Classification: 11.1 External routines: Routines in the NMSSMTools package: At least one of the routines in the directory main (e.g. nmhdecay.f), all routines in the directory sources. (All software is included in the distribution package.) Nature of problem: Calculation of all decay widths and decay branching fractions of all particles in the Next-to-Minimal Supersymmetric Standard Model. Solution method: Suitable generalization of the code SDECAY [1] including the extended Higgs and neutralino sector of the Next-to-Minimal Supersymmetric Standard Model, and slepton 3-body decays. Additional comments: NMSDECAY is interfaced with NMSSMTools, available on the web page http://www.th.u-psud.fr/NMHDECAY/nmssmtools.html. Running time: On an Intel Core i7 with 2.8 GHZ: about 2 seconds per point in parameter space, if all flags flagqcd, flagmulti and flagloop are switched on.
Anatomy of Higgs mass in supersymmetric inverse seesaw models
NASA Astrophysics Data System (ADS)
Chun, Eung Jin; Mummidi, V. Suryanarayana; Vempati, Sudhir K.
2014-09-01
We compute the one loop corrections to the CP-even Higgs mass matrix in the supersymmetric inverse seesaw model to single out the different cases where the radiative corrections from the neutrino sector could become important. It is found that there could be a significant enhancement in the Higgs mass even for Dirac neutrino masses of O(30) GeV if the left-handed sneutrino soft mass is comparable or larger than the right-handed neutrino mass. In the case where right-handed neutrino masses are significantly larger than the supersymmetry breaking scale, the corrections can utmost account to an upward shift of 3 GeV. For very heavy multi TeV sneutrinos, the corrections replicate the stop corrections at 1-loop. We further show that general gauge mediation with inverse seesaw model naturally accommodates a 125 GeV Higgs with TeV scale stops.
Supersymmetric Model of ρ-Meson Propagator in Quark-Gluon Plasma
NASA Astrophysics Data System (ADS)
Rostampour, M.; Saadat, H.
2012-08-01
In this work we study supersymmetric model of ρ-meson propagation in quark-gluon plasma. Then we apply this method to total absorption cross sections of photon and photino. We use supersymmetric condition to find that absorption cross sections of photon should be equal to absorption cross sections of photino.
Target space pseudoduality in supersymmetric sigma models on symmetric spaces
NASA Astrophysics Data System (ADS)
Sarisaman, Mustafa
We discuss the target space pseudoduality in supersymmetric sigma models on symmetric spaces. We first consider the case where sigma models based on real compact connected Lie groups of the same dimensionality and give examples using three dimensional models on target spaces. We show explicit construction of nonlocal conserved currents on the pseudodual manifold. We then switch the Lie group valued pseudoduality equations to Lie algebra valued ones, which leads to an infinite number of pseudoduality equations. We obtain an infinite number of conserved currents on the tangent bundle of the pseudo-dual manifold. Since pseudoduality imposes the condition that sigma models pseudodual to each other are based on symmetric spaces with opposite curvatures (i.e. dual symmetric spaces), we investigate pseudoduality transformation on the symmetric space sigma models in the third chapter. We see that there can be mixing of decomposed spaces with each other, which leads to mixings of the following expressions. We obtain the pseudodual conserved currents which are viewed as the orthonormal frame on the pullback bundle of the tangent space of G˜ which is the Lie group on which the pseudodual model based. Hence we obtain the mixing forms of curvature relations and one loop renormalization group beta function by means of these currents. In chapter four, we generalize the classical construction of pseudoduality transformation to supersymmetric case. We perform this both by component expansion method on manifold M and by orthonormal coframe method on manifold SO( M). The component method produces the result that pseudoduality transformation is not invertible at all points and occurs from all points on one manifold to only one point where riemann normal coordinates valid on the second manifold. Torsion of the sigma model on M must vanish while it is nonvanishing on M˜, and curvatures of the manifolds must be constant and the same because of anticommuting grassmann numbers. We obtain
Realistic synthetic observations from radiative transfer models
NASA Astrophysics Data System (ADS)
Koepferl, Christine; Robitaille, Thomas
2013-07-01
When modeling young stars and star-forming regions throughout the Galaxy, it is important to correctly treat the limitations of the data such as finite resolution and sensitivity. In order to study these effects, and to make radiative transfer models directly comparable to real observations, we have developed a Python package that allows post-processing the output of the 3-d Monte Carlo Radiative Transfer code HYPERION (Robitaille 2011 A&A 536, A79, see poster 2S001). With this package, realistic synthetic observations can be generated, modeling the effects of convolution with arbitrary PSFs, transmission curves, finite pixel resolution, noise and reddening. Pipelines can be written to compute synthetic observations that simulate observatories such as the Spitzer Space Telescope or the Herschel Space Observatory. In this poster we describe the package and present examples of such synthetic observations.
More on supersymmetric and 2d analogs of the SYK model
NASA Astrophysics Data System (ADS)
Murugan, Jeff; Stanford, Douglas; Witten, Edward
2017-08-01
In this paper, we explore supersymmetric and 2d analogs of the SYK model. We begin by working out a basis of (super)conformal eigenfunctions appropriate for expanding a four-point function. We use this to clarify some details of the 1d supersymmetric SYK model. We then introduce new bosonic and supersymmetric analogs of SYK in two dimensions. These theories consist of N fields interacting with random q-field interactions. Although models built entirely from bosons appear to be problematic, we find a supersymmetric model that flows to a large N CFT with interaction strength of order one. We derive an integral formula for the four-point function at order 1 /N , and use it to compute the central charge, chaos exponent and some anomalous dimensions. We describe a problem that arises if one tries to find a 2d SYK-like CFT with a continuous global symmetry.
Mixed axion/neutralino cold dark matter in supersymmetric models
Baer, Howard; Lessa, Andre; Rajagopalan, Shibi; Sreethawong, Warintorn E-mail: lessa@nhn.ou.edu E-mail: wstan@nhn.ou.edu
2011-06-01
We consider supersymmetric (SUSY) models wherein the strong CP problem is solved by the Peccei-Quinn (PQ) mechanism with a concommitant axion/axino supermultiplet. We examine R-parity conserving models where the neutralino is the lightest SUSY particle, so that a mixture of neutralinos and axions serve as cold dark matter (a Z-tilde {sub 1} CDM). The mixed a Z-tilde {sub 1} CDM scenario can match the measured dark matter abundance for SUSY models which typically give too low a value of the usual thermal neutralino abundance, such as models with wino-like or higgsino-like dark matter. The usual thermal neutralino abundance can be greatly enhanced by the decay of thermally-produced axinos (ã) to neutralinos, followed by neutralino re-annihilation at temperatures much lower than freeze-out. In this case, the relic density is usually neutralino dominated, and goes as ∼ (f{sub a}/N)/m{sub ã}{sup 3/2}. If axino decay occurs before neutralino freeze-out, then instead the neutralino abundance can be augmented by relic axions to match the measured abundance. Entropy production from late-time axino decays can diminish the axion abundance, but ultimately not the neutralino abundance. In a Z-tilde {sub 1} CDM models, it may be possible to detect both a WIMP and an axion as dark matter relics. We also discuss possible modifications of our results due to production and decay of saxions. In the appendices, we present expressions for the Hubble expansion rate and the axion and neutralino relic densities in radiation, matter and decaying-particle dominated universes.
Probing neutrino oscillations in supersymmetric models at the Large Hadron Collider
Campos, F. de; Eboli, O. J. P.; Hirsch, M.; Valle, J. W. F.; Porod, W.
2010-10-01
The lightest supersymmetric particle may decay with branching ratios that correlate with neutrino oscillation parameters. In this case the CERN Large Hadron Collider (LHC) has the potential to probe the atmospheric neutrino mixing angle with sensitivity competitive to its low-energy determination by underground experiments. Under realistic detection assumptions, we identify the necessary conditions for the experiments at CERN's LHC to probe the simplest scenario for neutrino masses induced by minimal supergravity with bilinear R parity violation.
Aydin, Z.Z.; Sultansoy, S.; Yilmazer, A.U. )
1994-10-01
The number of mixing angles and phases in the two popular extensions of the standard model (SM), the [ital E][sub 6]-induced SM extension and the minimal supersymmetric standard model with soft symmetry-breaking terms, is discussed. It is found that two [ital CP]-violating phases appear in the minimal supersymmetric SM even for the simplest case of one family.
Alveolar mechanics using realistic acinar models
NASA Astrophysics Data System (ADS)
Kumar, Haribalan; Lin, Ching-Long; Tawhai, Merryn H.; Hoffman, Eric A.
2009-11-01
Accurate modeling of the mechanics in terminal airspaces of the lung is desirable for study of particle transport and pathology. The flow in the acinar region is traditionally studied by employing prescribed boundary conditions to represent rhythmic breathing and volumetric expansion. Conventional models utilize simplified spherical or polygonal units to represent the alveolar duct and sac. Accurate prediction of flow and transport characteristics may require geometries reconstructed from CT-based images and serve to understand the importance of physiologically realistic representation of the acinus. In this effort, we present a stabilized finite element framework, supplemented with appropriate boundary conditions at the alveolar mouth and septal borders for simulation of the alveolar mechanics and the resulting airflow. Results of material advection based on Lagrangian tracking are presented to complete the study of transport and compare the results with simplified acinar models. The current formulation provides improved understanding and realization of a dynamic framework for parenchymal mechanics with incorporation of alveolar pressure and traction stresses.
Sialendoscopy Training: Presentation of a Realistic Model.
Pascoto, Gabriela Robaskewicz; Stamm, Aldo Cassol; Lyra, Marcos
2017-01-01
Introduction Several surgical training simulators have been created for residents and young surgeons to gain experience with surgical procedures. Laboratory training is fundamental for acquiring familiarity with the techniques of surgery and skill in handing instruments. Objective The aim of this study is to present a novel simulator for training sialendoscopy. Method This realistic simulator was built with a synthetic thermo-retractile, thermo-sensible rubber which, when combined with different polymers, produces more than 30 different formulas. These formulas present textures, consistencies, and mechanical resistance are similar to many human tissues. Results The authors present a training model to practice sialendoscopy. All aspects of the procedure are simulated: month opening, dilatation of papillae, insert of the scope, visualization of stones, extraction of these stones with grasping or baskets, and finally, stone fragmentation with holmium laser. Conclusion This anatomical model for sialendoscopy training should be considerably useful to abbreviate the learning curve during the qualification of young surgeons while minimizing the consequences of technical errors.
Sialendoscopy Training: Presentation of a Realistic Model
Pascoto, Gabriela Robaskewicz; Stamm, Aldo Cassol; Lyra, Marcos
2016-01-01
Introduction Several surgical training simulators have been created for residents and young surgeons to gain experience with surgical procedures. Laboratory training is fundamental for acquiring familiarity with the techniques of surgery and skill in handing instruments. Objective The aim of this study is to present a novel simulator for training sialendoscopy. Method This realistic simulator was built with a synthetic thermo-retractile, thermo-sensible rubber which, when combined with different polymers, produces more than 30 different formulas. These formulas present textures, consistencies, and mechanical resistance are similar to many human tissues. Results The authors present a training model to practice sialendoscopy. All aspects of the procedure are simulated: month opening, dilatation of papillae, insert of the scope, visualization of stones, extraction of these stones with grasping or baskets, and finally, stone fragmentation with holmium laser. Conclusion This anatomical model for sialendoscopy training should be considerably useful to abbreviate the learning curve during the qualification of young surgeons while minimizing the consequences of technical errors. PMID:28050202
A realistic molecular model of cement hydrates.
Pellenq, Roland J-M; Kushima, Akihiro; Shahsavari, Rouzbeh; Van Vliet, Krystyn J; Buehler, Markus J; Yip, Sidney; Ulm, Franz-Josef
2009-09-22
Despite decades of studies of calcium-silicate-hydrate (C-S-H), the structurally complex binder phase of concrete, the interplay between chemical composition and density remains essentially unexplored. Together these characteristics of C-S-H define and modulate the physical and mechanical properties of this "liquid stone" gel phase. With the recent determination of the calcium/silicon (C/S = 1.7) ratio and the density of the C-S-H particle (2.6 g/cm(3)) by neutron scattering measurements, there is new urgency to the challenge of explaining these essential properties. Here we propose a molecular model of C-S-H based on a bottom-up atomistic simulation approach that considers only the chemical specificity of the system as the overriding constraint. By allowing for short silica chains distributed as monomers, dimers, and pentamers, this C-S-H archetype of a molecular description of interacting CaO, SiO2, and H2O units provides not only realistic values of the C/S ratio and the density computed by grand canonical Monte Carlo simulation of water adsorption at 300 K. The model, with a chemical composition of (CaO)(1.65)(SiO2)(H2O)(1.75), also predicts other essential structural features and fundamental physical properties amenable to experimental validation, which suggest that the C-S-H gel structure includes both glass-like short-range order and crystalline features of the mineral tobermorite. Additionally, we probe the mechanical stiffness, strength, and hydrolytic shear response of our molecular model, as compared to experimentally measured properties of C-S-H. The latter results illustrate the prospect of treating cement on equal footing with metals and ceramics in the current application of mechanism-based models and multiscale simulations to study inelastic deformation and cracking.
A realistic molecular model of cement hydrates
Pellenq, Roland J.-M.; Kushima, Akihiro; Shahsavari, Rouzbeh; Van Vliet, Krystyn J.; Buehler, Markus J.; Yip, Sidney; Ulm, Franz-Josef
2009-01-01
Despite decades of studies of calcium-silicate-hydrate (C-S-H), the structurally complex binder phase of concrete, the interplay between chemical composition and density remains essentially unexplored. Together these characteristics of C-S-H define and modulate the physical and mechanical properties of this “liquid stone” gel phase. With the recent determination of the calcium/silicon (C/S = 1.7) ratio and the density of the C-S-H particle (2.6 g/cm3) by neutron scattering measurements, there is new urgency to the challenge of explaining these essential properties. Here we propose a molecular model of C-S-H based on a bottom-up atomistic simulation approach that considers only the chemical specificity of the system as the overriding constraint. By allowing for short silica chains distributed as monomers, dimers, and pentamers, this C-S-H archetype of a molecular description of interacting CaO, SiO2, and H2O units provides not only realistic values of the C/S ratio and the density computed by grand canonical Monte Carlo simulation of water adsorption at 300 K. The model, with a chemical composition of (CaO)1.65(SiO2)(H2O)1.75, also predicts other essential structural features and fundamental physical properties amenable to experimental validation, which suggest that the C-S-H gel structure includes both glass-like short-range order and crystalline features of the mineral tobermorite. Additionally, we probe the mechanical stiffness, strength, and hydrolytic shear response of our molecular model, as compared to experimentally measured properties of C-S-H. The latter results illustrate the prospect of treating cement on equal footing with metals and ceramics in the current application of mechanism-based models and multiscale simulations to study inelastic deformation and cracking. PMID:19805265
Mechanical stabilization of the Levitron's realistic model
NASA Astrophysics Data System (ADS)
Olvera, Arturo; De la Rosa, Abraham; Giordano, Claudia M.
2016-11-01
The stability of the magnetic levitation showed by the Levitron was studied by M.V. Berry as a six degrees of freedom Hamiltonian system using an adiabatic approximation. Further, H.R. Dullin found critical spin rate bounds where the levitation persists and R.F. Gans et al. offered numerical results regarding the initial conditions' manifold where this occurs. In the line of this series of works, first, we extend the equations of motion to include dissipation for a more realistic model, and then introduce a mechanical forcing to inject energy into the system in order to prevent the Levitron from falling. A systematic study of the flying time as a function of the forcing parameters is carried out which yields detailed bifurcation diagrams showing an Arnold's tongues structure. The stability of these solutions were studied with the help of a novel method to compute the maximum Lyapunov exponent called MEGNO. The bifurcation diagrams for MEGNO reproduce the same Arnold's tongue structure.
Particle spectroscopy of supersymmetric SO(10) with nonuniversal gaugino masses
Okada, Nobuchika; Raza, Shabbar; Shafi, Qaisar
2011-11-01
We examine the low scale particle spectroscopy of an SO(10) [or equivalently SU(5)] inspired supersymmetric model with nonuniversal gaugino masses. The model assumes minimal supergravity and contains the same number of fundamental parameters as the constrained minimal supersymmetric standard model. Realistic solutions compatible with dark matter and other applicable experimental constraints are shown to exist for both positive and negative signs of the minimal supersymmetric standard model parameter {mu}. We present several benchmark points which will be tested at the LHC and by the ongoing direct and indirect dark matter detection experiments.
Implications of Lorentz symmetry violation on a 5D supersymmetric model
NASA Astrophysics Data System (ADS)
García-Aguilar, J. D.; Pérez-Lorenzana, A.
2017-04-01
Field models with n extra spatial dimensions have a larger SO(1, 3 + n) Lorentz symmetry which is broken down to the standard SO(1, 3) four-dimensional one by the compactification process. By considering Lorentz violating operators in a 5D supersymmetric Wess-Zumino model, which otherwise conserve the standard four-dimensional Poincaré invariance, we show that supersymmetry (SUSY) can be restored upon a simple deformation of the supersymmetric transformations. However, SUSY is not preserved in the effective 4D theory that arises after compactification when the 5D Lorentz violating operators do not preserve Z2 : y →-y bulk parity. Our mechanism unveils a possible connection among Lorentz violation and the Scherk-Schwarz mechanism. We also show that parity preserving models, on the other hand, do provide well defined supersymmetric KK models.
N = 1 supersymmetric indices and the four-dimensional A-model
NASA Astrophysics Data System (ADS)
Closset, Cyril; Kim, Heeyeon; Willett, Brian
2017-08-01
We compute the supersymmetric partition function of N = 1 supersymmetric gauge theories with an R-symmetry on M_4\\cong M_{g,p}× {S}^1 , a principal elliptic fiber bundle of degree p over a genus- g Riemann surface, Σ g . Equivalently, we compute the generalized supersymmetric index I_{M}{_{g,p}, with the supersymmetric three-manifold M_{g,p} as the spatial slice. The ordinary N = 1 supersymmetric index on the round three-sphere is recovered as a special case. We approach this computation from the point of view of a topological A-model for the abelianized gauge fields on the base Σ g . This A-model — or A-twisted two-dimensional N = (2 , 2) gauge theory — encodes all the information about the generalized indices, which are viewed as expectations values of some canonically-defined surface defects wrapped on T 2 inside Σ g × T 2. Being defined by compactification on the torus, the A-model also enjoys natural modular properties, governed by the four-dimensional 't Hooft anomalies. As an application of our results, we provide new tests of Seiberg duality. We also present a new evaluation formula for the three-sphere index as a sum over two-dimensional vacua.
NASA Astrophysics Data System (ADS)
Higaki, Tetsutaro; Nishida, Michinobu; Takeda, Naoyuki
2017-08-01
We study a supersymmetric model in which the Higgs mass, the muon anomalous magnetic moment, and the dark matter are simultaneously explained with extra vector-like generation multiplets. For the explanations, non-trivial flavor structures and a singlet field are required. In this paper, we study the flavor texture by using the Froggatt-Nielsen mechanism, and then find realistic flavor structures that reproduce the Cabbibo-Kobayashi-Maskawa matrix and fermion masses at low energy. Furthermore, we find that the fermion component of the singlet field becomes a good candidate for dark matter. In our model, flavor physics and dark matter are explained with moderate-size couplings through renormalization group flows, and the presence of dark matter supports the existence of just 3 generations in low-energy scales. We analyze the parameter region where the current thermal relic abundance of dark matter, the Higgs boson mass, and the muon g{-}2 can be explained simultaneously.
Predictions for m{sub t} and M{sub W} in minimal supersymmetric models
Buchmueller, O.; Cavanaugh, R.; De Roeck, A.; Ellis, J. R.; Flaecher, H.; Heinemeyer, S.; Isidori, G.; Olive, Keith A.; Ronga, F. J.; Weiglein, G.
2010-02-01
Using a frequentist analysis of experimental constraints within two versions of the minimal supersymmetric extension of the standard model, we derive the predictions for the top quark mass, m{sub t}, and the W boson mass, M{sub W}. We find that the supersymmetric predictions for both m{sub t} and M{sub W}, obtained by incorporating all the relevant experimental information and state-of-the-art theoretical predictions, are highly compatible with the experimental values with small remaining uncertainties, yielding an improvement compared to the case of the standard model.
Radiative breaking of the minimal supersymmetric left–right model
Okada, Nobuchika; Papapietro, Nathan
2016-03-03
We study a variation to the SUSY Left-Right symmetric model based on the gauge group SU(3)c×SU(2)L×SU(2)R×U(1)BL. Beyond the quark and lepton superfields we only introduce a second Higgs bidoublet to produce realistic fermion mass matrices. This model does not include any SU(2)R triplets. We also calculate renormalization group evolutions of soft SUSY parameters at the one-loop level down to low energy. We find that an SU(2)R slepton doublet acquires a negative mass squared at low energies, so that the breaking of SU(2)R×U(1)BL→U(1)Y is realized by a non-zero vacuum expectation value of a right-handed sneutrino. Small neutrino masses are produced throughmore » neutrino mixings with gauginos. We obtained mass limits on the SU(2)R×U(1)BL sector by direct search results at the LHC as well as lepton-gaugino mixing bounds from the LEP precision data.« less
Radiative breaking of the minimal supersymmetric left–right model
Okada, Nobuchika; Papapietro, Nathan
2016-03-03
We study a variation to the SUSY Left-Right symmetric model based on the gauge group SU(3)_{c}×SU(2)_{L}×SU(2)_{R}×U(1)_{BL}. Beyond the quark and lepton superfields we only introduce a second Higgs bidoublet to produce realistic fermion mass matrices. This model does not include any SU(2)_{R} triplets. We also calculate renormalization group evolutions of soft SUSY parameters at the one-loop level down to low energy. We find that an SU(2)_{R} slepton doublet acquires a negative mass squared at low energies, so that the breaking of SU(2)_{R}×U(1)_{BL}→U(1)_{Y} is realized by a non-zero vacuum expectation value of a right-handed sneutrino. Small neutrino masses are produced through neutrino mixings with gauginos. We obtained mass limits on the SU(2)_{R}×U(1)_{BL} sector by direct search results at the LHC as well as lepton-gaugino mixing bounds from the LEP precision data.
NASA Astrophysics Data System (ADS)
Barranco, Alejandro; Russo, Jorge G.
2012-06-01
We implement relativistic BCS superconductivity in {N} = 1 supersymmetric field theories with a U(1) R symmetry. The simplest model contains two chiral superfields with a Kähler potential modified by quartic terms. We study the phase diagram of the gap as a function of the temperature and the specific heat. The superconducting phase transition turns out to be first order, due to the scalar contribution to the one-loop potential. By virtue of supersymmetry, the critical curves depend logarithmically with the UV cutoff, rather than quadratically as in standard BCS theory. We comment on the difficulties in having fermion condensates when the chemical potential is instead coupled to a baryonic U(1) B current. We also discuss supersymmetric models of BCS with canonical Kähler potential constructed by "integrating-in" chiral superfields.
NASA Astrophysics Data System (ADS)
Quinto, A. G.; Ferrari, A. F.; Lehum, A. C.
2016-06-01
In this work, we investigate the consequences of the Renormalization Group Equation (RGE) in the determination of the effective superpotential and the study of Dynamical Symmetry Breaking (DSB) in an N = 1 supersymmetric theory including an Abelian Chern-Simons superfield coupled to N scalar superfields in (2 + 1) dimensional spacetime. The classical Lagrangian presents scale invariance, which is broken by radiative corrections to the effective superpotential. We calculate the effective superpotential up to two-loops by using the RGE and the beta functions and anomalous dimensions known in the literature. We then show how the RGE can be used to improve this calculation, by summing up properly defined series of leading logs (LL), next-to-leading logs (NLL) contributions, and so on... We conclude that even if the RGE improvement procedure can indeed be applied in a supersymmetric model, the effects of the consideration of the RGE are not so dramatic as it happens in the non-supersymmetric case.
Light minimal supersymmetric standard model Higgs boson scenario and its test at hadron colliders.
Belyaev, Alexander; Cao, Qing-Hong; Nomura, Daisuke; Tobe, Kazuhiro; Yuan, C-P
2008-02-15
We show that, in the minimal supersymmetric standard model, the possibility for the lightest CP-even Higgs boson to be lighter than Z boson (as low as about 60 GeV) is, contrary to the usual belief, not yet excluded by the CERN LEP2 Higgs search nor any direct searches for supersymmetric particles at high energy colliders. The characteristic of the light Higgs boson scenario (LHS) is that the ZZh coupling and the decay branching ratio Br(h/A-->bb) are simultaneously suppressed as a result of generic supersymmetric loop corrections. Consequently, the W(+/-)H(-/+)h coupling has to be large due to the sum rule of Higgs couplings to weak gauge bosons. We discuss the potential of the Fermilab Tevatron and B factories to test the LHS, and show that the associated neutral and charged Higgs boson production process, pp-->H(+/-)h(A), can completely probe the LHS at the CERN Large Hadron Collider.
Axion, μ term, and supersymmetric hybrid inflation
NASA Astrophysics Data System (ADS)
Lazarides, G.; Panagiotakopoulos, C.; Shafi, Q.
2017-03-01
We show how successful supersymmetric hybrid inflation is realized in realistic models where the resolution of the minimal supersymmetric standard model μ problem is intimately linked with axion physics. The scalar fields that accompany the axion, such as the saxion, are closely monitored during and after inflation to ensure that the axion isocurvature perturbations lie below the observational limits. The scalar spectral index ns≃0.96 - 0.97 , while the tensor-to-scalar ratio r , a canonical measure of gravity waves, lies well below the observable range in our example. The axion domain walls are inflated away, and depending on the axion decay constant fa and the magnitude of the μ parameter, the axions and/or the lightest supersymmetric particle compose the dark matter in the Universe. Nonthermal leptogenesis is naturally implemented in this class of models.
CP violation in neutrino oscillations in Minimal Supersymmetric extension of the Standard Model
Delepine, David; Gonzalez Macias, Vannia
2008-07-02
In this talk, we estimate the size of lepton flavor and CP violation in neutrino oscillations in the framework of Minimal Supersymmetric extension of the Standard Model (MSSM). We find that we may have significant CP-violating contributions up to an order of magnitude ({approx}10{sup -2}) smaller than the standard four-Fermi couplings.
Charged lepton flavor violation in supersymmetric low-scale seesaw models
NASA Astrophysics Data System (ADS)
Ilakovac, Amon; Pilaftsis, Apostolos; Popov, Luka
2013-03-01
We study charged lepton flavor violation in low-scale seesaw models of minimal supergravity, which realize large neutrino Yukawa couplings thanks to approximate lepton-number symmetries. There are two dominant sources of lepton flavor violation in such models. The first source originates from the usual soft supersymmetry-breaking sector, whilst the second one is entirely supersymmetric and comes from the supersymmetric neutrino Yukawa sector. Within the framework of minimal supergravity, we consider both sources of lepton flavor violation, soft and supersymmetric, and calculate a number of possible lepton-flavor-violating transitions, such as the photonic decays of muons and taus, μ→eγ, τ→eγ and τ→μγ, their neutrinoless three-body decays, μ→eee, τ→eee, τ→μμμ, τ→eeμ and τ→eμμ, and the coherent μ→e conversion in nuclei. After taking into account the exclusion bounds placed by present experiments of lepton flavor violation, we derive combined theoretical limits on the universal heavy Majorana mass scale mN and the light-to-heavy neutrino mixings. Supersymmetric low-scale seesaw models offer distinct correlated predictions for lepton-flavor-violating signatures, which might be discovered in current and projected experiments, such as MEG, COMET/PRISM, Mu2e, super-BELLE and LHCb.
Implications of improved Higgs mass calculations for supersymmetric models.
Buchmueller, O; Dolan, M J; Ellis, J; Hahn, T; Heinemeyer, S; Hollik, W; Marrouche, J; Olive, K A; Rzehak, H; de Vries, K J; Weiglein, G
We discuss the allowed parameter spaces of supersymmetric scenarios in light of improved Higgs mass predictions provided by FeynHiggs 2.10.0. The Higgs mass predictions combine Feynman-diagrammatic results with a resummation of leading and subleading logarithmic corrections from the stop/top sector, which yield a significant improvement in the region of large stop masses. Scans in the pMSSM parameter space show that, for given values of the soft supersymmetry-breaking parameters, the new logarithmic contributions beyond the two-loop order implemented in FeynHiggs tend to give larger values of the light CP-even Higgs mass, [Formula: see text], in the region of large stop masses than previous predictions that were based on a fixed-order Feynman-diagrammatic result, though the differences are generally consistent with the previous estimates of theoretical uncertainties. We re-analyse the parameter spaces of the CMSSM, NUHM1 and NUHM2, taking into account also the constraints from CMS and LHCb measurements of [Formula: see text]and ATLAS searches for [Formula: see text] events using 20/fb of LHC data at 8 TeV. Within the CMSSM, the Higgs mass constraint disfavours [Formula: see text], though not in the NUHM1 or NUHM2.
A Computational Framework for Realistic Retina Modeling.
Martínez-Cañada, Pablo; Morillas, Christian; Pino, Begoña; Ros, Eduardo; Pelayo, Francisco
2016-11-01
Computational simulations of the retina have led to valuable insights about the biophysics of its neuronal activity and processing principles. A great number of retina models have been proposed to reproduce the behavioral diversity of the different visual processing pathways. While many of these models share common computational stages, previous efforts have been more focused on fitting specific retina functions rather than generalizing them beyond a particular model. Here, we define a set of computational retinal microcircuits that can be used as basic building blocks for the modeling of different retina mechanisms. To validate the hypothesis that similar processing structures may be repeatedly found in different retina functions, we implemented a series of retina models simply by combining these computational retinal microcircuits. Accuracy of the retina models for capturing neural behavior was assessed by fitting published electrophysiological recordings that characterize some of the best-known phenomena observed in the retina: adaptation to the mean light intensity and temporal contrast, and differential motion sensitivity. The retinal microcircuits are part of a new software platform for efficient computational retina modeling from single-cell to large-scale levels. It includes an interface with spiking neural networks that allows simulation of the spiking response of ganglion cells and integration with models of higher visual areas.
Realistic molecular models for disordered porous carbons
NASA Astrophysics Data System (ADS)
Pikunic, Jorge Pablo
The complex pore morphology and topology of many non-graphitizable porous carbons is not captured by the current molecular models that are used in analysis of adsorption isotherms. We present a novel constrained reverse Monte Carlo method to build models that quantitatively match carbon-carbon pair correlation functions obtained from experimental diffraction data of real nanoporous carbons. Our approach is based on reverse Monte Carlo with carefully selected constraints on the bond angles and carbon coordination numbers that describe the three-body correlations. Through successive Monte Carlo moves, using a simulated annealing scheme, the model structure is matched to the experimental diffraction data, subject to the imposed three-body constraints. We modeled a series of saccharose-based carbons and tested the resulting models against high resolution transmission electron microscopy (TEM) data. Simulated TEM images of the resulting structural models are in very good agreement with experimental ones. For the carbons studied, the pore structure is highly convoluted, and the commonly used slit pore model is not appropriate. We simulated adsorption of nitrogen and argon at 77 K using grand canonical Monte Carlo, and diffusion of argon at 300 K using canonical molecular dynamics simulations. The isosteric heats of adsorption at 77 K are in excellent agreement with experimental results. The adsorption isotherms and heats of adsorption in these models do not resemble those for fluids in slit pores having the same pore size distribution. We found that diffusion in the structural models is non-Fickian. Instead, a strong single-file character is observed, revealed by the proportionality of the mean square displacement to the square root of time at relatively long times. The single-file mode is a consequence of the small sizes of the quasi one-dimensional pores in the adsorbent models. To the best of our knowledge, single-file mode or transitional behavior between normal and
Realistic power output modeling of CPV modules
NASA Astrophysics Data System (ADS)
Steiner, Marc; Siefer, Gerald; Bösch, Armin; Hornung, Thorsten; Bett, Andreas W.
2012-10-01
In this work, we introduce a new model called YieldOpt, which calculates the power output of CPV modules. It uses SMARTS2 to model the spectral irradiance, a ray tracing program to model the optics and SPICE network simulation to model the electrical characteristic of triple-junction (3J) cells. The calculated power output is compared to data measured of five CPV modules operating in Freiburg, Germany during a period from October 2011 to March 2012. Four of the modules use lattice-matched 3J cells; one of these modules has also reflective secondary optics. In one of the five modules novel metamorphic 3J cells are used. The agreement of the predicted power output calculated by YieldOpt with the measured data is quantified using the normalized root mean square error. A good agreement between simulation and measurement is achieved. Moreover, the predicted energy yield derived from the new model is compared with the measured energy yield. A good agreement between the measured data and simulated data is achieved. In addition, a high accuracy in predicting the energy yield of different CPV modules is demonstrated. Finally, the new model is compared with three empirical models.
Biophysically realistic minimal model of dopamine neuron
NASA Astrophysics Data System (ADS)
Oprisan, Sorinel
2008-03-01
We proposed and studied a new biophysically relevant computational model of dopaminergic neurons. Midbrain dopamine neurons are involved in motivation and the control of movement, and have been implicated in various pathologies such as Parkinson's disease, schizophrenia, and drug abuse. The model we developed is a single-compartment Hodgkin-Huxley (HH)-type parallel conductance membrane model. The model captures the essential mechanisms underlying the slow oscillatory potentials and plateau potential oscillations. The main currents involved are: 1) a voltage-dependent fast calcium current, 2) a small conductance potassium current that is modulated by the cytosolic concentration of calcium, and 3) a slow voltage-activated potassium current. We developed multidimensional bifurcation diagrams and extracted the effective domains of sustained oscillations. The model includes a calcium balance due to the fundamental importance of calcium influx as proved by simultaneous electrophysiological and calcium imaging procedure. Although there are significant evidences to suggest a partially electrogenic calcium pump, all previous models considered only elecrtogenic pumps. We investigated the effect of the electrogenic calcium pump on the bifurcation diagram of the model and compared our findings against the experimental results.
Realistic model for SU(5) grand unification
Oshimo, Noriyuki
2009-10-01
A grand unified model based on SU(5) and supersymmetry is presented. Pairs of superfields belonging to 15 and 15 representations are newly introduced, two pairs with even and one pair with odd matter parity. Improper mass relations in the minimal model between charged leptons and d-type quarks are corrected. Neutrinos have nonvanishing masses, with large angles for generation mixings of the leptons being compatible with the small angles of the quarks. A new source for lepton-number generation in the early universe is provided.
Realistic Real World Contexts: Model Eliciting Activities
ERIC Educational Resources Information Center
Doruk, Bekir Kürsat
2016-01-01
Researchers have proposed a variety of methods to make a connection between real life and mathematics so that it can be learned in a practical way and enable people to utilise mathematics in their daily lives. Model-eliciting activities (MEAs) were developed to fulfil this need and are very capable of serving this purpose. The reason MEAs are so…
Realistic Real World Contexts: Model Eliciting Activities
ERIC Educational Resources Information Center
Doruk, Bekir Kürsat
2016-01-01
Researchers have proposed a variety of methods to make a connection between real life and mathematics so that it can be learned in a practical way and enable people to utilise mathematics in their daily lives. Model-eliciting activities (MEAs) were developed to fulfil this need and are very capable of serving this purpose. The reason MEAs are so…
Realistic modeling of complex oxide materials
NASA Astrophysics Data System (ADS)
Solovyev, I. V.
2011-01-01
Since electronic and magnetic properties of many transition-metal oxides can be efficiently controlled by external factors such as the temperature, pressure, electric or magnetic field, they are regarded as promising materials for various applications. From the viewpoint of the electronic structure, these phenomena are frequently related to the behavior of a small group of states located near the Fermi level. The basic idea of this project is to construct a model for the low-energy states, derive all the parameters rigorously on the basis of density functional theory (DFT), and to study this model by modern techniques. After a brief review of the method, the abilities of this approach will be illustrated on a number of examples, including multiferroic manganites and spin-orbital-lattice coupled phenomena in RVO 3 (where R is the three-valent element).
A Realistic Accretion Disk Model for AGNs
NASA Technical Reports Server (NTRS)
Suleimanov, V.; Ghosh, K. K.; Austin, R. A.; Ramsey, B. D.; Rose, M. Franklin (Technical Monitor)
2001-01-01
We present a new relativistic accretion disk model of AGNs, based on alpha modified accretion disk theory, where alpha is a parameter that characterizes the efficiency of the mechanism of angular momentum transport. In this model we have considered a geometrically-thin, high-luminosity (alpha-accretion disk, around a supermassive black hole. The geometrically thin limit assumes a local energy balance within the accretion disk, which has been used to derive the plasma temperature of the disk. The energy balance equation has three solutions: low, medium and high temperature, depending on the heating rate of the accretion disk. We predict that the inner part of a high luminosity accretion disk is in the high- temperature (10(exp 7) to 10(exp 9) K) state and for this we obtain the high temperature solution of the energy balance equation using a Comptonization process. We find the local spectrum of each ring of the disk (we have divided the high temperature region of the disk into 50 rings) to be a diluted Wien spectrum. However, the emergent integral spectrum of the high temperature region is a power-law with a high-energy cutoff that depends on the basic parameters of AGNs (the accretion rate, the incidence angle, and the mass and the angular momentum of the central black hole). We have fitted the observed spectra of 28 AGNs using the present model and have derived the values of the basic parameters of these AGNs. Results of these spectral fittings have been discussed in the framework of the unification model of AGNs.
Dark Matter in Supersymmetric U(1){sub B-L} Model
Khalil, S.; Okada, H.
2009-04-17
We analyze the dark matter problem in the context of supersymmetric, U(1){sub B-L} model. In this model, the lightest neutalino can be B-L gaugino Z-tilde{sub B-L} or Higgsinos {chi}-tilde{sub 1,2} dominated. We examine the thermal relic abundance of these particles and discuss the prospects for their direct detection if they form part of our galactic halo.
Towards Realistic Modeling of Massive Star Clusters
NASA Astrophysics Data System (ADS)
Gnedin, O.; Li, H.
2016-06-01
Cosmological simulations of galaxy formation are rapidly advancing towards smaller scales. Current models can now resolve giant molecular clouds in galaxies and predict basic properties of star clusters forming within them. I will describe new theoretical simulations of the formation of the Milky Way throughout cosmic time, with the adaptive mesh refinement code ART. However, many challenges - physical and numerical - still remain. I will discuss how observations of massive star clusters and star forming regions can help us overcome some of them. Video of the talk is available at https://goo.gl/ZoZOfX
Recent developments for realistic solar models
Serenelli, Aldo M.
2014-05-02
The 'solar abundance problem' has triggered a renewed interest in revising the concept of SSM from different perspectives: 1) constituent microphysics: equation of state, nuclear rates, radiative opacities; 2) constituent macrophysics: the physical processes impact the evolution of the Sun and its present-day structure, e.g. dynamical processes induced by rotation, presence of magnetic fields; 3) challenge the hypothesis that the young Sun was chemically homogeneous: the possible interaction of the young Sun with its protoplanetary disk. Here, I briefly review and then present a (personal) view on recent advances and developments on solar modeling, part of them carried out as attempts to solve the solar abundance problem.
Recent developments for realistic solar models
NASA Astrophysics Data System (ADS)
Serenelli, Aldo M.
2014-05-01
The "solar abundance problem" has triggered a renewed interest in revising the concept of SSM from different perspectives: 1) constituent microphysics: equation of state, nuclear rates, radiative opacities; 2) constituent macrophysics: the physical processes impact the evolution of the Sun and its present-day structure, e.g. dynamical processes induced by rotation, presence of magnetic fields; 3) challenge the hypothesis that the young Sun was chemically homogeneous: the possible interaction of the young Sun with its protoplanetary disk. Here, I briefly review and then present a (personal) view on recent advances and developments on solar modeling, part of them carried out as attempts to solve the solar abundance problem.
Realistic modeling of neurons and networks: towards brain simulation.
D'Angelo, Egidio; Solinas, Sergio; Garrido, Jesus; Casellato, Claudia; Pedrocchi, Alessandra; Mapelli, Jonathan; Gandolfi, Daniela; Prestori, Francesca
2013-01-01
Realistic modeling is a new advanced methodology for investigating brain functions. Realistic modeling is based on a detailed biophysical description of neurons and synapses, which can be integrated into microcircuits. The latter can, in turn, be further integrated to form large-scale brain networks and eventually to reconstruct complex brain systems. Here we provide a review of the realistic simulation strategy and use the cerebellar network as an example. This network has been carefully investigated at molecular and cellular level and has been the object of intense theoretical investigation. The cerebellum is thought to lie at the core of the forward controller operations of the brain and to implement timing and sensory prediction functions. The cerebellum is well described and provides a challenging field in which one of the most advanced realistic microcircuit models has been generated. We illustrate how these models can be elaborated and embedded into robotic control systems to gain insight into how the cellular properties of cerebellar neurons emerge in integrated behaviors. Realistic network modeling opens up new perspectives for the investigation of brain pathologies and for the neurorobotic field.
Realistic modeling of neurons and networks: towards brain simulation
D’Angelo, Egidio; Solinas, Sergio; Garrido, Jesus; Casellato, Claudia; Pedrocchi, Alessandra; Mapelli, Jonathan; Gandolfi, Daniela; Prestori, Francesca
Summary Realistic modeling is a new advanced methodology for investigating brain functions. Realistic modeling is based on a detailed biophysical description of neurons and synapses, which can be integrated into microcircuits. The latter can, in turn, be further integrated to form large-scale brain networks and eventually to reconstruct complex brain systems. Here we provide a review of the realistic simulation strategy and use the cerebellar network as an example. This network has been carefully investigated at molecular and cellular level and has been the object of intense theoretical investigation. The cerebellum is thought to lie at the core of the forward controller operations of the brain and to implement timing and sensory prediction functions. The cerebellum is well described and provides a challenging field in which one of the most advanced realistic microcircuit models has been generated. We illustrate how these models can be elaborated and embedded into robotic control systems to gain insight into how the cellular properties of cerebellar neurons emerge in integrated behaviors. Realistic network modeling opens up new perspectives for the investigation of brain pathologies and for the neurorobotic field. PMID:24139652
Search for mono-Higgs signals at the LHC in the B -L supersymmetric standard model
NASA Astrophysics Data System (ADS)
Abdallah, W.; Hammad, A.; Khalil, S.; Moretti, S.
2017-03-01
We study mono-Higgs signatures emerging in the B -L supersymmetric standard model induced by new channels not present in the minimal supersymmetric standard model, i.e., via topologies in which the mediator is either a heavy Z', with mass of O (2 TeV ) , or an intermediate h' (the lightest C P -even Higgs state of B -L origin), with a mass of O (0.2 TeV ) . The mono-Higgs probe considered is the standard model-like Higgs state recently discovered at the Large Hadron Collider, so as to enforce its mass reconstruction for background reduction purposes. With this in mind, its two cleanest signatures are selected: γ γ and Z Z*→4 l (l =e , μ ). We show how both of these can be accessed with foreseen energy and luminosity options using a dedicated kinematic analysis performed in the presence of partonic, showering, hadronization and detector effects.
[Realistic surgical training. The Aachen model].
Krones, C J; Binnebösel, M; Stumpf, M; Schumpelick, V
2010-01-01
The Aachen model is a practical mode in teaching and advanced training, which is closely geared to the areas of academic acquisition and training. During medical education optional student courses with constitutive curricula offer practical points of contact to the surgical department at all times. Besides improvement of manual training the aims are enhancing interests and acquisition of talents. This guided structure will be intensified with progression into advanced education. Next to the formal guidelines of the curriculum, education logbook and progression conversations, quality, transparency and reliability are particularly emphasized. An evaluation of both the reforms and the surgical trainers is still to be made. In addition procurement of an affirmative occupational image is essential.
Quasifixed point scenarios and the Higgs mass in the E6 inspired supersymmetric models
NASA Astrophysics Data System (ADS)
Nevzorov, R.
2014-03-01
We analyze the two-loop renormalization group (RG) flow of the gauge and Yukawa couplings within the E6 inspired supersymmetric models with extra U(1)N gauge symmetry under which right-handed neutrinos have zero charge. In these models, single discrete Z stretchy="false">˜2H symmetry forbids the tree-level flavor-changing transitions and the most dangerous baryon and lepton number violating operators. We consider two different scenarios A and B that involve extra matter beyond the minimal supersymmetric Standard Model contained in three and four 5+5¯ representations of SU(5), respectively, plus three SU(5) singlets which carry U(1)N charges. In scenario A, the measured values of the SU(2)W and U(1)Y gauge couplings lie near the fixed points of the RG equations. In scenario B, the contribution of two-loop corrections spoils the unification of gauge couplings, resulting in the appearance of the Landau pole below the grand unification scale MX. The solutions for the Yukawa couplings also approach the quasifixed points with increasing their values at the scale MX. We calculate the two-loop upper bounds on the lightest Higgs boson mass in the vicinity of these quasifixed points and compare the results of our analysis with the corresponding ones in the next-to-minimal supersymmetric Standard Model. In all these cases, the theoretical restrictions on the Standard-Model-like Higgs boson mass are rather close to 125 GeV.
Determining fundamental parameters from the chargino sector in left right supersymmetric models
NASA Astrophysics Data System (ADS)
Alvarez-Moraga, Nibaldo
2006-07-01
Analytical expressions relating the fundamental parameters describing the chargino sector in the context of the left-right supersymmetric model are constructed. A general complex extension of the real non-symmetric chargino mass matrix including all possible CP-violating phases is considered. The method used for such an effect is the projector formalism based on the explicit knowledge of two unitary matrices diagonalizing the chargino mass matrix. Some possible scenarios allowing us to extract analytical and numerical values for the unknown parameters are considered. Moreover, an algorithm allowing us to disentangle the fundamental parameters of the chargino sector, based on possible measurements of some class of cross-section observables related to the chargino pair production in e+e- annihilation processes, is described. Some comparisons with the corresponding results in the context of the minimal supersymmetric standard model are given.
Nonlocal charge of the CP/sup n/-1 model and its supersymmetric extension to all orders
Abdalla, E.; Abdalla, M.C.B.; Gomes, M.
1983-02-15
We prove that the conservation of quantum nonlocal charge of the CP/sup n/-1 model is spoiled by an anomaly calculable to all orders in the 1/n expansion, while for its supersymmetric extension it is restored.
Extra matters decree the relatively heavy Higgs of mass about 125 GeV in the supersymmetric model
NASA Astrophysics Data System (ADS)
Moroi, Takeo; Sato, Ryosuke; Yanagida, Tsutomu T.
2012-03-01
We show that the Higgs mass about 125 GeV is easily realized in supersymmetric model with extra matters, simultaneously explaining the anomaly in the muon anomalous magnetic moment and the dark matter density.
Signals of dark matter in a supersymmetric two dark matter model
Fukuoka, Hiroki; Suematsu, Daijiro; Toma, Takashi E-mail: suematsu@hep.s.kanazawa-u.ac.jp
2011-07-01
Supersymmetric radiative neutrino mass models have often two dark matter candidates. One is the usual lightest neutralino with odd R parity and the other is a new neutral particle whose stability is guaranteed by a discrete symmetry that forbids tree-level neutrino Yukawa couplings. If their relic abundance is comparable, dark matter phenomenology can be largely different from the minimal supersymmetric standard model (MSSM). We study this in a supersymmetric radiative neutrino mass model with the conserved R parity and a Z{sub 2} symmetry weakly broken by the anomaly effect. The second dark matter with odd parity of this new Z{sub 2} is metastable and decays to the neutralino dark matter. Charged particles and photons associated to this decay can cause the deviation from the expected background of the cosmic rays. Direct search of the neutralino dark matter is also expected to show different features from the MSSM since the relic abundance is not composed of the neutralino dark matter only. We discuss the nature of dark matter in this model by analyzing these signals quantitatively.
Family of fish-eye-related models and their supersymmetric partners
Makowski, Adam J.
2010-05-15
A large family of potentials related to the Maxwell fish-eye model is derived with the help of conformal mappings. It is shown that the whole family admits square-integrable E=0 solutions of the Schroedinger equation for discrete values of the coupling constant. A corresponding supersymmetric family of partner potentials to the preceding ones is derived as well. Some applications of the considered potentials are also discussed.
Exact Gell-Mann-Low function of supersymmetric Kähler sigma models
NASA Astrophysics Data System (ADS)
Morozov, Alexei Y.; Perelomov, Askold M.; Shifman, Michael A.
We consider a broad class of Kähler supersymmetric sigma models in two-dimensional space-time. The exact Gell-Mann-Low function is found within the framework of the method proposed earlier [1, 2] and based on analysis of classical solutions. It is shown that the exact beta function accounting for all orders in the coupling constant actually coincides with the one-loop result.
Impacts of supersymmetric higher derivative terms on inflation models in supergravity
Aoki, Shuntaro; Yamada, Yusuke
2015-07-14
We show the effects of supersymmetric higher derivative terms on inflation models in supergravity. The results show that such terms generically modify the effective kinetic coefficient of the inflaton during inflation if the cut off scale of the higher derivative operators is sufficiently small. In such a case, the η-problem in supergravity does not occur, and we find that the effective potential of the inflaton generically becomes a power type potential with a power smaller than two.
Mass and mixing angle patterns in the Standard Model and its material Supersymmetric Extension
Ramond, P.
1992-01-01
Using renormalization group techniques, we examine several interesting relations among masses and mixing angles of quarks and lepton in the Standard Model of Elementary Particle Interactions as a functionof scale. We extend the analysis to the minimal Supersymmetric Extension to determine its effect on these mass relations. For a heavy to quark, and minimal supersymmetry, most of these relations, can be made to agree at one unification scale.
Impacts of supersymmetric higher derivative terms on inflation models in supergravity
Aoki, Shuntaro; Yamada, Yusuke E-mail: yuusuke-yamada@asagi.waseda.jp
2015-07-01
We show the effects of supersymmetric higher derivative terms on inflation models in supergravity. The results show that such terms generically modify the effective kinetic coefficient of the inflaton during inflation if the cut off scale of the higher derivative operators is sufficiently small. In such a case, the η-problem in supergravity does not occur, and we find that the effective potential of the inflaton generically becomes a power type potential with a power smaller than two.
Ferrer, Francesc; Krauss, Lawrence M.; Profumo, Stefano
2006-12-01
We explore the prospects for indirect detection of neutralino dark matter in supersymmetric models with an extended Higgs sector (next-to-minimal supersymmetric standard model, or NMSSM). We compute, for the first time, one-loop amplitudes for NMSSM neutralino pair annihilation into two photons and two gluons, and point out that extra diagrams (with respect to the minimal supersymmetric standard model, or MSSM), featuring a potentially light CP-odd Higgs boson exchange, can strongly enhance these radiative modes. Expected signals in neutrino telescopes due to the annihilation of relic neutralinos in the Sun and in the Earth are evaluated, as well as the prospects of detection of a neutralino annihilation signal in space-based gamma-ray, antiproton and positron search experiments, and at low-energy antideuteron searches. We find that in the low mass regime the signals from capture in the Earth are enhanced compared to the MSSM, and that NMSSM neutralinos have a remote possibility of affecting solar dynamics. Also, antimatter experiments are an excellent probe of galactic NMSSM dark matter. We also find enhanced two-photon decay modes that make the possibility of the detection of a monochromatic gamma-ray line within the NMSSM more promising than in the MSSM, although likely below the sensitivity of next generation gamma-ray telescopes.
Differentiating U (1)' supersymmetric models with right sneutrino and neutralino dark matter
NASA Astrophysics Data System (ADS)
Araz, Jack Y.; Frank, Mariana; Fuks, Benjamin
2017-07-01
We perform a detailed analysis of dark matter signals of supersymmetric models containing an extra U (1)'gauge group. We investigate scenarios in which either the right sneutrino or the lightest neutralino are phenomenologically acceptable dark matter candidates and we explore the parameter spaces of different supersymmetric realisations featuring an extra U (1)'. We impose consistency with low energy observables, with known mass limits for the superpartners and Z' bosons, as well as with Higgs boson signal strengths, and we moreover verify that predictions for the anomalous magnetic moment of the muon agree with the experimental value and require that the dark matter candidate satisfies the observed relic density and direct and indirect dark matter detection constraints. For the case where the sneutrino is the dark matter candidate, we find distinguishing characteristics among different U (1)' mixing angles. If the neutralino is the lightest supersymmetric particle, its mass is heavier than that of the light sneutrino in scenarios where the latter is a dark matter candidate, the parameter space is less restricted and differentiation between models is more difficult. We finally comment on the possible collider tests of these models.
Bottom-tau unification in supersymmetric SU(5) models with extra matters
NASA Astrophysics Data System (ADS)
Chigusa, So; Moroi, Takeo
2017-06-01
We consider b-\\tau unification in supersymmetric SU(5) grand unified theories (GUTs) with extra matters. The renormalization group runnings of b and \\tau Yukawa coupling constants may be significantly affected by the existence of extra matters. If the extra matters interact with the standard-model particles (and their superpartners) only through gauge interaction, the ratio of the b to \\tau Yukawa coupling constants at the GUT scale becomes suppressed compared to the case without extra matters. This is mainly due to the change of the renormalization group running of the SU(3)_C gauge coupling constant. If the extra matters have Yukawa couplings, on the contrary, the (effective) b Yukawa coupling at the GUT scale can be enhanced due to the new Yukawa interaction. Such an effect may improve the b-\\tau unification in supersymmetric GUTs.
A SPATIALLY REALISTIC MODEL FOR INFORMING FOREST MANAGEMENT DECISIONS
Spatially realistic population models (SRPMs) address a fundamental
problem commonly confronted by wildlife managers - predicting the
effects of landscape-scale habitat management on an animal population.
SRPMs typically consist of three submodels: (1) a habitat submodel...
A SPATIALLY REALISTIC MODEL FOR INFORMING FOREST MANAGEMENT DECISIONS
Spatially realistic population models (SRPMs) address a fundamental
problem commonly confronted by wildlife managers - predicting the
effects of landscape-scale habitat management on an animal population.
SRPMs typically consist of three submodels: (1) a habitat submodel...
Fermionic Fields with Mass Dimension One as Supersymmetric Extension of the O'Raifeartaigh Model
NASA Astrophysics Data System (ADS)
Wunderle, Kai E.
The objective of this thesis is to derive a supersymmetric Lagrangian for fermionic fields with mass dimension one and to discuss their coupling to the O'Raifeartaigh model which is the simplest model permitting supersymmetry breaking. In addition it will be shown that eigenspinors of the charge conjugation operator (ELKO) exhibit a different transformation behaviour under discrete symmetries than previously assumed. The calculations confirm that ELKO spinors are not eigenspinors of the parity operator and satisfy (CPT)2 = -- I which identifies them as representation of a nonstandard Wigner class. However, it is found that ELKO spinors transform symmetrically under parity instead of the previously assumed asymmetry. Furthermore, it is demonstrated that ELKO spinors transform asymmetrically under time reversal which is opposite to the previously reported symmetric behaviour. These changes affect the (anti)commutation relations that are satisfied by the operators acting on ELKO spinors. Therefore, ELKO spinors satisfy the same (anti)commutation relations as Dirac spinors, even though they belong to two different representations of the Lorentz group. Afterwards, a supersymmetric model for fermionic fields with mass dimension one based on a general superfield with one spinor index is formulated. It includes the systematic derivation of all associated chiral and anti-chiral superfields up to third order in covariant derivatives. Starting from these fundamental superfields a supersymmetric on-shell Lagrangian that contains a kinetic term for the fermionic fields with mass dimension one is constructed. This on-shell Lagrangian is subsequently used to derive the on-shell super-current and to successfully formulate a consistent second quantisation for the component fields. In addition, the Hamiltonian in position space that corresponds to the supersymmetric Lagrangian is calculated. As the Lagrangian is by construction supersymmetric and the second quantisation of the
Comparison between realistic and spherical approaches in EEG forward modelling.
Meneghini, Fabio; Vatta, Federica; Esposito, Fabrizio; Mininel, Stefano; Di Salle, Francesco
2010-06-01
In electroencephalography (EEG) a valid conductor model of the head (forward model) is necessary for predicting measurable scalp voltages from intra-cranial current distributions. All inverse models, capable of inferring the spatial distribution of the neural sources generating measurable electrical and magnetic signals outside the brain are normally formulated in terms of a pre-estimated forward model, which implies considering one (or more) current dipole(s) inside the head and computing the electrical potentials generated at the electrode sites on the scalp surface. Therefore, the accuracy of the forward model strongly affects the reliability of the source reconstruction process independently of the specific inverse model. So far, it is as yet unclear which brain regions are more sensitive to the choice of different model geometry, from both quantitative and qualitative points of view. In this paper, we compare the finite difference method-based realistic model with the four-layers sensor-fitted spherical model using simulated cortical sources in the MNI152 standard space. We focused on the investigation of the spatial variation of the lead fields produced by simulated cortical sources which were placed on the reconstructed mesh of the neocortex along the surface electrodes of a 62-channel configuration. This comparison is carried out by evaluating a point spread function all over the brain cortex, with the aim of finding the lead fields mismatch between realistic and spherical geometry. Realistic geometry turns out to be a relevant factor of improvement which is particularly important when considering sources placed in the temporal or in the occipital cortex. In these situations, using a realistic head model will allow a better spatial discrimination of neural sources when compared to the spherical model.
An Exactly Solvable Supersymmetric Model of Semimagic Nuclei
Balantekin, A. B.; Gueven, Nurtac; Pehlivan, Yamac
2008-11-11
A simple model of nucleons coupled to angular momentum zero (s-pairs) occupying the valance shell of a semi-magic nuclei is considered. The model has a separable, orbit dependent pairing interaction which dominates over the kinetic term. It is shown that such an interaction leads to an exactly solvable model whose (0{sup +}) eigenstates and energies can be computed very easily with the help of the algebraic Bethe ansatz method. It is also shown that the model has a supersymmetry which connects the spectra of some semimagic nuclei. The results obtained from this model for the semimagic Ni isotopes from {sup 58}Ni to {sup 68}Ni are given. In addition, a new and easier technique for calculating the energy eigenvalues from the Bethe ansatz equations is also presented.
An Exactly Solvable Supersymmetric Model of Semimagic Nuclei
NASA Astrophysics Data System (ADS)
Balantekin, A. B.; Güven, Nurtaç; Pehlivan, Yamaç
2008-11-01
A simple model of nucleons coupled to angular momentum zero (s-pairs) occupying the valance shell of a semi-magic nuclei is considered. The model has a separable, orbit dependent pairing interaction which dominates over the kinetic term. It is shown that such an interaction leads to an exactly solvable model whose (0+) eigenstates and energies can be computed very easily with the help of the algebraic Bethe ansatz method. It is also shown that the model has a supersymmetry which connects the spectra of some semimagic nuclei. The results obtained from this model for the semimagic Ni isotopes from 58Ni to 68Ni are given. In addition, a new and easier technique for calculating the energy eigenvalues from the Bethe ansatz equations is also presented.
A viable supersymmetric model with UV insensitive anomaly mediation
Ibe, Masahiro; Kitano, Ryuichiro; Murayama, Hitoshi
2004-12-14
We propose an electroweak model which is compatible with the UV insensitive anomaly mediated supersymmetry breaking. The model is an extension of the NMSSM by adding vector-like matter fields which can drive the soft scalar masses of the singlet Higgs field negative and the successful electroweak symmetry breaking is achieved. Viable parameter regions are found to preserve perturbativity of all the coupling constants up to the Planck scale. With this success, the model becomes a perfect candidate of physics beyond the standard model without the FCNC and CP problem. The cosmology is also quite interesting. The lightest neutralino is the wino which is a perfect cold dark matter candidate assuming the non-thermal production from the gravitino decay. There is no gravitino problem because it decays before the BBN era, and thus the thermal leptogenesis works. The cosmological domain wall problem inherent in the NMSSM is absent since the Z_3 symmetry is broken by the QCD instanton effect in the presence of the vector-like quarks. We also briefly comment on a possible solution to the strong CP problem a la the Nelson-Barr mechanism.
Exact Gell-Mann-Low function of supersymmetric Kähler σ-models (II)
NASA Astrophysics Data System (ADS)
Perelomov, A. M.; Prati, M. C.
We extend the analysis carried out in [1] to a new class of Kähler supersymmetric σ-models in the two-dimensional space-time. Here the fields take values in the flag space F n, n = 1, 2 … and there are n topological charges. It turns out that also for these models the Gell-Mann-Low β-function to all orders coincides with the one-loop approximation, for which we calculate explicitly the exact value of the multiplicative constant.
Supersymmetric U(1)Y‧⊗ U(1)B-L extension of the Standard Model
NASA Astrophysics Data System (ADS)
Montero, J. C.; Pleitez, V.; Sánchez-Vega, B. L.; Rodriguez, M. C.
2017-06-01
We build a supersymmetric version with SU(3)C ⊗ SU(2)L ⊗ U(1)Y‧⊗ U(1)B-L gauge symmetry, where Y‧ is a new charge and B and L are the usual baryonic and leptonic numbers. The model has three right-handed neutrinos with identical B - L charges, and can accommodate all fermion masses at the tree level. In particular, the type I seesaw mechanism is implemented for the generation of the active neutrino masses. We obtain the mass spectra of all sectors and for the scalar one we also give the flat directions allowed by the model.
Lectures on localization and matrix models in supersymmetric Chern-Simons-matter theories
NASA Astrophysics Data System (ADS)
Mariño, Marcos
2011-11-01
In these lectures, I give a pedagogical presentation of some of the recent progress in supersymmetric Chern-Simons-matter theories, coming from the use of localization and matrix model techniques. The goal is to provide a simple derivation of the exact interpolating function for the free energy of ABJM theory on the three-sphere, which implies in particular the N3/2 behavior at strong coupling. I explain in detail part of the background needed to understand this derivation, like holographic renormalization, localization of path integrals and large N techniques in matrix models.
Standard model and supersymmetric Higgs searches at CDF
Kilminster, Ben; /Ohio State U.
2005-10-01
We present the results on the searches for the SM and the MSSM Higgs boson production in proton-antiproton collisions at {radical}s = 1.96 GeV with the CDF detector. The Higgs bosons are searched for in various production and decay channels, with data samples corresponding to 400 pb{sup -1}. Using these measurements, we set an upper limit on the production cross section times branching fraction for the Standard Model Higgs as a function of the Higgs mass, and we obtain exclusion regions in the tan{beta} vs mass for the neutral MSSM Higgs, and branching fraction vs mass for the charged Higgs.
Supersymmetric invariant theories
NASA Astrophysics Data System (ADS)
Esipova, S. R.; Lavrov, P. M.; Radchenko, O. V.
2014-04-01
We study field models for which a quantum action (i.e. the action appearing in the generating functional of Green functions) is invariant under supersymmetric transformations. We derive the Ward identity which is a direct consequence of this invariance. We consider a change of variables in functional integral connected with supersymmetric transformations when its parameter is replaced by a nilpotent functional of fields. Exact form of the corresponding Jacobian is found. We find restrictions on generators of supersymmetric transformations when a consistent quantum description of given field theories exists.
Unified minimal supersymmetric model with large Yukawa couplings
Rattazzi, R.; Sarid, U.
1996-02-01
The consequences of assuming the third-generation Yukawa couplings are all large and comparable are studied in the context of the minimal sypersymmetric extension of the standard model. General aspects of the RG evolution of the parameters, theoretical constraints needed to ensure proper electroweak symmetry breaking, and experimental and cosmological bounds on low-energy parameters are presented. We also present complete and exact semianalytic solutions to the one-loop RG equations. Focusing on SU(5) or SO(10) unification, we analyze the relationship between the top and bottom masses and the superspectrum, and the phenomenological implications of the GUT conditions on scalar masses. Future experimental measurements of the superspectrum and of the strong coupling will distinguish between various GUT-scale scenarios. And if present experimental knowledge is to be accounted for most naturally, a particular set of predictions is singled out. {copyright} {ital 1996 The American Physical Society.}
Resonance and continuum Gamow shell model with realistic nuclear forces
NASA Astrophysics Data System (ADS)
Sun, Z. H.; Wu, Q.; Zhao, Z. H.; Hu, B. S.; Dai, S. J.; Xu, F. R.
2017-06-01
Starting from realistic nuclear forces, we have developed a core Gamow shell model which can describe resonance and continuum properties of loosely-bound or unbound nuclear systems. To describe properly resonance and continuum, the Berggren representation has been employed, which treats bound, resonant and continuum states on equal footing in a complex-momentum (complex-k) plane. To derive the model-space effective interaction based on realistic forces, the full Q ˆ -box folded-diagram renormalization has been, for the first time, extended to the nondegenerate complex-k space. The CD-Bonn potential is softened by using the Vlow-k method. Choosing 16O as the inert core, we have calculated sd-shell neutron-rich oxygen isotopes, giving good descriptions of both bound and resonant states. The isotopes 25,26O are calculated to be resonant even in their ground states.
A realistic model for charged strange quark stars
NASA Astrophysics Data System (ADS)
Thirukkanesh, S.; Ragel, F. C.
2017-01-01
We report a general approach to solve an Einstein-Maxwell system to describe a static spherically symmetric anisotropic strange matter distribution with linear equation of state in terms of two generating functions. It is examined by choosing Tolmann IV type potential for one of the gravitational potentials and a physically reasonable choice for the electric field. Hence, the generated model satisfies all the required major physical properties of a realistic star. The effect of electric charge on physical properties is highlighted.
Realistic modeling of chamber transport for heavy-ion fusion
Sharp, W.M.; Grote, D.P.; Callahan, D.A.; Tabak, M.; Henestroza, E.; Yu, S.S.; Peterson, P.F.; Welch, D.R.; Rose, D.V.
2003-05-01
Transport of intense heavy-ion beams to an inertial-fusion target after final focus is simulated here using a realistic computer model. It is found that passing the beam through a rarefied plasma layer before it enters the fusion chamber can largely neutralize the beam space charge and lead to a usable focal spot for a range of ion species and input conditions.
Higgs mass and right-handed sneutrino WIMP in a supersymmetric 3 -3 -1 model
NASA Astrophysics Data System (ADS)
Pires, C. A. de S.; da Silva, P. S. Rodrigues; Santos, A. C. O.; Siqueira, Clarissa
2016-09-01
This work deals with the right-handed sneutrino as thermal cold dark matter candidate. This scalar emerges in a supersymmetric version of the S U (3 )c⊗S U (3 )L⊗U (1 )X gauge model where right-handed neutrinos are a natural component of leptonic chiral scalar supermultiplets. We first consider the issue of a 125 GeV Higgs boson mass in this model, showing that constraints on the stop mass and trilinear soft coupling are considerably alleviated compared to the minimal supersymmetric standard model. Then, we investigate the region of parameter space that is consistent with right-handed sneutrino as thermal cold dark matter, under the light of Planck results on the relic abundance and direct detection from the LUX experiment. This sneutrino mainly annihilates through an extra neutral gauge boson, Z', and Higgs exchange so that the physics of dark matter is somewhat related to the parameters determining Higgs and Z' masses. We then obtain that the right-handed sneutrino in this model must be heavier than 400 GeV to conform with Planck and LUX, simultaneously constraining the Z' mass to be above 2400 GeV, which is in perfect agreement with LHC searches in a nonsupersymmetric version of this model.
Higher Dimensional Operators and Their Effects in (non)supersymmetric Models
NASA Astrophysics Data System (ADS)
Ghilencea, D. M.
It is shown that a 4D N = 1 softly broken supersymmetric theory with higher derivative operators in the Kahler or the superpotential part of the Lagrangian and with an otherwise arbitrary superpotential, can be re-formulated as a theory without higher derivatives but with additional (ghost) superfields and modified interactions. The importance of the analytical continuation Minkowski-Euclidean space-time for the UV behaviour of such theories is discussed in detail. In particular it is shown that power counting for divergences in Minkowski space-time does not always work in models with higher dimensional (derivative) operators.
Gravitational waves from domain walls in the next-to-minimal supersymmetric standard model
Kadota, Kenji; Kawasaki, Masahiro; Saikawa, Ken’ichi
2015-10-16
The next-to-minimal supersymmetric standard model predicts the formation of domain walls due to the spontaneous breaking of the discrete Z{sub 3}-symmetry at the electroweak phase transition, and they collapse before the epoch of big bang nucleosynthesis if there exists a small bias term in the potential which explicitly breaks the discrete symmetry. Signatures of gravitational waves produced from these unstable domain walls are estimated and their parameter dependence is investigated. It is shown that the amplitude of gravitational waves becomes generically large in the decoupling limit, and that their frequency is low enough to be probed in future pulsar timing observations.
Gravitational waves from domain walls in the next-to-minimal supersymmetric standard model
Kadota, Kenji; Kawasaki, Masahiro; Saikawa, Ken'ichi E-mail: kawasaki@icrr.u-tokyo.ac.jp
2015-10-01
The next-to-minimal supersymmetric standard model predicts the formation of domain walls due to the spontaneous breaking of the discrete Z{sub 3}-symmetry at the electroweak phase transition, and they collapse before the epoch of big bang nucleosynthesis if there exists a small bias term in the potential which explicitly breaks the discrete symmetry. Signatures of gravitational waves produced from these unstable domain walls are estimated and their parameter dependence is investigated. It is shown that the amplitude of gravitational waves becomes generically large in the decoupling limit, and that their frequency is low enough to be probed in future pulsar timing observations.
More about the (2,0) supersymmetric WZNW model in (2,0) superspace
NASA Astrophysics Data System (ADS)
Gates, S. James; Ketov, Sergay V.
1991-11-01
We re-examine the action and classical symmetries of the (2, 0) supersymmetric two-dimensional Wess-Zumino-Novikov- Witten model in (2, 0) superspace. The (2, 0) super-Kac-Moody symmetry is shown to be incompatible with the ``physical'' WZNW action. It is still possible to incorporate the (1, 0) super-Kac-Moody symmetry or the chiral (2, 0) super-Kac-Moody symmetry within the WZNW theory in a way consistent with (2, 0) superconformal invariance. On leave of absence from: High Current Electronics Institute, SB AS USSR, Akademicheskii 4, SU-634 055 Tomsk, USSR.
Dubinin, M. N. Petrova, E. Yu.
2016-07-15
Constraints on the parameter space of theMinimal Supersymmetric StandardModel (MSSM) that are imposed by the experimentally observed mass of the Higgs boson (m{sub H} = 125 GeV) upon taking into account radiative corrections within an effective theory for the Higgs sector in the decoupling limit are examined. It is also shown that simplified approximations for radiative corrections in theMSSM Higgs sector could reduce, to a rather high degree of precision, the dimensionality of the multidimensionalMSSM parameter space to two.
Realistic modeling of the electronic properties of doped amorphous silicon
Hack, M.; Street, R.A.
1988-09-19
In this letter we describe a fundamental approach to calculating the electronic properties of doped amorphous silicon which takes into account the thermal history of the material. Above the equilibrium temperature, the material is in a thermodynamically stable state, and this is derived by minimizing the free energy using a simple density of states model. The calculations are based on the defect compensation model of doping, introducing distributions of formation energies for neutral dangling bonds and fourfold dopant atoms while preserving charge neutrality. Our results are in good agreement with experimental data providing a realistic model for use in device simulation programs.
Toward the classification of the realistic free fermionic models
Faraggi, A.E.
1997-08-01
The realistic free fermionic models have had remarkable success in providing plausible explanations for various properties of the Standard Model which include the natural appearance of three generations, the explanation of the heavy top quark mass and the qualitative structure of the fermion mass spectrum in general, the stability of the proton and more. These intriguing achievements makes evident the need to understand the general space of these models. While the number of possibilities is large, general patterns can be extracted. In this paper the author presents a detailed discussion on the construction of the realistic free fermionic models with the aim of providing some insight into the basic structures and building blocks that enter the construction. The role of free phases in the determination of the phenomenology of the models is discussed in detail. The author discusses the connection between the free phases and mirror symmetry in (2,2) models and the corresponding symmetries in the case of (2,0) models. The importance of the free phases in determining the effective low energy phenomenology is illustrated in several examples. The classification of the models in terms of boundary condition selection rules, real world-sheet fermion pairings, exotic matter states and the hidden sector is discussed.
Supersymmetric fits after the Higgs discovery and implications for model building.
Ellis, John
The data from the first run of the LHC at 7 and 8 TeV, together with the information provided by other experiments such as precision electroweak measurements, flavour measurements, the cosmological density of cold dark matter and the direct search for the scattering of dark matter particles in the LUX experiment, provide important constraints on supersymmetric models. Important information is provided by the ATLAS and CMS measurements of the mass of the Higgs boson, as well as the negative results of searches at the LHC for events with [Formula: see text] accompanied by jets, and the LHCb and CMS measurements of [Formula: see text]. Results are presented from frequentist analyses of the parameter spaces of the CMSSM and NUHM1. The global [Formula: see text] functions for the supersymmetric models vary slowly over most of the parameter spaces allowed by the Higgs mass and the [Formula: see text] search, with best-fit values that are comparable to the [Formula: see text] for the standard model. The 95 % CL lower limits on the masses of gluinos and squarks allow significant prospects for observing them during the LHC runs at higher energies.
Design for and efficient dynamic climate model with realistic geography
NASA Technical Reports Server (NTRS)
Suarez, M. J.; Abeles, J.
1984-01-01
The long term climate sensitivity which include realistic atmospheric dynamics are severely restricted by the expense of integrating atmospheric general circulation models are discussed. Taking as an example models used at GSFC for this dynamic model is an alternative which is of much lower horizontal or vertical resolution. The model of Heid and Suarez uses only two levels in the vertical and, although it has conventional grid resolution in the meridional direction, horizontal resolution is reduced by keeping only a few degrees of freedom in the zonal wavenumber spectrum. Without zonally asymmetric forcing this model simulates a day in roughly 1/2 second on a CRAY. The model under discussion is a fully finite differenced, zonally asymmetric version of the Heid-Suarez model. It is anticipated that speeds can be obtained a few seconds a day roughly 50 times faster than moderate resolution, multilayer GCM's.
Design for and efficient dynamic climate model with realistic geography
NASA Technical Reports Server (NTRS)
Suarez, M. J.; Abeles, J.
1984-01-01
The long term climate sensitivity which include realistic atmospheric dynamics are severely restricted by the expense of integrating atmospheric general circulation models are discussed. Taking as an example models used at GSFC for this dynamic model is an alternative which is of much lower horizontal or vertical resolution. The model of Heid and Suarez uses only two levels in the vertical and, although it has conventional grid resolution in the meridional direction, horizontal resolution is reduced by keeping only a few degrees of freedom in the zonal wavenumber spectrum. Without zonally asymmetric forcing this model simulates a day in roughly 1/2 second on a CRAY. The model under discussion is a fully finite differenced, zonally asymmetric version of the Heid-Suarez model. It is anticipated that speeds can be obtained a few seconds a day roughly 50 times faster than moderate resolution, multilayer GCM's.
An inexpensive yet realistic model for teaching vasectomy.
Coe, Taylor M; Curington, John
2015-01-01
Teaching the no-scalpel vasectomy is important, since vasectomy is a safe, simple, and cost-effective method of contraception. This minimally invasive vasectomy technique involves delivering the vas through the skin with specialized tools. This technique is associated with fewer complications than the traditional incisional vasectomy (1). One of the most challenging steps is the delivery of the vas through a small puncture in the scrotal skin, and there is a need for a realistic and inexpensive scrotal model for beginning learners to practice this step. After careful observation using several scrotal models while teaching residents and senior trainees, we developed a simplified scrotal model that uses only three components-bicycle inner tube, latex tubing, and a Penrose drain. This model is remarkably realistic and allows learners to practice a challenging step in the no-scalpel vasectomy. The low cost and simple construction of the model allows wide dissemination of training in this important technique. We propose a simple, inexpensive model that will enable learners to master the hand movements involved in delivering the vas through the skin while mitigating the risks of learning on patients.
The neutralino sector in the U(1)-extended supersymmetric Standard Model
NASA Astrophysics Data System (ADS)
Choi, S. Y.; Haber, H. E.; Kalinowski, J.; Zerwas, P. M.
2007-08-01
Motivated by grand unified theories and string theories we analyze the general structure of the neutralino sector in the USSM, an extension of the minimal supersymmetric Standard Model that involves a broken extra U(1) gauge symmetry. This supersymmetric U(1)-extended model includes an Abelian gauge superfield and a Higgs singlet superfield in addition to the standard gauge and Higgs superfields of the MSSM. The interactions between the MSSM fields and the new fields are in general weak and the mixing is small, so that the coupling of the two subsystems can be treated perturbatively. As a result, the mass spectrum and mixing matrix in the neutralino sector can be analyzed analytically and the structure of this 6-state system is under good theoretical control. We describe the decay modes of the new states and the impact of this extension on decays of the original MSSM neutralinos, including radiative transitions in cross-over zones. Production channels in cascade decays at the LHC and pair production at ee colliders are also discussed.
Deformed Matrix Models, Supersymmetric Lattice Twists and N=1/4 Supersymmetry
Unsal, Mithat
2008-09-24
A manifestly supersymmetric nonperturbative matrix regularization for a twisted version of N = (8, 8) theory on a curved background (a two-sphere) is constructed. Both continuum and the matrix regularization respect four exact scalar supersymmetries under a twisted version of the supersymmetry algebra. We then discuss a succinct Q = 1 deformed matrix model regularization of N = 4 SYM in d = 4, which is equivalent to a non-commutative A*{sub 4} orbifold lattice formulation. Motivated by recent progress in supersymmetric lattices, we also propose a N = 1/4 supersymmetry preserving deformation of N = 4 SYM theory on R{sup 4}. In this class of N = 1/4 theories, both the regularized and continuum theory respect the same set of (scalar) supersymmetry. By using the equivalence of the deformed matrix models with the lattice formulations, we give a very simple physical argument on why the exact lattice supersymmetry must be a subset of scalar subalgebra. This argument disagrees with the recent claims of the link approach, for which we give a new interpretation.
SL(2,R) matrix model and supersymmetric Yang-Mills integrals
Tierz, Miguel
2007-11-15
The density of states of Yang-Mills integrals in the supersymmetric case is characterized by power-law tails whose decay is independent of N, the rank of the gauge group. It is believed that this has no counterpart in matrix models, but we construct a matrix model that exactly exhibits this property. In addition, we show that the eigenfunctions employed to construct the matrix model are invariant under the collinear subgroup of conformal transformations, SL(2,R). We also show that the matrix model itself is invariant under a fractional linear transformation. The wave functions of the model appear in the trigonometric Rosen-Morse potential and in free relativistic motion on anti-de Sitter space.
Modeling of Transmembrane Potential in Realistic Multicellular Structures before Electroporation.
Murovec, Tomo; Sweeney, Daniel C; Latouche, Eduardo; Davalos, Rafael V; Brosseau, Christian
2016-11-15
Many approaches for studying the transmembrane potential (TMP) induced during the treatment of biological cells with pulsed electric fields have been reported. From the simple analytical models to more complex numerical models requiring significant computational resources, a gamut of methods have been used to recapitulate multicellular environments in silico. Cells have been modeled as simple shapes in two dimensions as well as more complex geometries attempting to replicate realistic cell shapes. In this study, we describe a method for extracting realistic cell morphologies from fluorescence microscopy images to generate the piecewise continuous mesh used to develop a finite element model in two dimensions. The preelectroporation TMP induced in tightly packed cells is analyzed for two sets of pulse parameters inspired by clinical irreversible electroporation treatments. We show that high-frequency bipolar pulse trains are better, and more homogeneously raise the TMP of tightly packed cells to a simulated electroporation threshold than conventional irreversible electroporation pulse trains, at the expense of larger applied potentials. Our results demonstrate the viability of our method and emphasize the importance of considering multicellular effects in the numerical models used for studying the response of biological tissues exposed to electric fields. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.
Supersymmetric models on magnetized orbifolds with flux-induced Fayet-Iliopoulos terms
NASA Astrophysics Data System (ADS)
Abe, Hiroyuki; Kobayashi, Tatsuo; Sumita, Keigo; Tatsuta, Yoshiyuki
2017-01-01
We study supersymmetric (SUSY) models derived from the ten-dimensional SUSY Yang-Mills theory compactified on magnetized orbifolds, with nonvanishing Fayet-Iliopoulos (FI) terms induced by magnetic fluxes in extra dimensions. Allowing the presence of FI-terms relaxes a constraint on flux configurations in SUSY model building based on magnetized backgrounds. In this case, charged fields develop their vacuum expectation values to cancel the FI-terms in the D-flat directions of fluxed gauge symmetries, which break the gauge symmetries and lead to a SUSY vacuum. Based on this idea, we propose a new class of SUSY magnetized orbifold models with three generations of quarks and leptons. Especially, we construct a model where the right-handed sneutrinos develop their vacuum expectation values which restore the supersymmetry but yield lepton number violating terms below the compactification scale, and show their phenomenological consequences.
Ring Current Modeling in a Realistic Magnetic Field Configuration
NASA Technical Reports Server (NTRS)
Fok, M.-C.; Moore, T. E.
1997-01-01
A 3-dimensional kinetic model has been developed to study the dynamics of the storm time ring current in a dipole magnetic field. In this paper, the ring current model is extended to include a realistic, time-varying magnetic field model. The magnetic field is expressed as the cross product of the gradients of two Euler potentials and the bounce-averaged particle drifts are calculated in the Euler potential coordinates. A dipolarization event is modeled by collapsing a tail-like magnetosphere to a dipole-like configuration. Our model is able to simulate the sudden enhancements in the ring current ion fluxes and the corresponding ionospheric precipitation during the substorm expansion.
Towards Modeling Realistic Mobility for Performance Evaluations in MANET
NASA Astrophysics Data System (ADS)
Aravind, Alex; Tahir, Hassan
Simulation modeling plays crucial role in conducting research on complex dynamic systems like mobile ad hoc networks and often the only way. Simulation has been successfully applied in MANET for more than two decades. In several recent studies, it is observed that the credibility of the simulation results in the field has decreased while the use of simulation has steadily increased. Part of this credibility crisis has been attributed to the simulation of mobility of the nodes in the system. Mobility has such a fundamental influence on the behavior and performance of mobile ad hoc networks. Accurate modeling and knowledge of mobility of the nodes in the system is not only helpful but also essential for the understanding and interpretation of the performance of the system under study. Several ideas, mostly in isolation, have been proposed in the literature to infuse realism in the mobility of nodes. In this paper, we attempt a holistic analysis of creating realistic mobility models and then demonstrate creation and analysis of realistic mobility models using a software tool we have developed. Using our software tool, desired mobility of the nodes in the system can be specified, generated, analyzed, and then the trace can be exported to be used in the performance studies of proposed algorithms or systems.
Dark radiation and dark matter in supersymmetric axion models with high reheating temperature
Graf, Peter; Steffen, Frank Daniel E-mail: steffen@mpp.mpg.de
2013-12-01
Recent studies of the cosmic microwave background, large scale structure, and big bang nucleosynthesis (BBN) show trends towards extra radiation. Within the framework of supersymmetric hadronic axion models, we explore two high-reheating-temperature scenarios that can explain consistently extra radiation and cold dark matter (CDM), with the latter residing either in gravitinos or in axions. In the gravitino CDM case, axions from decays of thermal saxions provide extra radiation already prior to BBN and decays of axinos with a cosmologically required TeV-scale mass can produce extra entropy. In the axion CDM case, cosmological constraints are respected with light eV-scale axinos and weak-scale gravitinos that decay into axions and axinos. These decays lead to late extra radiation which can coexist with the early contributions from saxion decays. Recent results of the Planck satellite probe extra radiation at late times and thereby both scenarios. Further tests are the searches for axions at ADMX and for supersymmetric particles at the LHC.
Toward realistic effective models of quantum-Hall edges
NASA Astrophysics Data System (ADS)
Zülicke, U.; MacDonald, A. H.
1998-01-01
We have investigated the dynamical properties of edge excitations in the (fractional) quantum-Hall regime for a sharp confining potential, emphasizing the effects resulting from the presence of long-range interaction. Our study uses chiral-Luttinger-liquid models that are motivated by the close analogy between the physics of edge excitations and that of plasmons in quasi-one-dimensional electron systems. We find that incorporating realistic long-range interaction is especially important for multi-branch edges. Results are presented for the tunneling-IV-curve power-law exponent and the two-terminal conductance.
de la Puente, Alejandro
2012-05-01
In this work, I present a generalization of the Next-to-Minimal Supersymmetric Standard Model (NMSSM), with an explicit μ-term and a supersymmetric mass for the singlet superfield, as a route to alleviating the little hierarchy problem of the Minimal Supersymmetric Standard Model (MSSM). I analyze two limiting cases of the model, characterized by the size of the supersymmetric mass for the singlet superfield. The small and large limits of this mass parameter are studied, and I find that I can generate masses for the lightest neutral Higgs boson up to 140 GeV with top squarks below the TeV scale, all couplings perturbative up to the gauge unification scale, and with no need to fine tune parameters in the scalar potential. This model, which I call the S-MSSM is also embedded in a gauge-mediated supersymmetry breaking scheme. I find that even with a minimal embedding of the S-MSSM into a gauge mediated scheme, the mass for the lightest Higgs boson can easily be above 114 GeV, while keeping the top squarks below the TeV scale. Furthermore, I also study the forward-backward asymmetry in the t¯t system within the framework of the S-MSSM. For this purpose, non-renormalizable couplings between the first and third generation of quarks to scalars are introduced. The two limiting cases of the S-MSSM, characterized by the size of the supersymmetric mass for the singlet superfield is analyzed, and I find that in the region of small singlet supersymmetric mass a large asymmetry can be obtained while being consistent with constraints arising from flavor physics, quark masses and top quark decays.
Hyperkählerian manifolds and exact β-functions of two-dimensional N = 4 supersymmetric σ-models
NASA Astrophysics Data System (ADS)
Morozov, A. Yu.; Perelomov, A. M.
1986-06-01
Two-dimensional supersymmetric sigma-models on cotangent bundles over CP n are investigated. These manifolds are supplied with hyperkählerian metrics, and the corresponding σ-models possess N = 4 supersymmetry. Also they admit instantonic solutions, which allows us to apply the NSVZ method to calculate exact β-functions. β( g2) = 0, as was expected.
Realistic Mobility Modeling for Vehicular Ad Hoc Networks
NASA Astrophysics Data System (ADS)
Akay, Hilal; Tugcu, Tuna
2009-08-01
Simulations used for evaluating the performance of routing protocols for Vehicular Ad Hoc Networks (VANET) are mostly based on random mobility and fail to consider individual behaviors of the vehicles. Unrealistic assumptions about mobility produce misleading results about the behavior of routing protocols in real deployments. In this paper, a realistic mobility modeling tool, Mobility for Vehicles (MOVE), which considers the basic mobility behaviors of vehicles, is proposed for a more accurate evaluation. The proposed model is tested against the Random Waypoint (RWP) model using AODV and OLSR protocols. The results show that the mobility model significantly affects the number of nodes within the transmission range of a node, the volume of control traffic, and the number of collisions. It is shown that number of intersections, grid size, and node density are important parameters when dealing with VANET performance.
SuperLFV: An SLHA tool for lepton flavor violating observables in supersymmetric models
NASA Astrophysics Data System (ADS)
Murakami, Brandon
2014-02-01
We introduce SuperLFV, a numerical tool for calculating low-energy observables that exhibit charged lepton flavor violation (LFV) in the context of the minimal supersymmetric standard model (MSSM). As the Large Hadron Collider and MEG, a dedicated μ+→e+γ experiment, are presently acquiring data, there is need for tools that provide rapid discrimination of models that exhibit LFV. SuperLFV accepts a spectrum file compliant with the SUSY Les Houches Accord (SLHA), containing the MSSM couplings and masses with complex phases at the supersymmetry breaking scale. In this manner, SuperLFV is compatible with but divorced from existing SLHA spectrum calculators that provide the low energy spectrum. Hence, input spectra are not confined to the LFV sources provided by established SLHA spectrum calculators. Input spectra may be generated by personal code or by hand, allowing for arbitrary models not supported by existing spectrum calculators.
Kaehler potentials for the minimally supersymmetric standard model inflation and the spectral index
Nurmi, Sami
2008-01-15
Recently it has been argued that some of the fine-tuning problems of the minimally supersymmetric standard model (MSSM) inflation associated with the existence of a saddle point along a flat direction may be solved naturally in a class of supergravity models. Here we extend the analysis and show that the constraints on the Kaehler potentials in these models are considerably relaxed when the location of the saddle point is treated as a free variable. We also examine the effect of supergravity corrections on inflationary predictions and find that they can slightly alter the value of the spectral index. As an example, for flat direction field values | {phi}-bar {sub 0}|=1 Multiplication-Sign 10{sup -4}M{sub P} we find n{approx}0.92...0.94 while the prediction of the MSSM inflation without any corrections is n{approx}0.92.
Rapidly recomputable EEG forward models for realistic head shapes.
Ermer, J J; Mosher, J C; Baillet, S; Leah, R M
2001-04-01
With the increasing availability of surface extraction techniques for magnetic resonance and x-ray computed tomography images, realistic head models can be readily generated as forward models in the analysis of electroencephalography (EEG) and magnetoencephalography (MEG) data. Inverse analysis of this data, however, requires that the forward model be computationally efficient. We propose two methods for approximating the EEG forward model using realistic head shapes. The 'sensor-fitted sphere' approach fits a multilayer sphere individually to each sensor, and the 'three-dimensional interpolation' scheme interpolates using a grid on which a numerical boundary element method (BEM) solution has been precomputed. We have characterized the performance of each method in terms of magnitude and subspace error metrics, as well as computational and memory requirements. We have also made direct performance comparisons with traditional spherical models. The approximation provided by the interpolative scheme had an accuracy nearly identical to full BEM, even within 3 mm of the inner skull surface. Forward model computation during inverse procedures was approximately 30 times faster than for a traditional three-shell spherical model. Cast in this framework, high-fidelity numerical solutions currently viewed as computationally prohibitive for solving the inverse problem (e.g. linear Galerkin BEM) can be rapidly recomputed in a highly efficient manner. The sensor-fitting method has a similar one-time cost to the BEM method, and while it produces some improvement over a standard three-shell sphere, its performance does not approach that of the interpolation method. In both methods, there is a one-time cost associated with precomputing the forward solution over a set of grid points.
Electron percolation in realistic models of carbon nanotube networks
NASA Astrophysics Data System (ADS)
Simoneau, Louis-Philippe; Villeneuve, Jérémie; Rochefort, Alain
2015-09-01
The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models.
Electron percolation in realistic models of carbon nanotube networks
Simoneau, Louis-Philippe Villeneuve, Jérémie Rochefort, Alain
2015-09-28
The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models.
Modelling pulsar glitches with realistic pinning forces: a hydrodynamical approach
NASA Astrophysics Data System (ADS)
Haskell, B.; Pizzochero, P. M.; Sidery, T.
2012-02-01
Although pulsars are some of the most stable clocks in the Universe, many of them are observed to 'glitch', i.e. to suddenly increase their spin frequency ? with fractional increases that range from ? to ?. In this paper, we focus on the 'giant' glitches, i.e. glitches with fractional increases in the spin rate of the order of ?, that are observed in a subclass of pulsars including the Vela. We show that giant glitches can be modelled with a two-fluid hydrodynamical approach. The model is based on the formalism for superfluid neutron stars of Andersson & Comer and on the realistic pinning forces of Grill & Pizzochero. We show that all stages of Vela glitches, from the rise to the post-glitch relaxation, can be reproduced with a set of physically reasonable parameters and that the sizes and waiting times between giant glitches in other pulsars are also consistent with our model.
Modeling and Analysis of Realistic Fire Scenarios in Spacecraft
NASA Technical Reports Server (NTRS)
Brooker, J. E.; Dietrich, D. L.; Gokoglu, S. A.; Urban, D. L.; Ruff, G. A.
2015-01-01
An accidental fire inside a spacecraft is an unlikely, but very real emergency situation that can easily have dire consequences. While much has been learned over the past 25+ years of dedicated research on flame behavior in microgravity, a quantitative understanding of the initiation, spread, detection and extinguishment of a realistic fire aboard a spacecraft is lacking. Virtually all combustion experiments in microgravity have been small-scale, by necessity (hardware limitations in ground-based facilities and safety concerns in space-based facilities). Large-scale, realistic fire experiments are unlikely for the foreseeable future (unlike in terrestrial situations). Therefore, NASA will have to rely on scale modeling, extrapolation of small-scale experiments and detailed numerical modeling to provide the data necessary for vehicle and safety system design. This paper presents the results of parallel efforts to better model the initiation, spread, detection and extinguishment of fires aboard spacecraft. The first is a detailed numerical model using the freely available Fire Dynamics Simulator (FDS). FDS is a CFD code that numerically solves a large eddy simulation form of the Navier-Stokes equations. FDS provides a detailed treatment of the smoke and energy transport from a fire. The simulations provide a wealth of information, but are computationally intensive and not suitable for parametric studies where the detailed treatment of the mass and energy transport are unnecessary. The second path extends a model previously documented at ICES meetings that attempted to predict maximum survivable fires aboard space-craft. This one-dimensional model implies the heat and mass transfer as well as toxic species production from a fire. These simplifications result in a code that is faster and more suitable for parametric studies (having already been used to help in the hatch design of the Multi-Purpose Crew Vehicle, MPCV).
BPS states in N = 2 supersymmetric G2 and F4 models
NASA Astrophysics Data System (ADS)
Ahl Laamara, R.; Mellal, O.; Saidi, E. H.
2017-07-01
In BPS quiver theory of N = 2 supersymmetric pure gauge models with gauge invariance G, primitive BPS quivers Q0G are of two types: Q0ADE and Q0BCFG. In this study, we first show that Q0ADE have outer-automorphism symmetries inherited from the outer-automorphisms of the Dynkin diagrams of ADE Lie algebras. Then, we extend the usual folding operation of Dynkin diagrams ADE → BCFG to obtain the two following things: (i) relate Q0BCFG quivers and their mutations to the Q0ADE ones and their mutations; and (ii) link the BPS chambers of the N = 2ADE theories with the corresponding BCFG ones. As an illustration of this construction, we derive the BPS and anti-BPS states of the strong chambers QstgG2 and QstgF4 of the 4d N = 2 pure G2 and F4 gauge models.
Quark masses and mixing in a supersymmetric left-right model with singlet quark
NASA Astrophysics Data System (ADS)
Babu, K. S.; Roszkowski, L.
1989-04-01
Recently, del Aguila, Kane and Quirós (dAKQ) have proposed an ansatz for the structure of the quark mass matrices. They assume that the quark mass eigenstates coincide with the weak-interaction eigenstates in the absence of mixing of the down-type quarks with a new vector-like singlet quark. In this paper we present a supersymmetric model which provides a natural realization of this ansatz. The model, based on a left-right gauge group, does not require any horizontal symmetry and leads to quark mass matrices more restrictive than the dAKQ ansatz. The resulting phenomenology is also discussed. We obtain upper limits on the masses of the top quark and the singlet quark D: mtop < 46GeV whereas mD < 104GeV is favored, and therefore they both should be discovered at the Tevatron.
Naturalness and dark matter in the supersymmetric B -L extension of the standard model
NASA Astrophysics Data System (ADS)
Delle Rose, Luigi; Khalil, Shaaban; King, Simon J. D.; Marzo, Carlo; Moretti, Stefano; Un, Cem S.
2017-09-01
We study the naturalness properties of the B -L supersymmetric standard model (BLSSM) with type-I seesaw and compare them to those of the minimal supersymmetric standard model (MSSM) at both low (i.e., Large Hadron Collider) energies and high (i.e., unification) scales. By adopting standard measures of naturalness, we assess that, in the presence of full unification of the additional gauge couplings and scalar/fermionic masses of the BLSSM, such a scenario reveals a somewhat higher degree of fine-tuning (FT) than the MSSM, when the latter is computed at the unification scale and all available theoretical and experimental constraints, but the dark matter (DM) ones, are taken into account. Yet, such a difference, driven primarily by the collider limits requiring a high mass for the gauge boson associated to the breaking of the additional U (1 )B -L gauge group of the BLSSM in addition to the S U (3 )C×S U (2 )L×U (1 )Y of the MSSM, should be regarded as a modest price to pay for the former in relation to the latter, if one notices that the nonminimal scenario offers a significant volume of parameter space where numerous DM solutions of different compositions can be found to the relic density constraints, unlike the case of the minimal structure, wherein only one type of solution is accessible over an ever diminishing parameter space. In fact, this different level of tension within the two SUSY models in complying with current data is well revealed when the FT measure is recomputed in terms of the low-energy spectra of the two models, over their allowed regions of parameter space now in the presence of all DM bounds, as it is shown that the tendency is now opposite, with the BLSSM appearing more natural than the MSSM.
Realistic test cases for limited area ocean modelling
NASA Astrophysics Data System (ADS)
Herzfeld, M.; Schmidt, M.; Griffies, S. M.; Liang, Z.
The applicability of Modular Ocean Model version 4 (MOM4p1) as a code base to study regional physical oceanographic phenomena is presented, highlighting features recently implemented for use in limited area domains. Central to the successful operation of limited area model applications are the inclusion of a comprehensive suite of open boundary conditions, turbulence closure and vertical discretization. The open boundary problem, in particular, is considered and we present the open boundary condition implementation and performance in limited area model configurations corresponding to three realistic test cases. These tests represent typical configurations the physical oceanographer may encounter, and consist of (1) a coastal shelf model application where a two-tiered model configuration is used for down-scaling from a coarse grid model to supply sufficiently resolved boundary values for active cross-shelf open boundaries of a regional model; (2) tidal response of a gulf with one open boundary across the mouth of the gulf; (3) response of a coastal region to the passage of a tropical cyclone, where the open boundaries behave in primarily a passive capacity. Although the code base used in the test cases is MOM4p1, emphasis is placed on general features of the tests that are necessary for the scientific and operational use of any limited area model, hence key findings may be applied to limited area models in general.
Dynamic Modeling of EMIC Wave Activity in a Realistic Magnetosphere
NASA Astrophysics Data System (ADS)
McCollough, J. P., II; Elkington, S. R.; Usanova, M.; Bortnik, J.
2015-12-01
On 14-16 December 2006, A geomagnetic storm was observed accompanied by electromagnetic ion-cyclotron (EMIC) wave activity. We use a 3D test particle simulation in a realistic magnetosphere from the global Lyon-Fedder-Mobarry (LFM) MHD code to compute the phase space density dynamics of warm electrons responsible for chorus wave growth. We use these results to compute the temperature anisotropy and density for input into a linear convective wave growth rate for EMIC waves. We then follow Bortnik et al. [2010] to compute EMIC saturation amplitudes to provide a global dynamical picture of EMIC wave activity for this event. We will perform a data-model comparison of the modeled wave amplitudes with the observed wave activity, aiding in understanding the spatio-temporal and spectral response of EMIC wave activity to geomagnetic disturbances.
Modeling integrated sensor/actuator functions in realistic environments
NASA Astrophysics Data System (ADS)
Kim, Jae-Wan; Varadan, Vasundara V.; Varadan, Vijay K.
1993-07-01
Smart materials are expected to adapt to their environment and provide a useful response to changes in the environment. Both the sensor and actuator functions with the appropriate feedback mechanism must be integrated and comprise the `brains' of the material. Piezoelectric ceramics have proved to be effective as both sensors and actuators for a wide variety of applications. Thus, realistic simulation models are needed that can predict the performance of smart materials that incorporate piezoceramics. The environment may include the structure on which the transducers are mounted, fluid medium and material damping. In all cases, the smart material should sense the change and make a useful response. A hybrid numerical method involving finite element modeling in the plate structure and transducer region and a plane wave representation in the fluid region is used. The simulation of the performance of smart materials are performed.
Natural h{yields}4g in supersymmetric models and R-hadrons at the LHC
Luty, Markus A.; Phalen, Daniel J.; Pierce, Aaron
2011-04-01
We construct a simple and natural supersymmetric model where the dominant Higgs decay is h{yields}aa followed by a{yields}gg. In this case m{sub h}
MHD Modeling of the Transition Region Using Realistic Transport Coefficients
NASA Astrophysics Data System (ADS)
Goodman, Michael L.
1997-05-01
Most of the transition region (TR) consists of a collision dominated plasma. The dissipation and transport of energy in such a plasma is accurately described by the well known classical transport coefficients which include the electrical and thermal conductivity, viscosity, and thermo- electric tensors. These tensors are anisotropic and are functions of local values of temperature, density, and magnetic field. They may be used in an MHD model to obtain a self consistent, physically realistic description of the TR. The physics of kinetic processes is included in the MHD model through the transport coefficients. As a first step in studying heating and cooling processes in the TR in a realistic, quantitative manner, a 1.5 dimensional, steady state MHD model with a specified temperature profile is considered. The momentum equation includes the inertial, pressure gradient, Lorentz, and gravitational forces. The Ohm's law includes the exact expressions for the electrical conductivity and thermo- electric tensors. The electrical conductivity relates the generalized electric field to the conduction current density while the thermo-electric tensor relates the temperature gradient to the thermo-electric current density. The total current density is the sum of the two. It is found that the thermo-electric current density can be as large as the conduction current density, indicating that thermo-electric effects are probably important in modeling the dynamics of energy dissipation, such as wave dissipation, in the TR. Although the temperature gradient is in the vertical direction, the thermo-electric current density is in the horizontal direction, indicating the importance of the effects of anisotropic transport. The transport coefficients are valid for all magnetic field strengths, and so may be used to study the physics of weakly as well as strongly magnetized regions of the TR. Numerical examples are presented.
The B ‑ L supersymmetric standard model with inverse seesaw at the large hadron collider
NASA Astrophysics Data System (ADS)
Khalil, S.; Moretti, S.
2017-03-01
We review the TeV scale B ‑ L extension of the minimal supersymmetric standard model (BLSSM) where an inverse seesaw mechanism of light neutrino mass generation is naturally implemented and concentrate on its hallmark manifestations at the large hadron collider (LHC).
Schulze-Halberg, Axel E-mail: xbataxel@gmail.com; Wang, Jie
2015-07-15
We obtain series solutions, the discrete spectrum, and supersymmetric partners for a quantum double-oscillator system. Its potential features a superposition of the one-parameter Mathews-Lakshmanan interaction and a one-parameter harmonic or inverse harmonic oscillator contribution. Furthermore, our results are transferred to a generalized Pöschl-Teller model that is isospectral to the double-oscillator system.
Spontaneous breaking of R parity in the minimal supersymmetric standard model revisited
NASA Astrophysics Data System (ADS)
Comelli, D.; Masiero, A.; Pietroni, M.; Riotto, A.
1994-04-01
We reconsider the possibility of spontaneous breaking of R parity in the minimal supersymmetric standard model. By a renormalization group analysis we find the parameter space in which a sneutrino gets a vacuum expectation value, leading to the spontaneous breaking of the lepton number and to the appearance of a phenomenologically unacceptable massless Goldstone boson. We then analyze the effect of operators giving rise to a tiny amount of explicit violation of lepton number, which could emerge as remnants of physics at some superheavy (Planck or GUT) scale in the low energy effective theory. We show that the conspiracy between the spontaneous and the explicit breaking scales can provide a mass to the Goldstone boson larger than the Z0 boson mass, hence allowing for a non vanishing sneutrino vacuum expectation value without increasing the invisible width of the Z0.
Ma, J
2004-01-06
The authors searched for the light neutral scalar Higgs boson h{sup o} and the pseudoscalar Higgs boson A{sup o} of the Minimal Supersymmetric Extension of the Standard Model (MSSM) for the case tan {beta} < 1. The experiment was done with the SLD detector at the Stanford Linear Accelerator Center (SLAC). This analysis is based on the data set collected during the 1993 physics run which contained about 50,000 hadronic Z{sup o} events. After the event selection cuts for hadronic Z{sup 0} decays with CDC information, they select 27,560 events. The Monte Carlo (MC) simulated event distributions agree very well with the data. Good agreement is achieved between MC and the data on the number of events passing each of the event selection cuts.
Matrix models for supersymmetric Chern-Simons theories with an ADE classification
NASA Astrophysics Data System (ADS)
Gulotta, Daniel R.; Ang, J. P.; Herzog, Christopher P.
2012-01-01
We consider mathcal{N} = 3 supersymmetric Chern-Simons (CS) theories that contain product U(N ) gauge groups and bifundamental matter fields. Using the matrix model of Kapustin, Willett and Yaakov, we examine the Euclidean partition function of these theories on an S 3 in the large N limit. We show that the only such CS theories for which the long range forces between the eigenvalues cancel have quivers which are in one-to-one correspondence with the simply laced affine Dynkin diagrams. As the A n series was studied in detail before, in this paper we compute the partition function for the D 4 quiver. The D 4 example gives further evidence for a conjecture that the saddle point eigenvalue distribution is determined by the distribution of gauge invariant chiral operators. We also see that the partition function is invariant under a generalized Seiberg duality for CS theories.
The photino sector and a confining potential in a supersymmetric Lorentz-symmetry-violating model
NASA Astrophysics Data System (ADS)
Belich, H.; Bernald, L. D.; Gaete, Patricio; Helayël-Neto, J. A.
2013-11-01
We study the spectrum of the minimal supersymmetric extension of the Carroll-Field-Jackiw model for Electrodynamics with a topological Chern-Simons-like Lorentz-symmetry violating term. We identify a number of independent background fermion condensates, work out the gaugino dispersion relation and propose a photonic effective action to consider aspects of confinement induced by the SUSY background fermion condensates, which also appear to signal Lorentz-symmetry violation in the photino sector of the action. Our calculations of the static potential are carried out within the framework of the gauge-invariant but path-dependent variables formalism which are alternative to the Wilson loop approach. Our results show that the interaction energy contains a linear term leading to the confinement of static probe charges.
Area term of the entanglement entropy of a supersymmetric O (N ) vector model in three dimensions
NASA Astrophysics Data System (ADS)
Hung, Ling-Yan; Jiang, Yikun; Wang, Yixu
2017-04-01
We studied the leading area term of the entanglement entropy of the N =1 supersymmetric O (N ) vector model in 2 +1 dimensions close to the line of the second order phase transition in the large N limit. We found that the area term is independent of the varying interaction coupling along the critical line, unlike what is expected in a perturbative theory. Along the way, we studied noncommuting limits n -1 →0 vs UV cutoff r →0 when evaluating the gap equation and found a match only when the appropriate counterterm is introduced and the coupling of which is chosen to take its fixed point value. As a bonus, we also studied fermionic Green functions in the conical background. We made the observation of a map between the problem and the relativistic hydrogen atom.
Impact of future lepton flavor violation measurements in the minimal supersymmetric standard model
NASA Astrophysics Data System (ADS)
Ellis, Sebastian A. R.; Pierce, Aaron
2016-07-01
Working within the context of the minimal supersymmetric standard model, we compare current bounds from quark flavor changing processes with current and upcoming bounds on lepton flavor violation. We assume supersymmetry breaking approximately respects C P invariance. Under the further assumption that flavor violating insertions in the quark and lepton scalar masses are comparable, we explore when lepton flavor violation provides the strongest probe of new physics. We quote results both for spectra with all superpartners near the TeV scale and where scalars are multi-TeV. Constraints from quark flavor changing neutral currents are in many cases already stronger than those expected from future lepton flavor violation bounds, but large regions of parameter space remain where the latter could provide a discovery mode for supersymmetry.
Unsteady velocity measurements in a realistic intracranial aneurysm model
NASA Astrophysics Data System (ADS)
Ugron, Ádám; Farinas, Marie-Isabelle; Kiss, László; Paál, György
2012-01-01
The initiation, growth and rupture of intracranial aneurysms are intensively studied by computational fluid dynamics. To gain confidence in the results of numerical simulations, validation of the results is necessary. To this end the unsteady flow was measured in a silicone phantom of a realistic intracranial aneurysm. A flow circuit was built with a novel unsteady flow rate generating method, used to model the idealised shape of the heartbeat. This allowed the measurement of the complex three-dimensional velocity distribution by means of laser-optical methods such as laser doppler anemometry (LDA) and particle image velocimetry (PIV). The PIV measurements, available with high temporal and spatial distribution, were found to have good agreement with the control LDA measurements. Furthermore, excellent agreement was found with the numerical results.
Electron distribution in polar heterojunctions within a realistic model
NASA Astrophysics Data System (ADS)
Tien, Nguyen Thanh; Thao, Dinh Nhu; Thao, Pham Thi Bich; Quang, Doan Nhat
2015-12-01
We present a theoretical study of the electron distribution, i.e., two-dimensional electron gas (2DEG) in polar heterojunctions (HJs) within a realistic model. The 2DEG is confined along the growth direction by a triangular quantum well with a finite potential barrier and a bent band figured by all confinement sources. Therein, interface polarization charges take a double role: they induce a confining potential and, furthermore, they can make some change in other confinements, e.g., in the Hartree potential from ionized impurities and 2DEG. Confinement by positive interface polarization charges is necessary for the ground state of 2DEG existing at a high sheet density. The 2DEG bulk density is found to be increased in the barrier, so that the scattering occurring in this layer (from interface polarization charges and alloy disorder) becomes paramount in a polar modulation-doped HJ.
Air-Flow Simulation in Realistic Models of the Trachea
Deschamps, T; Schwartz, P; Trebotich, D
2004-12-09
In this article we present preliminary results from a new technique for flow simulation in realistic anatomical airways. The airways are extracted by means of Level-Sets methods that accurately model the complex and varying surfaces of anatomical objects. The surfaces obtained are defined at the sub-pixel level where they intersect the Cartesian grid of the image domain. It is therefore straightforward to construct embedded boundary representations of these objects on the same grid, for which recent work has enabled discretization of the Navier- Stokes equations for incompressible fluids. While most classical techniques require construction of a structured mesh that approximates the surface in order to extrapolate a 3D finite-element gridding of the whole volume, our method directly simulates the air-flow inside the extracted surface without losing any complicated details and without building additional grids.
RADAR realistic animal model series for dose assessment.
Keenan, Mary A; Stabin, Michael G; Segars, William P; Fernald, Michael J
2010-03-01
Rodent species are widely used in the testing and approval of new radiopharmaceuticals, necessitating murine phantom models. As more therapy applications are being tested in animal models, calculating accurate dose estimates for the animals themselves becomes important to explain and control potential radiation toxicity or treatment efficacy. Historically, stylized and mathematically based models have been used for establishing doses to small animals. Recently, a series of anatomically realistic human phantoms was developed using body models based on nonuniform rational B-spline. Realistic digital mouse whole-body (MOBY) and rat whole-body (ROBY) phantoms were developed on the basis of the same NURBS technology and were used in this study to facilitate dose calculations in various species of rodents. Voxel-based versions of scaled MOBY and ROBY models were used with the Vanderbilt multinode computing network (Advanced Computing Center for Research and Education), using geometry and tracking radiation transport codes to calculate specific absorbed fractions (SAFs) with internal photon and electron sources. Photon and electron SAFs were then calculated for relevant organs in all models. The SAF results were compared with values from similar studies found in reference literature. Also, the SAFs were used with standardized decay data to develop dose factors to be used in radiation dose calculations. Representative plots were made of photon electron SAFs, evaluating the traditional assumption that all electron energy is absorbed in the source organs. The organ masses in the MOBY and ROBY models are in reasonable agreement with models presented by other investigators noting that considerable variation can occur between reported masses. Results consistent with those found by other investigators show that absorbed fractions for electrons for organ self-irradiation were significantly less than 1.0 at energies above 0.5 MeV, as expected for many of these small-sized organs
Supersymmetric classical cosmology
Escamilla-Rivera, Celia; Obregón, Octavio; Ureña-López, L. Arturo E-mail: octavio@fisica.ugto.mx
2010-12-01
In this work a supersymmetric cosmological model is analyzed in which we consider a general superfield action of a homogeneous scalar field supermultiplet interacting with the scale factor in a supersymmetric FRW model. There appear fermionic superpartners associated with both the scale factor and the scalar field, and classical equations of motion are obtained from the super-Wheeler-DeWitt equation through the usual WKB method. The resulting supersymmetric Einstein-Klein-Gordon equations contain extra radiation and stiff matter terms, and we study their solutions in flat space for different scalar field potentials. The solutions are compared to the standard case, in particular those corresponding to the exponential potential, and their implications for the dynamics of the early Universe are discussed in turn.
Huh, Ji-Haeng; Kim, Jihn E.; Kyae, Bumseok
2009-03-15
We present a dark matter extension of the minimal supersymmetric standard model to give the recent trend of the high energy positron spectrum of the PAMELA/HEAT experiments. If the trend is caused indeed by dark matter, the minimal supersymmetric standard model needs to be extended. Here, we minimally extend the minimal supersymmetric standard model with one more dark matter component N together with a heavy lepton E and introduce the coupling e{sub R}E{sub R}{sup c}N{sub R}. This coupling naturally appears in the flipped SU(5) grand unification models. We also present the needed parameter ranges of these additional particles.
Higgs bosons in a minimal R-parity conserving left-right supersymmetric model
Frank, Mariana; Korutlu, Beste
2011-04-01
We revisit the Higgs sector of the left-right supersymmetric model. We study the scalar potential in a version of the model in which the minimum is the charge-conserving vacuum state, without R-parity violation or additional nonrenormalizable terms in the Lagrangian. We analyze the dependence of the potential and of the Higgs mass spectrum on the various parameters of the model, pinpointing the most sensitive ones. We also show that the model can predict light neutral flavor-conserving Higgs bosons, while the flavor-violating ones are heavy and within the limits from K{sup 0}-K{sup 0}, D{sup 0}-D{sup 0}, and B{sub d,s}{sup 0}-B{sub d,s}{sup 0} mixings. We study variants of the model in which at least one doubly charged Higgs boson is light and show that the parameter space for such Higgs masses and mixings is very restrictive, thus making the model more predictive.
Towards a realistic dielectric tissue model: a multiscale approach.
Huclova, Sonja; Fröhlich, Jürg
2010-01-01
In the past, mainly analytical mixing formulas were used for modeling of dielectric properties of biological cells. General drawbacks of such formulas are the restriction to simple shapes and small cellular volume fractions. Assuming cell suspensions or tissues being quasi-periodic the problem size can be reduced to a cubic unit cell containing a single biological cell. Under this assumption numerical, e.g. Finite- Element models of such unit cells provide effective dielectric parameters for the entire tissue or cell suspension. In this work a flexible shape parametrization method allowing for a realistic representation of biological cells is applied to eight different cell types. A non-axisymmetric columnar epithelium cell occurring e.g. in the epidermis is chosen as an example. Numerical simulations of the columnar cell exposed to a time-harmonic electric field are performed for two different, high volume fractions, followed by the extraction of effective dielectric parameters of the bulk material. The simulation results are compared to two analytical approximations for ellipsoidal particles. The results suggest, that the calculation of effective dielectric properties of arbitrarily shaped cells in the frequency range between 100kHz and 1GHz requires at least a numerical cell model.
Supersymmetric extensions of K field theories
NASA Astrophysics Data System (ADS)
Adam, C.; Queiruga, J. M.; Sanchez-Guillen, J.; Wereszczynski, A.
2012-02-01
We review the recently developed supersymmetric extensions of field theories with non-standard kinetic terms (so-called K field theories) in two an three dimensions. Further, we study the issue of topological defect formation in these supersymmetric theories. Specifically, we find supersymmetric K field theories which support topological kinks in 1+1 dimensions as well as supersymmetric extensions of the baby Skyrme model for arbitrary nonnegative potentials in 2+1 dimensions.
Dynamical coarse grained models with realistic time dependence
NASA Astrophysics Data System (ADS)
Andersen, Hans
2015-03-01
Coarse grained (CG) models of molecular systems, with fewer mechanical degrees of freedom than an all-atom model, are used extensively in chemical physics. It is generally accepted that a coarse grained model that accurately describes equilibrium structural properties (as a result of having a well constructed CG potential energy function) does not necessarily exhibit appropriate dynamical behavior when simulated using conservative Hamiltonian dynamics for the CG degrees of freedom on the CG potential energy surface. Attempts to develop accurate CG dynamic models usually focus on replacing Hamiltonian motion by stochastic but Markovian dynamics on that surface, such as Langevin or Brownian dynamics. However, depending on the nature of the system and the extent of the coarse graining, a Markovian dynamics for the CG degrees of freedom may not be appropriate. We consider the problem of constructing dynamic CG models within the context of the Multi-Scale Coarse Graining (MS-CG) method of Voth and coworkers. We propose a method of converting an MS-CG model into a dynamic CG model by adding degrees of freedom to it in the form of a small number of fictitious particles that interact with the CG degrees of freedom in simple ways and that are subject to Langevin forces. The dynamic models are members of a class of nonlinear systems interacting with special heat baths that was studied by Zwanzig [R. Zwanzig, J. Stat. Phys. 9, 215 (1973)]. The dynamic models generate a non-Markovian dynamics for the CG degrees of freedom, but they can be easily simulated using standard molecular dynamics simulation programs. We present tests of this method on a series of simple examples that demonstrate that the method provides realistic dynamical CG models that have non-Markovian or close to Markovian behavior that is consistent with the actual dynamical behavior of the all-atom system used to construct the CG model. The dynamic CG models have computational requirements that are similar to
Koehn, Michael; Trodden, Mark
2016-03-03
In supersymmetric theories, topological defects can have nontrivial behaviors determined purely by whether or not supersymmetry is restored in the defect core. A well-known example of this is that some supersymmetric cosmic strings are automatically superconducting, leading to important cosmological effects and constraints. We investigate the impact of nontrivial kinetic interactions, present in a number of particle physics models of interest in cosmology, on the relationship between supersymmetry and supercurrents on strings. Furthermore, we find that in some cases it is possible for superconductivity to be disrupted by the extra interactions.
NASA Astrophysics Data System (ADS)
Koehn, Michael; Trodden, Mark
2016-04-01
In supersymmetric theories, topological defects can have nontrivial behaviors determined purely by whether or not supersymmetry is restored in the defect core. A well-known example of this is that some supersymmetric cosmic strings are automatically superconducting, leading to important cosmological effects and constraints. We investigate the impact of nontrivial kinetic interactions, present in a number of particle physics models of interest in cosmology, on the relationship between supersymmetry and supercurrents on strings. We find that in some cases it is possible for superconductivity to be disrupted by the extra interactions.
Improved transcranial magnetic stimulation coil design with realistic head modeling
NASA Astrophysics Data System (ADS)
Crowther, Lawrence; Hadimani, Ravi; Jiles, David
2013-03-01
We are investigating Transcranial magnetic stimulation (TMS) as a noninvasive technique based on electromagnetic induction which causes stimulation of the neurons in the brain. TMS can be used as a pain-free alternative to conventional electroconvulsive therapy (ECT) which is still widely implemented for treatment of major depression. Development of improved TMS coils capable of stimulating subcortical regions could also allow TMS to replace invasive deep brain stimulation (DBS) which requires surgical implantation of electrodes in the brain. Our new designs allow new applications of the technique to be established for a variety of diagnostic and therapeutic applications of psychiatric disorders and neurological diseases. Calculation of the fields generated inside the head is vital for the use of this method for treatment. In prior work we have implemented a realistic head model, incorporating inhomogeneous tissue structures and electrical conductivities, allowing the site of neuronal activation to be accurately calculated. We will show how we utilize this model in the development of novel TMS coil designs to improve the depth of penetration and localization of stimulation produced by stimulator coils.
Supersymmetric model for dark matter and baryogenesis motivated by the recent CDMS result.
Allahverdi, Rouzbeh; Dutta, Bhaskar; Mohapatra, Rabindra N; Sinha, Kuver
2013-08-02
We discuss a supersymmetric model for cogenesis of dark and baryonic matter where the dark matter (DM) has mass in the 8-10 GeV range as indicated by several direct detection searches, including most recently the CDMS experiment with the desired cross section. The DM candidate is a real scalar field. Two key distinguishing features of the model are the following: (i) in contrast with the conventional weakly interacting massive particle dark matter scenarios where thermal freeze-out is responsible for the observed relic density, our model uses nonthermal production of dark matter after reheating of the Universe caused by moduli decay at temperatures below the QCD phase transition, a feature which alleviates the relic overabundance problem caused by small annihilation cross section of light DM particles and (ii) baryogenesis occurs also at similar low temperatures from the decay of TeV scale mediator particles arising from moduli decay. A possible test of this model is the existence of colored particles with TeV masses accessible at the LHC.
Renormalization group running of fermion observables in an extended non-supersymmetric SO(10) model
NASA Astrophysics Data System (ADS)
Meloni, Davide; Ohlsson, Tommy; Riad, Stella
2017-03-01
We investigate the renormalization group evolution of fermion masses, mixings and quartic scalar Higgs self-couplings in an extended non-supersymmetric SO(10) model, where the Higgs sector contains the 10 H, 120 H, and 126 H representations. The group SO(10) is spontaneously broken at the GUT scale to the Pati-Salam group and subsequently to the Standard Model (SM) at an intermediate scale M I. We explicitly take into account the effects of the change of gauge groups in the evolution. In particular, we derive the renormalization group equations for the different Yukawa couplings. We find that the computed physical fermion observables can be successfully matched to the experimental measured values at the electroweak scale. Using the same Yukawa couplings at the GUT scale, the measured values of the fermion observables cannot be reproduced with a SM-like evolution, leading to differences in the numerical values up to around 80%. Furthermore, a similar evolution can be performed for a minimal SO(10) model, where the Higgs sector consists of the 10 H and 126 H representations only, showing an equally good potential to describe the low-energy fermion observables. Finally, for both the extended and the minimal SO(10) models, we present predictions for the three Dirac and Majorana CP-violating phases as well as three effective neutrino mass parameters.
Development and validation of a realistic head model for EEG
NASA Astrophysics Data System (ADS)
Bangera, Nitin Bhalchandra
The utility of extracranial electrical or magnetic field recordings (EEG or MEG) is greatly enhanced if the generators of the bioelectromagnetic fields can be determined accurately from the measured fields. This procedure, known as the 'inverse method,' depends critically on calculations of the projection from generators in the brain to the EEG and MEG sensors. Improving and validating this calculation, known as the 'forward solution,' is the focus of this dissertation. The improvements involve more accurate modeling of the structures of the brain and thus understanding how current flows within the brain as a result of addition of structures in the forward model. Validation compares calculations using different forward models to the experimental results obtained by stimulating with implanted dipole electrodes. The human brain tissue displays inhomogeneity in electrical conductivity and also displays anisotropy, notably in the skull and brain white matter. In this dissertation, a realistic head model has been implemented using the finite element method to calculate the effects of inhomogeneity and anisotropy in the human brain. Accurate segmentation of the brain tissue type is implemented using a semi-automatic method to segment multimodal imaging data from multi-spectral MRI scans (different flip angles) in conjunction with the regular T1-weighted scans and computed x-ray tomography images. The electrical conductivity in the anisotropic white matter tissue is quantified from diffusion tensor MRI. The finite element model is constructed using AMIRA, a commercial segmentation and visualization tool and solved using ABAQUS, a commercial finite element solver. The model is validated using experimental data collected from intracranial stimulation in medically intractable epileptic patients. Depth electrodes are implanted in medically intractable epileptic patients in order to direct surgical therapy when the foci cannot be localized with the scalp EEG. These patients
Khoury, Justin; Lehners, Jean -Luc; Ovrut, Burt A.
2011-08-15
Galileon theories are of considerable interest since they allow for stable violations of the null energy condition. Since such violations could have occurred during a high-energy regime in the history of our universe, we are motivated to study supersymmetric extensions of these theories. This is carried out in this paper, where we construct generic classes of N = 1 supersymmetric Galileon Lagrangians. They are shown to admit non-equivalent stress-energy tensors and, hence, vacua manifesting differing conditions for violating the null energy condition. The temporal and spatial fluctuations of all component fields of the supermultiplet are analyzed and shown to bemore » stable on a large number of such backgrounds. In the process, we uncover a surprising connection between conformal Galileon and ghost condensate theories, allowing for a deeper understanding of both types of theories.« less
Khoury, Justin; Lehners, Jean -Luc
2011-08-15
Galileon theories are of considerable interest since they allow for stable violations of the null energy condition. Since such violations could have occurred during a high-energy regime in the history of our universe, we are motivated to study supersymmetric extensions of these theories. This is carried out in this paper, where we construct generic classes of N = 1 supersymmetric Galileon Lagrangians. They are shown to admit non-equivalent stress-energy tensors and, hence, vacua manifesting differing conditions for violating the null energy condition. The temporal and spatial fluctuations of all component fields of the supermultiplet are analyzed and shown to be stable on a large number of such backgrounds. In the process, we uncover a surprising connection between conformal Galileon and ghost condensate theories, allowing for a deeper understanding of both types of theories.
On the Bethe states of the one-dimensional supersymmetric t - J model with generic open boundaries
NASA Astrophysics Data System (ADS)
Sun, Pei; Wen, Fakai; Hao, Kun; Cao, Junpeng; Li, Guang-Liang; Yang, Tao; Yang, Wen-Li; Shi, Kangjie
2017-07-01
By combining the algebraic Bethe ansatz and the off-diagonal Bethe ansatz, we investigate the supersymmetric t - J model with generic open boundaries. The eigenvalues of the transfer matrix are given in terms of an inhomogeneous T - Q relation, and the corresponding eigenstates are expressed in terms of nested Bethe states which have welldefined homogeneous limit. This exact solution provides basis for further analyzing the thermodynamic properties and correlation functions of the model.
Large tensor spectrum of BICEP2 in the natural supersymmetric hybrid model
NASA Astrophysics Data System (ADS)
Choi, Ki-Young; Kyae, Bumseok
2014-07-01
The large tensor spectrum recently observed by the BICEP2 Collaboration requires a super-Planckian field variation of the inflaton in the single-field inflationary scenario. The required slow-roll parameter ɛ ≈0.01 would restrict the e-folding number to around 7 in (sub-)Planckian inflationary models. To overcome such problems, we consider a two-field scenario based on the natural assisted supersymmetric (SUSY) hybrid model {"natural SUSY hybrid inflation" [K.-Y. Choi and B. Kyae, Phys. Lett. B 706, 243 (2012)]}, which combines the SUSY hybrid and the natural inflation models. The axionic inflaton field from the natural inflation sector can admit the right values for the tensor spectrum as well as a spectral index of 0.96 with a decay constant smaller than the Planck scale, f ≲MP. On the other hand, the vacuum energy of 2×1016 GeV with 50 e-folds is provided by the inflaton coming from the SUSY hybrid sector, avoiding the eta problem. These are achieved by introducing both the U(1)R and a shift symmetry, and employing the minimal Kähler potential.
Ibrahim, Tarek; Nath, Pran
2010-09-01
The electric dipole moment (EDM) of the top quark is calculated in a model with a vector like multiplet which mixes with the third generation in an extension of the minimal supersymmetric standard model. Such mixings allow for new CP violating phases. Including these new CP phases, the EDM of the top in this class of models is computed. The top EDM arises from loops involving the exchange of the W, the Z as well as from the exchange involving the charginos, the neutralinos, the gluino, and the vector like multiplet and their superpartners. The analysis of the EDM of the top is more complicated than for the light quarks because the mass of the external fermion, in this case the top quark mass cannot be ignored relative to the masses inside the loops. A numerical analysis is presented and it is shown that the top EDM could be close to 10{sup -19} ecm consistent with the current limits on the EDM of the electron, the neutron and on atomic EDMs. A top EDM of size 10{sup -19} ecm could be accessible in collider experiments such as the International Linear Collider.
The ABCDEF's of matrix models for supersymmetric Chern-Simons theories
NASA Astrophysics Data System (ADS)
Gulotta, Daniel R.; Herzog, Christopher P.; Nishioka, Tatsuma
2012-04-01
We consider {N} = {3} supersymmetric Chern-Simons gauge theories with product unitary and orthosymplectic groups and bifundamental and fundamental fields. We study the partition functions on an S 3 by using the Kapustin-Willett-Yaakov matrix model. The saddlepoint equations in a large N limit lead to a constraint that the long range forces between the eigenvalues must cancel; the resulting quiver theories are of affine Dynkin type. We introduce a folding/unfolding trick which lets us, at the level of the large N matrix model, (i) map quivers with orthosymplectic groups to those with unitary groups, and (ii) obtain non-simply laced quivers from the corresponding simply laced quivers using a {{{Z}}_{{2}}} outer automorphism. The brane configurations of the quivers are described in string theory and the folding/unfolding is interpreted as the addition/subtraction of orientifold and orbifold planes. We also relate the U( N) quiver theories to the affine ADE quiver matrix models with a Stieltjes-Wigert type potential, and derive the generalized Seiberg duality in 2 + 1 dimensions from Seiberg duality in 3 + 1 dimensions.
Krishna, S.; Shukla, A.; Malik, R.P.
2014-12-15
Using the supersymmetric (SUSY) invariant restrictions on the (anti-)chiral supervariables, we derive the off-shell nilpotent symmetries of the general one (0+1)-dimensional N=2 SUSY quantum mechanical (QM) model which is considered on a (1, 2)-dimensional supermanifold (parametrized by a bosonic variable t and a pair of Grassmannian variables θ and θ-bar with θ{sup 2}=(θ-bar){sup 2}=0,θ(θ-bar)+(θ-bar)θ=0). We provide the geometrical meanings to the two SUSY transformations of our present theory which are valid for any arbitrary type of superpotential. We express the conserved charges and Lagrangian of the theory in terms of the supervariables (that are obtained after the application of SUSY invariant restrictions) and provide the geometrical interpretation for the nilpotency property and SUSY invariance of the Lagrangian for the general N=2 SUSY quantum theory. We also comment on the mathematical interpretation of the above symmetry transformations. - Highlights: • A novel method has been proposed for the derivation of N=2 SUSY transformations. • General N=2 SUSY quantum mechanical (QM) model with a general superpotential, is considered. • The above SUSY QM model is generalized onto a (1, 2)-dimensional supermanifold. • SUSY invariant restrictions are imposed on the (anti-)chiral supervariables. • Geometrical meaning of the nilpotency property is provided.
Inter-Hemispherical Currents for Realistic Model of Ionospheric Conductivity
NASA Astrophysics Data System (ADS)
Lyatsky, S.; Khazanov, G. V.
2013-12-01
We present results of modeling of the global 3-D ionosphere-magnetosphere current system including in addition to the R1 and R2 field-aligned currents also inter-hemispherical currents. The inter-hemispherical currents flow between Northern and Southern conjugate ionospheres in case of a North-South asymmetry in ionospheric conductivity in two hemispheres. These currents link together the ionospheric currents in two hemispheres, so the currents observed in one hemisphere can provide us with information about currents in the opposite hemisphere, which is especially important when their magnitude can not be obtained from direct observation (e.g., in Antarctica). In this study, we investigate the generation of the inter-hemispherical currents for several distributions of ionospheric conductivity in two hemispheres including a simplified model of ionospheric conductivity, which is important for better understanding of the expected distribution and magnitude of these currents, and a more realistic model of ionospheric conductivity, which is observed during magnetospheric substorms, when the geometry of the inter-hemispherical currents is more complicated. Simulation results show that the inter-hemispherical currents during substorms could play a very significant role, and neglecting these currents does not allow obtaining the correct picture of 3-D magnetosphere-ionosphere current system. These currents are an important part of 3-D field-aligned current system, and they are especially strong during summer-winter months, when they are comparable in magnitude with the R2 currents (about ~0.5 MA). Inter-hemispherical currents map. Left panel is related to Northern hemisphere, right panel to Southern. R1 and R2 currents are not shown; their locations are indicated by the red and blue dashed circles, respectively. The inter-hemispherical currents appear inside the auroral zone in the region of conductivity gradient. The currents in both hemispheres are equal in magnitude and
Yukawa unified supersymmetric SO(10) model: Cosmology, rare decays, and collider searches
NASA Astrophysics Data System (ADS)
Baer, Howard; Brhlik, Michal; Díaz, Marco A.; Ferrandis, Javier; Mercadante, Pedro; Quintana, Pamela; Tata, Xerxes
2001-01-01
It has recently been pointed out that viable sparticle mass spectra can be generated in Yukawa unified SO(10) supersymmetric grand unified models consistent with radiative breaking of electroweak symmetry. Model solutions are obtained only if tan β~50, μ<0 and positive D-term contributions to scalar masses from SO(10) gauge symmetry breaking are used. In this paper, we attempt to systematize the parameter space regions where solutions are obtained. We go on to calculate the relic density of neutralinos as a function of parameter space. No regions of the parameter space explored were actually cosmologically excluded, and very reasonable relic densities were found in much of parameter space. Direct neutralino detection rates could exceed 1 event/kg/day for a 73Ge detector, for low values of GUT scale gaugino mass m1/2. We also calculate the branching fraction for b-->sγ decays, and find that it is beyond the 95% C.L. experimental limits in much, but not all, of the parameter space regions explored. For the Fermilab Tevatron collider, significant regions of parameter space can be explored via bb¯A and bb¯H searches. There also exist some limited regions of parameter space where a trilepton signal can be seen at TeV33. Finally, there exist significant regions of parameter space where direct detection of bottom squark pair production can be made, especially for large negative values of the GUT parameter A0.
GUT-inspired supersymmetric model for h → γ γ and the muon g - 2
Ajaib, M. Adeel; Gogoladze, Ilia; Shafi, Qaisar
2015-05-06
We study a grand unified theories inspired supersymmetric model with nonuniversal gaugino masses that can explain the observed muon g-2 anomaly while simultaneously accommodating an enhancement or suppression in the h→γγ decay channel. In order to accommodate these observations and mh≅125 to 126 GeV, the model requires a spectrum consisting of relatively light sleptons whereas the colored sparticles are heavy. The predicted stau mass range corresponding to Rγγ≥1.1 is 100 GeV≲mτ˜≲200 GeV. The constraint on the slepton masses, particularly on the smuons, arising from considerations of muon g-2 is somewhat milder. The slepton masses in this case are predicted tomore » lie in the few hundred GeV range. The colored sparticles turn out to be considerably heavier with mg˜≳4.5 TeV and mt˜₁≳3.5 TeV, which makes it challenging for these to be observed at the 14 TeV LHC.« less
Source of Kerr-Newman solution as supersymmetric bag model: 50 years of the problem
NASA Astrophysics Data System (ADS)
Burinskii, A.
The ultra extreme Kerr-Newman (KN) solution(a = J/m >> m) produces the gravitational and EM fields of the electron. It has a naked singular ring - a topological defect which may be regularized by a solitonic source forming the pseudo-vacuum bubble filled by Higgs condensate in a supersymmetric superconducting state. Structure and stability of this source is determined by Bogomolnyi equations as a BPS-saturated soliton. The Principal Null Congruences of the KN solution determine consistent embedding of the Dirac equation, which acquires the mass from the Higgs condensate inside the soliton, indicating that this soliton forms a bag model. Shape of this bag is unambiguously determined by BPS-bound. The bag turns out to be flexible and takes the form of a very thin disk, which is completed by a ring-string along its sharp boundary. The ring-string traveling waves generate extra deformations of the bag creating a circulating singular pole. Bag model of the KN source integrates the dressed and pointlike electron in a bag-string-quark system, which removes the conflict between gravity and the point-like electron of the Dirac theory.
Realistic Models for Filling Factors in HII Regions
NASA Astrophysics Data System (ADS)
Spangler, Steven R.; Costa, Allison H.; Bergerud, Brandon M.; Beauchamp, Kara M.
2017-01-01
One of the parameters used to describe HII regions and other ionized parts of the interstellar medium is the filling factor, defined as the volume fraction of an HII region occupied by matter. The best observational evidence for the existence of a filling factor less than unity is a discrepancy between the electron density derived from density-sensitive line ratios and the root mean square density obtained from emission measure measurements. Following the early, influential study by Osterbrock and Flather (ApJ 129, 26, 1959), most investigations of HII regions envision these objects as a group of isolated cells of high gas density embedded in a vacuum. This picture is at serious odds with more direct measurements of other astrophysical plasmas like the solar wind, where the density follows a less extreme probability distribution function (pdf) such as an exponential or lognormal. We have carried out a set of simulations in which model HII regions are created with different density pdfs such as exponential and lognormal as well as the extreme case of two delta functions. We calculate the electron density as inferred from spectroscopic line ratios and emission measures for all lines of sight through the model nebulas. In the cases of exponential and lognormal pdfs, the spectroscopically derived densities are higher than those obtained by the emission measures by factors of 20 to 100 percent. These are considerably smaller than values often reported in the literature, which can be an order of magnitude or greater. We will discuss possible ways to reconcile realistic density pdfs such as measured in space and laboratory plasmas with the results from astronomical spectroscopic measurements. Finally, we point out that for the Orion Nebula, the density discrepancy is due to geometry, not filling factor (O'Dell, ARAA 39, 99, 2001).
A description of the Galactic Center excess in the Minimal Supersymmetric Standard Model
Achterberg, Abraham; Caron, Sascha; Hendriks, Luc; Amoroso, Simone; De Austri, Roberto Ruiz
2015-08-01
Observations with the Fermi Large Area Telescope (LAT) indicate an excess in gamma rays originating from the center of our Galaxy. A possible explanation for this excess is the annihilation of Dark Matter particles. We have investigated the annihilation of neutralinos as Dark Matter candidates within the phenomenological Minimal Supersymmetric Standard Model (pMSSM) . An iterative particle filter approach was used to search for solutions within the pMSSM . We found solutions that are consistent with astroparticle physics and collider experiments, and provide a fit to the energy spectrum of the excess. The neutralino is a Bino/Higgsino or Bino/Wino/Higgsino mixture with a mass in the range 84–92 GeV or 87–97 GeV annihilating into W bosons. A third solutions is found for a neutralino of mass 174–187 GeV annihilating into top quarks. The best solutions yield a Dark Matter relic density 0.06 < Ω h{sup 2} <0.13. These pMSSM solutions make clear forecasts for LHC, direct and indirect DM detection experiments. If the pMSSM explanation of the excess seen by Fermi-LAT is correct, a DM signal might be discovered soon.
Conformal invariance beyond the leading order in the supersymmetric nonlinear σ model with dilaton
NASA Astrophysics Data System (ADS)
Diamandis, G. A.; Georgalas, B. C.; Lahanas, A. B.
1990-12-01
We calculate the O(α'3) contributions to the renormalization-group β functions in the N=1 supersymmetric σ model with a dilaton. At this order both metric and dilaton β functions are found to depend nontrivially on the dilaton field and vanish if the dilaton satisfies ∇μ∇νφ=0. By employing the Curci-Paffuti relation it is shown that such dilaton backgrounds in Ricci-flat spaces Rμν=0 satisfy the conformal invariance conditions up to this order. The particular class of Ricci-flat, compact, and orientable manifolds naturally emerge as appropriate internal-space configurations consistent with local scale invariance. We further explore the cosmological consequences of these dilaton configurations. In a Robertson-Walker four-dimensional background we find all dilatons satisfying ∇μ∇νφ=0. Except for the constant and the time-dependent dilaton φ(t)=-2 lnt+λ whose cosmological implications have been already discussed in the literature, additional solutions are found. These may be of relevance beyond leading order and for nonvanishing background values for the antisymmetric tensor Bμν. For these solutions, also the cosmic scale factor is at most linear in time therefore giving rise to either a static or a linearly expanding (contracting) universe.
Supersymmetric moose models: An extra dimension from a broken deformed conformal field theory
Erlich, Joshua; Anly Tan, Jong
2006-09-15
We find a class of four dimensional deformed conformal field theories which appear extra dimensional when their gauge symmetries are spontaneously broken. The theories are supersymmetric moose models which flow to interacting conformal fixed points at low energies, deformed by superpotentials. Using a-maximization we give strong nonperturbative evidence that the hopping terms in the resulting latticized action are relevant deformations of the fixed-point theories. These theories have an intricate structure of RG flows between conformal fixed points. Our results suggest that at the stable fixed points each of the bulk gauge couplings and superpotential hopping terms is turned on, in favor of the extra-dimensional interpretation of the theory. However, we argue that the higher-dimensional gauge coupling is generically small compared to the size of the extra dimension. In the presence of a brane the topology of the extra dimension is determined dynamically and depends on the numbers of colors and bulk and brane flavors, which suggests phenomenological applications. The RG flows between fixed points in these theories provide a class of tests of Cardy's conjectured a-theorem.
Diamandis, G.A.; Georgalas, B.C.; Lahanas, A.B. )
1990-12-15
We calculate the {ital O}({alpha}{prime}{sup 3}) contributions to the renormalization-group {beta} functions in the {ital N}=1 supersymmetric {sigma} model with a dilaton. At this order both metric and dilaton {beta} functions are found to depend nontrivially on the dilaton field and vanish if the dilaton satisfies {del}{sub {mu}}{del}{sub {nu}}{phi}=0. By employing the Curci-Paffuti relation it is shown that such dilaton backgrounds in Ricci-flat spaces {ital R}{sub {mu}{nu}}=0 satisfy the conformal invariance conditions up to this order. The particular class of Ricci-flat, compact, and orientable manifolds naturally emerge as appropriate internal-space configurations consistent with local scale invariance. We further explore the cosmological consequences of these dilaton configurations. In a Robertson-Walker four-dimensional background we find all dilatons satisfying {del}{sub {mu}}{del}{sub {nu}}{phi}=0. Except for the constant and the time-dependent dilaton {phi}({ital t})={minus}2 ln{ital t}+{lambda} whose cosmological implications have been already discussed in the literature, additional solutions are found. These may be of relevance beyond leading order and for nonvanishing background values for the antisymmetric tensor {ital B}{sub {mu}{nu}}. For these solutions, also the cosmic scale factor is at most linear in time therefore giving rise to either a static or a linearly expanding (contracting) universe.
A description of the Galactic Center excess in the Minimal Supersymmetric Standard Model
Achterberg, Abraham; Amoroso, Simone; Caron, Sascha; Hendriks, Luc; Austri, Roberto Ruiz de
2015-08-03
Observations with the Fermi Large Area Telescope (LAT) indicate an excess in gamma rays originating from the center of our Galaxy. A possible explanation for this excess is the annihilation of Dark Matter particles. We have investigated the annihilation of neutralinos as Dark Matter candidates within the phenomenological Minimal Supersymmetric Standard Model (pMSSM). An iterative particle filter approach was used to search for solutions within the pMSSM. We found solutions that are consistent with astroparticle physics and collider experiments, and provide a fit to the energy spectrum of the excess. The neutralino is a Bino/Higgsino or Bino/Wino/Higgsino mixture with a mass in the range 84–92 GeV or 87–97 GeV annihilating into W bosons. A third solutions is found for a neutralino of mass 174–187 GeV annihilating into top quarks. The best solutions yield a Dark Matter relic density 0.06<Ωh{sup 2}<0.13. These pMSSM solutions make clear forecasts for LHC, direct and indirect DM detection experiments. If the pMSSM explanation of the excess seen by Fermi-LAT is correct, a DM signal might be discovered soon.
Supersymmetric Model of a Bose-Einstein Condensate in a 𝓟𝓣-Symmetric Double-delta Trap
NASA Astrophysics Data System (ADS)
Abt, Nikolas; Cartarius, Holger; Wunner, Günter
2015-11-01
The most important properties of a Bose-Einstein condensate subject to balanced gain and loss can be modelled by a Gross-Pitaevskii equation with an external 𝓟𝓣-symmetric double-delta potential. We study its linear variant with a supersymmetric extension. It is shown that both in the 𝓟𝓣-symmetric as well as in the 𝓟𝓣-broken phase arbitrary stationary states can be removed in a supersymmetric partner potential without changing the energy eigenvalues of the other state. The characteristic structure of the singular delta potential in the supersymmetry formalism is discussed, and the applicability of the formalism to the nonlinear Gross-Pitaevskii equation is analysed. In the latter case the formalism could be used to remove 𝓟𝓣-broken states introducing an instability to the stationary 𝓟𝓣-symmetric states.
Modeling Computer Communication Networks in a Realistic 3D Environment
2010-03-01
visualization in OPNET . . . . . . . . . . . . 13 6. Sample NetViz visualization . . . . . . . . . . . . . . . . . . . 15 7. Realistic 3D terrains...scenario in OPNET . . . 19 10. OPNET 3DNV only displays connectivity . . . . . . . . . . . . 29 11. The digitally connected battlefield...confirmation tool 12 OPNET Optimized Network Evaluation Tool . . . . . . . . . . . . 13 NetViz Network Visualization
Nearly Supersymmetric Dark Atoms
Behbahani, Siavosh R.; Jankowiak, Martin; Rube, Tomas; ...
2011-01-01
Theories of dark matter that support bound states are an intriguing possibility for the identity of the missing mass of the Universe. This article proposes a class of models of supersymmetric composite dark matter where the interactions with the Standard Model communicate supersymmetry breaking to the dark sector. In these models, supersymmetry breaking can be treated as a perturbation on the spectrum of bound states. Using a general formalism, the spectrum with leading supersymmetry effects is computed without specifying the details of the binding dynamics. The interactions of the composite states with the Standard Model are computed, and several benchmarkmore » models are described. General features of nonrelativistic supersymmetric bound states are emphasized.« less
Nearly Supersymmetric Dark Atoms
Behbahani, Siavosh R.; Jankowiak, Martin; Rube, Tomas; Wacker, Jay G.; /SLAC /Stanford U., ITP
2011-08-12
Theories of dark matter that support bound states are an intriguing possibility for the identity of the missing mass of the Universe. This article proposes a class of models of supersymmetric composite dark matter where the interactions with the Standard Model communicate supersymmetry breaking to the dark sector. In these models supersymmetry breaking can be treated as a perturbation on the spectrum of bound states. Using a general formalism, the spectrum with leading supersymmetry effects is computed without specifying the details of the binding dynamics. The interactions of the composite states with the Standard Model are computed and several benchmark models are described. General features of non-relativistic supersymmetric bound states are emphasized.
Weakly-interacting massive particles in non-supersymmetric SO(10) grand unified models
NASA Astrophysics Data System (ADS)
Nagata, Natsumi; Olive, Keith A.; Zheng, Jiaming
2015-10-01
Non-supersymmetric SO(10) grand unified theories provide a framework in which the stability of dark matter is explained while gauge coupling unification is realized. In this work, we systematically study this possibility by classifying weakly interacting dark matter candidates in terms of their quantum numbers of SU(2) L ⊗ U(1) Y , B - L, and SU(2) R . We consider both scalar and fermion candidates. We show that the requirement of a sufficiently high unification scale to ensure a proton lifetime compatible with experimental constraints plays a strong role in selecting viable candidates. Among the scalar candidates originating from either a 16 or 144 of SO(10), only SU(2) L singlets with zero hypercharge or doublets with Y = 1 /2 satisfy all constraints for SU(4) C ⊗ SU(2) L ⊗ SU(2) R and SU(3) C ⊗ SU(2) L ⊗ SU(2) R ⊗ U(1) B- L intermediate scale gauge groups. Among fermion triplets with zero hypercharge, only a triplet in the 45 with intermediate group SU(4) C ⊗ SU(2) L ⊗ SU(2) R leads to solutions with M GUT > M int and a long proton lifetime. We find three models with weak doublets and Y = 1 /2 as dark matter candidates for the SU(4) C ⊗ SU(2) L ⊗ SU(2) R and SU(4) C ⊗ SU(2) L ⊗ U(1) R intermediate scale gauge groups assuming a minimal Higgs content. We also discuss how these models may be tested at accelerators and in dark matter detection experiments.
Are supersymmetric models with minimal particle content under tension for testing at LHC?
NASA Astrophysics Data System (ADS)
Samanta, Abhijit; Mandal, Sujoy Kumar; Manna, Himadri
2016-12-01
In supersymmetric models with minimal particle content and without large left-right squarks mixing, the conventional knowledge is that the Higgs Boson mass around 125 GeV leads to top squark masses O (10) TeV, far beyond the reach of colliders. Here, we pointed out that this conclusion is subject to several theoretical uncertainties. We find that electroweak symmetry breaking and evaluation of Higgs mass at a scale far away from the true electroweak symmetry breaking scale introduce a large uncertainty in Higgs mass calculation. We show that the electroweak symmetry breaking at the scale near the true vacuum expectation value of Higgs field can increase the Higgs Boson mass about 4-5 GeV and can lower the bounds on squarks and slepton masses to 1 TeV. Here we pointed out that the Higgs mass even with inclusion of radiative corrections can vary with electroweak symmetry breaking scale. We calculate it at two loop level and show that it varies substantially. We argue that Higgs mass like other coupling parameters can vary with energy scale and the Higgs potential with all orders loop corrections is scale invariant. This uncertainty to the Higgs mass calculation due to electroweak symmetry breaking around the supersymmetry breaking scale, normally taken as √{mt˜Lmt˜R }, to minimize the 1-loop radiative corrections can be removed if one considers all significant radiative contributions to make Higgs potential renormalization group evolution scale invariant and evaluates electroweak symmetry breaking at the scale near the electroweak symmetry breaking scale. A large parameter space becomes allowed when one considers electroweak symmetry breaking at its true scale not only for producing correct values of the Higgs masses, but also for providing successful breaking of this symmetry in more parameter spaces.
Dynamics of supersymmetric chameleons
Brax, Philippe
2013-10-01
We investigate the cosmological dynamics of a class of supersymmetric chameleon models coupled to cold dark matter fermions. The model includes a cosmological constant in the form of a Fayet-Illiopoulos term, which emerges at late times due to the coupling of the chameleon to two charged scalars. Supergravity corrections ensure that the supersymmetric chameleons are efficiently screened in all astrophysical objects of interest, however this does not preclude the enhancement of gravity on linear cosmological scales. We solve the modified equations for the growth of cold dark matter density perturbations in closed form in the matter era. Using this, we go on to derive the modified linear power spectrum which is characterised by two scales, the horizon size at matter-radiation equality and at the redshift when the chameleon reaches the minimum of its effective potential. We analyse the deviations from the ΛCDM predictions in the linear regime. We find that there is generically a region in the model's parameter space where the model's background cosmology coincides with that of the ΛCDM model. Furthermore, we find that characteristic deviations from ΛCDM are present on the matter power spectrum providing a clear signature of supersymmetric chameleons.
A supersymmetric extension of quantum gauge theory
NASA Astrophysics Data System (ADS)
Grigore, D. R.; Scharf, G.
2003-01-01
We consider a supersymmetric extension of quantum gauge theory based on a vector multiplet containing supersymmetric partners of spin 3/2 for the vector fields. The constructions of the model follows closely the usual construction of gauge models in the Epstein-Glaser framework for perturbative field theory. Accordingly, all the arguments are completely of quantum nature without reference to a classical supersymmetric theory. As an application we consider the supersymmetric electroweak theory. The resulting self-couplings of the gauge bosons agree with the standard model up to a divergence.
Supersymmetric biorthogonal quantum systems
Curtright, Thomas; Mezincescu, Luca; Schuster, David
2007-09-15
We discuss supersymmetric biorthogonal systems, with emphasis given to the periodic solutions that occur at spectral singularities of PT symmetric models. For these periodic solutions, the dual functions are associated polynomials that obey inhomogeneous equations. We construct in detail some explicit examples for the supersymmetric pairs of potentials V{sub {+-}}(z)=-U(z){sup 2}{+-}z(d/dz)U(z) where U(z){identical_to}{sigma}{sub k>0}{upsilon}{sub k}z{sup k}. In particular, we consider the cases generated by U(z)=z and z/(1-z). We also briefly consider the effects of magnetic vector potentials on the partition functions of these systems.
NASA Astrophysics Data System (ADS)
Allanach, B. C.; Martin, Stephen P.; Robertson, David G.; Ruiz de Austri, Roberto
2017-10-01
We describe an extension of the SOFTSUSY spectrum calculator to include two-loop supersymmetric QCD (SUSYQCD) corrections of order O(αs2) to gluino and squark pole masses, either in the minimal supersymmetric standard model (MSSM) or the next-to-minimal supersymmetric standard model (NMSSM). This document provides an overview of the program and acts as a manual for the new version of SOFTSUSY, which includes the increase in accuracy in squark and gluino pole mass predictions.
The Collider Detector at Fermilab (CDF) is a Tevatron experiment at Fermilab. The Tevatron, a powerful particle accelerator, accelerates protons and antiprotons close to the speed of light, and then makes them collide head-on inside the CDF detector. The CDF detector is used to study the products of such collisions. The CDF Physics Group at Fermilab is organized into six working groups, each with a specific focus. The Higgs group searches for Standard Model and Supersymmetric Higgs bosons. Their public web page makes data and numerous figures available from both CDF Runs I and II.
Exact solution of the one-dimensional super-symmetric t-J model with unparallel boundary fields
NASA Astrophysics Data System (ADS)
Zhang, Xin; Cao, Junpeng; Yang, Wen-Li; Shi, Kangjie; Wang, Yupeng
2014-04-01
The exact solution of the one-dimensional super-symmetric t-J model under generic integrable boundary conditions is obtained via the Bethe ansatz methods. With the coordinate Bethe ansatz, the corresponding R-matrix and K-matrices are derived for the second eigenvalue problem associated with spin degrees of freedom. It is found that the second eigenvalue problem can be transformed into that of the transfer matrix of the inhomogeneous XXX spin chain, which allows us to obtain the spectrum of the Hamiltonian and the associated Bethe ansatz equations by the off-diagonal Bethe ansatz method.
Lorentz violation in supersymmetric field theories.
Nibbelink, Stefan Groot; Pospelov, Maxim
2005-03-04
We construct supersymmetric Lorentz violating operators for matter and gauge fields. We show that in the supersymmetric standard model the lowest possible dimension for such operators is five, and therefore they are suppressed by at least one power of an ultraviolet energy scale, providing a possible explanation for the smallness of Lorentz violation and its stability against radiative corrections. Supersymmetric Lorentz noninvariant operators do not lead to modifications of dispersion relations at high energies thereby escaping constraints from astrophysical searches for Lorentz violation.
Gauge unification in supersymmetric intersecting brane worlds
NASA Astrophysics Data System (ADS)
Blumenhagen, Ralph; Lüst, Dieter; Stieberger, Stephan
2003-07-01
We show that contrary to first expectations realistic three generation supersymmetric intersecting brane world models give rise to phenomenologically interesting predictions about gauge coupling unification. Assuming the most economical way of realizing the matter content of the MSSM via intersecting branes we obtain a model independent relation among the three gauge coupling constants at the string scale. In order to correctly reproduce the experimentally known values of sin2[thetaW(Mz)] and alphas(Mz) this relation leads to natural gauge coupling unification at a string scale close to the standard GUT scale 2 x 1016 GeV. Additional vector-like matter can push the unification scale up to the Planck scale.
Hahn, T; Heinemeyer, S; Hollik, W; Rzehak, H; Weiglein, G
2014-04-11
For the interpretation of the signal discovered in the Higgs searches at the LHC it will be crucial in particular to discriminate between the minimal Higgs sector realized in the standard model (SM) and its most commonly studied extension, the minimal supersymmetric standard model (MSSM). The measured mass value, having already reached the level of a precision observable with an experimental accuracy of about 500 MeV, plays an important role in this context. In the MSSM the mass of the light CP-even Higgs boson, Mh, can directly be predicted from the other parameters of the model. The accuracy of this prediction should at least match the one of the experimental result. The relatively high mass value of about 126 GeV has led to many investigations where the scalar top quarks are in the multi-TeV range. We improve the prediction for Mh in the MSSM by combining the existing fixed-order result, comprising the full one-loop and leading and subleading two-loop corrections, with a resummation of the leading and subleading logarithmic contributions from the scalar top sector to all orders. In this way for the first time a high-precision prediction for the mass of the light CP-even Higgs boson in the MSSM is possible all the way up to the multi-TeV region of the relevant supersymmetric particles. The results are included in the code FEYNHIGGS.
Fornengo, N.; Scopel, S.; Bottino, A.
2011-01-01
We examine the status of light neutralinos in an effective minimal supersymmetric extension of the standard model at the electroweak scale which was considered in the past and discussed in terms of the available data of direct searches for dark matter particles. Our reanalysis is prompted by new measurements at the Tevatron and B factories which might potentially provide significant constraints on the minimal supersymmetric extension of the standard model. Here we examine in detail all these new data and show that the present published results from the Tevatron and B factories have only a mild effect on the original light-neutralino population. This population, which fits quite well the DAMA/LIBRA annual modulation data, would also agree with the preliminary results of CDMS, CoGeNT, and CRESST, should these data, which are at present only hints of excesses of events over the expected backgrounds, be interpreted as authentic signals of dark matter. For the neutralino mass we find a lower bound of 7-8 GeV. Our results differ from some recent conclusions by other authors because of a few crucial points which we try to single out and elucidate.
Pomeron in the N=4 supersymmetric gauge model at strong couplings
NASA Astrophysics Data System (ADS)
Kotikov, A. V.; Lipatov, L. N.
2013-09-01
We find the BFKL Pomeron intercept at N=4 supersymmetric gauge theory in the form of the inverse coupling expansion j0=2-2λ-λ-1+1/4λ+2(1+3ζ3)λ-2+O(λ) with the use of the AdS/CFT correspondence in terms of string energies calculated recently. The corresponding slope γ‧(2) of the anomalous dimension calculated directly up to the fifth order of perturbation theory turns out to be in an agreement with the closed expression obtained from the recent Basso results.
Morrissey, David E.; Pierce, Aaron
2008-10-01
In the next-to-minimal supersymmetric standard model (NMSSM), the presence of light pseudoscalars can have a dramatic effect on the decays of the standard model-like Higgs boson. These pseudoscalars are naturally light if supersymmetry breaking preserves an approximate U(1){sub R} symmetry, spontaneously broken when the Higgs bosons take on their expectation values. We investigate two classes of theories that possess such an approximate U(1){sub R} at the mediation scale: modifications of gauge and gaugino mediation. In the models we consider, we find two disjoint classes of phenomenologically allowed parameter regions. One of these regions corresponds to a limit where the singlet of the NMSSM largely decouples. The other can give rise to a standard model-like Higgs boson with dominant branching into light pseudoscalars.
Comparison of realistic head modeling methods in EEG source imaging - biomed 2010.
Vatta, F; Meneghini, F; Esposito, F; Mininel, S; Disalle, F
2010-01-01
EEG inverse source imaging aims at reconstructing the underlying current distribution in the human brain using potential differences measured non-invasively from the head surface. A critical component of source reconstruction is the head volume conductor model used to reach an accurate solution of the associated forward problem, i.e., the simulation of the EEG for a known current source in the brain. The volume conductor model contains both the geometry and the electrical conduction properties of the head tissues and the accuracy of both parameters has direct impact on the accuracy of the source analysis. This was examined in detail with two different human head models. Two realistic head models derived from an averaged T1-weighted MRI dataset of the Montreal Neurological Institute (MNI) were used for this study. These models were: (1) BEM Model: a four-shell surface-based Boundary Elements (BEM) head model; (2) FDM Model: a volume-based Finite Difference (FDM) model, which allows better modeling accuracy than BEM as it better represents the cortical structures, such as, sulci and gyri in the brain in a three-dimensional head model. How model accuracy description influences the EEG source localizations was studied with the above realistic models of the head. We present here a detailed computer simulation study in which the performances of the two realistic four-shell head models are compared, the realistic MNI-based BEM Model and the FDM Model. As figures of merit for the comparative analysis, the point spread function (PSF) maps and the lead field (LF) correlation coefficients are used. The obtained results demonstrate that a better description of realistic geometry can provide a factor of improvement particularly important when considering sources placed in the temporal or in the occipital cortex. In these situations, using a more refined realistic head model will allow a better spatial discrimination of neural sources.
Harnik, Roni
2004-10-27
Supersymmetric models have traditionally been assumed to be perturbative up to high scales due to the requirement of calculable unification. In this note I review the recently proposed `Fat Higgs' model which relaxes the requirement of perturbativity. In this framework, an NMSSM-like trilinear coupling becomes strong at some intermediate scale. The NMSSM Higgses are meson composites of an asymptotically-free gauge theory. This allows us to raise the mass of the Higgs, thus alleviating the MSSM of its fine tuning problem. Despite the strong coupling at an intermediate scale, the UV completion allows us to maintain gauge coupling unification.
Constructing realistic Szekeres models from initial and final data
Walters, Anthony; Hellaby, Charles E-mail: charles.hellaby@uct.ac.za
2012-12-01
The Szekeres family of inhomogeneous solutions, which are defined by six arbitrary metric functions, offers a wide range of possibilities for modelling cosmic structure. Here we present a model construction procedure for the quasispherical case using given data at initial and final times. Of the six arbitrary metric functions, the three which are common to both Szekeres and Lemaître-Tolman models are determined by the model construction procedure of Krasinski and Hellaby. For the remaining three functions, which are unique to Szekeres models, we derive exact analytic expressions in terms of more physically intuitive quantities — density profiles and dipole orientation angles. Using MATLAB, we implement the model construction procedure and simulate the time evolution.
More-Realistic Digital Modeling of a Human Body
NASA Technical Reports Server (NTRS)
Rogge, Renee
2010-01-01
A MATLAB computer program has been written to enable improved (relative to an older program) modeling of a human body for purposes of designing space suits and other hardware with which an astronaut must interact. The older program implements a kinematic model based on traditional anthropometric measurements that do provide important volume and surface information. The present program generates a three-dimensional (3D) whole-body model from 3D body-scan data. The program utilizes thin-plate spline theory to reposition the model without need for additional scans.
A Simple, Realistic Stochastic Model of Gastric Emptying
Yokrattanasak, Jiraphat; De Gaetano, Andrea; Panunzi, Simona; Satiracoo, Pairote; Lawton, Wayne M.; Lenbury, Yongwimon
2016-01-01
Several models of Gastric Emptying (GE) have been employed in the past to represent the rate of delivery of stomach contents to the duodenum and jejunum. These models have all used a deterministic form (algebraic equations or ordinary differential equations), considering GE as a continuous, smooth process in time. However, GE is known to occur as a sequence of spurts, irregular both in size and in timing. Hence, we formulate a simple stochastic process model, able to represent the irregular decrements of gastric contents after a meal. The model is calibrated on existing literature data and provides consistent predictions of the observed variability in the emptying trajectories. This approach may be useful in metabolic modeling, since it describes well and explains the apparently heterogeneous GE experimental results in situations where common gastric mechanics across subjects would be expected. PMID:27057750
A Simple, Realistic Stochastic Model of Gastric Emptying.
Yokrattanasak, Jiraphat; De Gaetano, Andrea; Panunzi, Simona; Satiracoo, Pairote; Lawton, Wayne M; Lenbury, Yongwimon
2016-01-01
Several models of Gastric Emptying (GE) have been employed in the past to represent the rate of delivery of stomach contents to the duodenum and jejunum. These models have all used a deterministic form (algebraic equations or ordinary differential equations), considering GE as a continuous, smooth process in time. However, GE is known to occur as a sequence of spurts, irregular both in size and in timing. Hence, we formulate a simple stochastic process model, able to represent the irregular decrements of gastric contents after a meal. The model is calibrated on existing literature data and provides consistent predictions of the observed variability in the emptying trajectories. This approach may be useful in metabolic modeling, since it describes well and explains the apparently heterogeneous GE experimental results in situations where common gastric mechanics across subjects would be expected.
Enhancement of Br ( B d → μ + μ - ) / Br ( B s → μ + μ - ) in supersymmetric unified models
Dutta, Bhaskar; Mimura, Yukihiro
2015-05-14
We explain the 2.3σ deviation in the recent measurements of the neutral B meson decays into muon pairs from the standard model prediction in the framework of supersymmetric grand unified models using antisymmetric coupling as a new source of flavor violation. We show a correlation between the Bd→μ⁺μ⁻ decay and the CP phase in the Bd→J/ψK decay and that their deviations from the standard model predictions can be explained after satisfying constraints arising from various hadronic and leptonic rare decay processes, B-B¯, K-K¯ oscillation data, and electric dipole moments of electron and neutron. The allowed parameter space is typically representedmore » by pseudoscalar Higgs mass mA≤1 TeV and tanβH(≡vu/vd)≲20 for squark and gluino masses around 2 TeV.« less
A realistic dynamic blower energy consumption model for wastewater applications.
Amerlinck, Y; De Keyser, W; Urchegui, G; Nopens, I
2016-10-01
At wastewater treatment plants (WWTPs) aeration is the largest energy consumer. This high energy consumption requires an accurate assessment in view of plant optimization. Despite the ever increasing detail in process models, models for energy production still lack detail to enable a global optimization of WWTPs. A new dynamic model for a more accurate prediction of aeration energy costs in activated sludge systems, equipped with submerged air distributing diffusers (producing coarse or fine bubbles) connected via piping to blowers, has been developed and demonstrated. This paper addresses the model structure, its calibration and application to the WWTP of Mekolalde (Spain). The new model proved to give an accurate prediction of the real energy consumption by the blowers and captures the trends better than the constant average power consumption models currently being used. This enhanced prediction of energy peak demand, which dominates the price setting of energy, illustrates that the dynamic model is preferably used in multi-criteria optimization exercises for minimizing the energy consumption.
Towards realistic standard model from D-brane configurations
Leontaris, G. K.; Tracas, N. D.; Korakianitis, O.; Vlachos, N. D.
2007-12-01
Effective low energy models arising in the context of D-brane configurations with standard model (SM) gauge symmetry extended by several gauged Abelian factors are discussed. The models are classified according to their hypercharge embeddings consistent with the SM spectrum hypercharge assignment. Particular cases are analyzed according to their perspectives and viability as low energy effective field theory candidates. The resulting string scale is determined by means of a two-loop renormalization group calculation. Their implications in Yukawa couplings, neutrinos and flavor changing processes are also presented.
Constraints on realistic Gauge-Higgs unified models
Aranda, Alfredo; Wudka, Jose
2010-11-01
We investigate the general group structure of gauge-Higgs unified models. We find that a given embedding of the standard model gauge group will imply the presence of additional light vectors, except for a small set of special cases, which we determine; the arguments presented are independent of the compactification scheme. For this set of models we then find those that can both accommodate quarks and have a vanishing oblique T parameter at tree level. We show that none of the resulting models can have |s{sub w}|{approx}1/2 (the sine of the weak-mixing angle) at tree level and briefly discuss possible solutions to this problem.
Emergence of Supersymmetric Quantum Electrodynamics.
Jian, Shao-Kai; Lin, Chien-Hung; Maciejko, Joseph; Yao, Hong
2017-04-21
Supersymmetric (SUSY) gauge theories such as the minimal supersymmetric standard model play a fundamental role in modern particle physics, but have not been verified so far in nature. Here, we show that a SUSY gauge theory with dynamical gauge bosons and fermionic gauginos emerges naturally at the pair-density-wave (PDW) quantum phase transition on the surface of a correlated topological insulator hosting three Dirac cones, such as the topological Kondo insulator SmB_{6}. At the quantum tricritical point between the surface Dirac semimetal and nematic PDW phases, three massless bosonic Cooper pair fields emerge as the superpartners of three massless surface Dirac fermions. The resulting low-energy effective theory is the supersymmetric XYZ model, which is dual by mirror symmetry to N=2 supersymmetric quantum electrodynamics in 2+1 dimensions, providing a first example of emergent supersymmetric gauge theory in condensed matter systems. Supersymmetry allows us to determine certain critical exponents and the optical conductivity of the surface states at the strongly coupled tricritical point exactly, which may be measured in future experiments.
Emergence of Supersymmetric Quantum Electrodynamics
NASA Astrophysics Data System (ADS)
Jian, Shao-Kai; Lin, Chien-Hung; Maciejko, Joseph; Yao, Hong
2017-04-01
Supersymmetric (SUSY) gauge theories such as the minimal supersymmetric standard model play a fundamental role in modern particle physics, but have not been verified so far in nature. Here, we show that a SUSY gauge theory with dynamical gauge bosons and fermionic gauginos emerges naturally at the pair-density-wave (PDW) quantum phase transition on the surface of a correlated topological insulator hosting three Dirac cones, such as the topological Kondo insulator SmB6 . At the quantum tricritical point between the surface Dirac semimetal and nematic PDW phases, three massless bosonic Cooper pair fields emerge as the superpartners of three massless surface Dirac fermions. The resulting low-energy effective theory is the supersymmetric X Y Z model, which is dual by mirror symmetry to N =2 supersymmetric quantum electrodynamics in 2 +1 dimensions, providing a first example of emergent supersymmetric gauge theory in condensed matter systems. Supersymmetry allows us to determine certain critical exponents and the optical conductivity of the surface states at the strongly coupled tricritical point exactly, which may be measured in future experiments.
Multi-dimensional Modeling of Nova with Realistic Nuclear Physics
Krueger, B.; Zingale, M.; Hoffman, R.
2011-10-10
Over the past year, we continued our exploration of novae explosions through multidimensional simulations with the MAESTRO code. The basic physics needed for these simulations was already in place, but a lot of optimization and refining was needed to produce plausible models. Work focused both on the initial model and the reaction network, and simulations were performed using an NSF TeraGrid allocation on the Kraken machine.
Towards a more realistic biomechanical modelling of breast malignant tumours.
Wessel, Carolina; Schnabel, Julia A; Brady, Michael
2012-02-07
We develop a biomechanical model of an isolated stellate breast tumour under mammographic compression forces for a range of reported mechanical properties, both linear elastic and hyperelastic. We also introduce different volumes of increased density/stiffness around the tumour as well as a solid pressure effect. We show that each of these issues--well known to clinicians but ignored to date in models--has a non-negligible effect on stresses and strains/deformations.
Cirrus cloud model parameterizations: Incorporating realistic ice particle generation
NASA Technical Reports Server (NTRS)
Sassen, Kenneth; Dodd, G. C.; Starr, David OC.
1990-01-01
Recent cirrus cloud modeling studies have involved the application of a time-dependent, two dimensional Eulerian model, with generalized cloud microphysical parameterizations drawn from experimental findings. For computing the ice versus vapor phase changes, the ice mass content is linked to the maintenance of a relative humidity with respect to ice (RHI) of 105 percent; ice growth occurs both with regard to the introduction of new particles and the growth of existing particles. In a simplified cloud model designed to investigate the basic role of various physical processes in the growth and maintenance of cirrus clouds, these parametric relations are justifiable. In comparison, the one dimensional cloud microphysical model recently applied to evaluating the nucleation and growth of ice crystals in cirrus clouds explicitly treated populations of haze and cloud droplets, and ice crystals. Although these two modeling approaches are clearly incompatible, the goal of the present numerical study is to develop a parametric treatment of new ice particle generation, on the basis of detailed microphysical model findings, for incorporation into improved cirrus growth models. For example, the relation between temperature and the relative humidity required to generate ice crystals from ammonium sulfate haze droplets, whose probability of freezing through the homogeneous nucleation mode are a combined function of time and droplet molality, volume, and temperature. As an example of this approach, the results of cloud microphysical simulations are presented showing the rather narrow domain in the temperature/humidity field where new ice crystals can be generated. The microphysical simulations point out the need for detailed CCN studies at cirrus altitudes and haze droplet measurements within cirrus clouds, but also suggest that a relatively simple treatment of ice particle generation, which includes cloud chemistry, can be incorporated into cirrus cloud growth.
Model of Ni-63 battery with realistic PIN structure
Munson, Charles E.; Voss, Paul L.; Ougazzaden, Abdallah; Arif, Muhammad; Salvestrini, Jean-Paul; Streque, Jeremy; El Gmili, Youssef; Belahsene, Sofiane; Martinez, Anthony; Ramdane, Abderrahim
2015-09-14
GaN, with its wide bandgap of 3.4 eV, has emerged as an efficient material for designing high-efficiency betavoltaic batteries. An important part of designing efficient betavoltaic batteries involves a good understanding of the full process, from the behavior of the nuclear material and the creation of electron-hole pairs all the way through the collection of photo-generated carriers. This paper presents a detailed model based on Monte Carlo and Silvaco for a GaN-based betavoltaic battery device, modeled after Ni-63 as an energy source. The accuracy of the model is verified by comparing it with experimental values obtained for a GaN-based p-i-n structure under scanning electron microscope illumination.
Model of Ni-63 battery with realistic PIN structure
NASA Astrophysics Data System (ADS)
Munson, Charles E.; Arif, Muhammad; Streque, Jeremy; Belahsene, Sofiane; Martinez, Anthony; Ramdane, Abderrahim; El Gmili, Youssef; Salvestrini, Jean-Paul; Voss, Paul L.; Ougazzaden, Abdallah
2015-09-01
GaN, with its wide bandgap of 3.4 eV, has emerged as an efficient material for designing high-efficiency betavoltaic batteries. An important part of designing efficient betavoltaic batteries involves a good understanding of the full process, from the behavior of the nuclear material and the creation of electron-hole pairs all the way through the collection of photo-generated carriers. This paper presents a detailed model based on Monte Carlo and Silvaco for a GaN-based betavoltaic battery device, modeled after Ni-63 as an energy source. The accuracy of the model is verified by comparing it with experimental values obtained for a GaN-based p-i-n structure under scanning electron microscope illumination.
Reaction Diffusion Modeling of Calcium Dynamics with Realistic ER Geometry
Means, Shawn; Smith, Alexander J.; Shepherd, Jason; Shadid, John; Fowler, John; Wojcikiewicz, Richard J. H.; Mazel, Tomas; Smith, Gregory D.; Wilson, Bridget S.
2006-01-01
We describe a finite-element model of mast cell calcium dynamics that incorporates the endoplasmic reticulum's complex geometry. The model is built upon a three-dimensional reconstruction of the endoplasmic reticulum (ER) from an electron tomographic tilt series. Tetrahedral meshes provide volumetric representations of the ER lumen, ER membrane, cytoplasm, and plasma membrane. The reaction-diffusion model simultaneously tracks changes in cytoplasmic and ER intraluminal calcium concentrations and includes luminal and cytoplasmic protein buffers. Transport fluxes via PMCA, SERCA, ER leakage, and Type II IP3 receptors are also represented. Unique features of the model include stochastic behavior of IP3 receptor calcium channels and comparisons of channel open times when diffusely distributed or aggregated in clusters on the ER surface. Simulations show that IP3R channels in close proximity modulate activity of their neighbors through local Ca2+ feedback effects. Cytoplasmic calcium levels rise higher, and ER luminal calcium concentrations drop lower, after IP3-mediated release from receptors in the diffuse configuration. Simulation results also suggest that the buffering capacity of the ER, and not restricted diffusion, is the predominant factor influencing average luminal calcium concentrations. PMID:16617072
Fast, Automated, Photo realistic, 3D Modeling of Building Interiors
2016-09-12
important for applications in augmented and virtual reality , indoor navigation, and building simulation software. This paper presents a method to...navigation, augmented and virtual reality , as well as building energy simulation software. These applications require watertight models with limited...preservation, entertainment, and augmented reality , the demand for both fast and accurate scanning technologies has dramatically increased. In this
Stochastic fire-diffuse-fire model with realistic cluster dynamics
NASA Astrophysics Data System (ADS)
Calabrese, Ana; Fraiman, Daniel; Zysman, Daniel; Ponce Dawson, Silvina
2010-09-01
Living organisms use waves that propagate through excitable media to transport information. Ca2+ waves are a paradigmatic example of this type of processes. A large hierarchy of Ca2+ signals that range from localized release events to global waves has been observed in Xenopus laevis oocytes. In these cells, Ca2+ release occurs trough inositol 1,4,5-trisphosphate receptors (IP3Rs) which are organized in clusters of channels located on the membrane of the endoplasmic reticulum. In this article we construct a stochastic model for a cluster of IP3R ’s that replicates the experimental observations reported in [D. Fraiman , Biophys. J. 90, 3897 (2006)10.1529/biophysj.105.075911]. We then couple this phenomenological cluster model with a reaction-diffusion equation, so as to have a discrete stochastic model for calcium dynamics. The model we propose describes the transition regimes between isolated release and steadily propagating waves as the IP3 concentration is increased.
Core polarization and modern realistic shell-model Hamiltonians
NASA Astrophysics Data System (ADS)
Coraggio, L.; Covello, A.; Gargano, A.; Itaco, N.
The understanding of the convergence properties of the shell-model effective Hamiltonian, within the framework of the many-body perturbation theory, is a long-standing problem. The infinite summation of a certain class of diagrams, the so-called "bubble diagrams," may be provided calculating the Kirson-Babu-Brown induced interaction, and provides a valid instrument to study whether or not the finite summation of the perturbative series is well-grounded. Here, we perform an application of the calculation of the Kirson-Babu-Brown induced interaction to derive the shell-model effective Hamiltonian for p-shell nuclei starting from a modern nucleon-nucleon potential, obtained by way of the chiral perturbation theory. The outcome of our calculation is compared with a standard calculation of the shell-model Hamiltonian, where the core-polarization effects are calculated only up to third-order in perturbation theory. The results of the two calculations are very close to each other, evidencing that the perturbative approach to the derivation of the shell-model Hamiltonian is still a valid tool for nuclear structure studies.
Core polarization and modern realistic shell-model Hamiltonians
NASA Astrophysics Data System (ADS)
Coraggio, L.; Covello, A.; Gargano, A.; Itaco, N.
The understanding of the convergence properties of the shell-model effective Hamiltonian, within the framework of the many-body perturbation theory, is a long-standing problem. The infinite summation of a certain class of diagrams, the so-called “bubble diagrams,” may be provided calculating the Kirson-Babu-Brown induced interaction, and provides a valid instrument to study whether or not the finite summation of the perturbative series is well-grounded. Here, we perform an application of the calculation of the Kirson-Babu-Brown induced interaction to derive the shell-model effective Hamiltonian for p-shell nuclei starting from a modern nucleon-nucleon potential, obtained by way of the chiral perturbation theory. The outcome of our calculation is compared with a standard calculation of the shell-model Hamiltonian, where the core-polarization effects are calculated only up to third-order in perturbation theory. The results of the two calculations are very close to each other, evidencing that the perturbative approach to the derivation of the shell-model Hamiltonian is still a valid tool for nuclear structure studies.
Realistic thermal evolution models for Superearth Exo-solar planets
NASA Astrophysics Data System (ADS)
van den Berg, A.; Yuen, D.; Umemoto, K.; Wentzcovitch, R.; Jacobs, M.
2012-04-01
Massive superearth exoplanets in the range of one to ten times the Earth's mass have a much extended pressure regime compared to Earth, up to about 1 TPa, that may give rise to different material behavior. This has an impact on planetary evolution, and the evolution of a magnetic field and planetary atmosphere, and is therefore also relevant for habitability conditions. The material properties concerned include the mantle rheology where pressure affects both deep mantle viscosity and the brittle-ductile transition, both with a direct impact on lithosphere dynamics and the heat transport capacity of superearth mantle convection. Besides rheological considirations, other material properties also show strong variation with both pressure and temperature, in particular thermal expansivity and thermal conductivity. At ultra-high pressure they will exert a strong impact on the effectiveness of convective heat transport. The commonly used (extended) Boussinesq (EBA) convection model is not well suited for the pressure regime of superearth exoplanets becuase of the high value of the surface dissipation number involved, typically Di ~ 5 (van den Berg et al., Phys. Earth Planet. Inter.,178, 136-154). We therefore use a compressible convection model based on the anelastic liquid approximation and apply a selfconsistent model for the thermophysical properties based on ab-initio and lattice dynamics for relevant mantle silicates, perovskite, post-perovskite and periclase (Umemoto et al., Science,311, 983-986, 2006; Jacobs and van den Berg, Phys., Earth Planet. Inter.,186, 36-48, 2011). In particular our model includes, in a selfconsistent way, the significant temperature dependence of thermal expansivity, important in controlling the dynamics of cold downwellings in the upper mantle. We present results of convection modelling experiments exploring the forementioned model sensitivities on mantle heat transport both in transient cooling models and expressed in terms of Nusselt
Anisotropic, nonsingular early universe model leading to a realistic cosmology
Dechant, Pierre-Philippe; Lasenby, Anthony N.; Hobson, Michael P.
2009-02-15
We present a novel cosmological model in which scalar field matter in a biaxial Bianchi IX geometry leads to a nonsingular 'pancaking' solution: the hypersurface volume goes to zero instantaneously at the 'big bang', but all physical quantities, such as curvature invariants and the matter energy density remain finite, and continue smoothly through the big bang. We demonstrate that there exist geodesics extending through the big bang, but that there are also incomplete geodesics that spiral infinitely around a topologically closed spatial dimension at the big bang, rendering it, at worst, a quasiregular singularity. The model is thus reminiscent of the Taub-NUT vacuum solution in that it has biaxial Bianchi IX geometry and its evolution exhibits a dimensionality reduction at a quasiregular singularity; the two models are, however, rather different, as we will show in a future work. Here we concentrate on the cosmological implications of our model and show how the scalar field drives both isotropization and inflation, thus raising the question of whether structure on the largest scales was laid down at a time when the universe was still oblate (as also suggested by [T. S. Pereira, C. Pitrou, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 9 (2007) 6.][C. Pitrou, T. S. Pereira, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 4 (2008) 4.][A. Guemruekcueoglu, C. Contaldi, and M. Peloso, J. Cosmol. Astropart. Phys. 11 (2007) 005.]). We also discuss the stability of our model to small perturbations around biaxiality and draw an analogy with cosmological perturbations. We conclude by presenting a separate, bouncing solution, which generalizes the known bouncing solution in closed FRW universes.
Midisuperspace supersymmetric quantum cosmology
Macias, Alfredo; Camacho, Abel; Kunz, Jutta; Laemmerzahl, Claus
2008-03-15
We investigate the canonical quantization in the framework of N=1 simple supergravity for the case of a very simple gravitational midisuperspace described by Gowdy T{sup 3} cosmological models. We consider supersymmetric quantum cosmology in the mentioned midisuperspace, where a matrix representation for the gravitino covector-spinor is used. The full Lorentz constraint and its implications for the wave function of the Universe are analyzed in detail. We found that there are indeed physical states in the midisuperspace sector of the theory in contrast to the case of minisuperspace where there exist no physical states.
Coarse-grained theory of a realistic tetrahedral liquid model
NASA Astrophysics Data System (ADS)
Procaccia, I.; Regev, I.
2012-02-01
Tetrahedral liquids such as water and silica-melt show unusual thermodynamic behavior such as a density maximum and an increase in specific heat when cooled to low temperatures. Previous work had shown that Monte Carlo and mean-field solutions of a lattice model can exhibit these anomalous properties with or without a phase transition, depending on the values of the different terms in the Hamiltonian. Here we use a somewhat different approach, where we start from a very popular empirical model of tetrahedral liquids —the Stillinger-Weber model— and construct a coarse-grained theory which directly quantifies the local structure of the liquid as a function of volume and temperature. We compare the theory to molecular-dynamics simulations and show that the theory can rationalize the simulation results and the anomalous behavior.
A new model for realistic random perturbations of stochastic oscillators
NASA Astrophysics Data System (ADS)
Dieci, Luca; Li, Wuchen; Zhou, Haomin
2016-08-01
Classical theories predict that solutions of differential equations will leave any neighborhood of a stable limit cycle, if white noise is added to the system. In reality, many engineering systems modeled by second order differential equations, like the van der Pol oscillator, show incredible robustness against noise perturbations, and the perturbed trajectories remain in the neighborhood of a stable limit cycle for all times of practical interest. In this paper, we propose a new model of noise to bridge this apparent discrepancy between theory and practice. Restricting to perturbations from within this new class of noise, we consider stochastic perturbations of second order differential systems that -in the unperturbed case- admit asymptotically stable limit cycles. We show that the perturbed solutions are globally bounded and remain in a tubular neighborhood of the underlying deterministic periodic orbit. We also define stochastic Poincaré map(s), and further derive partial differential equations for the transition density function.
A realistic model for quantum theory with a locality property
Eberhard, P.H.
1987-04-01
A model reproducing the predictions of relativistic quantum theory to any desired degree of accuracy is described in this paper. It involves quantities that are independent of the observer's knowledge, and therefore can be called real, and which are defined at each point in space, and therefore can be called local in a rudimentary sense. It involves faster-than-light, but not instantaneous, action at distance.
Modelling disease outbreaks in realistic urban social networks
NASA Astrophysics Data System (ADS)
Eubank, Stephen; Guclu, Hasan; Anil Kumar, V. S.; Marathe, Madhav V.; Srinivasan, Aravind; Toroczkai, Zoltán; Wang, Nan
2004-05-01
Most mathematical models for the spread of disease use differential equations based on uniform mixing assumptions or ad hoc models for the contact process. Here we explore the use of dynamic bipartite graphs to model the physical contact patterns that result from movements of individuals between specific locations. The graphs are generated by large-scale individual-based urban traffic simulations built on actual census, land-use and population-mobility data. We find that the contact network among people is a strongly connected small-world-like graph with a well-defined scale for the degree distribution. However, the locations graph is scale-free, which allows highly efficient outbreak detection by placing sensors in the hubs of the locations network. Within this large-scale simulation framework, we then analyse the relative merits of several proposed mitigation strategies for smallpox spread. Our results suggest that outbreaks can be contained by a strategy of targeted vaccination combined with early detection without resorting to mass vaccination of a population.
Realistic Mathematics Learning Using Cooperative Strategy Model in Junior High School
ERIC Educational Resources Information Center
Dwiyana
2015-01-01
This study aims to develop a realistic mathematics learning model using cooperative strategy. This study applies research and development approach conducted at Junior High School "Laboratorium," State University of Malang. The implementation of this model is conducted through five stages: 1) previous study phase; 2) model planning phase;…
Supersymmetric vacua in random supergravity
NASA Astrophysics Data System (ADS)
Bachlechner, Thomas C.; Marsh, David; McAllister, Liam; Wrase, Timm
2013-01-01
We determine the spectrum of scalar masses in a supersymmetric vacuum of a general mathcal{N}=1 supergravity theory, with the Kähler potential and superpotential taken to be random functions of N complex scalar fields. We derive a random matrix model for the Hessian matrix and compute the eigenvalue spectrum. Tachyons consistent with the Breitenlohner-Freedman bound are generically present, and although these tachyons cannot destabilize the supersymmetric vacuum, they do influence the likelihood of the existence of an `uplift' to a metastable vacuum with positive cosmological constant. We show that the probability that a supersymmetric AdS vacuum has no tachyons is formally equivalent to the probability of a large fluctuation of the smallest eigenvalue of a certain real Wishart matrix. For normally-distributed matrix entries and any N, this probability is given exactly by P=exp left( {{{{-2{N^2}{{{left| W right|}}^2}}} left/ {{m_{susy}^2}} right.}} right) , with W denoting the superpotential and m susy the supersymmetric mass scale; for more general distributions of the entries, our result is accurate when N ≫ 1. We conclude that for left| W right|gtrsim {{{{m_{susy}}}} left/ {N} right.} , tachyonic instabilities are ubiquitous in configurations obtained by uplifting supersymmetric vacua.
Quantitative description of realistic wealth distributions by kinetic trading models
NASA Astrophysics Data System (ADS)
Lammoglia, Nelson; Muñoz, Víctor; Rogan, José; Toledo, Benjamín; Zarama, Roberto; Valdivia, Juan Alejandro
2008-10-01
Data on wealth distributions in trading markets show a power law behavior x-(1+α) at the high end, where, in general, α is greater than 1 (Pareto’s law). Models based on kinetic theory, where a set of interacting agents trade money, yield power law tails if agents are assigned a saving propensity. In this paper we are solving the inverse problem, that is, in finding the saving propensity distribution which yields a given wealth distribution for all wealth ranges. This is done explicitly for two recently published and comprehensive wealth datasets.
Validating a Dynamic Earthquake Model to Produce Realistic Ground Motion
NASA Astrophysics Data System (ADS)
Andrews, D. J.; Ma, S.
2015-12-01
A dynamic earthquake model is validated by finding good agreement with an empirical ground motion prediction equation. The model replaces detailed deterministic processes on the fault with a stochastic emergent law. Initial stress on a fault plane is heterogeneous with a power-law spectrum that is self-similar. Rupture stops naturally. Rupture extent and moment are determined primarily by the specified lowest Fourier mode of initial stress. Higher modes are random with a self-similar spectrum that is tied to the amplitude of the lowest mode. Ten random realizations are calculated with a velocity structure for a hard rock site. The calculated mean response spectrum for M7 at a distance of 10 km agrees the with the GMPE of Boore et al (2013) within 0.25 of one standard deviation at periods from 0.3 seconds to 10 seconds. The agreement could be improved by using a more refined relation of the spatial stress spectrum to the amplitude of the lowest mode. The standard deviation of the calculated ground motion is somewhat smaller than the GMPE, but it depends on other rupture parameters and needs more investigation.
Realistic Representation of Trees in an Urban Canopy Model
NASA Astrophysics Data System (ADS)
Ryu, Young-Hee; Bou-Zeid, Elie; Wang, Zhi-Hua; Smith, James A.
2016-05-01
A single-layer urban canopy model that captures sub-facet heterogeneity and various hydrological processes is further developed to explicitly incorporate trees within the urban canyon. The physical processes associated with trees are shortwave/longwave radiation exchange, including mutual interception and shading by trees and buildings and multiple reflections, sensible heat and latent heat (through transpiration) exchange, and root water uptake. A computationally-efficient geometric approach is applied to the radiation exchanges, requiring a priori knowledge of view factors. These view factors are first obtained from independent Monte Carlo ray-tracing simulations, and subsequently simple relations, which are functions of canyon aspect ratio and tree-crown ratio, are proposed to estimate them. The developed model is evaluated against field observations at two urban sites and one suburban site, showing improved performance for latent heat flux compared to the previous version that only includes ground vegetation. The trees in the urban canopy act to considerably decrease sensible heat flux and increase latent heat flux, and these effects are found to be more significant in the more dense urban site. Sensitivity tests are then performed to examine the effects of tree geometry relative to canyon geometry. The results indicate that the tree-crown size relative to canyon width is the most influential parameter to decrease sensible heat flux and increase latent heat flux, resulting in cooling of the urban area.
Reliable modeling of the electronic spectra of realistic uranium complexes
NASA Astrophysics Data System (ADS)
Tecmer, Paweł; Govind, Niranjan; Kowalski, Karol; de Jong, Wibe A.; Visscher, Lucas
2013-07-01
We present an EOMCCSD (equation of motion coupled cluster with singles and doubles) study of excited states of the small [UO2]2+ and [UO2]+ model systems as well as the larger UVIO2(saldien) complex. In addition, the triples contribution within the EOMCCSDT and CR-EOMCCSD(T) (completely renormalized EOMCCSD with non-iterative triples) approaches for the [UO2]2+ and [UO2]+ systems as well as the active-space variant of the CR-EOMCCSD(T) method—CR-EOMCCSd(t)—for the UVIO2(saldien) molecule are investigated. The coupled cluster data were employed as benchmark to choose the "best" appropriate exchange-correlation functional for subsequent time-dependent density functional (TD-DFT) studies on the transition energies for closed-shell species. Furthermore, the influence of the saldien ligands on the electronic structure and excitation energies of the [UO2]+ molecule is discussed. The electronic excitations as well as their oscillator dipole strengths modeled with TD-DFT approach using the CAM-B3LYP exchange-correlation functional for the [UVO2(saldien)]- with explicit inclusion of two dimethyl sulfoxide molecules are in good agreement with the experimental data of Takao et al. [Inorg. Chem. 49, 2349 (2010), 10.1021/ic902225f].
NASA Astrophysics Data System (ADS)
Aristovich, K. Y.; Khan, S. H.
2010-07-01
Realistic computer modelling of biological objects requires building of very accurate and realistic computer models based on geometric and material data, type, and accuracy of numerical analyses. This paper presents some of the automatic tools and algorithms that were used to build accurate and realistic 3D finite element (FE) model of whole-brain. These models were used to solve the forward problem in magnetic field tomography (MFT) based on Magnetoencephalography (MEG). The forward problem involves modelling and computation of magnetic fields produced by human brain during cognitive processing. The geometric parameters of the model were obtained from accurate Magnetic Resonance Imaging (MRI) data and the material properties - from those obtained from Diffusion Tensor MRI (DTMRI). The 3D FE models of the brain built using this approach has been shown to be very accurate in terms of both geometric and material properties. The model is stored on the computer in Computer-Aided Parametrical Design (CAD) format. This allows the model to be used in a wide a range of methods of analysis, such as finite element method (FEM), Boundary Element Method (BEM), Monte-Carlo Simulations, etc. The generic model building approach presented here could be used for accurate and realistic modelling of human brain and many other biological objects.
Order Matters: Sequencing Scale-Realistic Versus Simplified Models to Improve Science Learning
NASA Astrophysics Data System (ADS)
Chen, Chen; Schneps, Matthew H.; Sonnert, Gerhard
2016-10-01
Teachers choosing between different models to facilitate students' understanding of an abstract system must decide whether to adopt a model that is simplified and striking or one that is realistic and complex. Only recently have instructional technologies enabled teachers and learners to change presentations swiftly and to provide for learning based on multiple models, thus giving rise to questions about the order of presentation. Using disjoint individual growth modeling to examine the learning of astronomical concepts using a simulation of the solar system on tablets for 152 high school students (age 15), the authors detect both a model effect and an order effect in the use of the Orrery, a simplified model that exaggerates the scale relationships, and the True-to-scale, a proportional model that more accurately represents the realistic scale relationships. Specifically, earlier exposure to the simplified model resulted in diminution of the conceptual gain from the subsequent realistic model, but the realistic model did not impede learning from the following simplified model.
Towards Noncommutative Supersymmetric Quantum Cosmology
Sabido, M.; Socorro, J.; Guzman, W.
2010-12-07
In this work a construction of supersymmetric noncommutative cosmology is presented. We start with a ''noncommutative'' deformation of the minisuperspace variables, and by using the time reparametrization invariance of the noncommutative bosonic model we proceed to construct a super field description of the model.
A Model of Biological Attacks on a Realistic Population
NASA Astrophysics Data System (ADS)
Carley, Kathleen M.; Fridsma, Douglas; Casman, Elizabeth; Altman, Neal; Chen, Li-Chiou; Kaminsky, Boris; Nave, Demian; Yahja, Alex
The capability to assess the impacts of large-scale biological attacks and the efficacy of containment policies is critical and requires knowledge-intensive reasoning about social response and disease transmission within a complex social system. There is a close linkage among social networks, transportation networks, disease spread, and early detection. Spatial dimensions related to public gathering places such as hospitals, nursing homes, and restaurants, can play a major role in epidemics [Klovdahl et. al. 2001]. Like natural epidemics, bioterrorist attacks unfold within spatially defined, complex social systems, and the societal and networked response can have profound effects on their outcome. This paper focuses on bioterrorist attacks, but the model has been applied to emergent and familiar diseases as well.
Realistic NLTE Radiative Transfer for Modeling Stellar Winds
NASA Technical Reports Server (NTRS)
Bennett, Philip D.
1999-01-01
This NASA grant supported the development of codes to solve the non-LTE multi-level spherical radiative transfer problem in the presence of velocity fields. Much of this work was done in collaboration with Graham Harper (CASA, University of Colorado). These codes were developed for application to the cool, low-velocity winds of evolved late-type stars. Particular emphasis was placed on modeling the wind of lambda Velorum (K4 lb), the brightest K supergiant in the sky, based on extensive observations of the ultraviolet spectrum with the HST/GHRS from GO program 5307. Several solution techniques were examined, including the Eddington factor Approach described in detail by Bennett & Harper (1997). An Eddington factor variant of Harper's S-MULTI code (Harper 1994) for stationary atmospheres was developed and implemented, although full convergence was not realized. The ratio of wind terminal velocity to turbulent velocity is large (approx. 0.3-0.5) in these cool star winds so this assumption of stationarity provides reasonable starting models. Final models, incorporating specified wind laws, were converged using the comoving CRD S-MULTI code. Details of the solution procedure were published by Bennett & Harper (1997). Our analysis of the wind of lambda Vel, based on wind absorption superimposed on chromospheric emission lines in the ultraviolet, can be found in Carpenter et al. (1999). In this paper, we compare observed wind absorption features to an exact CRD calculation in the comoving frame, and also to a much quicker, but approximate, method using the SEI (Sobolev with Exact Integration) code of Lamers, Cerruti-Sola, & Perinotto (1987). Carpenter et al. (1999) provide detailed comparisons of the exact CRD and approximate SEI results and discuss when SEI is adequate to use for computing wind line profiles. Unfortunately, the observational material is insufficient to unambiguously determine the wind acceleration law for lambda Vel. Relatively few unblended Fe II lines
Multi-Dimensional Modeling of Nova with Realistic Nuclear Physics
Zingale, M; Hoffman, R D
2011-01-27
This contract covered the period from 03/09/2010 to 09/30/2010. Over this period, we adapted the low Mach number hydrodynamics code MAESTRO to perform simulations of novae. A nova is the thermonuclear runaway of an accreted hydrogen layer on the surface of a white dwarf. As the accreted layer grows in mass, the temperature and density at the base increase to the point where hydrogen fusion can begin by the CNO cycle - a burning process that uses carbon, nitrogen, and oxygen to complete the fusion of four hydrogen nuclei into one helium-4 nucleus. At this point, we are running initial models of nova, exploring the details of the convection. In the follow-on contract to this one, we will continue this investigation.
Cross-tail ion drift in a realistic model magnetotail
NASA Technical Reports Server (NTRS)
Propp, K.; Beard, D. B.
1984-01-01
By integrating the exact equations of motion, particle orbits have been followed in a good model magnetospheric field consisting of a planetary dipole, forward magnetosphere, and magnetotail current system. Proton energies from 2 eV to 20 keV were used for the full range of equatorial pitch angles and phase. Despite considerable pitch angle scattering in the equatorial plane crossings, it is found, first, that the bounce-averaged cross-tail drift velocity is approximately independent of pitch angle. Second, it is found that, averaged over initial gyrophase, the drift velocity (due to field curvature and gradient) is proportional to proton energy and is given to good approximation by adiabatic approximations, even up to 20 keV, despite the extreme lack of meeting the adiabatic criteria.
Realistic NLTE Radiative Transfer for Modeling Stellar Winds
NASA Technical Reports Server (NTRS)
Bennett, Philip D.
1999-01-01
This NASA grant supported the development of codes to solve the non-LTE multi-level spherical radiative transfer problem in the presence of velocity fields. Much of this work was done in collaboration with Graham Harper (CASA, University of Colorado). These codes were developed for application to the cool, low-velocity winds of evolved late-type stars. Particular emphasis was placed on modeling the wind of lambda Velorum (K4 lb), the brightest K supergiant in the sky, based on extensive observations of the ultraviolet spectrum with the HST/GHRS from GO program 5307. Several solution techniques were examined, including the Eddington factor Approach described in detail by Bennett & Harper (1997). An Eddington factor variant of Harper's S-MULTI code (Harper 1994) for stationary atmospheres was developed and implemented, although full convergence was not realized. The ratio of wind terminal velocity to turbulent velocity is large (approx. 0.3-0.5) in these cool star winds so this assumption of stationarity provides reasonable starting models. Final models, incorporating specified wind laws, were converged using the comoving CRD S-MULTI code. Details of the solution procedure were published by Bennett & Harper (1997). Our analysis of the wind of lambda Vel, based on wind absorption superimposed on chromospheric emission lines in the ultraviolet, can be found in Carpenter et al. (1999). In this paper, we compare observed wind absorption features to an exact CRD calculation in the comoving frame, and also to a much quicker, but approximate, method using the SEI (Sobolev with Exact Integration) code of Lamers, Cerruti-Sola, & Perinotto (1987). Carpenter et al. (1999) provide detailed comparisons of the exact CRD and approximate SEI results and discuss when SEI is adequate to use for computing wind line profiles. Unfortunately, the observational material is insufficient to unambiguously determine the wind acceleration law for lambda Vel. Relatively few unblended Fe II lines
Realistic uncertainties on Hapke model parameters from photometric measurement
NASA Astrophysics Data System (ADS)
Schmidt, Frédéric; Fernando, Jennifer
2015-11-01
The single particle phase function describes the manner in which an average element of a granular material diffuses the light in the angular space usually with two parameters: the asymmetry parameter b describing the width of the scattering lobe and the backscattering fraction c describing the main direction of the scattering lobe. Hapke proposed a convenient and widely used analytical model to describe the spectro-photometry of granular materials. Using a compilation of the published data, Hapke (Hapke, B. [2012]. Icarus 221, 1079-1083) recently studied the relationship of b and c for natural examples and proposed the hockey stick relation (excluding b > 0.5 and c > 0.5). For the moment, there is no theoretical explanation for this relationship. One goal of this article is to study a possible bias due to the retrieval method. We expand here an innovative Bayesian inversion method in order to study into detail the uncertainties of retrieved parameters. On Emission Phase Function (EPF) data, we demonstrate that the uncertainties of the retrieved parameters follow the same hockey stick relation, suggesting that this relation is due to the fact that b and c are coupled parameters in the Hapke model instead of a natural phenomena. Nevertheless, the data used in the Hapke (Hapke, B. [2012]. Icarus 221, 1079-1083) compilation generally are full Bidirectional Reflectance Diffusion Function (BRDF) that are shown not to be subject to this artifact. Moreover, the Bayesian method is a good tool to test if the sampling geometry is sufficient to constrain the parameters (single scattering albedo, surface roughness, b, c , opposition effect). We performed sensitivity tests by mimicking various surface scattering properties and various single image-like/disk resolved image, EPF-like and BRDF-like geometric sampling conditions. The second goal of this article is to estimate the favorable geometric conditions for an accurate estimation of photometric parameters in order to provide
Carena, Marcela; Hooper, Dan; Skands, Peter
2006-08-04
In regions of large tanbeta and small mAlpha, searches for heavy neutral minimal supersymmetric standard model (MSSM) Higgs bosons at the Tevatron are promising. At the same time, rates in direct dark matter experiments, such as CDMS, are enhanced in the case of large tanbeta and small mAlpha. As a result, there is a natural interplay between the heavy, neutral Higgs searches at the Tevatron and the region of parameter space explored by CDMS. We show that if the lightest neutralino makes up the dark matter of our universe, current limits from CDMS strongly constrain the prospects of heavy, neutral MSSM Higgs discovery at the Tevatron unless |mu| greater or approximately 400 GeV. The limits of CDMS projected for 2007 will increase this constraint to |mu| greater or approximately 800 GeV. If CDMS does observe neutralinos in the near future, however, it will make the discovery of Higgs bosons at the Tevatron far more likely.
Wilson loops in supersymmetric gauge theories
NASA Astrophysics Data System (ADS)
Pestun, Vasily
This thesis is devoted to several exact computations in four-dimensional supersymmetric gauge field theories. In the first part of the thesis we prove conjecture due to Erickson-Semenoff-Zarembo and Drukker-Gross which relates supersymmetric circular Wilson loop operators in the N = 4 supersymmetric Yang-Mills theory with a Gaussian matrix model. We also compute the partition function and give a new matrix model formula for the expectation value of a supersymmetric circular Wilson loop operator for the pure N = 2 and the N* = 2 supersymmetric Yang-Mills theory on a four-sphere. Circular supersymmetric Wilson loops in four-dimensional N = 2 superconformal gauge theory are treated similarly. In the second part we consider supersymmetric Wilson loops of arbitrary shape restricted to a two-dimensional sphere in the four-dimensional N = 4 supersymmetric Yang-Mills theory. We show that expectation value for these Wilson loops can be exactly computed using a two-dimensional theory closely related to the topological two-dimensional Higgs-Yang-Mills theory, or two-dimensional Yang-Mills theory for the complexified gauge group.
Order Matters: Sequencing Scale-Realistic versus Simplified Models to Improve Science Learning
ERIC Educational Resources Information Center
Chen, Chen; Schneps, Matthew H.; Sonnert, Gerhard
2016-01-01
Teachers choosing between different models to facilitate students' understanding of an abstract system must decide whether to adopt a model that is simplified and striking or one that is realistic and complex. Only recently have instructional technologies enabled teachers and learners to change presentations swiftly and to provide for learning…
Order Matters: Sequencing Scale-Realistic versus Simplified Models to Improve Science Learning
ERIC Educational Resources Information Center
Chen, Chen; Schneps, Matthew H.; Sonnert, Gerhard
2016-01-01
Teachers choosing between different models to facilitate students' understanding of an abstract system must decide whether to adopt a model that is simplified and striking or one that is realistic and complex. Only recently have instructional technologies enabled teachers and learners to change presentations swiftly and to provide for learning…
Non-minimal quartic inflation in supersymmetric SO(10)
NASA Astrophysics Data System (ADS)
Leontaris, George K.; Okada, Nobuchika; Shafi, Qaisar
2017-02-01
We describe how quartic (λϕ4) inflation with non-minimal coupling to gravity is realized in realistic supersymmetric SO (10) models. In a well-motivated example the 16 - 16 ‾ Higgs multiplets, which break SO (10) to SU (5) and yield masses for the right-handed neutrinos, provide the inflaton field ϕ. Thus, leptogenesis is a natural outcome in this class of SO (10) models. Moreover, the adjoint (45-plet) Higgs also acquires a GUT scale value during inflation so that the monopole problem is evaded. The scalar spectral index ns is in good agreement with the observations and r, the tensor to scalar ratio, is predicted for realistic values of GUT parameters to be of order 10-3-10-2.
Non-minimal quartic inflation in supersymmetric SO(10)
Leontaris, George K.; Okada, Nobuchika; Shafi, Qaisar
2016-12-16
Here, we describe how quartic (λφ4) inflation with non-minimal coupling to gravity is realized in realistic supersymmetric SO(10)models. In a well-motivated example the 16 -more » $$\\overline{16}$$ Higgs multiplets, which break SO(10) to SU(5) and yield masses for the right-handed neutrinos, provide the inflaton field φ. Thus, leptogenesis is a natural outcome in this class of SO(10) models. Moreover, the adjoint (45-plet) Higgs also acquires a GUT scale value during inflation so that the monopole problem is evaded. The scalar spectral index ns in good agreement with the observations and r, the tensor to scalar ratio, is predicted for realistic values of GUT parameters to be of order 10-3-10-2.« less
Comparative analysis of realistic CT-scan and simplified human airway models in airflow simulation.
Johari, Nasrul Hadi; Osman, Kahar; Helmi, Nor Harris N; Abdul Kadir, Mohammed A Rafiq
2015-01-01
Efforts to model the human upper respiratory system have undergone many phases. Geometrical proximity to the realistic shape has been the subject of many research projects. In this study, three different geometries of the trachea and main bronchus were modelled, which were reconstructed from computed tomography (CT) scan images. The geometrical variations were named realistic, simplified and oversimplified. Realistic refers to the lifelike image taken from digital imaging and communications in medicine format CT scan images, simplified refers to the reconstructed image based on natural images without realistic details pertaining to the rough surfaces, and oversimplified describes the straight wall geometry of the airway. The characteristics of steady state flows with different flow rates were investigated, simulating three varied physical activities and passing through each model. The results agree with previous studies where simplified models are sufficient for providing comparable results for airflow in human airways. This work further suggests that, under most exercise conditions, the idealised oversimplified model is not favourable for simulating either airflow regimes or airflow with particle depositions. However, in terms of immediate analysis for the prediction of abnormalities of various dimensions of human airways, the oversimplified techniques may be used.
Transport and deposition of micro-aerosols in realistic and simplified models of the oral airway.
Xi, Jinxiang; Longest, P Worth
2007-04-01
A number of in vivo, in vitro and numerical studies have considered flow field characteristics and micro-particle deposition in the oral airway extending from the mouth through the larynx. These studies have highlighted the effects of flow rates, turbulence and particle characteristics on deposition values in realistic and simplified geometries. However, the effect of geometry simplifications on regional and local deposition patterns remains largely un-quantified for the oral airway and throughout the respiratory tract. The objective of this study is to assess the effects of geometry simplifications on regionally averaged and local micro-aerosol deposition characteristics in models of the extrathoracic oral airway. To achieve this objective, a realistic model of the oral airway has been constructed based on CT scans of a healthy adult in conjunction with measurements reported in the literature. Three other geometries with descending degrees of physical realism were constructed based on successive geometric simplifications of the realistic model. A validated low Reynolds number (LRN) k-omega turbulence model was employed to simulate laminar, transitional and fully turbulent flow regimes for 1-31 microm particles. Geometric simplifications were found to have a significant effect on aerosol dynamics, hot spot formations and cellular-level deposition values in the extrathoracic airway models considered. For all models, regional deposition efficiency results were found to be approximately within one standard deviation of available experimental data when plotted as a function of Stokes number. The realistic geometry provided the best predictions of regional deposition in comparison to experimental data as a function of particle diameter. Considering localized deposition, maximum deposition enhancement factors, which represent the ratio of local to total deposition, were one to two orders of magnitude higher for the realistic model. Geometric factors that significantly
EEG/MEG error bounds for a dynamic dipole source with a realistic head model.
Muravchik, C; Bria, O; Nehorai, A
2000-06-01
This work presents the background and derivation of Cramér-Rao bounds on the errors of estimating the parameters (moment and location) of a dynamic current dipole source using data from electro- and magneto-encephalography. A realistic head model, based on knowledge of surfaces separating tissues of different conductivities, is used.
Cold and hot cognition: quantum probability theory and realistic psychological modeling.
Corr, Philip J
2013-06-01
Typically, human decision making is emotionally "hot" and does not conform to "cold" classical probability (CP) theory. As quantum probability (QP) theory emphasises order, context, superimposition states, and nonlinear dynamic effects, one of its major strengths may be its power to unify formal modeling and realistic psychological theory (e.g., information uncertainty, anxiety, and indecision, as seen in the Prisoner's Dilemma).
Local realistic photon model compatible with Malus' law for experiments testing Bell's inequalities
NASA Astrophysics Data System (ADS)
Ferrero, M.; Santos, E.
1985-04-01
A local realistic model is proposed that agrees approximately with quantum mechanics in the predictions about experiments testing Bell's inequalities by measuring polarization correlations of photon pairs emitted in atomic cascades. No free parameters exist, except polarizer efficiencies, which may be measured independently using Malus' law.
Ziegler, Erik; Chellappa, Sarah L; Gaggioni, Giulia; Ly, Julien Q M; Vandewalle, Gilles; André, Elodie; Geuzaine, Christophe; Phillips, Christophe
2014-12-01
We present a finite element modeling (FEM) implementation for solving the forward problem in electroencephalography (EEG). The solution is based on Helmholtz's principle of reciprocity which allows for dramatically reduced computational time when constructing the leadfield matrix. The approach was validated using a 4-shell spherical model and shown to perform comparably with two current state-of-the-art alternatives (OpenMEEG for boundary element modeling and SimBio for finite element modeling). We applied the method to real human brain MRI data and created a model with five tissue types: white matter, gray matter, cerebrospinal fluid, skull, and scalp. By calculating conductivity tensors from diffusion-weighted MR images, we also demonstrate one of the main benefits of FEM: the ability to include anisotropic conductivities within the head model. Root-mean square deviation between the standard leadfield and the leadfield including white-matter anisotropy showed that ignoring the directional conductivity of white matter fiber tracts leads to orientation-specific errors in the forward model. Realistic head models are necessary for precise source localization in individuals. Our approach is fast, accurate, open-source and freely available online. Copyright © 2014 Elsevier Inc. All rights reserved.
Supersymmetric Hybrid Inflation Redux
NASA Astrophysics Data System (ADS)
Rehman, Mansoor Ur; Shafi, Qaisar; Wickman, Joshua R.
2010-02-01
We discuss the important role played during inflation by one of the soft supersymmetry breaking terms in the inflationary potential of supersymmetric hybrid inflation models. With minimal Kahler potential, the inclusion of this term allows the prediction for the scalar spectral index to agree with the value ns = 0.963^+0.014 -0.015 found by WMAP5. In the absence of this soft term, and by taking into account only radiative and supergravity corrections, it is well known that ns >= 0.985. This same soft term has previously been shown to play a key role in resolving the MSSM μ problem. The tensor to scalar ratio r is quite small in these models, taking on values r <= 10-5 in the WMAP5 2σ range of ns. )
General solutions of the supersymmetric ℂP{sup 2} sigma model and its generalisation to ℂP{sup N−1}
Delisle, L.; Hussin, V.; Zakrzewski, W. J.
2016-02-15
A new approach for the construction of finite action solutions of the supersymmetric ℂP{sup N−1} sigma model is presented. We show that this approach produces more non-holomorphic solutions than those obtained in previous approaches. We study the ℂP{sup 2} model in detail and present its solutions in an explicit form. We also show how to generalise this construction to N > 3.
Cao Qinghong; Khalil, Shaaban; Ma, Ernest; Okada, Hiroshi
2011-10-01
We discuss how {theta}{sub 13}{ne}0 is accommodated in a recently proposed renormalizable model of neutrino mixing using the non-Abelian discrete symmetry T{sub 7} in the context of a supersymmetric extension of the standard model with gauged U(1){sub B-L}. We predict a correlation between {theta}{sub 13} and {theta}{sub 23}, as well as the effective neutrino mass m{sub ee} in neutrinoless double beta decay.
Interfaces in supersymmetric field theories
NASA Astrophysics Data System (ADS)
Galakhov, Dmitrii
Supersymmetry has proven to be a valuable tool in the study of non-perturbative dynamics in quantum field theory, gravity and string theory. In this thesis we consider supersymmetric interfaces. Interfaces are defects defined by spatially changing coupling constants. Interfaces can be used to probe the non-perturbative low energy dynamics of an underlying supersymmetric quantum field theory. We study interfaces in a set of four-dimensional quantum field theories with N = 2 supersymmetry known as theories of class S. Using these defects we probe the spin content of the spectrum of quantum states saturating the Bogomolnyi-Prasad-Sommerfeld bound. We also apply supersymmetric defects to the construction of knot and link invariants via quantum field theory. We associate to a knot -- presented as a tangle -- an interface de ned by a spatially varying superpotential in a 2d supersymmetric Landau-Ginzburg model. We construct explicitly the Hilbert space of ground states on this interface as the cohomology of a nilpotent supercharge and prove that this Hilbert space is bi-graded by integers and is an invariant of the knot (or link). In explicit examples we show that the corresponding Poincare polynomial coincides with the Poincar e polynomial of the renowned Khovanov homology that categori es the Jones polynomial.
Realistic avatar eye and head animation using a neurobiological model of visual attention
NASA Astrophysics Data System (ADS)
Itti, Laurent; Dhavale, Nitin; Pighin, Frederic
2004-01-01
We describe a neurobiological model of visual attention and eye/head movements in primates, and its application to the automatic animation of a realistic virtual human head watching an unconstrained variety of visual inputs. The bottom-up (image-based) attention model is based on the known neurophysiology of visual processing along the occipito-parietal pathway of the primate brain, while the eye/head movement model is derived from recordings in freely behaving Rhesus monkeys. The system is successful at autonomously saccading towards and tracking salient targets in a variety of video clips, including synthetic stimuli, real outdoors scenes and gaming console outputs. The resulting virtual human eye/head animation yields realistic rendering of the simulation results, both suggesting applicability of this approach to avatar animation and reinforcing the plausibility of the neural model.
Lampropoulos, Georgios K; Spengler, Paul M
2002-10-01
This series of articles attempts to redefine and reprioritize the role of science in search for a clinically meaningful and realistic version of the scientist-practitioner (S-P) model. To this end, science is discussed as both research-driven practice and clinically meaningful research, keeping practitioners and their needs in the center of attention. In this process, common problems in the actualization of the S-P model are discussed, and potential solutions are offered.
Realistic Image Rendition Using a Variable Exponent Functional Model for Retinex
Dou, Zeyang; Gao, Kun; Zhang, Bin; Yu, Xinyan; Han, Lu; Zhu, Zhenyu
2016-01-01
The goal of realistic image rendition is to recover the acquired image under imperfect illuminant conditions, where non–uniform illumination may degrade image quality with high contrast and low SNR. In this paper, the assumption regarding illumination is modified and a variable exponent functional model for Retinex is proposed to remove non–uniform illumination and reduce halo artifacts. The theoretical derivation is provided and experimental results are presented to illustrate the effectiveness of the proposed model. PMID:27338379
Vatta, F; Bruno, P; Di Salle, F; Esposito, F; Meneghini, F; Mininel, S; Rodaro, M
2008-01-01
Realistic electrical brain activity mapping implies reconstructing and visualizing sources of electrical brain activity within the specific patient's head. This requires the assumption of a precise and realistic volume conductor model of the specific subject's head, i.e., a 3-D representation of the head's electrical properties in terms of shape and electrical conductivities. Source reconstruction accuracy is influenced by errors committed in head modeling. Clinical images, MRI and CT, are used to identify the head structures to be included in the volume conductor head model. Modeling accuracy mainly relies on the correct image-based identification of head structures, characterized by different electrical conductivities, to be included as separate compartments in the model. This paper analyzes the imaging protocols used in clinical practice to define the most suitable procedures for identification of the various head structures necessary to build an accurate head model also in the presence of morphologic brain pathologies. Furthermore, tissues anisotropy is discussed and identified as well. With this work we have identified a protocol for the acquisition of multimodal patient's imaging data for realistic electrical brain activity mapping purposes, able to account for pathological conditions and for head tissues anisotropy.
Vatta, Federica; Meneghini, Fabio; Esposito, Fabrizio; Mininel, Stefano; Di Salle, Francesco
2010-01-01
The accuracy of forward models for electroencephalography (EEG) partly depends on head tissues geometry and strongly affects the reliability of the source reconstruction process, but it is not yet clear which brain regions are more sensitive to the choice of different model geometry. In this paper we compare different spherical and realistic head modeling techniques in estimating EEG forward solutions from current dipole sources distributed on a standard cortical space reconstructed from Montreal Neurological Institute (MNI) MRI data. Computer simulations are presented for three different four-shell head models, two with realistic geometry, either surface-based (BEM) or volume-based (FDM), and the corresponding sensor-fitted spherical-shaped model. Point Spread Function (PSF) and Lead Field (LF) cross-correlation analyses were performed for 26 symmetric dipole sources to quantitatively assess models' accuracy in EEG source reconstruction. Realistic geometry turns out to be a relevant factor of improvement, particularly important when considering sources placed in the temporal or in the occipital cortex. PMID:20169107
Vatta, Federica; Meneghini, Fabio; Esposito, Fabrizio; Mininel, Stefano; Di Salle, Francesco
2010-01-01
The accuracy of forward models for electroencephalography (EEG) partly depends on head tissues geometry and strongly affects the reliability of the source reconstruction process, but it is not yet clear which brain regions are more sensitive to the choice of different model geometry. In this paper we compare different spherical and realistic head modeling techniques in estimating EEG forward solutions from current dipole sources distributed on a standard cortical space reconstructed from Montreal Neurological Institute (MNI) MRI data. Computer simulations are presented for three different four-shell head models, two with realistic geometry, either surface-based (BEM) or volume-based (FDM), and the corresponding sensor-fitted spherical-shaped model. Point Spread Function (PSF) and Lead Field (LF) cross-correlation analyses were performed for 26 symmetric dipole sources to quantitatively assess models' accuracy in EEG source reconstruction. Realistic geometry turns out to be a relevant factor of improvement, particularly important when considering sources placed in the temporal or in the occipital cortex.
Supersymmetric Higgs Bosons in Weak Boson Fusion
Hollik, Wolfgang; Plehn, Tilman; Rauch, Michael; Rzehak, Heidi
2009-03-06
We compute the complete supersymmetric next-to-leading-order corrections to the production of a light Higgs boson in weak-boson fusion. The size of the electroweak corrections is of similar order as the next-to-leading-order corrections in the standard model. The supersymmetric QCD corrections turn out to be significantly smaller than expected and than their electroweak counterparts. These corrections are an important ingredient to a precision analysis of the (supersymmetric) Higgs sector at the LHC, either as a known correction factor or as a contribution to the theory error.
Zelenyak, Andreea-Manuela; Schorer, Nora; Sause, Markus G R
2017-06-20
This paper presents a method for embedding realistic defect geometries of a fiber reinforced material in a finite element modeling environment in order to simulate active ultrasonic inspection. When ultrasonic inspection is used experimentally to investigate the presence of defects in composite materials, the microscopic defect geometry may cause signal characteristics that are difficult to interpret. Hence, modeling of this interaction is key to improve our understanding and way of interpreting the acquired ultrasonic signals. To model the true interaction of the ultrasonic wave field with such defect structures as pores, cracks or delamination, a realistic three dimensional geometry reconstruction is required. We present a 3D-image based reconstruction process which converts computed tomography data in adequate surface representations ready to be embedded for processing with finite element methods. Subsequent modeling using these geometries uses a multi-scale and multi-physics simulation approach which results in quantitative A-Scan ultrasonic signals which can be directly compared with experimental signals. Therefore, besides the properties of the composite material, a full transducer implementation, piezoelectric conversion and simultaneous modeling of the attached circuit is applied. Comparison between simulated and experimental signals provides very good agreement in electrical voltage amplitude and the signal arrival time and thus validates the proposed modeling approach. Simulating ultrasound wave propagation in a medium with a realistic shape of the geometry clearly shows a difference in how the disturbance of the waves takes place and finally allows more realistic modeling of A-scans. Copyright © 2017 Elsevier B.V. All rights reserved.
𝒩 = 2 supersymmetric Pais-Uhlenbeck oscillator
NASA Astrophysics Data System (ADS)
Masterov, Ivan
2015-06-01
We construct an 𝒩 = 2 supersymmetric extension of the Pais-Uhlenbeck oscillator for distinct frequencies of oscillation. A link to a set of decoupled 𝒩 = 2 supersymmetric harmonic oscillators with alternating sign in the Hamiltonian is introduced. Symmetries of the model are discussed in detail. The investigation of a quantum counterpart of the constructed model shows that the corresponding Fock space contains negative norm states and the energy spectrum of the system is unbounded from below.
Multidimensional realistic modelling of Cepheid-like variables - II. Analysis of a Cepheid model
NASA Astrophysics Data System (ADS)
Mundprecht, Eva; Muthsam, Herbert J.; Kupka, Friedrich
2015-05-01
Non-local, time-dependent convection models have been used to explain the location of double-mode pulsations in Cepheids in the HR diagram as well as the existence and location of the red edge of the instability strip. These properties are highly sensitive to model parameters. We use 2D radiation-hydrodynamical simulations with realistic microphysics and grey radiative transfer to model a short-period Cepheid. The simulations show that the strength of the convection zone varies significantly over the pulsation period and exhibits a phase shift relative to the variations in radius. We evaluate the convective flux and the work integral as predicted by the most common convection models. It turns out that over one pulsation cycle the model parameter αc, has to be varied by up to a factor of beyond 2 to match the convective flux obtained from the simulations. To bring convective fluxes integrated over the He II convection zone and the overshoot zone below into agreement, this parameter has to be varied by a factor of up to ˜7.5 (Kuhfuß). We then present results on the energetics of the convection and overshoot zone by radially symmetric and fluctuating quantities. To successfully model this scenario by a static, 1D or even by a simple time-dependent model appears extremely challenging. We conclude that significant improvements are needed to make predictions based on 1D models more robust and to improve the reliability of conclusions on the convection-pulsation coupling drawn from them. Multidimensional simulations can provide guidelines for developing descriptions of convection then applied in traditional 1D modelling.
NASA Astrophysics Data System (ADS)
Khan, Saki
2016-06-01
We present a minimal renormalizable non-supersymmetric S O(10) grand unified model with a symmetry breaking sector consisting of Higgs fields in the 54H + 126H + 10H representations. This model admits a single intermediate scale associated with Pati-Salam symmetry along with a discrete parity. Spontaneous symmetry breaking, the unification of gauge couplings and proton lifetime estimates are studied in detail in this framework. Including threshold corrections self-consistently, obtained from a full analysis of the Higgs potential, we show that the model is compatible with the current experimental bound on proton lifetime. The model generally predicts an upper bound of few times 1035 yrs for proton lifetime, which is not too far from the present Super-Kamiokande limit of τp ≳ 1.29 × 1034 yrs. With the help of a Pecci-Quinn symmetry and the resulting axion, the model provides a suitable dark matter candidate while also solving the strong CP problem. The intermediate scale, MI ≈ (1013 - 1014) GeV which is also the B - L scale, is of the right order for the right-handed neutrino mass which enables a successful description of light neutrino masses and oscillations. The Yukawa sector of the model consists of only two matrices in family space and leads to a predictive scenario for quark and lepton masses and mixings. The branching ratios for proton decay are calculable with the leading modes being p → e+π0 and p →v ¯π+ . Even though the model predicts no new physics within the reach of LHC, the next generation proton decay detectors and axion search experiments have the capability to pass verdict on this minimal scenario.
Numerical Modeling of Plasmonic Nanoantennas with Realistic 3D Roughness and Distortion
Kildishev, Alexander V.; Borneman, Joshua D.; Chen, Kuo-Ping; Drachev, Vladimir P.
2011-01-01
Nanostructured plasmonic metamaterials, including optical nanoantenna arrays, are important for advanced optical sensing and imaging applications including surface-enhanced fluorescence, chemiluminescence, and Raman scattering. Although designs typically use ideally smooth geometries, realistic nanoantennas have nonzero roughness, which typically results in a modified enhancement factor that should be involved in their design. Herein we aim to treat roughness by introducing a realistic roughened geometry into the finite element (FE) model. Even if the roughness does not result in significant loss, it does result in a spectral shift and inhomogeneous broadening of the resonance, which could be critical when fitting the FE simulations of plasmonic nanoantennas to experiments. Moreover, the proposed approach could be applied to any model, whether mechanical, acoustic, electromagnetic, thermal, etc, in order to simulate a given roughness-generated physical phenomenon. PMID:22164010
NASA Astrophysics Data System (ADS)
Ding, Lei; Lai, Yuan; He, Bin
2005-01-01
It is of importance to localize neural sources from scalp recorded EEG. Low resolution brain electromagnetic tomography (LORETA) has received considerable attention for localizing brain electrical sources. However, most such efforts have used spherical head models in representing the head volume conductor. Investigation of the performance of LORETA in a realistic geometry head model, as compared with the spherical model, will provide useful information guiding interpretation of data obtained by using the spherical head model. The performance of LORETA was evaluated by means of computer simulations. The boundary element method was used to solve the forward problem. A three-shell realistic geometry (RG) head model was constructed from MRI scans of a human subject. Dipole source configurations of a single dipole located at different regions of the brain with varying depth were used to assess the performance of LORETA in different regions of the brain. A three-sphere head model was also used to approximate the RG head model, and similar simulations performed, and results compared with the RG-LORETA with reference to the locations of the simulated sources. Multi-source localizations were discussed and examples given in the RG head model. Localization errors employing the spherical LORETA, with reference to the source locations within the realistic geometry head, were about 20-30 mm, for four brain regions evaluated: frontal, parietal, temporal and occipital regions. Localization errors employing the RG head model were about 10 mm over the same four brain regions. The present simulation results suggest that the use of the RG head model reduces the localization error of LORETA, and that the RG head model based LORETA is desirable if high localization accuracy is needed.
Progress on realistic modeling of black hole-neutron star binary mergers
NASA Astrophysics Data System (ADS)
Duez, Matthew
2011-04-01
Black hole-neutron star (BHNS) binary mergers are important gravitational wave sources and (possibly) gamma ray burst progenitors. The current state of the art of BHNS simulations, while an impressive acheivement, is inadequate in a number of ways--most importantly in its treatment of neutron star matter and neutrino emission. We present a status report on the efforts of the Caltech-Cornell-CITA-WSU collaboration to accurately model BHNS binaries with realistic microphysics.
Advantages of Realistic Model Based on computational method: NDSHA versus Standard PSHA
NASA Astrophysics Data System (ADS)
Irwandi, I.
2017-02-01
Procedure of standard Seismic Hazard Assessment (PSHA) has a problem with over simplifying recurrence since being represented by a linear relationship. However, the relationship will be satisfied only if the size of the study area is large enough with respect to linear dimensions of sources.. PSHA lies in attenuation relations are usually not translation invariant in the phase space. Regarding the problem of completeness data, instead of using recurrence relationship DSHA select the most credible earthquakes. However, the DSHA remain lies in attenuation relations, assume the same propagation model for all the events, but such a hypothesis is not very realistic. On the contrary, NDSHA procedure has advantages in calculation strong ground motion from the realistic model of synthetic seismograms from source specific properties and cooperates with the available structural model. Additionally, The NDSHA produced more information such as PGD, PGV, PGA for horizontal and vertical components each. Using realistic computation for Banda Aceh, NDSHA provides an accurate value for each of those components, achieving probability of exceedance in the range between 10% to 2% probability of exceedance PGA from PSHA computation. Regarding some limitation from PSHA, Indonesia needs to establish research on NDSHA for the area has critical infrastructures to face the seismic hazard.
NASA Astrophysics Data System (ADS)
Heister, Timo; Dannberg, Juliane; Gassmöller, Rene; Bangerth, Wolfgang
2017-08-01
Computations have helped elucidate the dynamics of Earth's mantle for several decades already. The numerical methods that underlie these simulations have greatly evolved within this time span, and today include dynamically changing and adaptively refined meshes, sophisticated and efficient solvers, and parallelization to large clusters of computers. At the same time, many of the methods - discussed in detail in a previous paper in this series - were developed and tested primarily using model problems that lack many of the complexities that are common to the realistic models our community wants to solve today. With several years of experience solving complex and realistic models, we here revisit some of the algorithm designs of the earlier paper and discuss the incorporation of more complex physics. In particular, we re-consider time stepping and mesh refinement algorithms, evaluate approaches to incorporate compressibility, and discuss dealing with strongly varying material coefficients, latent heat, and how to track chemical compositions and heterogeneities. Taken together and implemented in a high-performance, massively parallel code, the techniques discussed in this paper then allow for high resolution, 3-D, compressible, global mantle convection simulations with phase transitions, strongly temperature dependent viscosity and realistic material properties based on mineral physics data.
Mono-jet, -photon and - Z signals of a supersymmetric ( B - L) model at the Large Hadron Collider
NASA Astrophysics Data System (ADS)
Abdallah, W.; Fiaschi, J.; Khalil, S.; Moretti, S.
2016-02-01
Search for invisible final states produced at the Large Hadron Collider (LHC) by new physics scenarios are normally carried out resorting to a variety of probes emerging from the initial state, in the form of single-jet, -photon and - Z boson signatures. These are particularly effective for models of Supersymmetry (SUSY) in presence of R-parity conservation, owing to the presence in their spectra of a stable neutralino as a Dark Matter (DM) candidate. We assume here as theoretical framework the Supersymmetric version of the ( B - L) extension of the Standard Model (BLSSM), wherein a mediator for invisible decays can be the Z ' boson present in this scenario. The peculiarity of the signal is thus that the final state objects carry a very large (transverse) missing energy, since the Z ' is naturally massive and constrained by direct searches and Electro-Weak Precision Tests (EWPTs) to be at least in the TeV scale region. Under these circumstances the efficiency in accessing the invisible final state and rejecting the Standard Model (SM) background is very high. This somehow compensates the rather meagre production rates. Another special feature of this invisible BLSSM signal is its composition, which is often dominated by sneutrino decays (alongside the more traditional neutrino and neutralino modes). Sensitivity of the CERN machine to these two features can therefore help disentangling the BLSSM from more popular SUSY models. We assess in this analysis the scope of the LHC in establishing the aforementioned invisible signals through a sophisticated signal-to-background simulation carried out in presence of parton shower, hadronisation as well as detector effects. We find that significant sensitivity exists already after 300 fb-1 during Run 2. We find that mono-jet events can be readily accessible at the LHC, so as to enable one to claim a prompt discovery, while mono-photon and - Z signals can be used as diagnostic tools of the underlying scenario.
Supersymmetric oscillator in optics
NASA Technical Reports Server (NTRS)
Chumakov, Sergey M.; Wolf, Kurt Bernardo
1995-01-01
We show that the supersymmetric structure (in the sense of supersymmetric quantum mechanics) appears in Helmholtz optics describing light propagation in waveguides. For the case of elliptical waveguides, with the accuracy of paraxial approximation it admits a simple physical interpretation. The supersymmetry connects light beams of different colors. The difference in light frequencies for the supersymmetric beams is determined by the transverse gradient of the refractive index. These beams have the save wavelength in the propagation direction and can form a stable interference pattern.
Modeling Time Resolved Light Propagation Inside a Realistic Human Head Model
Bazrafkan, Sh; Kazemi, K
2014-01-01
Background: Near infrared spectroscopy imaging is one of the new techniques used for investigating structural and functionality of different body tissues. This is done by injecting light into the medium and measuring the photon intensity at the surface of the tissue. Methods: In this paper the different medical applications, various imaging and simulation techniques of NIRS imaging is described. Each method is introduced and discussed. Then, the optimized model is prepared for numerical simulations. In this paper, the finite element method is used for solving the diffusion equation numerically. Results: Diffusion equation was solved for realistic human head model using finite element approach for a point light source and time resolved case. The photon intensity distribution in different head layers has been shown and the intensity orientation via the CSF layer has been illustrated. Conclusion: Simulating the photon transformation inside the tissue is essential for investigating the NIRS imaging technique. The finite element approach is a fast and accurate method for simulating this fact. The time resolved approach of this technique could illustrate the photon migration and intensity orientation in the tissue for time dependent light sources in tissues. PMID:25505770
Supersymmetric unification requires extra dimensions
Chen, Mu-Chun; Fallbacher, Maximilian; Ratz, Michael
2013-05-23
We discuss settings that predict precision gauge unification in the minimal supersymmetric standard model. We show that, if one requires anomaly freedom and fermion masses while demanding that unification is not an accident, only R symmetries can forbid the supersymmetric Higgs mass term {mu}. We then review the proof that R symmetries are not available in conventional grand unified theories (GUTs) and argue that this prevents natural solutions to the doublet-triplet splitting problem in four dimensions. On the other hand, higher-dimensional GUTs do not suffer from this problem. We briefly comment on an explicit string-derived model in which the {mu} and dimension five proton decay problems are solved by an order four discrete R symmetry, and comment on the higher-dimensional origin of this symmetry.
Simplified realistic human head model for simulating Tumor Treating Fields (TTFields).
Wenger, Cornelia; Bomzon, Ze'ev; Salvador, Ricardo; Basser, Peter J; Miranda, Pedro C
2016-08-01
Tumor Treating Fields (TTFields) are alternating electric fields in the intermediate frequency range (100-300 kHz) of low-intensity (1-3 V/cm). TTFields are an anti-mitotic treatment against solid tumors, which are approved for Glioblastoma Multiforme (GBM) patients. These electric fields are induced non-invasively by transducer arrays placed directly on the patient's scalp. Cell culture experiments showed that treatment efficacy is dependent on the induced field intensity. In clinical practice, a software called NovoTalTM uses head measurements to estimate the optimal array placement to maximize the electric field delivery to the tumor. Computational studies predict an increase in the tumor's electric field strength when adapting transducer arrays to its location. Ideally, a personalized head model could be created for each patient, to calculate the electric field distribution for the specific situation. Thus, the optimal transducer layout could be inferred from field calculation rather than distance measurements. Nonetheless, creating realistic head models of patients is time-consuming and often needs user interaction, because automated image segmentation is prone to failure. This study presents a first approach to creating simplified head models consisting of convex hulls of the tissue layers. The model is able to account for anisotropic conductivity in the cortical tissues by using a tensor representation estimated from Diffusion Tensor Imaging. The induced electric field distribution is compared in the simplified and realistic head models. The average field intensities in the brain and tumor are generally slightly higher in the realistic head model, with a maximal ratio of 114% for a simplified model with reasonable layer thicknesses. Thus, the present pipeline is a fast and efficient means towards personalized head models with less complexity involved in characterizing tissue interfaces, while enabling accurate predictions of electric field distribution.
Realistic microwave breast models through T1-weighted 3-D MRI data.
Tunçay, Ahmet Hakan; Akduman, Ibrahim
2015-02-01
In this paper we present an effective method for developing realistic numerical three-dimensional (3-D) microwave breast models of different shape, size, and tissue density. These models are especially convenient for microwave breast cancer imaging applications and numerical analysis of human breast-microwave interactions. As in the recent studies on this area, anatomical information of the breast tissue is collected from T1-weighted 3-D MRI data of different patients' in prone position. The method presented in this paper offers significant improvements including efficient noise reduction and tissue segmentation, nonlinear mapping of electromagnetic properties, realistically asymmetric phantom shape, and a realistic classification of breast phantoms. Our method contains a five-step approach where each MRI voxel is classified and mapped to the appropriate dielectric properties. In the first step, the MRI data are denoised by estimating and removing the bias field from each slice, after which the voxels are segmented into two main tissues as fibro-glandular and adipose. Using the distribution of the voxel intensities in MRI histogram, two nonlinear mapping functions are generated for dielectric permittivity and conductivity profiles, which allow each MRI voxel to map to its proper dielectric properties. Obtained dielectric profiles are then converted into 3-D numerical breast phantoms using several image processing techniques, including morphologic operations, filtering. Resultant phantoms are classified according to their adipose content, which is a critical parameter that affects penetration depth during microwave breast imaging.
Nummenmaa, Aapo; Stenroos, Matti; Ilmoniemi, Risto J.; Okada, Yoshio C.; Hämäläinen, Matti S.; Raij, Tommi
2013-01-01
Objective MRI-guided real-time transcranial magnetic stimulation (TMS) navigators that apply electromagnetic modeling have improved the utility of TMS. However, their accuracy and speed depends on the assumed volume conductor geometry. Spherical models found in present navigators are computationally fast but may be inaccurate in some areas. Realistically-shaped boundary-element models (BEMs) could increase accuracy at a moderate computational cost, but it is unknown which model features have the largest influence on accuracy. Thus, we compared different types of spherical models and BEMs. Methods Globally and locally fitted spherical models and different BEMs with either one or three compartments and with different skull-to-brain conductivity ratios (1/1 – 1/80) were compared against a reference BEM. Results The one-compartment BEM at inner skull surface was almost as accurate as the reference BEM. Skull/brain conductivity ratio in the range 1/10 – 1/80 had only a minor influence. BEMs were superior to spherical models especially in frontal and temporal areas (up to 20 mm localization and 40% intensity improvement); in motor cortex all models provided similar results. Conclusions One-compartment BEMs offer a good balance between accuracy and computational cost. Significance Realistically-shaped BEMs may increase TMS navigation accuracy in several brain areas, such as in prefrontal regions often targeted in clinical applications. PMID:23890512
The effect of a realistic thermal diffusivity on numerical model of a subducting slab
NASA Astrophysics Data System (ADS)
Maierova, P.; Steinle-Neumann, G.; Cadek, O.
2010-12-01
A number of numerical studies of subducting slab assume simplified (constant or only depth-dependent) models of thermal conductivity. The available mineral physics data indicate, however, that thermal diffusivity is strongly temperature- and pressure-dependent and may also vary among different mantle materials. In the present study, we examine the influence of realistic thermal properties of mantle materials on the thermal state of the upper mantle and the dynamics of subducting slabs. On the basis of the data published in mineral physics literature we compile analytical relationships that approximate the pressure and temperature dependence of thermal diffusivity for major mineral phases of the mantle (olivine, wadsleyite, ringwoodite, garnet, clinopyroxenes, stishovite and perovskite). We propose a simplified composition of mineral assemblages predominating in the subducting slab and the surrounding mantle (pyrolite, mid-ocean ridge basalt, harzburgite) and we estimate their thermal diffusivity using the Hashin-Shtrikman bounds. The resulting complex formula for the diffusivity of each aggregate is then approximated by a simpler analytical relationship that is used in our numerical model as an input parameter. For the numerical modeling we use the Elmer software (open source finite element software for multiphysical problems, see http://www.csc.fi/english/pages/elmer). We set up a 2D Cartesian thermo-mechanical steady-state model of a subducting slab. The model is partly kinematic as the flow is driven by a boundary condition on velocity that is prescribed on the top of the subducting lithospheric plate. Reology of the material is non-linear and is coupled with the thermal equation. Using the realistic relationship for thermal diffusivity of mantle materials, we compute the thermal and flow fields for different input velocity and age of the subducting plate and we compare the results against the models assuming a constant thermal diffusivity. The importance of the
What Is the Most Realistic Single-Compartment Model of Spike Initiation?
Brette, Romain
2015-01-01
A large variety of neuron models are used in theoretical and computational neuroscience, and among these, single-compartment models are a popular kind. These models do not explicitly include the dendrites or the axon, and range from the Hodgkin-Huxley (HH) model to various flavors of integrate-and-fire (IF) models. The main classes of models differ in the way spikes are initiated. Which one is the most realistic? Starting with some general epistemological considerations, I show that the notion of realism comes in two dimensions: empirical content (the sort of predictions that a model can produce) and empirical accuracy (whether these predictions are correct). I then examine the realism of the main classes of single-compartment models along these two dimensions, in light of recent experimental evidence. PMID:25856629
Supersymmetric Sneutrino-Higgs inflation
NASA Astrophysics Data System (ADS)
Deen, Rehan; Ovrut, Burt A.; Purves, Austin
2016-11-01
It is shown that in the phenomenologically realistic supersymmetric B - L MSSM theory, a linear combination of the neutral, up Higgs field with the third family left- and right-handed sneutrinos can play the role of the cosmological inflaton. Assuming that supersymmetry is softly broken at a mass scale of order 1013 GeV, the potential energy associated with this field allows for 60 e-foldings of inflation with the cosmological parameters being consistent with all Planck2015 data. The theory does not require any non-standard coupling to gravity and the physical fields are all sub-Planckian during the inflationary epoch. It will be shown that there is a "robust" set of initial conditions which, in addition to satisfying the Planck data, simultaneously are consistent with all present LHC phenomenological requirements.
Uncertainty Quantification of Tracer Dispersion with the PMVP Model under Realistic Conditions
NASA Astrophysics Data System (ADS)
Meyer, D. W.; Duenser, S.
2015-12-01
The polar Markovian velocity process (PVMP) model provides a computationally efficient method to propagate input uncertainty stemming from unknown permeability fields to output flow and transport statistics [Meyer and Tchelepi, WRR, 2010; Meyer, Jenny, and Tchelepi, WRR, 2010; Meyer et al., WRR, 2013]. Compared with classical Monte Carlo (MC) sampling, the PMVP model provides predictions of tracer concentration statistics at computing times that are three orders of magnitude smaller. Consequently, the PMVP model is as well significantly faster than accelerated sampling techniques such as multi-level MC or polynomial chaos expansions. In this work, we further evaluate the PMVP model performance by applying the model for tracer dispersion predictions in a setup derived from the well-known MADE field experiment [Boggs et al., WRR, 1992]. We perform detailed model validations against reference MC simulations and conclude that the model provides overall accurate dispersion predictions under realistic conditions.
From Kuo-Brown to today's realistic shell-model calculations
NASA Astrophysics Data System (ADS)
Coraggio, L.; Covello, A.; Gargano, A.; Itaco, N.
2014-08-01
This paper is an homage to the seminal work of Gerry Brown and Tom Kuo, where shell model calculations were performed for 18O and 18F using an effective interaction derived from the Hamada-Johnston nucleon-nucleon potential. That work has been the first successful attempt to provide a description of nuclear structure properties starting from the free nucleon-nucleon potential. We shall compare the approach employed in the 1966 paper with the derivation of a modern realistic shell-model interaction for sd-shell nuclei, evidencing the progress that has been achieved during the last decades.
Realistic models of amorphous silica: A comparative study of different potentials
NASA Astrophysics Data System (ADS)
von Alfthan, S.; Kuronen, A.; Kaski, K.
2003-08-01
The creation of realistic models of amorphous silica has been studied using the Monte Carlo based method of Wooten, Winer, and Weaire, where the bond-topology is optimized with respect to an interatomic potential model. The commonly used Keating potentials are compared and their strengths and weaknesses are assessed. The mean oxygen bond-angle obtained using these potentials turned out to be too small. A modification of the potential parameters is shown to correct this feature and thus produce better results when used with the Wooten-Winer-Weaire method.
Introducing a more realistic model for opinion formation considering instability in social structure
NASA Astrophysics Data System (ADS)
Salehi, Sajjad; Taghiyareh, Fattaneh
2016-06-01
Opinion formation is a process through which interactions of individuals and dynamism of their opinions in effect of neighbors are modeled. In this paper, in an effort to model the opinion formation more realistically, we have introduced a model that considers the role of network structure in opinion dynamics. In this model, each individual changes his opinion in a way so as to decrease its difference with the opinion of trusted neighbors while he intensifies his dissention with the untrusted ones. Considering trust/distrust relations as a signed network, we have defined a structural indicator which shows the degree of instability in social structure and is calculated based on the structural balance theory. It is also applied as feedback to the opinion formation process affecting its dynamics. Our simulation results show formation of a set of clusters containing individuals holding opinions having similar values. Also, the opinion value of each individual is far from the ones of distrusted neighbors. Since this model considers distrust and instability of relations in society, it can offer a more realistic model of opinion formation.
More Realistic Face Model Surface Improves Relevance of Pediatric In-Vitro Aerosol Studies.
Amirav, Israel; Halamish, Asaf; Gorenberg, Miguel; Omar, Hamza; Newhouse, Michael T
2015-01-01
Various hard face models are commonly used to evaluate the efficiency of aerosol face masks. Softer more realistic "face" surface materials, like skin, deform upon mask application and should provide more relevant in-vitro tests. Studies that simultaneously take into consideration many of the factors characteristic of the in vivo face are lacking. These include airways, various application forces, comparison of various devices, comparison with a hard-surface model and use of a more representative model face based on large numbers of actual faces. To compare mask to "face" seal and aerosol delivery of two pediatric masks using a soft vs. a hard, appropriately representative, pediatric face model under various applied forces. Two identical face models and upper airways replicas were constructed, the only difference being the suppleness and compressibility of the surface layer of the "face." Integrity of the seal and aerosol delivery of two different masks [AeroChamber (AC) and SootherMask (SM)] were compared using a breath simulator, filter collection and realistic applied forces. The soft "face" significantly increased the delivery efficiency and the sealing characteristics of both masks. Aerosol delivery with the soft "face" was significantly greater for the SM compared to the AC (p< 0.01). No statistically significant difference between the two masks was observed with the hard "face." The material and pliability of the model "face" surface has a significant influence on both the seal and delivery efficiency of face masks. This finding should be taken into account during in-vitro aerosol studies.
Beta Functions in Chirally Deformed Supersymmetric Sigma Models in Two Dimensions
NASA Astrophysics Data System (ADS)
Vainshtein, Arkady
We study two-dimensional sigma models where the chiral deformation diminished the original 𝒩 =(2, 2) supersymmetry to the chiral one, 𝒩 =(0, 2). Such heterotic models were discovered previously on the world sheet of non-Abelian stringy solitons supported by certain four-dimensional 𝒩 = 1 theories. We study geometric aspects and holomorphic properties of these models, and derive a number of exact expressions for the β functions in terms of the anomalous dimensions analogous to the NSVZ β function in four-dimensional Yang-Mills. Instanton calculus provides a straightforward method for the derivation.
Supersymmetric Froggatt-Nielsen Models with Baryon- and Lepton-Number Violation
Dreiner, Herbi K.; Thormeier, Marc
2004-04-16
We systematically investigate the embedding of U(1)_X Froggatt-Nielsen models in (four-dimensional) local supersymmetry. We restrict ourselves to models with a single flavon field. We do not impose a discrete symmetry by hand, e.g., R-parity, baryon-parity or lepton-parity. Thus we determine the order of magnitude of the baryon- and/or lepton violating coupling constants through the Froggatt-Nielsen mechanism. We then scrutinize whether the predicted coupling constants are in accord with weak or GUT scale constraints. Many models turn out to be incompatible.
Beta functions in Chirally deformed supersymmetric sigma models in two dimensions
NASA Astrophysics Data System (ADS)
Vainshtein, Arkady
2016-10-01
We study two-dimensional sigma models where the chiral deformation diminished the original 𝒩 = (2, 2) supersymmetry to the chiral one, 𝒩 = (0, 2). Such heterotic models were discovered previously on the world sheet of non-Abelian stringy solitons supported by certain four-dimensional 𝒩 = 1 theories. We study geometric aspects and holomorphic properties of these models, and derive a number of exact expressions for the β functions in terms of the anomalous dimensions analogous to the NSVZ β function in four-dimensional Yang-Mills. Instanton calculus provides a straightforward method for the derivation.
Supersymmetric Froggatt-Nielsen models with baryon- and lepton-number violation
NASA Astrophysics Data System (ADS)
Dreiner, Herbi K.; Thormeier, Marc
2004-03-01
We systematically investigate the embedding of U(1)X Froggatt-Nielsen models in (four-dimensional) local supersymmetry. We restrict ourselves to models with a single flavon field. We do not impose a discrete symmetry by hand, e.g., R parity, baryon parity, or lepton parity. Thus we determine the order of magnitude of the baryon- and/or lepton-violating coupling constants through the Froggatt-Nielsen scenario. We then scrutinize whether the predicted coupling constants are in accord with weak or GUT scale constraints. Many models turn out to be incompatible.
Realistic spatial and temporal earthquake distributions in a modified Olami-Feder-Christensen model
NASA Astrophysics Data System (ADS)
Jagla, E. A.
2010-04-01
The Olami-Feder-Christensen model describes a limiting case of an elastic surface that slides on top of a substrate and is one of the simplest models that display some features observed in actual seismicity patterns. However, temporal and spatial correlations of real earthquakes are not correctly described by this model in its original form. I propose and study a modified version of the model, which includes a mechanism of structural relaxation. With this modification, realistic features of seismicity emerge, which are not obtained with the original version, mainly: aftershocks that cluster spatially around the slip surface of the main shock and follow the Omori law, and averaged frictional properties similar to those observed in rock friction, in particular the velocity-weakening effect. In addition, a Gutenberg-Richter law for the decaying of number of earthquakes with magnitude is obtained, with a decaying exponent within the range of experimentally observed values. Contrary to the original version of the model, a realistic value of the exponent appears without the necessity to fine tune any parameter.
The ultimate signal-to-noise ratio in realistic body models.
Guérin, Bastien; Villena, Jorge F; Polimeridis, Athanasios G; Adalsteinsson, Elfar; Daniel, Luca; White, Jacob K; Wald, Lawrence L
2016-12-04
We compute the ultimate signal-to-noise ratio (uSNR) and G-factor (uGF) in a realistic head model from 0.5 to 21 Tesla. We excite the head model and a uniform sphere with a large number of electric and magnetic dipoles placed at 3 cm from the object. The resulting electromagnetic fields are computed using an ultrafast volume integral solver, which are used as basis functions for the uSNR and uGF computations. Our generalized uSNR calculation shows good convergence in the sphere and the head and is in close agreement with the dyadic Green's function approach in the uniform sphere. In both models, the uSNR versus B0 trend was linear at shallow depths and supralinear at deeper locations. At equivalent positions, the rate of increase of the uSNR with B0 was greater in the sphere than in the head model. The uGFs were lower in the realistic head than in the sphere for acceleration in the anterior-posterior direction, but similar for the left-right direction. The uSNR and uGFs are computable in nonuniform body models and provide fundamental performance limits for human imaging with close-fitting MRI array coils. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.
Fate of supersymmetric flat directions and their role in reheating
Olive, Keith A.; Peloso, Marco
2006-11-15
We consider the role of supersymmetric flat directions in reheating the Universe after inflation. One or more flat directions can develop large vevs during inflation, which can potentially affect reheating by slowing down scattering processes among inflaton decay products or by coming to dominate the energy density of the Universe. Both effects occur only if flat directions are sufficiently long-lived. The computation of their perturbative decay rate, and a simple estimate of their nonperturbative decay have led to the conclusion that this is indeed the case. In contrast, we show that flat directions can decay quickly through nonperturbative channels in realistic models. The mass matrix for minimal supersymmetric standard model (MSSM) excitations around flat directions has nondiagonal entries, which vary with the phase of the (complex) flat directions. The quasiperiodic motion of the flat directions results in a strong parametric resonance, leading to the rapid depletion of the flat direction within its first few rotations. This may preclude any significant role for the flat directions in reheating the Universe after inflation in models in which the inflaton decays perturbatively.
Fixing the EW scale in supersymmetric models after the Higgs discovery
NASA Astrophysics Data System (ADS)
Ghilencea, D. M.
2013-11-01
TeV-scale supersymmetry was originally introduced to solve the hierarchy problem and therefore fix the electroweak (EW) scale in the presence of quantum corrections. Numerical methods testing the SUSY models often report a good likelihood L (or χ2=-2ln L) to fit the data including the EW scale itself (mZ0) with a simultaneously large fine-tuning i.e. a large variation of this scale under a small variation of the SUSY parameters. We argue that this is inconsistent and we identify the origin of this problem. Our claim is that the likelihood (or χ2) to fit the data that is usually reported in such models does not account for the χ2 cost of fixing the EW scale. When this constraint is implemented, the likelihood (or χ2) receives a significant correction (δχ2) that worsens the current data fits of SUSY models. We estimate this correction for the models: constrained MSSM (CMSSM), models with non-universal gaugino masses (NUGM) or higgs soft masses (NUHM1, NUHM2), the NMSSM and the general NMSSM (GNMSSM). For a higgs mass mh≈126 GeV, one finds that in these models δχ2/n⩾1.5 (≈1 for GNMSSM), which violates the usual condition of a good fit (total χ2/n≈1) already before fitting observables other than the EW scale itself (n=number of degrees of freedom). This has (negative) implications for SUSY models and it is suggested that future data fits properly account for this effect, if one remains true to the original goal of SUSY. Since the expression of δχ2 that emerges from our calculation depends on a familiar measure of fine-tuning, one concludes that fine-tuning is an intrinsic part of the likelihood to fit the data that includes the EW scale (mZ0).
Realistic image generation using model-driven processing in an interactive system
NASA Astrophysics Data System (ADS)
Miyagi, Toshifumi; Hori, Atsushi; Sugama, Hideo; Murao, Yo; Enomoto, Hajime
1997-05-01
For efficient generation of realistic images, 4 kinds of generic models (data-, object-, role- and process-models) are introduced in the system based on the extensible well (window- based elaboration language) which has been reported previously. These models are constructed so that they have hierarchical interfaces from data to processes. In order to satisfy multiple intentions interacting with each other, concepts of roles are introduced. Each role is recognized as a set of the object-networks, and the respective user's intentions are referred to a set of executions of many roles. Object-networks which consists of noun-objects and verb objects express transitions of states. In each occurrence of transition, the user's intention is issued in an event driven manner, and it provides concurrent processes Multiple roles are made interactive with each other by using the common platform which consists of windows. Each role is specified as a structure of the object-network, which is defined by a graph structure. Every object has templates which define data structure. Data of objects are specified by constraint- relating attributes of objects or referring to user's data driven action. By concepts of constraints and models, roles, realistic images are obtained with the least data. Some examples for human movements are demonstrated.
Realistic multi-cellular dosimetry for 177Lu-labelled antibodies: model and application
NASA Astrophysics Data System (ADS)
Marcatili, S.; Pichard, A.; Courteau, A.; Ladjohounlou, R.; Navarro-Teulon, I.; Repetto-Llamazares, A.; Heyerdahl, H.; Dahle, J.; Pouget, J. P.; Bardiès, M.
2016-10-01
Current preclinical dosimetric models often fail to take account of the complex nature of absorbed dose distribution typical of in vitro clonogenic experiments in targeted radionuclide therapy. For this reason, clonogenic survival is often expressed as a function of added activity rather than the absorbed dose delivered to cells/cell nuclei. We designed a multi-cellular dosimetry model that takes into account the realistic distributions of cells in the Petri dish, for the establishment of survival curves as a function of the absorbed dose. General-purpose software tools were used for the generation of realistic, randomised 3D cell culture geometries based on experimentally determined parameters (cell size, cell density, cluster density, average cluster size, cell cumulated activity). A mixture of Monte Carlo and analytical approaches was implemented in order to achieve as accurate as possible results while reducing calculation time. The model was here applied to clonogenic survival experiments carried out to compare the efficacy of Betalutin®, a novel 177Lu-labelled antibody radionuclide conjugate for the treatment of non-Hodgkin lymphoma, to that of 177Lu-labelled CD20-specific (rituximab) and non-specific antibodies (Erbitux) on lymphocyte B cells. The 3D cellular model developed allowed a better understanding of the radiative and non-radiative processes associated with cellular death. Our approach is generic and can also be applied to other radiopharmaceuticals and cell distributions.
Mohiuddin, Mohammad W.; Rihani, Ryan J.; Laine, Glen A.
2012-01-01
The mechanism of the well-documented increase in aortic pulse pressure (PP) with age is disputed. Investigators assuming a classical windkessel model believe that increases in PP arise from decreases in total arterial compliance (Ctot) and increases in total peripheral resistance (Rtot) with age. Investigators assuming a more sophisticated pulse transmission model believe PP rises because increases in pulse wave velocity (cph) make the reflected pressure wave arrive earlier, augmenting systolic pressure. It has recently been shown, however, that increases in cph do not have a commensurate effect on the timing of the reflected wave. We therefore used a validated, large-scale, human arterial system model that includes realistic pulse wave transmission to determine whether increases in cph cause increased PP with age. First, we made the realistic arterial system model age dependent by altering cardiac output (CO), Rtot, Ctot, and cph to mimic the reported changes in these parameters from age 30 to 70. Then, cph was theoretically maintained constant, while Ctot, Rtot, and CO were altered. The predicted increase in PP with age was similar to the observed increase in PP. In a complementary approach, Ctot, Rtot, and CO were theoretically maintained constant, and cph was increased. The predicted increase in PP was negligible. We found that increases in cph have a limited effect on the timing of the reflected wave but cause the system to degenerate into a windkessel. Changes in PP can therefore be attributed to a decrease in Ctot. PMID:22561301
Realistic multi-cellular dosimetry for (177)Lu-labelled antibodies: model and application.
Marcatili, S; Pichard, A; Courteau, A; Ladjohounlou, R; Navarro-Teulon, I; Repetto-Llamazares, A; Heyerdahl, H; Dahle, J; Pouget, J P; Bardiès, M
2016-10-07
Current preclinical dosimetric models often fail to take account of the complex nature of absorbed dose distribution typical of in vitro clonogenic experiments in targeted radionuclide therapy. For this reason, clonogenic survival is often expressed as a function of added activity rather than the absorbed dose delivered to cells/cell nuclei. We designed a multi-cellular dosimetry model that takes into account the realistic distributions of cells in the Petri dish, for the establishment of survival curves as a function of the absorbed dose. General-purpose software tools were used for the generation of realistic, randomised 3D cell culture geometries based on experimentally determined parameters (cell size, cell density, cluster density, average cluster size, cell cumulated activity). A mixture of Monte Carlo and analytical approaches was implemented in order to achieve as accurate as possible results while reducing calculation time. The model was here applied to clonogenic survival experiments carried out to compare the efficacy of Betalutin(®), a novel (177)Lu-labelled antibody radionuclide conjugate for the treatment of non-Hodgkin lymphoma, to that of (177)Lu-labelled CD20-specific (rituximab) and non-specific antibodies (Erbitux) on lymphocyte B cells. The 3D cellular model developed allowed a better understanding of the radiative and non-radiative processes associated with cellular death. Our approach is generic and can also be applied to other radiopharmaceuticals and cell distributions.
Development of a realistic in vivo bone metastasis model of human renal cell carcinoma.
Valta, Maija P; Zhao, Hongjuan; Ingels, Alexandre; Thong, Alan E; Nolley, Rosalie; Saar, Matthias; Peehl, Donna M
2014-06-01
About one-third of patients with advanced renal cell carcinoma (RCC) have bone metastases. The incidence of RCC is increasing and bone metastatic RCC merits greater focus. Realistic preclinical bone metastasis models of RCC are lacking, hampering the development of effective therapies. We developed a realistic in vivo bone metastasis model of human RCC by implanting precision-cut tissue slices under the renal capsule of immunodeficient mice. The presence of disseminated cells in bone marrow of tissue slice graft (TSG)-bearing mice was screened by human-specific polymerase chain reaction and confirmed by immunohistology using human-specific antibody. Disseminated tumor cells in bone marrow of TSG-bearing mice derived from three of seven RCC patients were detected as early as 1 month after tissue implantation at a high frequency with close resemblance to parent tumors (e.g., CAIX expression and high vascularity). The metastatic patterns of TSGs correlated with disease progression in patients. In addition, TSGs retained capacity to metastasize to bone at high frequency after serial passaging and cryopreservation. Moreover, bone metastases in mice responded to Temsirolimus treatment. Intratibial injections of single cells generated from TSGs showed 100 % engraftment and produced X-ray-visible tumors as early as 3 weeks after cancer cell inoculation. Micro-computed tomography (μCT) and histological analysis revealed osteolytic characteristics of these lesions. Our results demonstrated that orthotopic RCC TSGs have potential to develop bone metastases that respond to standard therapy. This first reported primary RCC bone metastasis model provides a realistic setting to test therapeutics to prevent or treat bone metastases in RCC.
Geometrical order-of-magnitude estimates for spatial curvature in realistic models of the Universe
NASA Astrophysics Data System (ADS)
Buchert, Thomas; Ellis, George F. R.; van Elst, Henk
2009-09-01
The thoughts expressed in this article are based on remarks made by Jürgen Ehlers at the Albert-Einstein-Institut, Golm, Germany in July 2007. The main objective of this article is to demonstrate, in terms of plausible order-of-magnitude estimates for geometrical scalars, the relevance of spatial curvature in realistic models of the Universe that describe the dynamics of structure formation since the epoch of matter-radiation decoupling. We introduce these estimates with a commentary on the use of a quasi-Newtonian metric form in this context.
Bray, O.H. |
1994-04-01
This paper describes a natural language based, semantic information modeling methodology and explores its use and value in clarifying and comparing political science theories and frameworks. As an example, the paper uses this methodology to clarify and compare some of the basic concepts and relationships in the realist (e.g. Waltz) and the liberal (e.g. Rosenau) paradigms for international relations. The methodology can provide three types of benefits: (1) it can clarify and make explicit exactly what is meant by a concept; (2) it can often identify unanticipated implications and consequence of concepts and relationships; and (3) it can help in identifying and operationalizing testable hypotheses.
Fractional supersymmetric Liouville theory and the multi-cut matrix models
NASA Astrophysics Data System (ADS)
Irie, Hirotaka
2009-10-01
We point out that the non-critical version of the k-fractional superstring theory can be described by k-cut critical points of the matrix models. In particular, in comparison with the spectrum structure of fractional super-Liouville theory, we show that (p,q) minimal fractional superstring theories appear in the Z-symmetry breaking critical points of the k-cut two-matrix models and the operator contents and string susceptibility coincide on both sides. By using this correspondence, we also propose a set of primary operators of the fractional superconformal ghost system which consistently produces the correct gravitational scaling critical exponents of the on-shell vertex operators.
The galactic center region gamma ray excess from a supersymmetric leptophilic Higgs model
NASA Astrophysics Data System (ADS)
Marshall, Gardner; Primulando, Reinard
2011-05-01
In a recent paper by Hooper and Goodenough, data from the Fermi Gamma Ray Telescope was analyzed and an excess of gamma rays was claimed to be found in the emission spectrum from the Galactic Center Region. Hooper and Goodenough suggest that the claimed excess can be well explained by 7-10 GeV annihilating dark matter with a power law density profile if the dark matter annihilates predominantly to tau pairs. In this paper we present such a dark matter model by extending the MSSM to include four Higgs doublets and one scalar singlet. A {mathbb{Z}_2} symmetry is imposed that enforces a Yukawa structure so that the up quarks, down quarks, and leptons each receive mass from a distinct doublet. This leads to an enhanced coupling of scalars to leptons and allows the model to naturally achieve the required phenomenology in order to explain the gamma ray excess. Our model yields the correct dark matter thermal relic density and avoids collider bounds from measurements of the Z width as well as direct production at LEP.
Axion and neutrino physics in a U (1 )-enhanced supersymmetric model
NASA Astrophysics Data System (ADS)
Ahn, Y. H.
2017-07-01
Motivated by the flavored Peccei-Quinn symmetry for unifying the flavor physics and string theory, we construct an explicit model by introducing a U (1 ) symmetry such that the U (1 )X-[gravity]2 anomaly-free condition together with the standard model flavor structure demands additional sterile neutrinos as well as no axionic domain-wall problem. Such additional sterile neutrinos play the role of realizing baryogenesis via a new Affleck-Dine leptogenesis. We provide grounds for interpreting the U (1 )X symmetry as a fundamental symmetry of nature. The model will resolve rather recent but fast-growing issues in astroparticle physics, including leptonic mixings and C P violation in neutrino oscillation, high-energy neutrinos, QCD axions, and axion cooling of stars. The QCD axion decay constant, through its connection to the astrophysical constraints of stellar evolution and the SM fermion masses, is shown to be fixed at FA=1.30-0.54+0.66×1 09 GeV (consequently, its mass is ma=4.3 4-1.49+3.37 meV and the axion-photon coupling is |ga γ γ|=1.30-0.45+1.01×10-12 GeV-1 ). Interestingly enough, we show that neutrino oscillations at low energies could be connected to astronomical-scale baseline neutrino oscillations. The model predicts the nonobservational neutrinoless double beta (0 ν β β ) decay rate as well as a remarkable pattern between the leptonic Dirac C P phase (δC P) and the atmospheric mixing angle (θ23); e.g., δC P≃22 0 ° - 24 0 ° , 120°-140° for θ23=42.3 ° for normal mass ordering, and δC P≃28 3 ° , 250°, 100°, 70° for θ23=49.5 ° for the inverted one. We stress that future measurements on the θ23, 0 ν β β decay rate, the sum of active neutrino masses, the track-to-shower ratio of a cosmic neutrino, astrophysical constraints on axions, QCD axion mass, and the axion-photon coupling are of importance to test the model in the near future.
Fast Realistic MRI Simulations Based on Generalized Multi-Pool Exchange Tissue Model.
Liu, Fang; Velikina, Julia V; Block, Walter F; Kijowski, Richard; Samsonov, Alexey A
2017-02-01
We present MRiLab, a new comprehensive simulator for large-scale realistic MRI simulations on a regular PC equipped with a modern graphical processing unit (GPU). MRiLab combines realistic tissue modeling with numerical virtualization of an MRI system and scanning experiment to enable assessment of a broad range of MRI approaches including advanced quantitative MRI methods inferring microstructure on a sub-voxel level. A flexible representation of tissue microstructure is achieved in MRiLab by employing the generalized tissue model with multiple exchanging water and macromolecular proton pools rather than a system of independent proton isochromats typically used in previous simulators. The computational power needed for simulation of the biologically relevant tissue models in large 3D objects is gained using parallelized execution on GPU. Three simulated and one actual MRI experiments were performed to demonstrate the ability of the new simulator to accommodate a wide variety of voxel composition scenarios and demonstrate detrimental effects of simplified treatment of tissue micro-organization adapted in previous simulators. GPU execution allowed ∼ 200× improvement in computational speed over standard CPU. As a cross-platform, open-source, extensible environment for customizing virtual MRI experiments, MRiLab streamlines the development of new MRI methods, especially those aiming to infer quantitatively tissue composition and microstructure.
Bahrami, Hadi; Gosselin, Benoit; Rusch, Leslie A
2012-01-01
Several emerging medical applications require that a miniature data acquisition device be implanted into the head to extract and wirelessly communicate brain activity to other devices. Designing a reliable communication link for such an application requires a realistic model of the surrounding biological tissues. This paper exploits a realistic model of the biological channel to design a suitable wireless ultra wideband communication link in a brain monitoring application. Two scenarios for positioning the implanted transmitting antenna are considered. The 1(st) scenario places the antenna under the skull, whereas the 2(nd) scenario places the antenna under the skin, above the skull. The propagation characteristics of the signal through the tissues of the human head have been determined with full-wave electromagnetic simulation based on Finite Element Method. The implantable antenna and the external antenna are key components to establish an electromagnetic link between an implanted transmitter and an external receiver. The average specific absorption rate (ASAR) of the implantable antennas are evaluated and compared for the two proposed scenarios. Moreover, the maximum available power from the implanted antenna is evaluated to characterize the performance of the communication link established between the implantable antenna and the external antenna, with respect to spectrum and safety regulations. We show how sensitive the receiver must be in order to implement a reliable telemetry link based on the proposed model of the channel.
An improved boundary element method for realistic volume-conductor modeling.
Fuchs, M; Drenckhahn, R; Wischmann, H A; Wagner, M
1998-08-01
An improved boundary element method (BEM) with a virtual triangle refinement using the vertex normals, an optimized auto solid angle approximation, and a weighted isolated problem approach is presented. The performance of this new approach is compared to analytically solvable spherical shell models and highly refined reference BEM models for tangentially and radially oriented dipoles at different eccentricities. The lead fields of several electroencephalography (EEG) and magnetoencephalography (MEG) setups are analyzed by singular-value decompositions for realistically shaped volume-conductor models. Dipole mislocalizations due to simplified volume-conductor models are investigated for EEG and MEG examinations for points on a three dimensional (3-D) grid with 10-mm spacing inside the conductor and all principal dipole orientations. The applicability of the BEM in view of the computational effort is tested with a standard workstation. Finally, an application of the new method to epileptic spike data is studied and the results are compared to the spherical-shells approximation.
Modeling short-term dynamics and variability for realistic interactive facial animation.
Stoiber, Nicolas; Breton, Gaspard; Seguier, Renaud
2010-01-01
Modern modeling and rendering techniques have produced nearly photorealistic face models, but truly expressive digital faces also require natural-looking movements. Virtual characters in today's applications often display unrealistic facial expressions. Indeed, facial animation with traditional schemes such as keyframing and motion capture demands expertise. Moreover, the traditional schemes aren't adapted to interactive applications that require the real-time generation of context-dependent movements. A new animation system produces realistic expressive facial motion at interactive speed. The system relies on a set of motion models controlling facial-expression dynamics. The models are fitted on captured motion data and therefore retain the dynamic signature of human facial expressions. They also contain a nondeterministic component that ensures the variety of the long-term visual behavior. This system can efficiently animate any synthetic face. The video illustrates interactive use of a system that generates facial-animation sequences.
Effects of local tissue conductivity on spherical and realistic head models.
Bashar, M R; Li, Y; Wen, P
2010-09-01
In this study, we consider different conductivity values based on tissue location in a human head model. We implement local conductivity (LC) to compute head surface potentials in three-, four-layered spherical and realistic head models using finite element method (FEM). Implementing LC for all head models, we obtain significant scalp potential variations in the term of relative difference measurement (RDM) and magnification (MAG) values with a maximum of 2.03±1.81 and 8.27±6.36, respectively. We also investigate the effects of conductivity variations (CVs) of head tissue layer on scalp potentials and find a maximum of 2.15±1.93 RDM and 8.57±6.61 MAG values. Our study concludes that it is important to assign LC to each tissue and it is also important to assign appropriate conductivity value in the construction of a head model for achieving accurate scalp potentials.
NASA Astrophysics Data System (ADS)
Puzari, Panchanan; Sarkar, Biplab; Adhikari, Satrajit
2006-11-01
We investigate the molecular dynamics of pyrazine after excitation to the S2 electronic state by using the time-dependent discrete variable representation (TDDVR) method. The investigation has been carried out with a realistic 24-mode model Hamiltonian consisting of all the vibrational degrees of freedom of pyrazine molecule. First, we perform the simulation on a basic four-mode model, and then by including additional eight important modes and finally, by introducing 20 bath modes on the basic model. This sequential inclusion of bath modes demonstrates the effect of weak modes on the subsystem, where the calculations of energy and population transfer from basic model to the bath quantify the same effect. The spectral profile obtained by using TDDVR approach shows reasonably good agreement with the results calculated by quantum mechanical approach. It appears that the TDDVR approach for those large systems where quantum mechanical description is needed in a restricted region is a good compromise between accuracy and speed.
Puzari, Panchanan; Sarkar, Biplab; Adhikari, Satrajit
2006-11-21
We investigate the molecular dynamics of pyrazine after excitation to the S2 electronic state by using the time-dependent discrete variable representation (TDDVR) method. The investigation has been carried out with a realistic 24-mode model Hamiltonian consisting of all the vibrational degrees of freedom of pyrazine molecule. First, we perform the simulation on a basic four-mode model, and then by including additional eight important modes and finally, by introducing 20 bath modes on the basic model. This sequential inclusion of bath modes demonstrates the effect of weak modes on the subsystem, where the calculations of energy and population transfer from basic model to the bath quantify the same effect. The spectral profile obtained by using TDDVR approach shows reasonably good agreement with the results calculated by quantum mechanical approach. It appears that the TDDVR approach for those large systems where quantum mechanical description is needed in a restricted region is a good compromise between accuracy and speed.
Modeling the Earth's magnetospheric magnetic field confined within a realistic magnetopause
NASA Technical Reports Server (NTRS)
Tsyganenko, N. A.
1995-01-01
Empirical data-based models of the magnetosphereic magnetic field have been widely used during recent years. However, the existing models (Tsyganenko, 1987, 1989a) have three serious deficiencies: (1) an unstable de facto magnetopause, (2) a crude parametrization by the K(sub p) index, and (3) inaccuracies in the equatorial magnetotail B(sub z) values. This paper describes a new approach to the problem; the essential new features are (1) a realistic shape and size of the magnetopause, based on fits to a large number of observed crossing (allowing a parametrization by the solar wind pressure), (2) fully controlled shielding of the magnetic field produced by all magnetospheric current systems, (3) new flexible representations for the tail and ring currents, and (4) a new directional criterion for fitting the model field to spacecraft data, providing improved accuracy for field line mapping. Results are presented from initial efforts to create models assembled from these modules and calibrated against spacecraft data sets.
Modeling the Earth's magnetospheric magnetic field confined within a realistic magnetopause
NASA Technical Reports Server (NTRS)
Tsyganenko, N. A.
1995-01-01
Empirical data-based models of the magnetosphereic magnetic field have been widely used during recent years. However, the existing models (Tsyganenko, 1987, 1989a) have three serious deficiencies: (1) an unstable de facto magnetopause, (2) a crude parametrization by the K(sub p) index, and (3) inaccuracies in the equatorial magnetotail B(sub z) values. This paper describes a new approach to the problem; the essential new features are (1) a realistic shape and size of the magnetopause, based on fits to a large number of observed crossing (allowing a parametrization by the solar wind pressure), (2) fully controlled shielding of the magnetic field produced by all magnetospheric current systems, (3) new flexible representations for the tail and ring currents, and (4) a new directional criterion for fitting the model field to spacecraft data, providing improved accuracy for field line mapping. Results are presented from initial efforts to create models assembled from these modules and calibrated against spacecraft data sets.
Hoshi, Koki; Irisawa, Atsushi; Shibukawa, Goro; Yamabe, Akane; Fujisawa, Mariko; Igarashi, Ryo; Yoshida, Yoshitsugu; Abe, Yoko; Imbe, Koh
2016-01-01
Background and study aims: Trainees are required to learn EUS-FNA using a model before working with a patient. The aim of the current study was to validate a new training model developed for EUS-FNA. Patients and methods: Several fresh chicken tenderloins were embedded as target lesions in the submucosal layer of an isolated porcine stomach. The stomach was fixed to a plate with nails, and was placed in a tub filled with water. The primary endpoint was feasibility of the newly developed model for EUS-FNA training, evaluated as follows: 1) visualization of the target lesion with blinding for lesion location; 2) penetrability of the needle; 3) sampling rate of macroscopic specimen; and 4) ROSE capability. Secondary endpoints were its durability and utility for multiple EUS-FNA procedures during EUS-FNA training, and the ease and cost of preparing the model. Results: Six endoscopists (1 expert, 5 trainees) attempted EUS-FNA procedures using this model. The target lesion could be identified clearly, and EUS-FNA could be performed with realistic resistance felt. In addition, rapid on-site evaluation could be easily achieved. Based on 10 needlings by each endoscopist, adequate specimens for histology could be macroscopically taken with an average 85 % success rate. Visibility and maneuverability were maintained throughout all needlings. Preparation time for this model was less than 30 minutes with a total cost of $ 22. Conclusions: An easy-to-use and inexpensive training model with a realistic feel of needling was created. This model can potentially enable beginners to practice safe and effective EUS-FNA procedures. PMID:27652292
Hoshi, Koki; Irisawa, Atsushi; Shibukawa, Goro; Yamabe, Akane; Fujisawa, Mariko; Igarashi, Ryo; Yoshida, Yoshitsugu; Abe, Yoko; Imbe, Koh
2016-09-01
Trainees are required to learn EUS-FNA using a model before working with a patient. The aim of the current study was to validate a new training model developed for EUS-FNA. Several fresh chicken tenderloins were embedded as target lesions in the submucosal layer of an isolated porcine stomach. The stomach was fixed to a plate with nails, and was placed in a tub filled with water. The primary endpoint was feasibility of the newly developed model for EUS-FNA training, evaluated as follows: 1) visualization of the target lesion with blinding for lesion location; 2) penetrability of the needle; 3) sampling rate of macroscopic specimen; and 4) ROSE capability. Secondary endpoints were its durability and utility for multiple EUS-FNA procedures during EUS-FNA training, and the ease and cost of preparing the model. Six endoscopists (1 expert, 5 trainees) attempted EUS-FNA procedures using this model. The target lesion could be identified clearly, and EUS-FNA could be performed with realistic resistance felt. In addition, rapid on-site evaluation could be easily achieved. Based on 10 needlings by each endoscopist, adequate specimens for histology could be macroscopically taken with an average 85 % success rate. Visibility and maneuverability were maintained throughout all needlings. Preparation time for this model was less than 30 minutes with a total cost of $ 22. An easy-to-use and inexpensive training model with a realistic feel of needling was created. This model can potentially enable beginners to practice safe and effective EUS-FNA procedures.
Realistic Modeling of Multi-Scale MHD Dynamics of the Solar Atmosphere
NASA Technical Reports Server (NTRS)
Kitiashvili, Irina; Mansour, Nagi N.; Wray, Alan; Couvidat, Sebastian; Yoon, Seokkwan; Kosovichev, Alexander
2014-01-01
Realistic 3D radiative MHD simulations open new perspectives for understanding the turbulent dynamics of the solar surface, its coupling to the atmosphere, and the physical mechanisms of generation and transport of non-thermal energy. Traditionally, plasma eruptions and wave phenomena in the solar atmosphere are modeled by prescribing artificial driving mechanisms using magnetic or gas pressure forces that might arise from magnetic field emergence or reconnection instabilities. In contrast, our 'ab initio' simulations provide a realistic description of solar dynamics naturally driven by solar energy flow. By simulating the upper convection zone and the solar atmosphere, we can investigate in detail the physical processes of turbulent magnetoconvection, generation and amplification of magnetic fields, excitation of MHD waves, and plasma eruptions. We present recent simulation results of the multi-scale dynamics of quiet-Sun regions, and energetic effects in the atmosphere and compare with observations. For the comparisons we calculate synthetic spectro-polarimetric data to model observational data of SDO, Hinode, and New Solar Telescope.
Realistic texture extraction for 3D face models robust to self-occlusion
NASA Astrophysics Data System (ADS)
Qu, Chengchao; Monari, Eduardo; Schuchert, Tobias; Beyerer, Jürgen
2015-02-01
In the context of face modeling, probably the most well-known approach to represent 3D faces is the 3D Morphable Model (3DMM). When 3DMM is fitted to a 2D image, the shape as well as the texture and illumination parameters are simultaneously estimated. However, if real facial texture is needed, texture extraction from the 2D image is necessary. This paper addresses the possible problems in texture extraction of a single image caused by self-occlusion. Unlike common approaches that leverage the symmetric property of the face by mirroring the visible facial part, which is sensitive to inhomogeneous illumination, this work first generates a virtual texture map for the skin area iteratively by averaging the color of neighbored vertices. Although this step creates unrealistic, overly smoothed texture, illumination stays constant between the real and virtual texture. In the second pass, the mirrored texture is gradually blended with the real or generated texture according to the visibility. This scheme ensures a gentle handling of illumination and yet yields realistic texture. Because the blending area only relates to non-informative area, main facial features still have unique appearance in different face halves. Evaluation results reveal realistic rendering in novel poses robust to challenging illumination conditions and small registration errors.
NASA Astrophysics Data System (ADS)
Yan, Dandan; Zhang, Jianwei; Wu, Weijuan; Ying, Xiaoyan; Wu, Xiangping
2009-10-01
This paper is focused on the sophisticated realistic head modeling based on inhomogeneous and anisotropic conductivity distribution of the head tissues. The finite element method (FEM) was used to model the five-layer head volume conductor models with hexahedral elements from segmentation and mapping of DT-MRI data. Then the inhomogeneous conductivities of the scalp, CSF and gray matter tissue were distributed according a normal distribution based on the mean value of respective tissues. The electric conductivity of the brain tissues dictates different inhomogeneous and anisotropic at some different microscopic levels. Including the inhomogeneous and anisotropy of the tissue would improve the accuracy of the MREIT, EEG and MEG problems in the simulation research.
A Madden-Julian oscillation event realistically simulated by a global cloud-resolving model.
Miura, Hiroaki; Satoh, Masaki; Nasuno, Tomoe; Noda, Akira T; Oouchi, Kazuyoshi
2007-12-14
A Madden-Julian Oscillation (MJO) is a massive weather event consisting of deep convection coupled with atmospheric circulation, moving slowly eastward over the Indian and Pacific Oceans. Despite its enormous influence on many weather and climate systems worldwide, it has proven very difficult to simulate an MJO because of assumptions about cumulus clouds in global meteorological models. Using a model that allows direct coupling of the atmospheric circulation and clouds, we successfully simulated the slow eastward migration of an MJO event. Topography, the zonal sea surface temperature gradient, and interplay between eastward- and westward-propagating signals controlled the timing of the eastward transition of the convective center. Our results demonstrate the potential making of month-long MJO predictions when global cloud-resolving models with realistic initial conditions are used.
Modeling wave propagation in realistic heart geometries using the phase-field method
NASA Astrophysics Data System (ADS)
Fenton, Flavio H.; Cherry, Elizabeth M.; Karma, Alain; Rappel, Wouter-Jan
2005-03-01
We present a novel algorithm for modeling electrical wave propagation in anatomical models of the heart. The algorithm uses a phase-field approach that represents the boundaries between the heart muscle and the surrounding medium as a spatially diffuse interface of finite thickness. The chief advantage of this method is to automatically handle the boundary conditions of the voltage in complex geometries without the need to track the location of these boundaries explicitly. The algorithm is shown to converge accurately in nontrivial test geometries with no-flux (zero normal current) boundary conditions as the width of the diffuse interface becomes small compared to the width of the cardiac action potential wavefront. Moreover, the method is illustrated for anatomically realistic models of isolated rabbit and canine ventricles as well as human atria.
Kybartaite, Asta
2012-11-01
Computational head and brain volume conductor modeling is a practical and non-invasive method to investigate neuroelectrical activity in the brain. Anatomical structures included in a model affect the flow of volume currents and the resulting scalp surface potentials. The influence of different tissues within the head on scalp surface potentials was investigated by constructing five highly detailed, realistic head models from segmented and processed Visible Human Man digital images. The models were: (1) model with 20 different tissues, that is, skin, dense connective tissue (fat), aponeurosis (muscle), outer, middle and inner tables of the scalp, dura matter, arachnoid layer (including cerebrospinal fluid), pia matter, six cortical layers, eye tissue, muscle around the eye, optic nerve, temporal muscle, white matter and internal air, (2) model with three main inhomogeneities, that is, scalp, skull, brain, (3) model with homogeneous scalp and remaining inhomogeneities, (4) model with homogeneous skull and remaining inhomogeneities, and (5) model with homogeneous brain matter and remaining inhomogeneities. Scalp potentials because of three different dipolar sources in the parietal-occipital lobe were computed for all five models. Results of a forward solution revealed that tissues included in the model and the dipole source location directly affect the simulated scalp surface potentials. The major finding indicates that significant change in the scalp surface potentials is observed when the brain's distinctions are removed. The other modifications, for example, layers of the scalp and skull are important too, but they have less effect on the overall results.
XCAT/DRASIM: a realistic CT/human-model simulation package
NASA Astrophysics Data System (ADS)
Fung, George S. K.; Stierstorfer, Karl; Segars, W. Paul; Taguchi, Katsuyuki; Flohr, Thomas G.; Tsui, Benjamin M. W.
2011-03-01
The aim of this research is to develop a complete CT/human-model simulation package by integrating the 4D eXtended CArdiac-Torso (XCAT) phantom, a computer generated NURBS surface based phantom that provides a realistic model of human anatomy and respiratory and cardiac motions, and the DRASIM (Siemens Healthcare) CT-data simulation program. Unlike other CT simulation tools which are based on simple mathematical primitives or voxelized phantoms, this new simulation package has the advantages of utilizing a realistic model of human anatomy and physiological motions without voxelization and with accurate modeling of the characteristics of clinical Siemens CT systems. First, we incorporated the 4D XCAT anatomy and motion models into DRASIM by implementing a new library which consists of functions to read-in the NURBS surfaces of anatomical objects and their overlapping order and material properties in the XCAT phantom. Second, we incorporated an efficient ray-tracing algorithm for line integral calculation in DRASIM by computing the intersection points of the rays cast from the x-ray source to the detector elements through the NURBS surfaces of the multiple XCAT anatomical objects along the ray paths. Third, we evaluated the integrated simulation package by performing a number of sample simulations of multiple x-ray projections from different views followed by image reconstruction. The initial simulation results were found to be promising by qualitative evaluation. In conclusion, we have developed a unique CT/human-model simulation package which has great potential as a tool in the design and optimization of CT scanners, and the development of scanning protocols and image reconstruction methods for improving CT image quality and reducing radiation dose.
More Realistic Face Model Surface Improves Relevance of Pediatric In-Vitro Aerosol Studies
Amirav, Israel; Halamish, Asaf; Gorenberg, Miguel; Omar, Hamza; Newhouse, Michael T.
2015-01-01
Background Various hard face models are commonly used to evaluate the efficiency of aerosol face masks. Softer more realistic “face” surface materials, like skin, deform upon mask application and should provide more relevant in-vitro tests. Studies that simultaneously take into consideration many of the factors characteristic of the in vivo face are lacking. These include airways, various application forces, comparison of various devices, comparison with a hard-surface model and use of a more representative model face based on large numbers of actual faces. Aim To compare mask to “face” seal and aerosol delivery of two pediatric masks using a soft vs. a hard, appropriately representative, pediatric face model under various applied forces. Methods Two identical face models and upper airways replicas were constructed, the only difference being the suppleness and compressibility of the surface layer of the “face.” Integrity of the seal and aerosol delivery of two different masks [AeroChamber (AC) and SootherMask (SM)] were compared using a breath simulator, filter collection and realistic applied forces. Results The soft “face” significantly increased the delivery efficiency and the sealing characteristics of both masks. Aerosol delivery with the soft “face” was significantly greater for the SM compared to the AC (p< 0.01). No statistically significant difference between the two masks was observed with the hard “face.” Conclusions The material and pliability of the model “face” surface has a significant influence on both the seal and delivery efficiency of face masks. This finding should be taken into account during in-vitro aerosol studies. PMID:26090661
Dynamic Rupture and Ground Motion Modeling on Realistically Complex Strike-Slip Faults
NASA Astrophysics Data System (ADS)
Lozos, Julian Charles
Faults are complex structures: they are geometrically complex, and have variable stress conditions and frictional behaviors along their length. In addition, faults exist in heterogeneous settings, in terms of surrounding geology, and in terms of regional and local stresses. These individual types of heterogeneity all contribute to complex dynamic rupture behaviors and ground motion distributions, as inferred from observational data and supported by previous modeling studies. In this study, we investigate the effects of individual types of complexity, and we combine different types of heterogeneity in order to enhance the realism of models of real-world faults. We use the finite element method to conduct dynamic rupture models of earthquakes on faults with complex geometry, initial stresses, frictional parameters, and surrounding geology, and with combinations of these factors, in order to investigate the effects of this complexity on fault interactions, rupture extent, and ground motion. In particular, we investigate the effect of critical weakening distance on the ability of rupture to propagate through a discontinuity in the fault trace, the effect of a small fault between the larger strands of a stepover on the ability of rupture to jump the stepover, and how zones of aseismic creep affect rupture through locked portions of the same fault. We also construct realistically complex models of the northern San Jacinto Fault, California, incorporating realistic geometry, velocity structure, and combined regional and stochastic stress fields. We find that the distribution of complexity of any type on the fault, which leads to heterogeneous fault strength, has the primary controlling effect on rupture behavior. The relative strength or weakness of the fault, rather than the actual value, is most important. We also find that the balance of the energy budget is crucial; if too much energy is redirected into fracture, rupture stops. Lastly, we find that each type of
Supersymmetric Higgs singlet effects on FCNC observables
Hodgkinson, Robert N.
2008-11-23
Higgs singlet superflelds, usually present in extensions of the Minimal Supersymmetric Standard Model (MSSM) which address the {mu}-problem, such as the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and the Minimal Nonminimal Supersymmetric Standard Model (mnSSM), can have significant contributions to B-meson flavour-changing neutral current observables for large values of tan{beta} > or approx. 50. Illustrative results are presented including effects on the B{sub s} and on the rare decay B{sub s}{yields}{mu}{sup +}{mu}{sup -}. In particular, we find that in the NMSSM, the branching ratio for B{sub s}{yields}{mu}{sup +}{mu}{sup -} can be enhanced or even suppressed with respect to the Standard Model prediction by more than one order of magnitude.
Kornelsen, Jude; McCartney, Kevin; Williams, Kim
2016-01-01
This article was developed as part of a larger realist review investigating the viability and efficacy of decentralized models of perinatal surgical services for rural women in the context of recent and ongoing service centralization witnessed in many developed nations. The larger realist review was commissioned by the British Columbia Ministry of Health and Perinatal Services of British Columbia, Canada. Findings from that review are addressed in this article specific to the sustainability of rural perinatal surgical sites and the satisfaction of providers that underpins their recruitment to and retention at such sites. A realist method was used in the selection and analysis of literature with the intention to iteratively develop a sophisticated understanding of how perinatal surgical services can best meet the needs of women who live in rural and remote environments. The goal of a realist review is to examine what works for whom under what circumstances and why. The high sensitivity search used language (English) and year (since 1990) limiters in keeping with both a realist and rapid review tradition of using reasoned contextual boundaries. No exclusions were made based on methodology or methodological approach in keeping with a realist review. Databases searched included MEDLINE, PubMed, EBSCO, CINAHL, EBM Reviews, NHS Economic Evaluation Database and PAIS International for literature in December 2013. Database searching produced 103 included academic articles. A further 59 resources were added through pearling and 13 grey literature reports were added on recommendation from the commissioner. A total of 42 of these 175 articles were included in this article as specific to provider satisfaction and service sustainability. Operative perinatal practice was found to be a lynchpin of sustainable primary and surgical services in rural communities. Rural shortages of providers, including challenges with recruitment and retention, were found to be a complex issue, with
The boundary layer over turbine blade models with realistic rough surfaces
NASA Astrophysics Data System (ADS)
McIlroy, Hugh M., Jr.
The impact of turbine blade surface roughness on aerodynamic performance and heat loads is well known. Over time, as the turbine blades are exposed to heat loads, the external surfaces of the blades become rough. Also, for film-cooled blades, surface degradation can have a significant impact on film-cooling effectiveness. Many studies have been conducted on the effects of surface degradation/roughness on engine performance but most investigations have modeled the rough surfaces with uniform or two-dimensional roughness patterns. The objective of the present investigation is to conduct measurements that will reveal the influence of realistic surface roughness on the near-wall behavior of the boundary layer. Measurements have been conducted at the Matched-Index-of-Refraction (MIR) Facility at the Idaho National Engineering and Environmental Laboratory with a laser Doppler velocimeter. A flat plate model of a turbine blade has been developed that produces a transitional boundary layer, elevated freestream turbulence and an accelerating freestream in order to simulate conditions on the suction side of a high-pressure turbine blade. Boundary layer measurements have been completed over a smooth plate model and over a model with a strip of realistic rough surface. The realistic rough surface was developed by scaling actual turbine blade surface data that was provided by U.S. Air Force Research Laboratory. The results indicate that bypass transition occurred very early in the flow over the model and that the boundary layer remained unstable throughout the entire length of the test plate; the boundary layer thickness and momentum thickness Reynolds numbers increased over the rough patch; and the shape factor increased over the rough patch but then decreased downstream of the patch relative to the smooth plate case; in the rough patch case the flow experienced two transition reversals with laminar-like behavior achieved by the end of the test plate; streamwise turbulence
NASA Astrophysics Data System (ADS)
Il'chenko, L. G.; Il'chenko, V. V.; Gavrilenko, A. V.; Gavrilenko, V. I.
2013-09-01
Efficient engineering of metamaterials involves modeling of electric field profiles around these structures. Realistic modeling of the electric field in metamaterials requires accurate knowledge of optical constants of the compo- nents for which traditionally the bulk values are taken. Further progress in the developing of metamaterials is characterized by a reduction of the pattern size, dimensions of single layers in multilayered structures etc. It has been understood that optical functions in low-dimensional and nano-sized materials substantially differ from their bulk values increasingly affecting by quantum processes. In this work we develop a complex method for analytical modeling of electric field profiles in metamaterials including quantum processes in nano-sized multi-layered structures. In particular based on first principles density functional theory we obtained simple analytical functions allowing predictions the optical functions variations with the size reduction of single metamaterial components over a wide spectral region. It is shown that optical functions of nano-sized films substantially (by 50 percent and more) differ from those in bulk. The new calculated optical functions of the components are used for electric field profile modeling of nano-sized multilayered structures by nonlocal Green function technique including effects of spatial dispersion. Silicon, silicon dioxide, and water layers are used as an example. The method effectively incorporates real atomic structure reconstruction on surfaces and inner interfaces thus providing with a more realistic picture for modeling. By comparison with experiment it is demonstrated that our method predicts image potential of the nanostructures in better agreement with experiment than if using traditional classic electrodynamics approach neglecting the quantum effects. The results are discussed in comparison with literature.
Supersymmetric higher spin theories
NASA Astrophysics Data System (ADS)
Sezgin, Ergin; Sundell, Per
2013-05-01
We revisit the higher spin extensions of the anti de Sitter algebra in four dimensions that incorporate internal symmetries and admit representations that contain fermions, classified long ago by Konstein and Vasiliev. We construct the dS4, Euclidean and Kleinian version of these algebras, as well as the corresponding fully nonlinear Vasiliev type higher spin theories, in which the reality conditions we impose on the master fields play a crucial role. The N=2 supersymmetric higher spin theory in dS4, on which we elaborate further, is included in this class of models. A subset of the Konstein-Vasiliev algebras are the minimal higher spin extensions of the AdS4 superalgebra osp(4|N ) with N=1, 2, 4 mod 4, whose R-symmetry can be realized using fermionic oscillators. We tensor these algebras with appropriate internal symmetry algebras, namely u(n) for N= 2 mod 4 and so(n) or usp(n) for N=1,4 mod 4. We show that the N= 3 mod 4 higher spin algebras are isomorphic to those with N = 4 mod 4. We describe the fully nonlinear higher spin theories based on these algebras, including the coupling between the adjoint and twisted-adjoint master fields. We elaborate further on the N = 6 model in AdS4, and provide two equivalent descriptions one of which exhibits manifestly its relation to the N = 8 model. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Higher spin theories and holography’.
Mordhorst, Mylena; Heidlauf, Thomas; Röhrle, Oliver
2015-01-01
This paper presents a novel multiscale finite element-based framework for modelling electromyographic (EMG) signals. The framework combines (i) a biophysical description of the excitation–contraction coupling at the half-sarcomere level, (ii) a model of the action potential (AP) propagation along muscle fibres, (iii) a continuum-mechanical formulation of force generation and deformation of the muscle, and (iv) a model for predicting the intramuscular and surface EMG. Owing to the biophysical description of the half-sarcomere, the model inherently accounts for physiological properties of skeletal muscle. To demonstrate this, the influence of membrane fatigue on the EMG signal during sustained contractions is investigated. During a stimulation period of 500 ms at 100 Hz, the predicted EMG amplitude decreases by 40% and the AP propagation velocity decreases by 15%. Further, the model can take into account contraction-induced deformations of the muscle. This is demonstrated by simulating fixed-length contractions of an idealized geometry and a model of the human tibialis anterior muscle (TA). The model of the TA furthermore demonstrates that the proposed finite element model is capable of simulating realistic geometries, complex fibre architectures, and can include different types of heterogeneities. In addition, the TA model accounts for a distributed innervation zone, different fibre types and appeals to motor unit discharge times that are based on a biophysical description of the α motor neurons. PMID:25844148
NASA Technical Reports Server (NTRS)
Kim, Yong-Cheol; Fox, Peter A.; Sofia, Sabatino; Demarque, Pierre
1995-01-01
In an attempt to understand the properties of convective energy transport in the solar convective zone, a numerical model has been constructed for turbulent flows in a compressible, radiation-coupled, nonmagnetic, gravitationally stratified medium using a realistic equation of state and realistic opacities. The time-dependent, three-dimensional hydrodynamic equations are solved with minimal simplifications. The statistical information obtained from the present simulation provides an improved undserstanding of solar photospheric convection. The characteristics of solar convection in shallow regions is parameterized and compared with the results of Chan & Sofia's (1989) simulations of deep and efficient convection. We assess the importance of the zones of partial ionization in the simulation and confirm that the radiative energy transfer is negliglble throughout the region except in the uppermost scale heights of the convection zone, a region of very high superadiabaticity. When the effects of partial ionization are included, the dynamics of flows are altered significantly. However, we confirm the Chan & Sofia result that kinetic energy flux is nonnegligible and can have a negative value in the convection zone.
NASA Astrophysics Data System (ADS)
Ladeinde, Foluso; Alabi, Ken; Li, Wenhai
2015-11-01
The problem of generating design data for the operation of a farm of wind turbines for clean energy production is quite complicated, if properly done. Potential flow theories provide some models, but these are not suitable for the massive aerodynamic separation and turbulence that characterize many realistic wind turbine applications. Procedures, such as computational fluid dynamics (CFD), which can potentially resolve some of the accuracy problems with the purely theoretical approach, are quite expensive to use, and often prohibit real-time design and control. In our work, we seek affordable and acceptably-accurate models derived from the foregoing approaches. The simulation used in our study is based on high-fidelity CFD, meaning that we use high-order (compact-scheme based), mostly large-eddy simulation methods, with due regards for the proper treatment of the stochastic inflow turbulence data. Progress on the project described herein will be presented.
Realistic tight-binding model for the electronic structure of II-VI semiconductors
NASA Astrophysics Data System (ADS)
Sapra, Sameer; Shanthi, N.; Sarma, D. D.
2002-11-01
We analyze the electronic structure of group II-VI semiconductors obtained within linearized muffin-tin-orbital approach in order to arrive at a realistic and minimal tight-binding model, parametrized to provide an accurate description of both valence and conduction bands. It is shown that a nearest-neighbor sp3 d5 model is fairly sufficient to describe the electronic structure of these systems over a wide energy range, obviating the use of any fictitious s* orbital. The obtained hopping parameters obey the universal scaling law proposed by Harrison, ensuring transferability to other systems. Furthermore, we show that certain subtle features in the bonding of these compounds require the inclusion of anion-anion interactions in addition to the nearest-neighbor cation-anion interactions.
NASA Astrophysics Data System (ADS)
Tanaka, Gaku; Hatori, Akihiro; Takano, Ryosuke
Turbulence in the oscillatory flow in realistic model human central airways was measured by particle image velocimetry (PIV) to reveal the nature of turbulence in a lung. The transparent silicone model of multi-branching airways was fabricated from X-ray CT images by rapid prototyping. The multi-branching airways comprise trachea, and right and left bronchi, with airway diameters ranging from 14 to 2 mm, respectively. Experiments were performed for a Reynolds number from 1200 to 2200 and a Womersley number from 1.9 to 2.3 in the trachea. Results showed that spatial and temporal variations of turbulent intensity strongly depends on the airway geometry and on the phase of oscillatory flow, and that expiratory flow generates strong turbulence which explosively occurs in the entire cross-section especially in the right bronchi, whereas inspiratory flow generates relatively weak turbulence near the airway wall.
Modeling and Simulation for Realistic Propagation Environments of Communications Signals at SHF Band
NASA Technical Reports Server (NTRS)
Ho, Christian
2005-01-01
In this article, most of widely accepted radio wave propagation models that have proven to be accurate in practice as well as numerically efficient at SHF band will be reviewed. Weather and terrain data along the signal's paths can be input in order to more accurately simulate the propagation environments under particular weather and terrain conditions. Radio signal degradation and communications impairment severity will be investigated through the realistic radio propagation channel simulator. Three types of simulation approaches in predicting signal's behaviors are classified as: deterministic, stochastic and attenuation map. The performance of the simulation can be evaluated under operating conditions for the test ranges of interest. Demonstration tests of a real-time propagation channel simulator will show the capabilities and limitations of the simulation tool and underlying models.
Model of a realistic InP surface quantum dot extrapolated from atomic force microscopy results.
Barettin, Daniele; De Angelis, Roberta; Prosposito, Paolo; Auf der Maur, Matthias; Casalboni, Mauro; Pecchia, Alessandro
2014-05-16
We report on numerical simulations of a zincblende InP surface quantum dot (QD) on In₀.₄₈Ga₀.₅₂ buffer. Our model is strictly based on experimental structures, since we extrapolated a three-dimensional dot directly by atomic force microscopy results. Continuum electromechanical, [Formula: see text] bandstructure and optical calculations are presented for this realistic structure, together with benchmark calculations for a lens-shape QD with the same radius and height of the extrapolated dot. Interesting similarities and differences are shown by comparing the results obtained with the two different structures, leading to the conclusion that the use of a more realistic structure can provide significant improvements in the modeling of QDs fact, the remarkable splitting for the electron p-like levels of the extrapolated dot seems to prove that a realistic experimental structure can reproduce the right symmetry and a correct splitting usually given by atomistic calculations even within the multiband [Formula: see text] approach. Moreover, the energy levels and the symmetry of the holes are strongly dependent on the shape of the dot. In particular, as far as we know, their wave function symmetries do not seem to resemble to any results previously obtained with simulations of zincblende ideal structures, such as lenses or truncated pyramids. The magnitude of the oscillator strengths is also strongly dependent on the shape of the dot, showing a lower intensity for the extrapolated dot, especially for the transition between the electrons and holes ground state, as a result of a relevant reduction of the wave functions overlap. We also compare an experimental photoluminescence spectrum measured on an homogeneous sample containing about 60 dots with a numerical ensemble average derived from single dot calculations. The broader energy range of the numerical spectrum motivated us to perform further verifications, which have clarified some aspects of the experimental
Monte Carlo simulated coronary angiograms of realistic anatomy and pathology models
NASA Astrophysics Data System (ADS)
Kyprianou, Iacovos S.; Badal, Andreu; Badano, Aldo; Banh, Diemphuc; Freed, Melanie; Myers, Kyle J.; Thompson, Laura
2007-03-01
We have constructed a fourth generation anthropomorphic phantom which, in addition to the realistic description of the human anatomy, includes a coronary artery disease model. A watertight version of the NURBS-based Cardiac-Torso (NCAT) phantom was generated by converting the individual NURBS surfaces of each organ into closed, manifold and non-self-intersecting tessellated surfaces. The resulting 330 surfaces of the phantom organs and tissues are now comprised of ~5×10 6 triangles whose size depends on the individual organ surface normals. A database of the elemental composition of each organ was generated, and material properties such as density and scattering cross-sections were defined using PENELOPE. A 300 μm resolution model of a heart with 55 coronary vessel segments was constructed by fitting smooth triangular meshes to a high resolution cardiac CT scan we have segmented, and was consequently registered inside the torso model. A coronary artery disease model that uses hemodynamic properties such as blood viscosity and resistivity was used to randomly place plaque within the artery tree. To generate x-ray images of the aforementioned phantom, our group has developed an efficient Monte Carlo radiation transport code based on the subroutine package PENELOPE, which employs an octree spatial data-structure that stores and traverses the phantom triangles. X-ray angiography images were generated under realistic imaging conditions (90 kVp, 10° Wanode spectra with 3 mm Al filtration, ~5×10 11 x-ray source photons, and 10% per volume iodine contrast in the coronaries). The images will be used in an optimization algorithm to select the optimal technique parameters for a variety of imaging tasks.
Realistic Modeling of Fast MHD Wave Trains in Coronal Active Regions
NASA Astrophysics Data System (ADS)
Ofman, Leon; Sun, Xudong
2017-08-01
Motivated by recent SDO/AIA observations we have developed realistic modeling of quasi-periodic, fast-mode propagating MHD wave trains (QFPs) using 3D MHD model initiated with potential magnetic field extrapolated from the solar coronal boundary. Localized quasi-periodic pulsations associated with C-class flares that drive the waves (as deduced from observations) are modeled with transverse periodic displacement of magnetic field at the lower coronal boundary. The modeled propagating speed and the form of the wave expansions matches the observed fast MHD waves speed >1000 km/s and topology. We study the parametric dependence of the amplitude, propagation, and damping of the waves for a range of key model parameters, such as the background temperature, density, and the location of the flaring site within the active region. We investigate the interaction of multiple QFP wave trains excited by adjacent flaring sources. We use the model results to synthesize EUV intensities in multiple AIA channels and obtain the model parameters that best reproduce the properties of observed QFPs, such as the recent DEM analysis. We discuss the implications of our modeling results for the seismological application of QFPs for the diagnostic of the active region field, flare pulsations, end estimate the energy flux carried by the waves.
Bubbles of nothing and supersymmetric compactifications
Blanco-Pillado, Jose J.; Sousa, Kepa; Urrestilla, Jon
2016-10-03
We investigate the non-perturbative stability of supersymmetric compactifications with respect to decay via a bubble of nothing. We show examples where this kind of instability is not prohibited by the spin structure, i.e., periodicity of fermions about the extra dimension. However, such “topologically unobstructed” cases do exhibit an extra-dimensional analog of the well-known Coleman-De Luccia suppression mechanism, which prohibits the decay of supersymmetric vacua. We demonstrate this explicitly in a four dimensional Abelian-Higgs toy model coupled to supergravity. The compactification of this model to M{sub 3}×S{sub 1} presents the possibility of vacua with different windings for the scalar field. Away from the supersymmetric limit, these states decay by the formation of a bubble of nothing, dressed with an Abelian-Higgs vortex. We show how, as one approaches the supersymmetric limit, the circumference of the topologically unobstructed bubble becomes infinite, thereby preventing the realization of this decay. This demonstrates the dynamical origin of the decay suppression, as opposed to the more familiar argument based on the spin structure. We conjecture that this is a generic mechanism that enforces stability of any topologically unobstructed supersymmetric compactification.
NASA Astrophysics Data System (ADS)
Vedula, Ravi Pramod Kumar
profiles, inherent in strain-engineered Ge nanofins, on their transport properties. Fully atomistic simulations, involving a combination molecular dynamics simulations with first-principles based force-fields and semi-empirical tight binding calculations, coupled with linearized Boltzmann model are used to calculate the hole transport properties of realistic Ge nanofins (heights 5-15nm and widths 5nm-40nm). Our simulations predict the technological limit of phonon limited hole mobility improvement in Ge channel PMOS devices (H<15nm) and present geometric guidelines for patterning nanofins to engineer high performance uniaxial devices conducive to the existing top-down fabrication approaches. From these calculations, we demonstrate that realistic modeling of the devices requires a reduction in the empiricism of fitting parameters and incorporation of new multi-scale, multi-resolution approach spanning across various spatial and temporal scales. Such physics based predictive multiscale models facilitate an integrated approach for rapid development and pave the way for designing new advanced materials and devices.
Supersymmetric leptogenesis with a light hidden sector
De Simone, Andrea; Garny, Mathias; Ibarra, Alejandro; Weniger, Christoph E-mail: mathias.garny@ph.tum.de E-mail: christoph.weniger@desy.de
2010-07-01
Supersymmetric scenarios incorporating thermal leptogenesis as the origin of the observed matter-antimatter asymmetry generically predict abundances of the primordial elements which are in conflict with observations. In this paper we propose a simple way to circumvent this tension and accommodate naturally thermal leptogenesis and primordial nucleosynthesis. We postulate the existence of a light hidden sector, coupled very weakly to the Minimal Supersymmetric Standard Model, which opens up new decay channels for the next-to-lightest supersymmetric particle, thus diluting its abundance during nucleosynthesis. We present a general model-independent analysis of this mechanism as well as two concrete realizations, and describe the relevant cosmological and astrophysical bounds and implications for this dark matter scenario. Possible experimental signatures at colliders and in cosmic-ray observations are also discussed.
What if the Higgsino is the lightest supersymmetric particles
Haber, H.E.
1985-11-01
A pedagogical introduction to the mixing of neutral gauginos and Higgsinos in supersymmetric models is given. The possibility that the Higgsino (rather than the photino) is the lightest supersymmetric particle is considered and implications for phenomenology are discussed with some emphasis on signatures of supersymmetry in Z decays. Some related aspects of Higgs boson detection in Z decays are mentioned.
Pulsations of rapidly rotating stars. II. Realistic modelling for intermediate-mass stars
NASA Astrophysics Data System (ADS)
Ouazzani, R.-M.; Roxburgh, I. W.; Dupret, M.-A.
2015-07-01
Context. Very high precision seismic space missions such as CoRoT and Kepler provide the means for testing the modelling of transport processes in stellar interiors. For some stars, such as δ Scuti, γ Doradus, and Be stars, the observed pulsation spectra are modified by rotation to such an extent that it prevents any fruitful interpretation. Aims: Our aim is to characterise acoustic pulsation spectra of realistic stellar models in order to be able to interpret asteroseismic data from such stars. Methods: The 2D oscillation code ACOR, which treats rotation in a non-perturbative manner, is used to study pulsation spectra of highly distorted evolved models of stars. Two-dimensional models of stars are obtained by a self-consistent method that distorts spherically averaged stellar models a posteriori, at any stage of evolution, and for any type of rotation law. Results: Four types of modes are calculated in a very dense frequency spectrum, among which are island modes. The regularity of the island modes spectrum is confirmed and yields a new set of quantum numbers, with which an échelle diagram can be built. Mixed gravito-acoustic modes are calculated in rapidly rotating models for the first time.
Natural supersymmetric spectrum in mirage mediation
NASA Astrophysics Data System (ADS)
Asano, Masaki; Higaki, Tetsutaro
2012-08-01
The current results of LHC experiments exclude a large area of the light new particle region, namely, natural parameter space, in supersymmetric extension models. One of the possibilities for achieving the correct electroweak symmetry breaking naturally is the low-scale messenger scenario. Actually, the next-to-minimal supersymmetric standard model with TeV scale mirage mediation realizes the natural electroweak symmetry breaking with various mass spectra. In this paper, we show the possible mass spectrum in the scenario, e.g., the degenerate and/or hierarchical mass spectrum, and discuss these features.
Realistic shell-model calculations and exotic nuclei around {sup 132}Sn
Covello, A.; Itaco, N.; Coraggio, L.; Gargano, A.
2008-11-11
We report on a study of exotic nuclei around doubly magic {sup 132}Sn in terms of the shell model employing a realistic effective interaction derived from the CD-Bonn nucleon-nucleon potential. The short-range repulsion of the latter is renormalized by constructing a smooth low-momentum potential, V{sub low-k}, that is used directly as input for the calculation of the effective interaction. In this paper, we focus attention on proton-neutron multiplets in the odd-odd nuclei {sup 134}Sb, {sup 136}Sb. We show that the behavior of these multiplets is quite similar to that of the analogous multiplets in the counterpart nuclei in the {sup 208}Pb region, {sup 210}Bi and {sup 212}Bi.
NASA Astrophysics Data System (ADS)
Metz, P. D.
A FORTRAN computer program called GROCS (GRound Coupled Systems) has been developed to study 3-dimensional underground heat flow. Features include the use of up to 30 finite elements or blocks of Earth which interact via finite difference heat flow equations and a subprogram which sets realistic time and depth dependent boundary conditions. No explicit consideration of mositure movement or freezing is given. GROCS has been used to model the thermal behavior of buried solar heat storage tanks (with and without insulation) and serpentine pipe fields for solar heat pump space conditioning systems. The program is available independently or in a form compatible with specially written TRNSYS component TYPE subroutines. The approach taken in the design of GROCS, the mathematics contained and the program architecture, are described. Then, the operation of the stand-alone version is explained. Finally, the validity of GROCS is discussed.
A realistic quantum capacitance model for quantum Hall edge state based Fabry-Pérot interferometers
NASA Astrophysics Data System (ADS)
Kilicoglu, O.; Eksi, D.; Siddiki, A.
2017-01-01
In this work, the classical and the quantum capacitances are calculated for a Fabry-Pérot interferometer operating in the integer quantized Hall regime. We first consider a rotationally symmetric electrostatic confinement potential and obtain the widths and the spatial distribution of the insulating (incompressible) circular strips using a charge density profile stemming from self-consistent calculations. Modelling the electrical circuit of capacitors composed of metallic gates and incompressible/compressible strips, we investigate the conditions to observe Aharonov-Bohm (quantum mechanical phase dependent) and Coulomb blockade (capacitive coupling dependent) effects reflected in conductance oscillations. In a last step, we solve the Schrödinger and the Poisson equations self-consistently in a numerical manner taking into account realistic experimental geometries. We find that, describing the conductance oscillations either by Aharanov-Bohm or Coulomb blockade strongly depends on sample properties also other than size, therefore, determining the origin of these oscillations requires further experimental and theoretical investigation.
NASA Astrophysics Data System (ADS)
Blanc-Benon, Philippe; Dallois, Laurent; Scott, Julian; Berger, Uwe; Allwright, David
2006-05-01
The shock waves generated by a supersonic aircraft are reflected in the upper part of the atmosphere. Back to the ground, they are indirect sonic booms called secondary sonic booms. The recorded signals of secondary sonic booms show a low amplitude and a low frequency. They sound like rumbling noises due to amplitude bursts. These signals strongly depend on the atmospheric conditions, in particular to the amplitude and to the direction of the wind in the stratopause. In the present work, the propagation of secondary sonic booms is studied using realistic atmospheric models up to the thermosphere. The secondary carpet position is investigated by solving temporal ray equations. An amplitude equation including nonlinearity, absorption and relaxation by various chemical species is coupled to the ray solver to get the secondary boom signature at the ground level. Multipath arrivals are directly linked to wind field or 3D inhomogeneities.
Study of airflow during respiratory cycle in semi-realistic model of human tracheobronchial tree
NASA Astrophysics Data System (ADS)
Elcner, Jakub; Zaremba, M.; Maly, M.; Jedelsky, J.; Lizal, F.; Jicha, M.
2016-06-01
This article deals with study of airflow under breathing process, which is characteristic by unsteady behavior. Simulations provided by computational fluid dynamics (CFD) was compared with experiments performed on similar geometry of human upper airways. This geometry was represented by mouth cavity of realistic shape connected to an idealized tracheobronchial tree up to fourth generation of branching. Commercial CFD software Star-CCM+ was used to calculate airflow inside investigated geometry and method of Reynolds averaging of Navier-Stokes equations was used for subscribing the turbulent behavior through model geometry. Conditions corresponding to resting state were considered. Comparisons with experiments were provided on several points through trachea and bronchial tree and results with respect to inspiratory and respiratory part of breathing cycle was discussed.
Ab Initio No-Core Shell Model Calculations Using Realistic Two- and Three-Body Interactions
Navratil, P; Ormand, W E; Forssen, C; Caurier, E
2004-11-30
There has been significant progress in the ab initio approaches to the structure of light nuclei. One such method is the ab initio no-core shell model (NCSM). Starting from realistic two- and three-nucleon interactions this method can predict low-lying levels in p-shell nuclei. In this contribution, we present a brief overview of the NCSM with examples of recent applications. We highlight our study of the parity inversion in {sup 11}Be, for which calculations were performed in basis spaces up to 9{Dirac_h}{Omega} (dimensions reaching 7 x 10{sup 8}). We also present our latest results for the p-shell nuclei using the Tucson-Melbourne TM three-nucleon interaction with several proposed parameter sets.
A realistic quantum capacitance model for quantum Hall edge state based Fabry-Pérot interferometers.
Kilicoglu, O; Eksi, D; Siddiki, A
2017-01-25
In this work, the classical and the quantum capacitances are calculated for a Fabry-Pérot interferometer operating in the integer quantized Hall regime. We first consider a rotationally symmetric electrostatic confinement potential and obtain the widths and the spatial distribution of the insulating (incompressible) circular strips using a charge density profile stemming from self-consistent calculations. Modelling the electrical circuit of capacitors composed of metallic gates and incompressible/compressible strips, we investigate the conditions to observe Aharonov-Bohm (quantum mechanical phase dependent) and Coulomb blockade (capacitive coupling dependent) effects reflected in conductance oscillations. In a last step, we solve the Schrödinger and the Poisson equations self-consistently in a numerical manner taking into account realistic experimental geometries. We find that, describing the conductance oscillations either by Aharanov-Bohm or Coulomb blockade strongly depends on sample properties also other than size, therefore, determining the origin of these oscillations requires further experimental and theoretical investigation.
Inflation from supersymmetric quantum cosmology
Socorro, J.; D'Oleire, Marco
2010-08-15
We derive a special scalar field potential using the anisotropic Bianchi type I cosmological model from canonical quantum cosmology under determined conditions in the evolution to anisotropic variables {beta}{sub {+-}}. In the process, we obtain a family of potentials that has been introduced by hand in the literature to explain cosmological data. Considering supersymmetric quantum cosmology, this family is scanned, fixing the exponential potential as more viable in the inflation scenario V({phi})=V{sub 0}e{sup -{radical}(3){phi}}.
NASA Astrophysics Data System (ADS)
Engdahl, N. B.; Maxwell, R. M.
2013-12-01
Descriptions of age in hydrologic systems are often limited to the residence time in the surface water system or the subsurface with little consideration of the interaction between the two, or the different ways geochemical tracers are altered in each domain. Understanding the way tracer concentrations change in each domain is essential to accurate estimation of age, but few models have explicitly modeled the fully coupled system or considered distributions of age. This work presents a numerical laboratory that is specifically designed to investigate composite age distributions (CADs) and their connections to tracer concentrations. The CAD is defined here as the combination of the residence time distributions for surface flows, vadose zone, and groundwater systems, providing an accounting for the total time a discrete fluid parcel has spent within the integrated hydrologic system. CADs are generated by particle tracking through a fully integrated flow model and it is straight forward to realistically simulate the transport of environmental tracers such as 85-Krypton and 39-Argon that can be used for estimating water ages. This framework allows explicit modeling of the different processes in each domain that affect tracer concentrations including the mixing of different source waters, partial equilibrium with the atmosphere through the vadose zone, evaporative enrichment in surface flows, and diffusive fractionation in the subsurface. Transient forcings, such as seasonal or daily variations in precipitation, can also be simulated and the effects of this transience on concentrations and age distributions can easily be investigated. The model domain used to demonstrate these tools is based on a well-defined watershed within Rocky Mountain National Park. The mountain pine beetle has devastated the park's forests and the massive tree-kill has begun to affect the quality and distribution of the water resources. Accurate modeling of the CADs in the park is a crucial step
NASA Astrophysics Data System (ADS)
Dobslaw, Henryk; Forootan, Ehsan; Bergmann-Wolf, Inga; Neumayer, Karl-Hans; Mayer-Gürr, Torsten; Kusche, Jürgen; Flechtner, Frank
2015-04-01
Recently completed performance studies of future gravity mission concepts arrived at sometimes contradicting conclusions about the importance of non-tidal aliasing errors that remain in the finally retrieved gravity field time-series. In those studies, typically a fraction of the differences between two different models of atmosphere and ocean mass variability determined the magnitude of the aliasing errors. Since differences among arbitrary pairs of the numerical models available might lead to widely different aliasing errors and thus conclusions regarding limiting error contributors of a candidate mission, we present here for the first time a version of a realistically perturbed de-aliasing model that is consistent with the updated ESA Earth System Model for gravity mission simulation studies (Dobslaw et al., 2015). The error model is available over the whole 12-year period of the ESA ESM and consists of two parts: (i) a component containing signals from physical processes that are intentionally omitted from de-aliasing models, as for a example, variations in global eustatic sea-level; and (ii) a series of true errors that consist of in total five different components with realistically re-scaled variability at both small and large spatial scales for different frequency bands ranging from sub-daily to sub-monthly periods. Based on a multi-model ensemble of atmosphere and ocean mass variability available to us for the year 2006, we will demonstrate that our re-scaled true errors have plausible magnitudes and correlation characteristics in all frequency bands considered. The realism of the selected scaling coefficients for periods between 1 and 30 days is tested further by means of a variance component estimation based on the constrained daily GRACE solution series ITSG-GRACE2014. Initial full-scale simulation experiments are used to re-assess the relative importance of non-tidal de-aliasing errors for the GRACE-FO mission, which might be subsequently expanded to
Spies, A.; Anton, G. E-mail: gisela.anton@physik.uni-erlangen.de
2013-06-01
In this paper we study a class of supersymmetric models with non-universal gaugino masses that arise from a mixture of SU(5) singlet and non-singlet representations, i.e. a combination of 1, 24, 75 and 200. Based on these models we calculate the expected dark matter signatures within the linear combination 1 ⊕ 24 ⊕ 75 ⊕ 200. We confront the model predictions with the detected boson as well as current experimental limits from selected indirect and direct dark matter search experiments ANTARES respective IceCube and XENON. We comment on the detection/exclusion capability of the future XENON 1t project. For the investigated parameter span we could not find a SU(5) singlet model that fulfils the Higgs mass and the relic density constraint. In contrary, allowing a mixture of 1 ⊕ 24 ⊕ 75 ⊕ 200 enables a number of models fulfilling these constraints.
Simulating realistic disc galaxies with a novel sub-resolution ISM model
NASA Astrophysics Data System (ADS)
Murante, Giuseppe; Monaco, Pierluigi; Borgani, Stefano; Tornatore, Luca; Dolag, Klaus; Goz, David
2015-02-01
We present results of cosmological simulations of disc galaxies carried out with the GADGET-3 TreePM+SPH code, where star formation and stellar feedback are described using our MUlti Phase Particle Integrator model. This description is based on a simple multiphase model of the interstellar medium at unresolved scales, where mass and energy flows among the components are explicitly followed by solving a system of ordinary differential equations. Thermal energy from supernovae is injected into the local hot phase, so as to avoid that it is promptly radiated away. A kinetic feedback prescription generates the massive outflows needed to avoid the overproduction of stars. We use two sets of zoomed-in initial conditions of isolated cosmological haloes with masses (2-3) × 1012 M⊙, both available at several resolution levels. In all cases we obtain spiral galaxies with small bulge-over-total stellar mass ratios (B/T ˜ 0.2), extended stellar and gas discs, flat rotation curves and realistic values of stellar masses. Gas profiles are relatively flat, molecular gas is found to dominate at the centre of galaxies, with star formation rates following the observed Schmidt-Kennicutt relation. Stars kinematically belonging to the bulge form early, while disc stars show a clear inside-out formation pattern and mostly form after redshift z = 2. However, the baryon conversion efficiencies in our simulations differ from the relation given by Moster et al. at a 3σ level, thus indicating that our stellar discs are still too massive for the dark matter halo in which they reside. Results are found to be remarkably stable against resolution. This further demonstrates the feasibility of carrying out simulations producing a realistic population of galaxies within representative cosmological volumes, at a relatively modest resolution.
Calculation of electrical potentials on the surface of a realistic head model by finite differences.
Lemieux, L; McBride, A; Hand, J W
1996-07-01
We present a method for the calculation of electrical potentials at the surface of realistic head models from a point dipole generator based on a 3D finite-difference algorithm. The model was validated by comparing calculated values with those obtained algebraically for a three-shell spherical model. For a 1.25 mm cubic grid size, the mean error was 4.9% for a superficial dipole (3.75 mm from the inner surface of the skull) pointing in the radial direction. The effect of generator discretization and node spacing on the accuracy of the model was studied. Three values of the node spacing were considered: 1, 1.25 and 1.5 mm. The mean relative errors were 4.2, 6.3 and 9.3% respectively. The quality of the approximation of a point dipole by an array of nodes in a spherical neighbourhood did not depend significantly on the number of nodes used. The application of the method to a conduction model derived from MRI data is demonstrated.
Laganà, K; Dubini, G; Migliavacca, F; Pietrabissa, R; Pennati, G; Veneziani, A; Quarteroni, A
2002-01-01
This work was motivated by the problems of analysing detailed 3D models of vascular districts with complex anatomy. It suggests an approach to prescribing realistic boundary conditions to use in order to obtain information on local as well as global haemodynamics. A method was developed which simultaneously solves Navier-Stokes equations for local information and a non-linear system of ordinary differential equations for global information. This is based on the principle that an anatomically detailed 3D model of a cardiovascular district can be achieved by using the finite element method. In turn the finite element method requires a specific boundary condition set. The approach outlined in this work is to include the system of ordinary differential equations in the boundary condition set. Such a multiscale approach was first applied to two controls: (i) a 3D model of a straight tube in a simple hydraulic network and (ii) a 3D model of a straight coronary vessel in a lumped-parameter model of the cardiovascular system. The results obtained are very close to the solutions available for the pipe geometry. This paper also presents preliminary results from the application of the methodology to a particular haemodynamic problem: namely the fluid dynamics of a systemic-to-pulmonary shunt in paediatric cardiac surgery.
von Thienen, Wolfhard; Metzler, Dirk; Witte, Volker
2015-05-07
The emergence of self-organizing behavior in ants has been modeled in various theoretical approaches in the past decades. One model explains experimental observations in which Argentine ants (Linepithema humile) selected the shorter of two alternative paths from their nest to a food source (shortest path experiments). This model serves as an important example for the emergence of collective behavior and self-organization in biological systems. In addition, it inspired the development of computer algorithms for optimization problems called ant colony optimization (ACO). In the model, a choice function describing how ants react to different pheromone concentrations is fundamental. However, the parameters of the choice function were not deduced experimentally but freely adapted so that the model fitted the observations of the shortest path experiments. Thus, important knowledge was lacking about crucial model assumptions. A recent study on the Argentine ant provided this information by measuring the response of the ants to varying pheromone concentrations. In said study, the above mentioned choice function was fitted to the experimental data and its parameters were deduced. In addition, a psychometric function was fitted to the data and its parameters deduced. Based on these findings, it is possible to test the shortest path model by applying realistic parameter values. Here we present the results of such tests using Monte Carlo simulations of shortest path experiments with Argentine ants. We compare the choice function and the psychometric function, both with parameter values deduced from the above-mentioned experiments. Our results show that by applying the psychometric function, the shortest path experiments can be explained satisfactorily by the model. The study represents the first example of how psychophysical theory can be used to understand and model collective foraging behavior of ants based on trail pheromones. These findings may be important for other
NASA Astrophysics Data System (ADS)
Wright, T. J.; Clarke, P.; Funning, G. J.
2002-12-01
The major source of error in InSAR measurements results from changes in tropospheric water vapour concentrations, creating phase delays that are unrelated to ground motion. These can be distributed over distances of tens of kilometres and, if interpreted as surface deformation, can cause errors in measurement as large as 10 cm. Here we present a simple modified Monte Carlo (MC) method for determining the impact of these errors on the accuracy of model parameters derived from InSAR data. In particular, we examine the reliability of InSAR-derived earthquake slip distributions. Conventional MC bootstrap methods are often used for determining errors in model parameters derived from InSAR data. An ensemble of best-fit parameter estimates is found using different input data sets. Each of these data sets is derived from the original, but has its individual phase measurements randomly perturbed in a normal distribution about their original value using an a priori standard deviation. Errors in model parameter estimates are found from the distribution of best-fit solutions to each perturbed data set. For InSAR data, however, conventional MC fails to account for the spatial correlation of atmospheric errors between multiple sampled phase measurements. When the interferogram is sampled densely compared to the wavelength of atmospheric errors, conventional MC can grossly underestimate the errors of model parameter estimates. To produce realistic error bars for parameter estimates, the interferogram's variance-covariance matrix (VCM) must first be determined. A practical approach for this is to determine the mean covariance vs distance function (autocorrelation function), either spatially or from the interferogram's power spectrum using the Wiener-Khinchine theorem (e.g. Hanssen, 2001). This must be done using a part of the interferogram away from the deformation, or, where this is not possible, after a first-pass model has been removed. Using the covariance vs distance function
NASA Astrophysics Data System (ADS)
Percival, Susan M.; Salaris, Maurizio
2011-04-01
The presence of an extended blue horizontal branch (HB) in a stellar population is known to affect the age inferred from spectral fitting to stellar population synthesis models. This is due to the hot blue component which increases the strength of the Balmer lines and can make an old population look spuriously young. However, most population synthesis models still rely on theoretical isochrones, which do not include realistic modelling of extended HBs. In this work, we create detailed models for a range of old simple stellar populations (SSPs), with metallicities ranging from [Fe/H]=-1.3 to solar, to create a variety of realistic HB morphologies, from extended red clumps, to extreme blue HBs. We achieve this by utilizing stellar tracks from the BaSTI data base and implementing a different mass-loss prescription for each SSP created. This includes setting an average mass and a Gaussian spread in masses of individual stars coming on to the zero-age HB for each model, and hence resulting in different HB morphologies. We find that, for each metallicity, there is some HB morphology which maximizes Hβ, making an underlying 14-Gyr population look ˜5-6 Gyr old for the low- and intermediate-metallicity cases, and as young as 2 Gyr in the case of the solar metallicity SSP. We explore whether there are any spectral indices capable of breaking the degeneracy between an old SSP with extended blue HB and a truly young or intermediate-age SSP, and find that the Ca II index of Rose and the strength of the Mg II doublet at 2800 Å are promising candidates, in combination with Hβ and other metallicity indicators, such as Mgb and Fe5406. We also run Monte Carlo simulations to investigate the level of statistical fluctuations in the spectra of typical stellar clusters. We find that fluctuations in spectral indices are significant even for average to large globular clusters and that various spectral indices are affected in different ways, which has implications for full
Simulations of magnetocardiographic signals using realistic geometry models of the heart and torso
NASA Astrophysics Data System (ADS)
Motrescu, C. V.; Klinkenbusch, L.
2012-09-01
Although the first measurement of the cardiac magnetic field was reported almost half a century ago magnetocardiography (MCG) is not yet widely used as a clinical diagnostic technique. With the development of a new generation of magnetoelectric sensors it is believed that MCG will become widely accepted in the clinical diagnosis. Our goal is to build a computer-based tool for medical diagnosis and to use it for the clarification of open electro-physiological questions. Here we present results from modelling of the cardiac electrical activity and computation of the generated magnetic field. For the simulations we use MRT-based anatomical models of the human atria and ventricles where the shape of the action potential is determined by ionic currents passing through the cardiac cell membranes. The monodomain reaction-diffusion equation is chosen for the description of the heart's electrical activity. This equation is solved for the transmembrane voltage which is in turn used to calculate current densities at discrete time instants. In subsequent simulations these current densities represent primary sources of magnetostatic fields arising from a volume conduction problem. In these simulations the heart is placed in a realistic torso model where the lungs are also considered. Both, the volume conduction problem as well as the reaction-diffusion problem are modelled using Finite-Element techniques.
Towards Realistic Global Geomagnetic Induction Modeling Using Scripted Finite Element Methods
NASA Astrophysics Data System (ADS)
Ribaudo, J. T.; Constable, C. G.
2008-12-01
We present recent progress in forward modeling the global induction problem with realistic external field structure, 3D Earth conductivity, and rotation. The modeling is performed in the time and frequency domains via a commercially-available, general-purpose, finite element modeling package called FlexPDE, and has been validated against known solutions to 3D steady state and time-dependent problems. The induction problem is formulated in terms of the magnetic vector potential and electric scalar potential, and mesh density is managed both explicitly and through adaptive mesh refinement. The modeling routine allows for arbitrary conductivity and external field structure. The strength of the external magnetic field generated by the magnetospheric ring current is known to vary as a function of local time, giving it an asymmetric spatial structure. Electromagnetic c-responses estimated from satellite data are known to be biased with respect to local time. We investigate the influence that Earth's rotation through the non-uniform external field should have on these c-responses.
NASA Astrophysics Data System (ADS)
Jeong, Woo Chul; Wi, Hun; Sajib, Saurav Z. K.; Oh, Tong In; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je
2015-08-01
Electromagnetic fields provide fundamental data for the imaging of electrical tissue properties, such as conductivity and permittivity, in recent magnetic resonance (MR)-based tissue property mapping. The induced voltage, current density, and magnetic flux density caused by externally injected current are critical factors for determining the image quality of electrical tissue conductivity. As a useful tool to identify bio-electromagnetic phenomena, precise approaches are required to understand the exact responses inside the human body subject to an injected currents. In this study, we provide the numerical simulation results of electromagnetic field mapping of brain tissues using a MR-based conductivity imaging method. First, we implemented a realistic three-dimensional human anisotropic head model using high-resolution anatomical and diffusion tensor MR images. The voltage, current density, and magnetic flux density of brain tissues were imaged by injecting 1 mA of current through pairs of electrodes on the surface of our head model. The current density map of anisotropic brain tissues was calculated from the measured magnetic flux density based on the linear relationship between the water diffusion tensor and the electrical conductivity tensor. Comparing the current density to the previous isotropic model, the anisotropic model clearly showed the differences between the brain tissues. This originates from the enhanced signals by the inherent conductivity contrast as well as the actual tissue condition resulting from the injected currents.
Investigations of sensitivity and resolution of ECG and MCG in a realistically shaped thorax model.
Mäntynen, Ville; Konttila, Teijo; Stenroos, Matti
2014-12-07
Solving the inverse problem of electrocardiography (ECG) and magnetocardiography (MCG) is often referred to as cardiac source imaging. Spatial properties of ECG and MCG as imaging systems are, however, not well known. In this modelling study, we investigate the sensitivity and point-spread function (PSF) of ECG, MCG, and combined ECG+MCG as a function of source position and orientation, globally around the ventricles: signal topographies are modelled using a realistically-shaped volume conductor model, and the inverse problem is solved using a distributed source model and linear source estimation with minimal use of prior information. The results show that the sensitivity depends not only on the modality but also on the location and orientation of the source and that the sensitivity distribution is clearly reflected in the PSF. MCG can better characterize tangential anterior sources (with respect to the heart surface), while ECG excels with normally-oriented and posterior sources. Compared to either modality used alone, the sensitivity of combined ECG+MCG is less dependent on source orientation per source location, leading to better source estimates. Thus, for maximal sensitivity and optimal source estimation, the electric and magnetic measurements should be combined.
Simulations of ion current in realistic models of ion channels: the KcsA potassium channel.
Burykin, A; Schutz, C N; Villá, J; Warshel, A
2002-05-15
Realistic studies of ion current in biologic channels present a major challenge for computer simulation approaches. All-atom molecular dynamics simulations involve serious time limitations that prevent their use in direct evaluation of ion current in channels with significant barriers. The alternative use of Brownian dynamics (BD) simulations can provide the current for simplified macroscopic models. However, the time needed for accurate calculations of electrostatic energies can make BD simulations of ion current expensive. The present work develops an approach that overcomes some of the above challenges and allows one to simulate ion currents in models of biologic channels. Our method provides a fast and reliable estimate of the energetics of the system by combining semimacroscopic calculations of the self-energy of each ion and an implicit treatment of the interactions between the ions, as well as the interactions between the ions and the protein-ionizable groups. This treatment involves the use of the semimacroscopic version of the protein dipole Langevin dipole (PDLD/S) model in its linear response approximation (LRA) implementation, which reduces the uncertainties about the value of the protein "dielectric constant." The resulting free energy surface is used to generate the forces for on-the-fly BD simulations of the corresponding ion currents. Our model is examined in a preliminary simulation of the ion current in the KcsA potassium channel. The complete free energy profile for a single ion transport reflects reasonable energetics and captures the effect of the protein-ionized groups. This calculated profile indicates that we are dealing with the channel in its closed state. Reducing the barrier at the gate region allows us to simulate the ion current in a reasonable computational time. Several limiting cases are examined, including those that reproduce the observed current, and the nature of the productive trajectories is considered. The ability to simulate
Odabaee, Maryam; Tokariev, Anton; Layeghy, Siamak; Mesbah, Mostefa; Colditz, Paul B; Ramon, Ceon; Vanhatalo, Sampsa
2014-08-01
The potential improvements in spatial resolution of neonatal EEG used in source localization have been challenged by the insufficiencies in realistic neonatal head models. Our present study aimed at using empirical methods to indirectly estimate skull conductivity; the model parameter that is known to significantly affect the behavior of newborn scalp EEG and cause it to be markedly different from that of an adult. To this end, we used 64 channel EEG recordings to study the spatial specificity of scalp EEG by assessing the spatial decays in focal transients using both amplitudes and between-c'hannels linear correlations. The findings showed that these amplitudes and correlations decay within few centimeters from the reference channel/electrode, and that the nature of the decay is independent of the scalp area. This decay in newborn infants was found to be approximately three times faster than the corresponding decay in adult EEG analyzed from a set of 256 channel recordings. We then generated realistic head models using both finite and boundary element methods along with a manually segmented magnetic resonance images to study the spatial decays of scalp potentials produced by single dipole in the cortex. By comparing the spatial decays due to real and simulated EEG for different skull conductivities (from 0.003 to 0.3S/m), we showed that a close match between the empirical and simulated decays was obtained when the selected skull conductivity for newborn was around 0.06-0.2S/m. This is over an order of magnitude higher than the currently used values in adult head modeling. The results also showed that the neonatal scalp EEG is less smeared than that of an adult and this characteristic is the same across the entire scalp, including the fontanel region. These results indicate that a focal cortical activity is generally only registered by electrodes within few centimeters from the source. Hence, the conventional 10 to 20 channel neonatal EEG acquisition systems give a
Seismic shaking scenarios in realistic 3D crustal model of Northern Italy
NASA Astrophysics Data System (ADS)
Molinari, I.; Morelli, A.; Basini, P.; Berbellini, A.
2013-12-01
Simulation of seismic wave propagation in realistic crustal structures is a fundamental tool to evaluate earthquake-generated ground shaking and assess seismic hazard. Current-generation numerical codes, and modern HPC infrastructures, allow for realistic simulations in complex 3D geologic structures. We apply such methodology to the Po Plain in Northern Italy -- a region with relatively rare earthquakes but having large property and industrial exposure, as it became clear during the two M~6 events of May 20-29, 2012. Historical seismicity is well known in this region, with maximum magnitudes estimates reaching M~7, and wave field amplitudes may be significantly amplified by the presence of the very thick sedimentary basin. Our goal is to produce estimates of expected ground shaking in Northern Italy through detailed deterministic simulations of ground motion due to expected earthquakes. We defined a three-dimensional model of the earth's crust using geo-statistical tools to merge the abundant information existing in the form of borehole data and seismic reflection profiles that had been shot in the '70s and the '80s for hydrocarbon exploration. Such information, that has been used by geologists to infer the deep structural setup, had never been merged to build a 3D model to be used for seismological simulations. We implement the model in SPECFEM3D_Cartesian and a hexahedral mesh with elements of ~2km, that allows us to simulate waves with minimum period of ~2 seconds. The model has then been optimized through comparison between simulated and recorded seismograms for the ~20 moderate-magnitude events (Mw > 4.5) that have been instrumentally recorded in the last 15 years. Realistic simulations in the frequency band of most common engineering relevance -- say, ~1 Hz -- at such a large scale would require an extremely detailed structural model, currently not available, and prohibitive computational resources. However, an interest is growing in longer period ground
NASA Astrophysics Data System (ADS)
Hejazi, Mohamad I.; Cai, Ximing
2011-06-01
In this paper, we promote a novel approach to develop reservoir operation routines by learning from historical hydrologic information and reservoir operations. The proposed framework involves a knowledge discovery step to learn the real drivers of reservoir decision making and to subsequently build a more realistic (enhanced) model formulation using stochastic dynamic programming (SDP). The enhanced SDP model is compared to two classic SDP formulations using Lake Shelbyville, a reservoir on the Kaskaskia River in Illinois, as a case study. From a data mining procedure with monthly data, the past month's inflow ( Qt-1 ), current month's inflow ( Qt), past month's release ( Rt-1 ), and past month's Palmer drought severity index ( PDSIt-1 ) are identified as important state variables in the enhanced SDP model for Shelbyville Reservoir. When compared to a weekly enhanced SDP model of the same case study, a different set of state variables and constraints are extracted. Thus different time scales for the model require different information. We demonstrate that adding additional state variables improves the solution by shifting the Pareto front as expected while using new constraints and the correct objective function can significantly reduce the difference between derived policies and historical practices. The study indicates that the monthly enhanced SDP model resembles historical records more closely and yet provides lower expected average annual costs than either of the two classic formulations (25.4% and 4.5% reductions, respectively). The weekly enhanced SDP model is compared to the monthly enhanced SDP, and it shows that acquiring the correct temporal scale is crucial to model reservoir operation for particular objectives.
Renormalizability of supersymmetric group field cosmology
NASA Astrophysics Data System (ADS)
Upadhyay, Sudhaker
2014-03-01
In this paper we consider the gauge invariant third quantized model of supersymmetric group field cosmology. The supersymmetric BRST invariance for such theory in non-linear gauge is also analysed. The path integral formulation to the case of a multiverse made up of homogeneous and isotropic spacetimes filled with a perfect fluid is presented. The renormalizability for the scattering of universes in multiverse are established with suitably constructed master equations for connected diagrams and proper vertices. The Slavnov-Taylor identities for this theory hold to all orders of radiative corrections.
Supersymmetric Ito equation: Bosonization and exact solutions
Ren Bo; Yu Jun; Lin Ji
2013-04-15
Based on the bosonization approach, the N=1 supersymmetric Ito (sIto) system is changed to a system of coupled bosonic equations. The approach can effectively avoid difficulties caused by intractable fermionic fields which are anticommuting. By solving the coupled bosonic equations, the traveling wave solutions of the sIto system are obtained with the mapping and deformation method. Some novel types of exact solutions for the supersymmetric system are constructed with the solutions and symmetries of the usual Ito equation. In the meanwhile, the similarity reduction solutions of the model are also studied with the Lie point symmetry theory.
Implications of introducing realistic fire response traits in a Dynamic Global Vegetation Model
NASA Astrophysics Data System (ADS)
Kelley, D.; Harrison, S. P.; Prentice, I. C.
2013-12-01
Bark thickness is a key trait protecting woody plants against fire damage, while the ability to resprout is a trait that confers competitive advantage over non-resprouting individuals in fire-prone landscapes. Neither trait is well represented in fire-enabled dynamic global vegetation models (DGVMs). Here we describe a version of the Land Processes and eXchanges (LPX-Mv1) DGVM that incorporates both of these traits in a realistic way. From a synthesis of a large number of field studies, we show there is considerable innate variability in bark thickness between species within a plant-functional type (PFT). Furthermore, bark thickness is an adaptive trait at ecosystem level, increasing with fire frequency. We use the data to specify the range of bark thicknesses characteristic of each model PFT. We allow this distribution to change dynamically: thinner-barked trees are killed preferentially by fire, shifting the distribution of bark thicknesses represented in a model grid cell. We use the PFT-specific bark-thickness probability range for saplings during re-establishment. Since it is rare to destroy all trees in a grid cell, this treatment results in average bark thickness increasing with fire frequency and intensity. Resprouting is a prominent adaptation of temperate and tropical trees in fire-prone areas. The ability to resprout from above-ground tissue (apical or epicormic resprouting) results in the fastest recovery of total biomass after disturbance; resprouting from basal or below-ground meristems results in slower recovery, while non-resprouting species must regenerate from seed and therefore take the longest time to recover. Our analyses show that resprouting species have thicker bark than non-resprouting species. Investment in resprouting is accompanied by reduced efficacy of regeneration from seed. We introduce resprouting PFTs in LPX-Mv1 by specifying an appropriate range of bark thickness, allowing resprouters to survive fire and regenerate vegetatively in
Realistic modeling of the pulse profile of PSR J0737-3039A
Perera, B. B. P.; Kim, C.; McLaughlin, M. A.; Ferdman, R. D.; Kramer, M.; Freire, P. C. C.; Stairs, I. H.; Possenti, A.
2014-05-20
The Double Pulsar, PSR J0737-3039A/B, is a unique system in which both neutron stars have been detected as radio pulsars. As shown in Ferdman et al., there is no evidence for pulse profile evolution of the A pulsar, and the geometry of the pulsar was fit well with a double-pole circular radio beam model. Assuming a more realistic polar cap model with a vacuum retarded dipole magnetosphere configuration including special relativistic effects, we create synthesized pulse profiles for A given the best-fit geometry from the simple circular beam model. By fitting synthesized pulse profiles to those observed from pulsar A, we constrain the geometry of the radio beam, namely the half-opening angle and the emission altitude, to be ∼30° and ∼10 neutron star radii, respectively. Combining the observational constraints of PSR J0737-3039A/B, we are able to construct the full three-dimensional orbital geometry of the Double Pulsar. The relative angle between the spin axes of the two pulsars (Δ{sub S}) is estimated to be ∼(138° ± 5°) at the current epoch and will likely remain constant until tidal interactions become important in ∼85 Myr, at merger.
Atomistic surface erosion and thin film growth modelled over realistic time scales
Scott, Chris; Blackwell, Sabrina; Vernon, Louis; Kenny, Steven; Smith, Roger; Walls, Michael
2011-11-07
We present results of atomistic modelling of surface growth and sputtering using a multi-time scale molecular dynamics-on-the-fly kinetic Monte Carlo scheme which allows simulations to be carried out over realistic experimental times. The method uses molecular dynamics to model the fast processes and then calculates the diffusion barriers for the slow processes on-the-fly, without any preconceptions about what transitions might occur. The method is applied to the growth of metal and oxide materials at impact energies typical for both vapour deposition and magnetron sputtering. The method can be used to explain growth processes, such as the filling of vacancies and the formation of stacking faults. By tuning the variable experimental parameters on the computer, a parameter set for optimum crystalline growth can be determined. The method can also be used to model sputtering where the particle interactions with the surface occur at a higher energy. It is shown how a steady state can arise in which interstitial clusters are continuously being formed below the surface during an atom impact event which also recombine or diffuse to the surface between impact events. For fcc metals the near surface region remains basically crystalline during the erosion process with a pitted topography which soon attains a steady state roughness.
Meitav, Nizan; Shoham, Shy
2016-01-01
Abstract In recent years, optogenetics has become a central tool in neuroscience research. Estimating the transmission of visible light through brain tissue is of crucial importance for controlling the activation levels of neurons in different depths, designing optical systems, and avoiding lesions from excessive power density. The Kubelka–Munk model and Monte Carlo simulations have previously been used to model light propagation through rodents' brain tissue, however, these prior attempts suffer from fundamental shortcomings. Here, we introduce and study two modified approaches for modeling the distributions of light emanating from a multimode fiber and scattering through tissue, using both realistic numerical Monte Carlo simulations and an analytical approach based on the beam-spread function approach. We demonstrate a good agreement of the new methods' predictions both with recently published data, and with new measurements in mouse brain cortical slices, where our results yield a new cortical scattering length estimate of ∼47 µm at λ = 473 nm, significantly shorter than ordinarily assumed in optogenetic applications. PMID:26866055
NASA Technical Reports Server (NTRS)
Weaver, Clark J.; Douglass, Anne R.; Rood, Richard B.
1995-01-01
A three-dimensional transport model, which uses winds from a stratospheric data assimilation system, is used to study the transport of supersonic aircraft exhaust in the lower stratosphere. A passive tracer is continuously injected into the transport model. The tracer source distribution is based on realistic scenarios for the daily emission rate of reactive nitrogen species for all forecasted flight routes. Winds are from northern hemisphere winter/spring months for 1979 and 1989; there are minimal differences between the tracer integrations for the 2 years. During the integration, peak tracer mixing ratios in the flight corridors are compared with the zonal mean and found to be greater by a factor of 2 or less. This implies that the zonal mean assumption used in two dimensional models is reasonable during winter and spring. There is a preference for pollutant buildup in the heavily traveled North Pacific and North Atlantic flight corridors. Pollutant concentration in the corridors depends on the position of the Aleutian anticyclone and the northern hemisphere polar vortex edge.
Flow in a Geometrically-Realistic, Vibrating Model of the Human Vocal Tract
NASA Astrophysics Data System (ADS)
Thomson, Scott; Seegmiller, Jayrin
2013-11-01
Airflow within the human vocal tract is an important component of voice quality. Understanding the nature of the airflow will help better understand voice production, potentially leading towards improved clinical diagnostics and treatments. An up-scaled experimental setup was developed to study three-dimensional flow features in a realistic model of the human larynx. The subglottal and supraglottal sections were made of clear silicone, with geometry derived from CT scan data. A cylindrically-shaped supraglottal section was also fabricated to compare flows with and without anatomically-accurate supraglottal sections. The glottal section consisted of two counter-rotating, mechanically-driven cams, covered by a silicone membrane, to approximate the alternating convergent-divergent profile of vibrating vocal folds. A mixture of water and glycerol was pumped through the system, the index of refraction matching that of the silicone for optical access into the sub- and supraglottal sections. Velocity fields throughout the glottal cycle were acquired using particle image velocimetry (PIV), giving particular attention to differences in flow features (e.g., jet skewing and axis switching) between models with CT-derived and cylindrically-shaped supraglottal geometry. In this presentation, the model design and characteristics will be given, and PIV flow results will be presented and discussed. Supported by NIH/NIDCD Grant R01 DC009616.
Ciesielski, Peter N.; Crowley, Michael F.; Nimlos, Mark R.; ...
2014-12-09
Biomass exhibits a complex microstructure of directional pores that impact how heat and mass are transferred within biomass particles during conversion processes. However, models of biomass particles used in simulations of conversion processes typically employ oversimplified geometries such as spheres and cylinders and neglect intraparticle microstructure. In this study, we develop 3D models of biomass particles with size, morphology, and microstructure based on parameters obtained from quantitative image analysis. We obtain measurements of particle size and morphology by analyzing large ensembles of particles that result from typical size reduction methods, and we delineate several representative size classes. Microstructural parameters, includingmore » cell wall thickness and cell lumen dimensions, are measured directly from micrographs of sectioned biomass. A general constructive solid geometry algorithm is presented that produces models of biomass particles based on these measurements. Next, we employ the parameters obtained from image analysis to construct models of three different particle size classes from two different feedstocks representing a hardwood poplar species (Populus tremuloides, quaking aspen) and a softwood pine (Pinus taeda, loblolly pine). Finally, we demonstrate the utility of the models and the effects explicit microstructure by performing finite-element simulations of intraparticle heat and mass transfer, and the results are compared to similar simulations using traditional simplified geometries. In conclusion, we show how the behavior of particle models with more realistic morphology and explicit microstructure departs from that of spherical models in simulations of transport phenomena and that species-dependent differences in microstructure impact simulation results in some cases.« less
Ciesielski, Peter N.; Crowley, Michael F.; Nimlos, Mark R.; Sanders, Aric W.; Wiggins, Gavin M.; Robichaud, David; Donohoe, Bryon S.; Foust, Thomas D.
2014-12-09
Biomass exhibits a complex microstructure of directional pores that impact how heat and mass are transferred within biomass particles during conversion processes. However, models of biomass particles used in simulations of conversion processes typically employ oversimplified geometries such as spheres and cylinders and neglect intraparticle microstructure. In this study, we develop 3D models of biomass particles with size, morphology, and microstructure based on parameters obtained from quantitative image analysis. We obtain measurements of particle size and morphology by analyzing large ensembles of particles that result from typical size reduction methods, and we delineate several representative size classes. Microstructural parameters, including cell wall thickness and cell lumen dimensions, are measured directly from micrographs of sectioned biomass. A general constructive solid geometry algorithm is presented that produces models of biomass particles based on these measurements. Next, we employ the parameters obtained from image analysis to construct models of three different particle size classes from two different feedstocks representing a hardwood poplar species (Populus tremuloides, quaking aspen) and a softwood pine (Pinus taeda, loblolly pine). Finally, we demonstrate the utility of the models and the effects explicit microstructure by performing finite-element simulations of intraparticle heat and mass transfer, and the results are compared to similar simulations using traditional simplified geometries. In conclusion, we show how the behavior of particle models with more realistic morphology and explicit microstructure departs from that of spherical models in simulations of transport phenomena and that species-dependent differences in microstructure impact simulation results in some cases.
Explicit all-atom modeling of realistically sized ligand-capped nanocrystals.
Kaushik, Ananth P; Clancy, Paulette
2012-03-21
We present a study of an explicit all-atom representation of nanocrystals of experimentally relevant sizes (up to 6 nm), "capped" with alkyl chain ligands, in vacuum. We employ all-atom molecular dynamics simulation methods in concert with a well-tested intermolecular potential model, MM3 (molecular mechanics 3), for the studies presented here. These studies include determining the preferred conformation of an isolated single nanocrystal (NC), pairs of isolated NCs, and (presaging studies of superlattice arrays) unit cells of NC superlattices. We observe that very small NCs (3 nm) behave differently in a superlattice as compared to larger NCs (6 nm and above) due to the conformations adopted by the capping ligands on the NC surface. Short ligands adopt a uniform distribution of orientational preferences, including some that lie against the face of the nanocrystal. In contrast, longer ligands prefer to interdigitate. We also study the effect of changing ligand length and ligand coverage on the NCs on the preferred ligand configurations. Since explicit all-atom modeling constrains the maximum system size that can be studied, we discuss issues related to coarse-graining the representation of the ligands, including a comparison of two commonly used coarse-grained models. We find that care has to be exercised in the choice of coarse-grained model. The data provided by these realistically sized ligand-capped NCs, determined using explicit all-atom models, should serve as a reference standard for future models of coarse-graining ligands using united atom models, especially for self-assembly processes.
A Realistic Gas Transport Model with application to Determining Shale Rock Characteristics
NASA Astrophysics Data System (ADS)
Ali, Iftikhar; Malik, Nadeem
2017-04-01
A nonlinear transport model with pressure-dependent parameters for the flow of shale gas in tight porous media, accounting for important physical processes such as continuous flow, transition flow, slip flow, Knudsen diffusion, surface diffusion, adsorption and desorption in to the rock material, and also including a nonlinear Forchheimer correction term for high flow rates (turbulence), has been developed [1,2]. The transport model is an advection-diffusion type of partial differential equation with pressure dependent model parameters and associated compressibility coefficients, and with nonlinear pressure-dependent apparent convective velocity U(p,p_x) and apparent diffusivity D(p) where p is the pressure field. The transient one-dimensional model without gravity and without external source is, partial p/partial t+Upartial p/partial x &=& Dpartial2 p/partial x2 where, D &=& ρ/μ FK_a/ρφζ1 +(1-φ)ζ2 U &=& -Dζ_3partial p/partial x and, ρ is the fluid density, μ is the fluid viscosity, Ka is the apparent rock permeability, φ is the rock porosity, and ζ_1(p), ζ_2(p), ζ_3(p) are various pressure dependent compressibility factors, and F is a factor incorporating the effects of high flow rates - see [1, 2] for details. The steady-state 1D model was used to determine the shale rock charcateristics by history matching the pressure distribution across a shale rock core sample obtained from pressure-pulse decay tests for different inflow pressure conditions [3]. The best results were obtained when the high flow rate Forchheimer correction term is included in the model; the estimates for the porosity and permeability are then much more realistic than previous models [4], which is a notable achievement. In the case considered, the porosity was determined to lie in the range, 0.1
NASA Astrophysics Data System (ADS)
Dalmonte, M.; Lechner, W.; Cai, Zi; Mattioli, M.; Läuchli, A. M.; Pupillo, G.
2015-07-01
We investigate the quantum phases of hard-core bosonic atoms in an extended Hubbard model where particles interact via soft-shoulder potentials in one dimension. Using a combination of field-theoretical methods and strong-coupling perturbation theory, we demonstrate that the low-energy phase can be a conformal cluster Luttinger liquid (CLL) phase with central charge c =1 , where the microscopic degrees of freedom correspond to mesoscopic ensembles of particles. Using numerical density-matrix renormalization-group methods, we demonstrate that the CLL phase [first predicted in M. Mattioli et al., Phys. Rev. Lett. 111, 165302 (2013), 10.1103/PhysRevLett.111.165302] is separated from a conventional Tomonaga-Luttinger liquid by an exotic critical point with central charge c =3/2 . The latter is expression of an emergent conformal supersymmetry, which is not present in the original Hamiltonian. We discuss the observability of the CLL phase in realistic experimental settings with weakly dressed Rydberg atoms confined to optical lattices. Using quantum Monte Carlo simulations, we show that the typical features of CLLs are stable up to comparatively high temperatures. Using exact diagonalizations and quantum trajectory methods, we provide a protocol for adiabatic state preparation as well as quantitative estimates on the effects of particle losses.
NASA Astrophysics Data System (ADS)
Davtyan, Aram; Dama, James F.; Voth, Gregory A.; Andersen, Hans C.
2015-04-01
the method provides realistic dynamical CG models that have non-Markovian or close to Markovian behavior that is consistent with the actual dynamical behavior of the all-atom system used to construct the CG model. Both the construction and the simulation of such a dynamic CG model have computational requirements that are similar to those of the corresponding MS-CG model and are good candidates for CG modeling of very large systems.
Davtyan, Aram; Dama, James F.; Voth, Gregory A.; Andersen, Hans C.
2015-04-21
the method provides realistic dynamical CG models that have non-Markovian or close to Markovian behavior that is consistent with the actual dynamical behavior of the all-atom system used to construct the CG model. Both the construction and the simulation of such a dynamic CG model have computational requirements that are similar to those of the corresponding MS-CG model and are good candidates for CG modeling of very large systems.
NASA Astrophysics Data System (ADS)
Jain, Vaibhav; Maiti, Prabal K.; Bharatam, Prasad V.
2016-09-01
Computational studies performed on dendrimer-drug complexes usually consider 1:1 stoichiometry, which is far from reality, since in experiments more number of drug molecules get encapsulated inside a dendrimer. In the present study, molecular dynamic (MD) simulations were implemented to characterize the more realistic molecular models of dendrimer-drug complexes (1:n stoichiometry) in order to understand the effect of high drug loading on the structural properties and also to unveil the atomistic level details. For this purpose, possible inclusion complexes of model drug Nateglinide (Ntg) (antidiabetic, belongs to Biopharmaceutics Classification System class II) with amine- and acetyl-terminated G4 poly(amidoamine) (G4 PAMAM(NH2) and G4 PAMAM(Ac)) dendrimers at neutral and low pH conditions are explored in this work. MD simulation analysis on dendrimer-drug complexes revealed that the drug encapsulation efficiency of G4 PAMAM(NH2) and G4 PAMAM(Ac) dendrimers at neutral pH was 6 and 5, respectively, while at low pH it was 12 and 13, respectively. Center-of-mass distance analysis showed that most of the drug molecules are located in the interior hydrophobic pockets of G4 PAMAM(NH2) at both the pH; while in the case of G4 PAMAM(Ac), most of them are distributed near to the surface at neutral pH and in the interior hydrophobic pockets at low pH. Structural properties such as radius of gyration, shape, radial density distribution, and solvent accessible surface area of dendrimer-drug complexes were also assessed and compared with that of the drug unloaded dendrimers. Further, binding energy calculations using molecular mechanics Poisson-Boltzmann surface area approach revealed that the location of drug molecules in the dendrimer is not the decisive factor for the higher and lower binding affinity of the complex, but the charged state of dendrimer and drug, intermolecular interactions, pH-induced conformational changes, and surface groups of dendrimer do play an
PIV-measured versus CFD-predicted flow dynamics in anatomically realistic cerebral aneurysm models.
Ford, Matthew D; Nikolov, Hristo N; Milner, Jaques S; Lownie, Stephen P; Demont, Edwin M; Kalata, Wojciech; Loth, Francis; Holdsworth, David W; Steinman, David A
2008-04-01
Computational fluid dynamics (CFD) modeling of nominally patient-specific cerebral aneurysms is increasingly being used as a research tool to further understand the development, prognosis, and treatment of brain aneurysms. We have previously developed virtual angiography to indirectly validate CFD-predicted gross flow dynamics against the routinely acquired digital subtraction angiograms. Toward a more direct validation, here we compare detailed, CFD-predicted velocity fields against those measured using particle imaging velocimetry (PIV). Two anatomically realistic flow-through phantoms, one a giant internal carotid artery (ICA) aneurysm and the other a basilar artery (BA) tip aneurysm, were constructed of a clear silicone elastomer. The phantoms were placed within a computer-controlled flow loop, programed with representative flow rate waveforms. PIV images were collected on several anterior-posterior (AP) and lateral (LAT) planes. CFD simulations were then carried out using a well-validated, in-house solver, based on micro-CT reconstructions of the geometries of the flow-through phantoms and inlet/outlet boundary conditions derived from flow rates measured during the PIV experiments. PIV and CFD results from the central AP plane of the ICA aneurysm showed a large stable vortex throughout the cardiac cycle. Complex vortex dynamics, captured by PIV and CFD, persisted throughout the cardiac cycle on the central LAT plane. Velocity vector fields showed good overall agreement. For the BA, aneurysm agreement was more compelling, with both PIV and CFD similarly resolving the dynamics of counter-rotating vortices on both AP and LAT planes. Despite the imposition of periodic flow boundary conditions for the CFD simulations, cycle-to-cycle fluctuations were evident in the BA aneurysm simulations, which agreed well, in terms of both amplitudes and spatial distributions, with cycle-to-cycle fluctuations measured by PIV in the same geometry. The overall good agreement
NASA Astrophysics Data System (ADS)
Iizuka, Norihiro
2007-09-01
By studying the equations of motion directly, we show that the attractor mechanism can work for non-supersymmetric extremal black holes. Two conditions are sufficient for this, they are conveniently stated in terms of an effective potential involving the scalars and the charges carried by the black hole. Our analysis applies to black holes in theories with N⩽1 supersymmetry, as well as non-supersymmetric black holes in theories with N=2 supersymmetry. Similar results are also obtained for extremal black holes in asymptotically Anti-de Sitter space and in higher dimensions. This proceeding is based on the work with K. Goldstein, R. P. Jena and S. P. Trivedi, eprint hep-th/0507096.
Dynamical supersymmetric Dirac Hamiltonians
Ginocchio, J.N.
1986-01-01
Using the language of quantum electrodynamics, the Dirac Hamiltonian of a neutral fermion interacting with a tensor field is examined. A supersymmetry found for a general Dirac Hamiltonian of this type is discussed, followed by consideration of the special case of a harmonic electric potential. The square of the Dirac Hamiltonian of a neutral fermion interacting via an anomalous magnetic moment in an electric potential is shown to be equivalent to a three-dimensional supersymmetric Schroedinger equation. It is found that for a potential that grows as a power of r, the lowest energy of the Hamiltonian equals the rest mass of the fermion, and the Dirac eigenfunction has only an upper component which is normalizable. It is also found that the higher energy states have upper and lower components which form a supersymmetric doublet. 15 refs. (LEW)
NASA Astrophysics Data System (ADS)
Brenders, A. J.; Pratt, R. G.
2007-01-01
A comprehensive validation of 2-D, frequency-domain, acoustic wave-equation tomography was undertaken in a `blind test', using third-party, realistic, elastic wave-equation data. The synthetic 2-D, wide-angle seismic data were provided prior to a recent workshop on the methods of controlled source seismology; the true model was not revealed to the authors until after the presentation of our waveform tomography results. The original model was specified on a detailed grid with variable P-wave velocity, S-wave velocity, density and viscoelastic Q-factor structure, designed to simulate a section of continental crust 250 km long and 40 km deep. Synthetic vertical and horizontal component data were available for 51 shot locations (spaced every 5 km), recorded at 2779 receivers (spaced every 90 m), evenly spread along the surface of the model. The data contained energy from 0.2 to 15 Hz. Waveform tomography, a combination of traveltime tomography and 2-D waveform inversion of the early arrivals of the seismic waveforms, was used to recover crustal P-velocity structure from the vertical component data, using data from 51 sources, 1390 receivers and frequencies between 0.8 and 7.0 Hz. The waveform tomography result contained apparent structure at wavelength-scale resolution that was not evident on the traveltime tomography result. The predicted (acoustic) waveforms in the final result matched the original elastic data to a high degree of accuracy. During the workshop, the exact model was revealed; over much of the model the waveform tomography results provided a good correspondence with the true model, from large- to intermediate-(wavelength) scales, with a resolution limit on the order of 1 km. A significant, near-surface low-velocity zone, invisible to traveltime methods, was correctly recovered; the results also provided a high-resolution image of the complex structure of the entire crust, and the depth and nature of the crust-mantle transition. Some inaccuracies were
Ultraviolet divergences in non-renormalizable supersymmetric theories
NASA Astrophysics Data System (ADS)
Smilga, A.
2017-03-01
We present a pedagogical review of our current understanding of the ultraviolet structure of N = (1,1) 6D supersymmetric Yang-Mills theory and of N = 8 4 D supergravity. These theories are not renormalizable, they involve power ultraviolet divergences and, in all probability, an infinite set of higherdimensional counterterms that contribute to on-mass-shell scattering amplitudes. A specific feature of supersymmetric theories (especially, of extended supersymmetric theories) is that these counterterms may not be invariant off shell under the full set of supersymmetry transformations. The lowest-dimensional nontrivial counterterm is supersymmetric on shell. Still higher counterterms may lose even the on-shell invariance. On the other hand, the full effective Lagrangian, generating the amplitudes and representing an infinite sum of counterterms, still enjoys the complete symmetry of original theory. We also discuss simple supersymmetric quantum-mechanical models that exhibit the same behaviour.
Interpolations from supersymmetric to nonsupersymmetric strings and their properties
NASA Astrophysics Data System (ADS)
Aaronson, Benedict; Abel, Steven; Mavroudi, Eirini
2017-05-01
The interpolation from supersymmetric to nonsupersymmetric heterotic theories is studied, via the Scherk-Schwarz compactification of supersymmetric 6 D theories to 4 D . A general modular-invariant Scherk-Schwarz deformation is deduced from the properties of the 6 D theories at the endpoints, which significantly extends previously known examples. This wider class of nonsupersymmetric 4 D theories opens up new possibilities for model building. The full one-loop cosmological constant of such theories is studied as a function of compactification radius for a number of cases, and the following interpolating configurations are found: two supersymmetric 6 D theories related by a T -duality transformation, with intermediate 4 D maximum or minimum at the string scale; a nonsupersymmetric 6 D theory interpolating to a supersymmetric 6 D theory, with the 4 D theory possibly having an anti-de Sitter minimum; and a "metastable" nonsupersymmetric 6 D theory interpolating via a 4 D theory to a supersymmetric 6 D theory.
Rapidly re-computable EEG (electroencephalography) forward models for realistic head shapes
Ermer, J. J.; Mosher, J. C.; Baillet, S.; Leahy, R. M.
2001-01-01
Solution of the EEG source localization (inverse) problem utilizing model-based methods typically requires a significant number of forward model evaluations. For subspace based inverse methods like MUSIC [6], the total number of forward model evaluations can often approach an order of 10{sup 3} or 10{sup 4}. Techniques based on least-squares minimization may require significantly more evaluations. The observed set of measurements over an M-sensor array is often expressed as a linear forward spatio-temporal model of the form: F = GQ + N (1) where the observed forward field F (M-sensors x N-time samples) can be expressed in terms of the forward model G, a set of dipole moment(s) Q (3xP-dipoles x N-time samples) and additive noise N. Because of their simplicity, ease of computation, and relatively good accuracy, multi-layer spherical models [7] (or fast approximations described in [1], [7]) have traditionally been the 'forward model of choice' for approximating the human head. However, approximation of the human head via a spherical model does have several key drawbacks. By its very shape, the use of a spherical model distorts the true distribution of passive currents in the skull cavity. Spherical models also require that the sensor positions be projected onto the fitted sphere (Fig. 1), resulting in a distortion of the true sensor-dipole spatial geometry (and ultimately the computed surface potential). The use of a single 'best-fitted' sphere has the added drawback of incomplete coverage of the inner skull region, often ignoring areas such as the frontal cortex. In practice, this problem is typically countered by fitting additional sphere(s) to those region(s) not covered by the primary sphere. The use of these additional spheres results in added complication to the forward model. Using high-resolution spatial information obtained via X-ray CT or MR imaging, a realistic head model can be formed by tessellating the head into a set of contiguous regions (typically the
NASA Astrophysics Data System (ADS)
Sourie, Aurélien; Oertel, Micaela; Novak, Jérôme
2016-04-01
We present a numerical model for uniformly rotating superfluid neutron stars in a fully general relativistic framework with, for the first time, realistic microphysics including entrainment. We compute stationary and axisymmetric configurations of neutron stars composed of two fluids, namely superfluid neutrons and charged particles (protons and electrons), rotating with different rates around a common axis. Both fluids are coupled by entrainment, a nondissipative interaction which in the case of a nonvanishing relative velocity between the fluids causes the fluid momenta to be not aligned with the respective fluid velocities. We extend the formalism put forth by Comer and Joynt in order to calculate the equation of state (EOS) and entrainment parameters for an arbitrary relative velocity as far as superfluidity is maintained. The resulting entrainment matrix fulfills all necessary sum rules, and in the limit of small relative velocity our results agree with Fermi liquid theory ones derived to lowest order in the velocity. This formalism is applied to two new nuclear equations of state which are implemented in the numerical model, which enables us to obtain precise equilibrium configurations. The resulting density profiles and moments of inertia are discussed employing both EOSs, showing the impact of entrainment and the dependence on the EOS.
Kalkman, Randy K; Briaire, Jeroen J; Dekker, David M T; Frijns, Johan H M
2014-09-01
Place pitch was investigated in a computational model of the implanted human cochlea containing nerve fibres with realistic trajectories that take the variable distance between the organ of Corti and spiral ganglion into account. The model was further updated from previous studies by including fluid compartments in the modiolus and updating the electrical conductivity values of (temporal) bone and the modiolus, based on clinical data. Four different cochlear geometries are used, modelled with both lateral and perimodiolar implants, and their neural excitation patterns were examined for nerve fibres modelled with and without peripheral processes. Additionally, equations were derived from the model geometries that describe Greenwood's frequency map as a function of cochlear angle at the basilar membrane as well as at the spiral ganglion. The main findings are: (I) in the first (basal) turn of the cochlea, cochlear implant induced pitch can be predicted fairly well using the Greenwood function. (II) Beyond the first turn this pitch becomes increasingly unpredictable, greatly dependent on stimulus level, state of the cochlear neurons and the electrode's distance from the modiolus. (III) After the first turn cochlear implant induced pitch decreases as stimulus level increases, but the pitch does not reach values expected from direct spiral ganglion stimulation unless the peripheral processes are missing. (IV) Electrode contacts near the end of the spiral ganglion or deeper elicit very unpredictable pitch, with broad frequency ranges that strongly overlap with those of neighbouring contacts. (V) The characteristic place pitch for stimulation at either the organ of Corti or the spiral ganglion can be described as a function of cochlear angle by the equations presented in this paper.
Towards realistic representation of hydrological processes in integrated WRF-urban modeling system
NASA Astrophysics Data System (ADS)
Yang, Jiachuan; Wang, Zhi-hua; Chen, Fei; Miao, Shiguang; Tewari, Mukul; Georgescu, Matei
2014-05-01
To meet the demand of the ever-increasing urbanized global population, substantial conversion of natural landscapes to urban terrains is expected in the next few decades. The landscape modification will emerge as the source of many adverse effects that challenge the environmental sustainability of cities under changing climatic patterns. To address these adverse effects and to develop corresponding adaptation/mitigation strategies, physically-based single layer urban canopy model (SLUCM) has been developed and implemented into the Weather Research and Forecasting (WRF) platform. However, due to the lack of realistic representation of urban hydrological processes, simulation of urban climatology by current coupled WRF/SLUCM is inevitably inadequate. Aiming at improving the accuracy of simulations, in this study we implement physically-based parameterization of urban hydrological processes into the model, including (1) anthropogenic latent heat, (2) urban irrigation, (3) evaporation over water-holding engineered pavements, (4) urban oasis effect, and (5) green roof. In addition, we use an advanced Monte Carlo approach to quantify the sensitivity of urban hydrological modeling to parameter uncertainties. Evaluated against field observations at four major metropolitan areas, results show that the enhanced model is significantly improved in accurately predicting turbulent fluxes arising from built surfaces, especially the latent heat flux. Case studies show that green roof is capable of reducing urban surface temperature and sensible heat flux effectively, and modifying local and regional hydroclimate. Meanwhile, it is efficient in decreasing energy loading of buildings, not only cooling demand in summers but also heating demand in winters, through the combined evaporative cooling and insulation effect. Effectiveness of green roof is found to be limited by availability of water resources and highly sensitive to surface roughness heights. The enhanced WRF/SLUCM model
Realistic expectations of prepulse inhibition in translational models for schizophrenia research
Swerdlow, Neal R.; Weber, Martin; Qu, Ying; Light, Gregory A.; Braff, David L.
2009-01-01
Introduction Under specific conditions, a weak lead stimulus, or “prepulse”, can inhibit the startling effects of a subsequent intense abrupt stimulus. This startle-inhibiting effect of the prepulse, termed “prepulse inhibition” (PPI), is widely used in translational models to understand the biology of brain based inhibitory mechanisms and their deficiency in neuropsychiatric disorders. In 1981, four published reports with “prepulse inhibition” as an index term were listed on Medline; over the past 5 years, new published Medline reports with “prepulse inhibition” as an index term have appeared at a rate exceeding once every 2.7 days (n = 678). Most of these reports focus on the use of PPI in translational models of impaired sensorimotor gating in schizophrenia. This rapid expansion and broad application of PPI as a tool for understanding schizophrenia has, at times, outpaced critical thinking and falsifiable hypotheses about the relative strengths vs. limitations of this measure. Objectives This review enumerates the realistic expectations for PPI in translational models for schizophrenia research, and provides cautionary notes for the future applications of this important research tool. Conclusion In humans, PPI is not “diagnostic”; levels of PPI do not predict clinical course, specific symptoms, or individual medication responses. In preclinical studies, PPI is valuable for evaluating models or model organisms relevant to schizophrenia, “mapping” neural substrates of deficient PPI in schizophrenia, and advancing the discovery and development of novel therapeutics. Across species, PPI is a reliable, robust quantitative phenotype that is useful for probing the neurobiology and genetics of gating deficits in schizophrenia. PMID:18568339
Successful N{sub 2} leptogenesis with flavour coupling effects in realistic unified models
Bari, Pasquale Di; King, Stephen F.
2015-10-02
In realistic unified models involving so-called SO(10)-inspired patterns of Dirac and heavy right-handed (RH) neutrino masses, the lightest right-handed neutrino N{sub 1} is too light to yield successful thermal leptogenesis, barring highly fine tuned solutions, while the second heaviest right-handed neutrino N{sub 2} is typically in the correct mass range. We show that flavour coupling effects in the Boltzmann equations may be crucial to the success of such N{sub 2} dominated leptogenesis, by helping to ensure that the flavour asymmetries produced at the N{sub 2} scale survive N{sub 1} washout. To illustrate these effects we focus on N{sub 2} dominated leptogenesis in an existing model, the A to Z of flavour with Pati-Salam, where the neutrino Dirac mass matrix may be equal to an up-type quark mass matrix and has a particular constrained structure. The numerical results, supported by analytical insight, show that in order to achieve successful N{sub 2} leptogenesis, consistent with neutrino phenomenology, requires a “flavour swap scenario” together with a less hierarchical pattern of RH neutrino masses than naively expected, at the expense of some mild fine-tuning. In the considered A to Z model neutrino masses are predicted to be normal ordered, with an atmospheric neutrino mixing angle well into the second octant and the Dirac phase δ≃20{sup ∘}, a set of predictions that will be tested in the next years in neutrino oscillation experiments. Flavour coupling effects may be relevant for other SO(10)-inspired unified models where N{sub 2} leptogenesis is necessary.
Successful N{sub 2} leptogenesis with flavour coupling effects in realistic unified models
Bari, Pasquale Di; King, Stephen F. E-mail: king@soton.ac.uk
2015-10-01
In realistic unified models involving so-called SO(10)-inspired patterns of Dirac and heavy right-handed (RH) neutrino masses, the lightest right-handed neutrino N{sub 1} is too light to yield successful thermal leptogenesis, barring highly fine tuned solutions, while the second heaviest right-handed neutrino N{sub 2} is typically in the correct mass range. We show that flavour coupling effects in the Boltzmann equations may be crucial to the success of such N{sub 2} dominated leptogenesis, by helping to ensure that the flavour asymmetries produced at the N{sub 2} scale survive N{sub 1} washout. To illustrate these effects we focus on N{sub 2} dominated leptogenesis in an existing model, the A to Z of flavour with Pati-Salam, where the neutrino Dirac mass matrix may be equal to an up-type quark mass matrix and has a particular constrained structure. The numerical results, supported by analytical insight, show that in order to achieve successful N{sub 2} leptogenesis, consistent with neutrino phenomenology, requires a ''flavour swap scenario'' together with a less hierarchical pattern of RH neutrino masses than naively expected, at the expense of some mild fine-tuning. In the considered A to Z model neutrino masses are predicted to be normal ordered, with an atmospheric neutrino mixing angle well into the second octant and the Dirac phase δ≅ 20{sup o}, a set of predictions that will be tested in the next years in neutrino oscillation experiments. Flavour coupling effects may be relevant for other SO(10)-inspired unified models where N{sub 2} leptogenesis is necessary.
Icosahedral quasicrystal decoration models. II. Optimization under realistic Al-Mn potentials
Mihalkovic, M. |; Zhu, W.; Henley, C.L.; Phillips, R.
1996-04-01
We have constructed and relaxed over 200 different finite structure models for the quasicrystal {ital i}-AlMn based on decorations of the {open_quote}{open_quote}canonical-cell tiling.{close_quote}{close_quote} We adopted {ital ab} {ital initio}-based pair potentials with strong Friedel oscillations, which reproduce the phase diagram of real Al-Mn intermetallic crystal structures fairly well. Our various decoration rules encompass cases with face-centered icosahedral (FCI) symmetry and with simple icosahedral (SI) symmetry, and include additional variations in the occupancy and/or chemistry of certain site types. Each decoration was applied to 11 distinct periodic approximants of the tiling. We found that (i) the relaxed atomic positions of each site type can be closely approximated by fixed positions on each tile type, even though the environments (beyond the first neighbor) are inequivalent. (ii) Models with simple icosahedral (SI) space-group symmetry were better than those with face-centered icosahedral (FCI) space-group symmetry. (iii) {open_quote}{open_quote}Loose{close_quote}{close_quote} decorations, containing voids almost large enough for an atom, were better than the {open_quote}{open_quote}dense{close_quote}{close_quote} decorations which were suggested by packing considerations. (iv) Our results depended on using the realistic potentials; {ital short}-range potentials favor the {open_quote}{open_quote}dense{close_quote}{close_quote} structures, and many details depend on the second or further oscillations in the potentials. (v) For our best model, there is relatively little variation of the energy when tiles are rearranged, i.e., a {ital random}-{ital tiling} {ital model} is a good zero-order description of the system. {copyright} {ital 1996 The American Physical Society.}
Successful N2 leptogenesis with flavour coupling effects in realistic unified models
NASA Astrophysics Data System (ADS)
Di Bari, Pasquale; King, Stephen F.
2015-10-01
In realistic unified models involving so-called SO(10)-inspired patterns of Dirac and heavy right-handed (RH) neutrino masses, the lightest right-handed neutrino N1 is too light to yield successful thermal leptogenesis, barring highly fine tuned solutions, while the second heaviest right-handed neutrino N2 is typically in the correct mass range. We show that flavour coupling effects in the Boltzmann equations may be crucial to the success of such N2 dominated leptogenesis, by helping to ensure that the flavour asymmetries produced at the N2 scale survive N1 washout. To illustrate these effects we focus on N2 dominated leptogenesis in an existing model, the A to Z of flavour with Pati-Salam, where the neutrino Dirac mass matrix may be equal to an up-type quark mass matrix and has a particular constrained structure. The numerical results, supported by analytical insight, show that in order to achieve successful N2 leptogenesis, consistent with neutrino phenomenology, requires a ``flavour swap scenario'' together with a less hierarchical pattern of RH neutrino masses than naively expected, at the expense of some mild fine-tuning. In the considered A to Z model neutrino masses are predicted to be normal ordered, with an atmospheric neutrino mixing angle well into the second octant and the Dirac phase δsimeq 20o, a set of predictions that will be tested in the next years in neutrino oscillation experiments. Flavour coupling effects may be relevant for other SO(10)-inspired unified models where N2 leptogenesis is necessary.
Supersymmetric fifth order evolution equations
Tian, K.; Liu, Q. P.
2010-03-08
This paper considers supersymmetric fifth order evolution equations. Within the framework of symmetry approach, we give a list containing six equations, which are (potentially) integrable systems. Among these equations, the most interesting ones include a supersymmetric Sawada-Kotera equation and a novel supersymmetric fifth order KdV equation. For the latter, we supply some properties such as a Hamiltonian structures and a possible recursion operator.
Underwriting information-theoretic accounts of quantum mechanics with a realist, psi-epistemic model
NASA Astrophysics Data System (ADS)
Stuckey, W. M.; Silberstein, Michael; McDevitt, Timothy
2016-05-01
We propose an adynamical interpretation of quantum theory called Relational Blockworld (RBW) where the fundamental ontological element is a 4D graphical amalgam of space, time and sources called a “spacetimesource element.” These are fundamental elements of space, time and sources, not source elements in space and time. The transition amplitude for a spacetimesource element is computed using a path integral with discrete graphical action. The action for a spacetimesource element is constructed from a difference matrix K and source vector J on the graph, as in lattice gauge theory. K is constructed from graphical field gradients so that it contains a non-trivial null space and J is then restricted to the row space of K, so that it is divergence-free and represents a conserved exchange of energy-momentum. This construct of K and J represents an adynamical global constraint between sources, the spacetime metric and the energy-momentum content of the spacetimesource element, rather than a dynamical law for time-evolved entities. To illustrate this interpretation, we explain the simple EPR-Bell and twin-slit experiments. This interpretation of quantum mechanics constitutes a realist, psi-epistemic model that might underwrite certain information-theoretic accounts of the quantum.
NASA Astrophysics Data System (ADS)
Riviere, Jim E.; Scoglio, Caterina; Sahneh, Faryad D.; Monteiro-Riviere, Nancy A.
2013-01-01
The field of nanomaterial pharmacokinetics is in its infancy, with major advances largely restricted by a lack of biologically relevant metrics, fundamental differences between particles and small molecules of organic chemicals and drugs relative to biological processes involved in disposition, a scarcity of sufficiently rich and characterized in vivo data and a lack of computational approaches to integrating nanomaterial properties to biological endpoints. A central concept that links nanomaterial properties to biological disposition, in addition to their colloidal properties, is the tendency to form a biocorona which modulates biological interactions including cellular uptake and biodistribution. Pharmacokinetic models must take this crucial process into consideration to accurately predict in vivo disposition, especially when extrapolating from laboratory animals to humans since allometric principles may not be applicable. The dynamics of corona formation, which modulates biological interactions including cellular uptake and biodistribution, is thereby a crucial process involved in the rate and extent of biodisposition. The challenge will be to develop a quantitative metric that characterizes a nanoparticle's surface adsorption forces that are important for predicting biocorona dynamics. These types of integrative quantitative approaches discussed in this paper for the dynamics of corona formation must be developed before realistic engineered nanomaterial risk assessment can be accomplished.
Kleimann, Jens; Fichtner, Horst; Röken, Christian; Heerikhuisen, Jacob E-mail: hf@tp4.rub.de E-mail: jacob.heerikhuisen@uah.edu
2016-01-01
Both physical arguments and simulations of the global heliosphere indicate that the tailward heliopause is flattened considerably in the direction perpendicular to both the incoming flow and the large-scale interstellar magnetic field. Despite this fact, all of the existing global analytical models of the outer heliosheath's magnetic field assume a circular cross section of the heliotail. To eliminate this inconsistency, we introduce a mathematical procedure by which any analytically or numerically given magnetic field can be deformed in such a way that the cross sections along the heliotail axis attain freely prescribed, spatially dependent values for their total area and aspect ratio. The distorting transformation of this method honors both the solenoidality condition and the stationary induction equation with respect to an accompanying flow field, provided that both constraints were already satisfied for the original magnetic and flow fields prior to the transformation. In order to obtain realistic values for the above parameters, we present the first quantitative analysis of the heliotail's overall distortion as seen in state-of-the-art three-dimensional hybrid MHD–kinetic simulations.
NASA Astrophysics Data System (ADS)
Kleimann, Jens; Röken, Christian; Fichtner, Horst; Heerikhuisen, Jacob
2016-01-01
Both physical arguments and simulations of the global heliosphere indicate that the tailward heliopause is flattened considerably in the direction perpendicular to both the incoming flow and the large-scale interstellar magnetic field. Despite this fact, all of the existing global analytical models of the outer heliosheath's magnetic field assume a circular cross section of the heliotail. To eliminate this inconsistency, we introduce a mathematical procedure by which any analytically or numerically given magnetic field can be deformed in such a way that the cross sections along the heliotail axis attain freely prescribed, spatially dependent values for their total area and aspect ratio. The distorting transformation of this method honors both the solenoidality condition and the stationary induction equation with respect to an accompanying flow field, provided that both constraints were already satisfied for the original magnetic and flow fields prior to the transformation. In order to obtain realistic values for the above parameters, we present the first quantitative analysis of the heliotail's overall distortion as seen in state-of-the-art three-dimensional hybrid MHD-kinetic simulations.
Multiresolution molecular dynamics algorithm for realistic materials modeling on parallel computers
NASA Astrophysics Data System (ADS)
Nakano, Aiichiro; Kalia, Rajiv K.; Vashishta, Priya
1994-12-01
For realistic modeling of materials, a molecular-dynamics (MD) algorithm is developed based on multiresolutions in both space and time. Materials of interest are characterized by the long-range Coulomb, steric and charge-dipole interactions as well as three-body covalent potentials. The long-range Coulomb interaction is computed with the fast multipole method. For bulk systems with periodic boundary conditions, infinite summation over repeated image charges is carried out with the reduced cell multipole method. Short- and medium-range non-Coulombic interactions are computed with the multiple time-step approach. A separable tensor decomposition scheme is used to compute three-body potentials. For a 4.2 million-particle SiO 2 system, one MD step takes only 4.8 seconds on the 512-node Intel Touchstone Delta machine and 10.3 seconds on 64 nodes of an IBM SP1 system. The constant-grain parallel efficiency of the program is η' = 0.92 and the communication overhead is 8% on the Delta machine. On the SP1 system, η' = 0.91 and communication overhead is 7%.
Fully 3D modeling of tokamak vertical displacement events with realistic parameters
NASA Astrophysics Data System (ADS)
Pfefferle, David; Ferraro, Nathaniel; Jardin, Stephen; Bhattacharjee, Amitava
2016-10-01
In this work, we model the complex multi-domain and highly non-linear physics of Vertical Displacement Events (VDEs), one of the most damaging off-normal events in tokamaks, with the implicit 3D extended MHD code M3D-C1. The code has recently acquired the capability to include finite thickness conducting structures within the computational domain. By exploiting the possibility of running a linear 3D calculation on top of a non-linear 2D simulation, we monitor the non-axisymmetric stability and assess the eigen-structure of kink modes as the simulation proceeds. Once a stability boundary is crossed, a fully 3D non-linear calculation is launched for the remainder of the simulation, starting from an earlier time of the 2D run. This procedure, along with adaptive zoning, greatly increases the efficiency of the calculation, and allows to perform VDE simulations with realistic parameters and high resolution. Simulations are being validated with NSTX data where both axisymmetric (toroidally averaged) and non-axisymmetric induced and conductive (halo) currents have been measured. This work is supported by US DOE Grant DE-AC02-09CH11466.
A realistic in silico model for structure/function studies of molybdenum-copper CO dehydrogenase.
Rokhsana, Dalia; Large, Tao A G; Dienst, Morgan C; Retegan, Marius; Neese, Frank
2016-07-01
CO dehydrogenase (CODH) is an environmentally crucial bacterial enzyme that oxidizes CO to CO2 at a Mo-Cu active site. Despite the close to atomic resolution structure (1.1 Å), significant uncertainties have remained with regard to the protonation state of the water-derived equatorial ligand coordinated at the Mo-center, as well as the nature of intermediates formed during the catalytic cycle. To address the protonation state of the equatorial ligand, we have developed a realistic in silico QM model (~179 atoms) containing structurally essential residues surrounding the active site. Using our QM model, we examined each plausible combination of redox states (Mo(VI)-Cu(I), Mo(V)-Cu(II), Mo(V)-Cu(I), and Mo(IV)-Cu(I)) and Mo-coordinated equatorial ligands (O(2-), OH(-), H2O), as well as the effects of second-sphere residues surrounding the active site. Herein, we present a refined computational model for the Mo(VI) state in which Glu763 acts as an active site base, leading to a MoO2-like core and a protonated Glu763. Calculated structural and spectroscopic data (hyperfine couplings) are in support of a MoO2-like core in agreement with XRD data. The calculated two-electron reduction potential (E = -467 mV vs. SHE) is in reasonable agreement with the experimental value (E = -558 mV vs. SHE) for the redox couple comprising an equatorial oxo ligand and protonated Glu763 in the Mo(VI)-Cu(I) state and an equatorial water in the Mo(IV)-Cu(I) state. We also suggest a potential role of second-sphere residues (e.g., Glu763, Phe390) based on geometric changes observed upon exclusion of these residues in the most plausible oxidized states.
Target patterns in a realistic model of the Belousov-Zhabotinskii reaction
NASA Astrophysics Data System (ADS)
Tyson, John J.; Fife, Paul C.
1980-09-01
Periodic expanding target patterns of chemical activity are observed in thin layers of solution containing bromate, malonic acid and ferroin in dilute sulfuric acid. Commonly these patterns appear as thin blue (oxidized) rings propagating out from a central point into red (reduced) bulk medium. Recently, the opposite pattern has been observed: red waves of reduction propagating through an oxidized bulk medium. We discuss both of these patterns under the assumption that there is a heterogeneity at the center of the pattern—most likely a dust particle or a scratch on the glass—which changes the kinetics locally from a stable excitable steady state to a stable periodic oscillatory state. The temporal oscillation at the origin triggers waves of chemical activity which propagate radially into the excitable medium. Our approach is to combine recent advances in the mathematical description of traveling wave front solutions of reaction-diffusion equations with a realistic model of the kinetics of the reaction medium. The model we use, the Oregonator, is based on known features of the reaction mechanism, gives an acceptable qualitative and semiquantitative account of the reaction dynamics, and yet is simple enough to yield to analytic techniques developed primarily for scalar reaction-diffusion equations. With this approach we can account in some detail for most of the important features of target patterns in the Belousov-Zhabotinskii reaction. In particular, the distinction between trigger waves and phase waves is clarified by our analysis, and the novel properties of reducing waves in an oxidized medium appear as natural consequences of our model.
Abazov V. M.; Abbott B.; Acharya B. S.; Adams M.; Adams T.; Alexeev G. D.; Alkhazov G.; Alton A.; Alverson G.; Aoki M.; Askew A.; Asman B.; Atkins S.; Atramentov O.; Augsten K.; Avila C.; BackusMayes J.; Badaud F.; Bagby L.; Baldin B.; Bandurin D. V.; Banerjee S.; Barberis E.; Baringer P.; Barreto J.; Bartlett J. F.; Bassler U.; Bazterra V.; Bean A.; Begalli M.; Belanger-Champagne C.; Bellantoni L.; Beri S. B.; Bernardi G.; Bernhard R.; Bertram I.; Besancon M.; Beuselinck R.; Bezzubov V. A.; Bhat P. C.; Bhatia S.; Bhatnagar V.; Blazey G.; Blessing S.; Bloom K.; Boehnlein A.; Boline D.; Boos E. E.; Borissov G.; Bose T.; Brandt A.; Brandt O.; Brock R.; Brooijmans G.; Bross A.; Brown D.; Brown J.; Bu X. B.; Buehler M.; Buescher V.; Bunichev V.; Burdin S.; Burnett T. H.; Buszello C. P.; Calpas B.; Camacho-Perez E.; Carrasco-Lizarraga M. A.; Casey B. C. K.; Castilla-Valdez H.; Chakrabarti S.; Chakraborty D.; Chan K. M.; Chandra A.; Chapon E.; Chen G.; Chevalier-Thery S.; Cho D. K.; Cho S. W.; Choi S.; Choudhary B.; Cihangir S.; Claes D.; Clutter J.; Cooke M.; Cooper W. E.; Corcoran M.; Couderc F.; Cousinou M. -C.; Croc A.; Cutts D.; Das A.; Davies G.; de Jong S. J.; De La Cruz-Burelo E.; Deliot F.; Demina R.; Denisov D.; Denisov S. P.; Desai S.; Deterre C.; DeVaughan K.; Diehl H. T.; Diesburg M.; Ding P. F.; Dominguez A.; Dorland T.; Dubey A.; Dudko L. V.; Duggan D.; Duperrin A.; Dutt S.; Dyshkant A.; Eads M.; Edmunds D.; Ellison J.; Elvira V. D.; Enari Y.; Evans H.; Evdokimov A.; Evdokimov V. N.; Facini G.; Ferbel T.; Fiedler F.; Filthaut F.; Fisher W.; Fisk H. E.; Fortner M.; Fox H.; Fuess S.; Garcia-Bellido A.; Garcia-Guerra G. A.; Gavrilov V.; Gay P.; Geng W.; Gerbaudo D.; Gerber C. E.; Gershtein Y.; Ginther G.; Golovanov G.; Goussiou A.; Grannis P. D.; Greder S.; Greenlee H.; Greenwood Z. D.; Gregores E. M.; Grenier G.; Gris Ph.; Grivaz J. -F.; Grohsjean A.; Gruenendahl S.; Gruenewald M. W.; Guillemin T.; Gutierrez G.; Gutierrez P.; Haas A.; Hagopian S.; Haley J.; Han L.; Harder K.; Harel A.; Hauptman J. M.; Hays J.; Head T.; Hebbeker T.; Hedin D.; Hegab H.; Heinson A. P.; Heintz U.; Hensel C.; Heredia-De La Cruz I.; Herner K.; Hesketh G.; Hildreth M. D.; Hirosky R.; Hoang T.; Hobbs J. D.; Hoeneisen B.; Hohlfeld M.; Hubacek Z.; Hynek V.; Iashvili I.; Ilchenko Y.; Illingworth R.; Ito A. S.; Jabeen S.; Jaffre M.; Jaminn D.; Jayasinghe A.; Jesik R.; Johns K.; Johnson M.; Jonckheere A.; Jonsson P.; Joshi J.; Jung A. W.; Juste A.; Kaadze K.; Kajfasz E.; Karmanov D.; Kasper P. A.; Katsanos I.; Kehoe R.; Kermiche S.; Khalatyan N.; Khanov A.; Kharchilava A.; Kharzheev Y. N.; Kohli J. M.; Kozelov A. V.; Kraus J.; Kulikov S.; Kumar A.; Kupco A.; Kurca T.; Kuzmin V. A.; Lammers S.; Landsberg G.; Lebrun P.; Lee H. S.; Lee S. W.; Lee W. M.; Lellouch J.; Li H.; Li L.; Li Q. Z.; Lietti S. M.; Lim J. K.; Lincoln D.; Linnemann J.; Lipaev V. V.; Lipton R.; Liu Y.; Lobodenko A.; Lokajicek M.; Lopes de Sa R.; Lubatti H. J.; Luna-Garcia R.; Lyon A. L.; Maciel A. K. A.; Mackin D.; Madar R.; Magana-Villalba R.; Malik S.; Malyshev V. L.; Maravin Y.; Martinez-Ortega J.; McCarthy R.; McGivern C. L.; Meijer M. M.; Melnitchouk A.; Menezes D.; Mercadante P. G.; Merkin M.; et al.
2012-04-20
We report results from searches for neutral Higgs bosons produced in p{bar p} collisions recorded by the D0 experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral Higgs boson in the {tau}{tau} final state and in association with a b quark in the b{tau}{tau} and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are set for Higgs boson masses ranging from 90 to 300 GeV. We exclude tan {beta} > 20-30 for Higgs boson masses below 180 GeV. These are the most stringent constraints on MSSM Higgs boson production in p{bar p} collisions.
Chatrchyan, S; Khachatryan, V; Sirunyan, A M; Tumasyan, A; Adam, W; Bergauer, T; Dragicevic, M; Erö, J; Fabjan, C; Friedl, M; Frühwirth, R; Ghete, V M; Hammer, J; Hänsel, S; Hoch, M; Hörmann, N; Hrubec, J; Jeitler, M; Kasieczka, G; Kiesenhofer, W; Krammer, M; Liko, D; Mikulec, I; Pernicka, M; Rohringer, H; Schöfbeck, R; Strauss, J; Teischinger, F; Wagner, P; Waltenberger, W; Walzel, G; Widl, E; Wulz, C-E; Mossolov, V; Shumeiko, N; Suarez Gonzalez, J; Benucci, L; De Wolf, E A; Janssen, X; Maes, T; Mucibello, L; Ochesanu, S; Roland, B; Rougny, R; Selvaggi, M; Van Haevermaet, H; Van Mechelen, P; Van Remortel, N; Blekman, F; Blyweert, S; D'Hondt, J; Devroede, O; Gonzalez Suarez, R; Kalogeropoulos, A; Maes, J; Maes, M; Van Doninck, W; Van Mulders, P; Van Onsem, G P; Villella, I; Charaf, O; Clerbaux, B; De Lentdecker, G; Dero, V; Gay, A P R; Hammad, G H; Hreus, T; Marage, P E; Thomas, L; Vander Velde, C; Vanlaer, P; Adler, V; Cimmino, A; Costantini, S; Grunewald, M; Klein, B; Lellouch, J; Marinov, A; McCartin, J; Ryckbosch, D; Thyssen, F; Tytgat, M; Vanelderen, L; Verwilligen, P; Walsh, S; Zaganidis, N; Basegmez, S; Bruno, G; Caudron, J; Ceard, L; Cortina Gil, E; De Favereau De Jeneret, J; Delaere, C; Favart, D; Giammanco, A; Grégoire, G; Hollar, J; Lemaitre, V; Liao, J; Militaru, O; Ovyn, S; Pagano, D; Pin, A; Piotrzkowski, K; Schul, N; Beliy, N; Caebergs, T; Daubie, E; Alves, G A; Damiao, D De Jesus; Pol, M E; Souza, M H G; Carvalho, W; Da Costa, E M; Martins, C De Oliveira; De Souza, S Fonseca; Mundim, L; Nogima, H; Oguri, V; Da Silva, W L Prado; Santoro, A; Do Amaral, S M Silva; Sznajder, A; De Araujo, F Torres Da Silva; Dias, F A; Tomei, T R Fernandez Perez; Gregores, E M; Lagana, C; Marinho, F; Mercadante, P G; Novaes, S F; Padula, Sandra S; Darmenov, N; Dimitrov, L; Genchev, V; Iaydjiev, P; Piperov, S; Rodozov, M; Stoykova, S; Sultanov, G; Tcholakov, V; Trayanov, R; Vankov, I; Dimitrov, A; Hadjiiska, R; Karadzhinova, A; Kozhuharov, V; Litov, L; Mateev, M; Pavlov, B; Petkov, P; 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Fabbro, B; Faure, J L; Ferri, F; Ganjour, S; Gentit, F X; Givernaud, A; Gras, P; de Monchenault, G Hamel; Jarry, P; Locci, E; Malcles, J; Marionneau, M; Millischer, L; Rander, J; Rosowsky, A; Shreyber, I; Titov, M; Verrecchia, P; Baffioni, S; Beaudette, F; Benhabib, L; Bianchini, L; Bluj, M; Broutin, C; Busson, P; Charlot, C; Dahms, T; Dobrzynski, L; Elgammal, S; de Cassagnac, R Granier; Haguenauer, M; Miné, P; Mironov, C; Ochando, C; Paganini, P; Sabes, D; Salerno, R; Sirois, Y; Thiebaux, C; Wyslouch, B; Zabi, A; Agram, J-L; Andrea, J; Bloch, D; Bodin, D; Brom, J-M; Cardaci, M; Chabert, E C; Collard, C; Conte, E; Drouhin, F; Ferro, C; Fontaine, J-C; Gelé, D; Goerlach, U; Greder, S; Juillot, P; Karim, M; Le Bihan, A-C; Mikami, Y; Van Hove, P; Fassi, F; Mercier, D; Baty, C; Beauceron, S; Beaupere, N; Bedjidian, M; Bondu, O; Boudoul, G; Boumediene, D; Brun, H; Chierici, R; Contardo, D; Depasse, P; El Mamouni, H; Fay, J; Gascon, S; Ille, B; Kurca, T; Le Grand, T; Lethuillier, M; Mirabito, L; 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2011-06-10
A search for neutral minimal supersymmetric standard model (MSSM) Higgs bosons in pp collisions at the LHC at a center-of-mass energy of 7 TeV is presented. The results are based on a data sample corresponding to an integrated luminosity of 36 pb(-1) recorded by the CMS experiment. The search uses decays of the Higgs bosons to tau pairs. No excess is observed in the tau-pair invariant-mass spectrum. The resulting upper limits on the Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, yield stringent new bounds in the MSSM parameter space.
Downscaling Ocean Conditions: Initial Results using a Quasigeostrophic and Realistic Ocean Model
NASA Astrophysics Data System (ADS)
Katavouta, Anna; Thompson, Keith
2014-05-01
Previous theoretical work (Henshaw et al, 2003) has shown that the small-scale modes of variability of solutions of the unforced, incompressible Navier-Stokes equation, and Burgers' equation, can be reconstructed with surprisingly high accuracy from the time history of a few of the large-scale modes. Motivated by this theoretical work we first describe a straightforward method for assimilating information on the large scales in order to recover the small scale oceanic variability. The method is based on nudging in specific wavebands and frequencies and is similar to the so-called spectral nudging method that has been used successfully for atmospheric downscaling with limited area models (e.g. von Storch et al., 2000). The validity of the method is tested using a quasigestrophic model configured to simulate a double ocean gyre separated by an unstable mid-ocean jet. It is shown that important features of the ocean circulation including the position of the meandering mid-ocean jet and associated pinch-off eddies can indeed be recovered from the time history of a small number of large-scales modes. The benefit of assimilating additional time series of observations from a limited number of locations, that alone are too sparse to significantly improve the recovery of the small scales using traditional assimilation techniques, is also demonstrated using several twin experiments. The final part of the study outlines the application of the approach using a realistic high resolution (1/36 degree) model, based on the NEMO (Nucleus for European Modelling of the Ocean) modeling framework, configured for the Scotian Shelf of the east coast of Canada. The large scale conditions used in this application are obtained from the HYCOM (HYbrid Coordinate Ocean Model) + NCODA (Navy Coupled Ocean Data Assimilation) global 1/12 degree analysis product. Henshaw, W., Kreiss, H.-O., Ystrom, J., 2003. Numerical experiments on the interaction between the larger- and the small-scale motion of
2017-01-01
Perovskite/Si tandem solar cells have the potential to considerably out-perform conventional solar cells. Under standard test conditions, perovskite/Si tandem solar cells already outperform the Si single junction. Under realistic conditions, however, as we show, tandem solar cells made from current record cells are hardly more efficient than the Si cell alone. We model the performance of realistic perovskite/Si tandem solar cells under real-world climate conditions, by incorporating parasitic cell resistances, nonradiative recombination, and optical losses into the detailed-balance limit. We show quantitatively that when optimizing these parameters in the perovskite top cell, perovskite/Si tandem solar cells could reach efficiencies above 38% under realistic conditions, even while leaving the Si cell untouched. Despite the rapid efficiency increase of perovskite solar cells, our results emphasize the need for further material development, careful device design, and light management strategies, all necessary for highly efficient perovskite/Si tandem solar cells. PMID:28920081
Futscher, Moritz H; Ehrler, Bruno
2017-09-08
Perovskite/Si tandem solar cells have the potential to considerably out-perform conventional solar cells. Under standard test conditions, perovskite/Si tandem solar cells already outperform the Si single junction. Under realistic conditions, however, as we show, tandem solar cells made from current record cells are hardly more efficient than the Si cell alone. We model the performance of realistic perovskite/Si tandem solar cells under real-world climate conditions, by incorporating parasitic cell resistances, nonradiative recombination, and optical losses into the detailed-balance limit. We show quantitatively that when optimizing these parameters in the perovskite top cell, perovskite/Si tandem solar cells could reach efficiencies above 38% under realistic conditions, even while leaving the Si cell untouched. Despite the rapid efficiency increase of perovskite solar cells, our results emphasize the need for further material development, careful device design, and light management strategies, all necessary for highly efficient perovskite/Si tandem solar cells.
ERIC Educational Resources Information Center
Shahbari, Juhaina Awawdeh; Peled, Irit
2015-01-01
This study investigates the effect of using a realistic situation with modeling characteristics in creating and resolving a cognitive conflict to promote understanding of a changing reference in fraction calculations. The study was conducted among 96 seventh graders divided into 2 experimental groups and 1 control group. The experimental groups…
ERIC Educational Resources Information Center
Shahbari, Juhaina Awawdeh; Peled, Irit
2015-01-01
This study investigates the effect of using a realistic situation with modeling characteristics in creating and resolving a cognitive conflict to promote understanding of a changing reference in fraction calculations. The study was conducted among 96 seventh graders divided into 2 experimental groups and 1 control group. The experimental groups…
How realistic are air quality hindcasts driven by forcings from climate model simulations?
NASA Astrophysics Data System (ADS)
Lacressonnière, G.; Peuch, V.-H.; Arteta, J.; Josse, B.; Joly, M.; Marécal, V.; Saint Martin, D.; Déqué, M.; Watson, L.
2012-12-01
Predicting how European air quality could evolve over the next decades in the context of changing climate requires the use of climate models to produce results that can be averaged in a climatologically and statistically sound manner. This is a very different approach from the one that is generally used for air quality hindcasts for the present period; analysed meteorological fields are used to represent specifically each date and hour. Differences arise both from the fact that a climate model run results in a pure model output, with no influence from observations (which are useful to correct for a range of errors), and that in a "climate" set-up, simulations on a given day, month or even season cannot be related to any specific period of time (but can just be interpreted in a climatological sense). Hence, although an air quality model can be thoroughly validated in a "realistic" set-up using analysed meteorological fields, the question remains of how far its outputs can be interpreted in a "climate" set-up. For this purpose, we focus on Europe and on the current decade using three 5-yr simulations performed with the multiscale chemistry-transport model MOCAGE and use meteorological forcings either from operational meteorological analyses or from climate simulations. We investigate how statistical skill indicators compare in the different simulations, discriminating also the effects of meteorology on atmospheric fields (winds, temperature, humidity, pressure, etc.) and on the dependent emissions and deposition processes (volatile organic compound emissions, deposition velocities, etc.). Our results show in particular how differing boundary layer heights and deposition velocities affect horizontal and vertical distributions of species. When the model is driven by operational analyses, the simulation accurately reproduces the observed values of O3, NOx, SO2 and, with some bias that can be explained by the set-up, PM10. We study how the simulations driven by climate
How realistic are air quality hindcasts driven by forcings from climate model simulations?
NASA Astrophysics Data System (ADS)
Lacressonnière, G.; Peuch, V.-H.; Arteta, J.; Josse, B.; Joly, M.; Marécal, V.; Saint Martin, D.; Déqué, M.; Watson, L.
2012-07-01
Predicting how European air quality could evolve over the next decades in the context of changing climate requires the use of climate models to produce results that can be averaged in a climatologically and statistically sound manner. This is a very different approach from the one that is generally used for air quality hindcasts for the present period: analysed meteorological fields are used to represent specifically each date and hour. Differences arise both from the fact that a climate model run is a pure model output, with no influence from observations (which are useful to correct for a range of errors), and that in a "climate" set-up, simulations on a given day, month or even season cannot be related to any specific period of time (but can just be interpreted in a climatological sense). Hence, although an air quality model can be thoroughly validated in a "realistic" set-up using analysed meteorological fields, the question remains of how far its outputs can be interpreted in a "climate" set-up. For this purpose, we focus on Europe and on the current decade using three 6-yr simulations performed with the multiscale chemistry-transport model MOCAGE and use meteorological forcings either from operational meteorological analyses or from climate simulations. We investigate how statistical skill indicators compare in the different simulations, discriminating also the effects of meteorology on atmospheric fields (winds, temperature, humidity, pressure ldots) and on the dependent emissions and deposition processes (volatile organic compound emissions, deposition velocities . . .). Our results show in particular how differing boundary layer heights and deposition velocities affect horizontal and vertical distributions of species. When the model is driven by operational analyses, the simulation accurately reproduces the observed values of O3, NOx, SO2 and, with some bias that can be explained by the set-up, PM10. We study how the simulations driven by climate forcings
Neutrino sector and proton lifetime in a realistic SUSY S O (10 ) model
NASA Astrophysics Data System (ADS)
Severson, Matthew
2015-11-01
In this work I present a complete analysis of proton decay in an S O (10 ) model previously proposed by Dutta, Mimura, and Mohapatra. The 10 , 126 ¯ , and 120 Yukawa couplings contributing to fermion masses in this model have well-motivated restrictions on their textures intended to give favorable results for proton lifetime as well as a realistic fermion sector without the need for fine-tuning and for either type-I or type-II dominance in the neutrino mass matrix. I obtain a valid fit for the entire fermion sector for both types of seesaw dominance, including θ13 in good agreement with the most recent data. For the case with type-II seesaw, I find that using the Yukawa couplings fixed by the successful fermion sector fit, proton partial lifetime limits are satisfied for nearly every pertinent decay mode, even for nearly arbitrary values of the triplet Higgs mixing parameters, with only the K+ν ¯ mode requiring a minor O (1 0-1) cancellation in order to satisfy the experimental limit. I also find a maximum lifetime for that mode of τ (K+ν ¯ )˜1036 yr , which should be tested by forthcoming experiments. For the type-I seesaw case, I find that all six pertinent decay modes of interest are satisfied for values of the triplet mixing parameters giving no major enhancement, with modes other than K+ν ¯ easily satisfied for arbitrary mixing values, and with a maximum lifetime for K+ν ¯ of nearly 1038 yr .
Jenkins, Dafyd J; Stekel, Dov J
2010-02-01
Gene regulation is one important mechanism in producing observed phenotypes and heterogeneity. Consequently, the study of gene regulatory network (GRN) architecture, function and evolution now forms a major part of modern biology. However, it is impossible to experimentally observe the evolution of GRNs on the timescales on which living species evolve. In silico evolution provides an approach to studying the long-term evolution of GRNs, but many models have either considered network architecture from non-adaptive evolution, or evolution to non-biological objectives. Here, we address a number of important modelling and biological questions about the evolution of GRNs to the realistic goal of biomass production. Can different commonly used simulation paradigms, in particular deterministic and stochastic Boolean networks, with and without basal gene expression, be used to compare adaptive with non-adaptive evolution of GRNs? Are these paradigms together with this goal sufficient to generate a range of solutions? Will the interaction between a biological goal and evolutionary dynamics produce trade-offs between growth and mutational robustness? We show that stochastic basal gene expression forces shrinkage of genomes due to energetic constraints and is a prerequisite for some solutions. In systems that are able to evolve rates of basal expression, two optima, one with and one without basal expression, are observed. Simulation paradigms without basal expression generate bloated networks with non-functional elements. Further, a range of functional solutions was observed under identical conditions only in stochastic networks. Moreover, there are trade-offs between efficiency and yield, indicating an inherent intertwining of fitness and evolutionary dynamics.
Perturbative stability along the supersymmetric directions of the landscape
Sousa, Kepa
2015-02-01
We consider the perturbative stability of non-supersymmetric configurations in N=1 supergravity models with a spectator sector not involved in supersymmetry breaking. Motivated by the supergravity description of complex structure moduli in Large Volume Compactifications of type IIB-superstrings, we concentrate on models where the interactions are consistent with the supersymmetric truncation of the spectator fields, and we describe their couplings by a random ensemble of generic supergravity theories. We characterise the mass spectrum of the spectator fields in terms of the statistical parameters of the ensemble and the geometry of the scalar manifold. Our results show that the non-generic couplings between the spectator and the supersymmetry breaking sectors can stabilise all the tachyons which typically appear in the spectator sector before including the supersymmetry breaking effects, and we find large regions of the parameter space where the supersymmetric sector remains stable with probability close to one. We discuss these results about the stability of the supersymmetric sector in two physically relevant situations: non-supersymmetric Minkowski vacua, and slow-roll inflation driven by the supersymmetry breaking sector. For the class of models we consider, we have reproduced the regimes in which the KKLT and Large Volume Scenarios stabilise all supersymmetric moduli. We have also identified a new regime in which the supersymmetric sector is stabilised at a very robust type of dS minimum without invoking a large mass hierarchy.
Realistic modeling of seismic input for megacities and large urban areas
NASA Astrophysics Data System (ADS)
Panza, G. F.; Unesco/Iugs/Igcp Project 414 Team
2003-04-01
The project addressed the problem of pre-disaster orientation: hazard prediction, risk assessment, and hazard mapping, in connection with seismic activity and man-induced vibrations. The definition of realistic seismic input has been obtained from the computation of a wide set of time histories and spectral information, corresponding to possible seismotectonic scenarios for different source and structural models. The innovative modeling technique, that constitutes the common tool to the entire project, takes into account source, propagation and local site effects. This is done using first principles of physics about wave generation and propagation in complex media, and does not require to resort to convolutive approaches, that have been proven to be quite unreliable, mainly when dealing with complex geological structures, the most interesting from the practical point of view. In fact, several techniques that have been proposed to empirically estimate the site effects using observations convolved with theoretically computed signals corresponding to simplified models, supply reliable information about the site response to non-interfering seismic phases. They are not adequate in most of the real cases, when the seismic sequel is formed by several interfering waves. The availability of realistic numerical simulations enables us to reliably estimate the amplification effects even in complex geological structures, exploiting the available geotechnical, lithological, geophysical parameters, topography of the medium, tectonic, historical, palaeoseismological data, and seismotectonic models. The realistic modeling of the ground motion is a very important base of knowledge for the preparation of groundshaking scenarios that represent a valid and economic tool for the seismic microzonation. This knowledge can be very fruitfully used by civil engineers in the design of new seismo-resistant constructions and in the reinforcement of the existing built environment, and, therefore
Inflation in supersymmetric SU(5)
Khalil, S.; Rehman, M. U.; Shafi, Q.; Zaakouk, E. A.
2011-03-15
We analyze the adjoint field inflation in supersymmetric (SUSY) SU(5) model. In minimal SUSY SU(5) hybrid inflation monopoles are produced at the end of inflation. We therefore explore the nonminimal model of inflation based on SUSY SU(5), like shifted hybrid inflation, which provides a natural solution for the monopole problem. We find that the supergravity corrections with nonminimal Kaehler potential are crucial to realize the central value of the scalar spectral index n{sub s{approx_equal}}0.96 consistent with the 7 yr WMAP data. The tensor to scalar ratio r is quite small, taking on values r < or approx. 10{sup -5}. Because of R symmetry massless SU(3) octet and SU(2) triplet supermultiplets are present and could spoil gauge coupling unification. To keep gauge coupling unification intact, light vectorlike particles are added which are expected to be observed at LHC.
Supersymmetric Galileons and auxiliary fields in 2 +1 dimensions
NASA Astrophysics Data System (ADS)
Queiruga, Jose M.
2017-06-01
In this work, we study various aspects of supersymmetric three-dimensional higher-derivative field theories. We classify all possible models without derivative terms of the auxiliary field in the fermionic sector and find that scalar field theories of the form P (X ,ϕ ), where X =-(∂ϕ )2/2 , belong to this kind of models. A ghost-free supersymmetric extension of Galileon models is found in three spacetime dimensions. Finally, the auxiliary field problem is discussed.
Supersymmetric Quantum Mechanics
NASA Astrophysics Data System (ADS)
David, J.; Fernández, C.
2010-10-01
Supersymmetric quantum mechanics (SUSY QM) is a powerful tool for generating new potentials with known spectra departing from an initial solvable one. In these lecture notes we will present some general formulae concerning SUSY QM of first second order for one-dimensional arbitrary systems, we will illustrate the method through the trigonometric Pöschl-Teller potentials. Some intrinsically related subjects, as the algebraic structure inherited by the new Hamiltonians and the corresponding coherent states will be analyzed. The technique will be as well implemented for periodic potentials, for which the corresponding spectrum is composed of allowed bands separated by energy gaps.
Luo, Yiqi; Ahlström, Anders; Allison, Steven D.; Batjes, Niels H.; Brovkin, Victor; Carvalhais, Nuno; Chappell, Adrian; Ciais, Philippe; Davidson, Eric A.; Finzi, Adien; Georgiou, Katerina; Guenet, Bertrand; Hararuk, Oleksandra; Harden, Jennifer W.; He, Yujie; Hopkins, Francesca; Jiang, Lifen; Koven, Charlie; Jackson, Robert B.; Jones, Chris D.; Lara, Mark J.; Liang, Junyi; McGuire, A. David; Parton, William; Peng, Changhui; Randerson, James T.; Salazar, Alejandro; Sierra, Carlos A.; Smith, Matthew J.; Tian, Hanqin; Todd-Brown, Katherine E. O.; Torn, Margaret; van Groenigen, Kees Jan; Wang, Ying Ping; West, Tristram O.; Wei, Yaxing; Wieder, William R.; Xia, Jianyang; Xu, Xia; Xu, Xiaofeng; Zhou, Tao
2016-01-21
Soil carbon (C) is a critical component of Earth system models (ESMs) and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the 3rd to 5th assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. Firstly, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by 1st-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic SOC dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Secondly, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based datasets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Thirdly, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable datasets are available to select the most representative model structure, constrain parameters, and
Lesperance, Marielle; Inglis-Whalen, M.; Thomson, R. M.
2014-02-15
Purpose : To investigate the effects of the composition and geometry of ocular media and tissues surrounding the eye on dose distributions for COMS eye plaque brachytherapy with{sup 125}I, {sup 103}Pd, or {sup 131}Cs seeds, and to investigate doses to ocular structures. Methods : An anatomically and compositionally realistic voxelized eye model with a medial tumor is developed based on a literature review. Mass energy absorption and attenuation coefficients for ocular media are calculated. Radiation transport and dose deposition are simulated using the EGSnrc Monte Carlo user-code BrachyDose for a fully loaded COMS eye plaque within a water phantom and our full eye model for the three radionuclides. A TG-43 simulation with the same seed configuration in a water phantom neglecting the plaque and interseed effects is also performed. The impact on dose distributions of varying tumor position, as well as tumor and surrounding tissue media is investigated. Each simulation and radionuclide is compared using isodose contours, dose volume histograms for the lens and tumor, maximum, minimum, and average doses to structures of interest, and doses to voxels of interest within the eye. Results : Mass energy absorption and attenuation coefficients of the ocular media differ from those of water by as much as 12% within the 20–30 keV photon energy range. For all radionuclides studied, average doses to the tumor and lens regions in the full eye model differ from those for the plaque in water by 8%–10% and 13%–14%, respectively; the average doses to the tumor and lens regions differ between the full eye model and the TG-43 simulation by 2%–17% and 29%–34%, respectively. Replacing the surrounding tissues in the eye model with water increases the maximum and average doses to the lens by 2% and 3%, respectively. Substituting the tumor medium in the eye model for water, soft tissue, or an alternate melanoma composition affects tumor dose compared to the default eye model
Lesperance, Marielle; Inglis-Whalen, M; Thomson, R M
2014-02-01
To investigate the effects of the composition and geometry of ocular media and tissues surrounding the eye on dose distributions for COMS eye plaque brachytherapy with(125)I, (103)Pd, or (131)Cs seeds, and to investigate doses to ocular structures. An anatomically and compositionally realistic voxelized eye model with a medial tumor is developed based on a literature review. Mass energy absorption and attenuation coefficients for ocular media are calculated. Radiation transport and dose deposition are simulated using the EGSnrc Monte Carlo user-code BrachyDose for a fully loaded COMS eye plaque within a water phantom and our full eye model for the three radionuclides. A TG-43 simulation with the same seed configuration in a water phantom neglecting the plaque and interseed effects is also performed. The impact on dose distributions of varying tumor position, as well as tumor and surrounding tissue media is investigated. Each simulation and radionuclide is compared using isodose contours, dose volume histograms for the lens and tumor, maximum, minimum, and average doses to structures of interest, and doses to voxels of interest within the eye. Mass energy absorption and attenuation coefficients of the ocular media differ from those of water by as much as 12% within the 20-30 keV photon energy range. For all radionuclides studied, average doses to the tumor and lens regions in the full eye model differ from those for the plaque in water by 8%-10% and 13%-14%, respectively; the average doses to the tumor and lens regions differ between the full eye model and the TG-43 simulation by 2%-17% and 29%-34%, respectively. Replacing the surrounding tissues in the eye model with water increases the maximum and average doses to the lens by 2% and 3%, respectively. Substituting the tumor medium in the eye model for water, soft tissue, or an alternate melanoma composition affects tumor dose compared to the default eye model simulation by up to 16%. In the full eye model
Linear inverse solutions: simulations from a realistic head model in MEG.
Soufflet, Laurent; Boeijinga, Peter H
2005-01-01
Distributed linear solutions are widely used in source localization to solve the ill-posed EEG/MEG inverse problem. In the classical approach based on dipole sources, these methods estimate the current densities at a great number of brain sites, typically at the nodes of a 3-D grid which discretizes the chosen solution space. The estimated current density distributions are displayed as brain electromagnetic tomography (BET) images. We have tested well known minimum norm solutions (MN, WMN, LORETA) and other linear inverse solutions [WROP, sLORETA, interference uniform, gain uniform, weight vector normalized (WVN), and a new solution named SLF (Standardized Lead Field)], using a MEG configuration (BTi Magnes 2500 WH with 148 axial magnetometers) and a realistic head model using BEM (Boundary Element Method). The solutions were compared in a noise-free condition and in the presence of noise using the classical dipole localization errors (DLE) together with a new figure of merit that we called max gain uniformity, which measures the capability of an inverse linear solution to show spots of activity with similar amplitudes on the brain electromagnetic tomographies when multiple dipole sources with similar moments are simultaneously active. Whereas some solutions (sLORETA, interference uniform and SLF) were capable of zero dipole localization errors in the noise-free case, none of them reached 100% of correct dipole localizations in the presence of a high level of Gaussian noise. The SLF solution, which has the advantage to be independent from any regularization parameter, presented the best results with the lowest max gain uniformities, with almost 100% of correct dipole localizations with 10% of noise and more than 90% of correct localizations with 30% of noise added to the data. Nevertheless, no solution was able to combine at the same time a correct localization of single sources and the capability to visualize multiple sources with comparable amplitudes on the
NASA Astrophysics Data System (ADS)
Marrufo, Oscar; Solis-Najera, Sergio; Pibarot, Philippe; Kadem, Lyes; Kesharvarz-Motamed, Zahra; Rodriguez, Alfredo O.; Garcia, Julio
2014-11-01
Aortic valve morphology and phenotype may alter the aortic wall structure and its normal flow hemodynamics. However, the relationship between altered flow patterns and progression of wall pathology is often not fully understood in patients with aortic coartation and needs larger experimental work. In this study, we introduced a compatible experimental setup with magnetic resonance imaging (MRI) using a realistic aortic coarctation (AoCo) silicon model which can replicate physiological flow conditions (pressure, flow-wave, and systemic load). We evaluated the aortic valve hemodynamics of a normal tricuspid valve and a stenotic bicuspid valve using valve effective orifice area (EOA), peak and mean transvalvular pressure gradient (TPG). AoCo severity was assessed by the AoCo pressure gradient. For the tricuspid valve we obtained an EOA = 1.89 cm2, a peak TPG = 10 mmHg, and a mean TPG = 5 mmHg. For the bicuspid valve we obtained an EOA = 1.03 cm2, a peak TPG = 37 mmHg and a mean TPG = 13 mmHg. Furthermore, AoCo with tricuspid valve led to a peak AoCo pressure gradient (PG) = 11 mmHg and a mean PG = 5 mmHg. AoCo with bicuspid valve led to a peak PG = 6 mmHg and a mean PG = 3 mmHg. Aortic flow reattachment was more evident in presence of bicuspid valve and helical flow was present in all cases. This study showed that silicon prototyping in combination with MRI velocity measurements could successfully be used to assess hemodynamic effects of aortic valve morphology in aortic coarctation flow.
Cortical sources of ERP in prosaccade and antisaccade eye movements using realistic source models
Richards, John E.
2013-01-01
The cortical sources of event-related-potentials (ERP) using realistic source models were examined in a prosaccade and antisaccade procedure. College-age participants were presented with a preparatory interval and a target that indicated the direction of the eye movement that was to be made. In some blocks a cue was given in the peripheral location where the target was to be presented and in other blocks no cue was given. In Experiment 1 the prosaccade and antisaccade trials were presented randomly within a block; in Experiment 2 procedures were compared in which either prosaccade and antisaccade trials were mixed in the same block, or trials were presented in separate blocks with only one type of eye movement. There was a central negative slow wave occurring prior to the target, a slow positive wave over the parietal scalp prior to the saccade, and a parietal spike potential immediately prior to saccade onset. Cortical source analysis of these ERP components showed a common set of sources in the ventral anterior cingulate and orbital frontal gyrus for the presaccadic positive slow wave and the spike potential. In Experiment 2 the same cued- and non-cued blocks were used, but prosaccade and antisaccade trials were presented in separate blocks. This resulted in a smaller difference in reaction time between prosaccade and antisaccade trials. Unlike the first experiment, the central negative slow wave was larger on antisaccade than on prosaccade trials, and this effect on the ERP component had its cortical source primarily in the parietal and mid-central cortical areas contralateral to the direction of the eye movement. These results suggest that blocked prosaccade and antisaccade trials results in preparatory or set effects that decreases reaction time, eliminates some cueing effects, and is based on contralateral parietal-central brain areas. PMID:23847476
NASA Astrophysics Data System (ADS)
Fung, George S. K.; Segars, W. Paul; Veress, Alexander I.; Gullberg, Grant T.; Tsui, Benjamin M. W.
2009-02-01
A realistic 3D coronary arterial tree (CAT) has been developed for the heart model of the computer generated 3D XCAT phantom. The CAT allows generation of a realistic model of the location, size and shape of the associated regional ischemia or infarction for a given coronary arterial stenosis or occlusion. This in turn can be used in medical imaging applications. An iterative rule-based generation method that systematically utilized anatomic, morphometric and physiologic knowledge was used to construct a detailed realistic 3D model of the CAT in the XCAT phantom. The anatomic details of the myocardial surfaces and large coronary arterial vessel segments were first extracted from cardiac CT images of a normal patient with right coronary dominance. Morphometric information derived from porcine data from the literature, after being adjusted by scaling laws, provided statistically nominal diameters, lengths, and connectivity probabilities of the generated coronary arterial segments in modeling the CAT of an average human. The largest six orders of the CAT were generated based on the physiologic constraints defined in the coronary generation algorithms. When combined with the heart model of the XCAT phantom, the realistic CAT provides a unique simulation tool for the generation of realistic regional myocardial ischemia and infraction. Together with the existing heart model, the new CAT provides an important improvement over the current 3D XCAT phantom in providing a more realistic model of the normal heart and the potential to simulate myocardial diseases in evaluation of medical imaging instrumentation, image reconstruction, and data processing methods.
Small numbers in supersymmetric theories of nature
Graesser, Michael Lawrence
1999-05-01
The Standard Model of particle interactions is a successful theory for describing the interactions of quarks, leptons and gauge bosons at microscopic distance scales. Despite these successes, the theory contains many unsatisfactory features. The origin of particle masses is a central mystery that has eluded experimental elucidation. In the Standard Model the known particles obtain their mass from the condensate of the so-called Higgs particle. Quantum corrections to the Higgs mass require an unnatural fine tuning in the Higgs mass of one part in 10^{-32} to obtain the correct mass scale of electroweak physics. In addition, the origin of the vast hierarchy between the mass scales of the electroweak and quantum gravity physics is not explained in the current theory. Supersymmetric extensions to the Standard Model are not plagued by this fine tuning issue and may therefore be relevant in Nature. In the minimal supersymmetric Standard Model there is also a natural explanation for electroweak symmetry breaking. Supersymmetric Grand Unified Theories also correctly predict a parameter of the Standard Model. This provides non-trivial indirect evidence for these theories. The most general supersymmetric extension to the Standard Model however, is excluded by many physical processes, such as rare flavor changing processes, and the non-observation of the instability of the proton. These processes provide important information about the possible structure such a theory. In particular, certain parameters in this theory must be rather small. A physics explanation for why this is the case would be desirable. It is striking that the gauge couplings of the Standard Model unify if there is supersymmetry close to the weak scale. This suggests that at high energies Nature is described by a supersymmetric Grand Unified Theory. But the mass scale of unification must be introduced into the theory since it does not coincide with the probable mass scale of strong quantum gravity
A realistic intersecting D6-brane model after the first LHC run
NASA Astrophysics Data System (ADS)
Li, Tianjun; Nanopoulos, D. V.; Raza, Shabbar; Wang, Xiao-Chuan
2014-08-01
With the Higgs boson mass around 125 GeV and the LHC supersymmetry search constraints, we revisit a three-family Pati-Salam model from intersecting D6-branes in Type IIA string theory on the T 6/(ℤ2 × ℤ2) orientifold which has a realistic phenomenology. We systematically scan the parameter space for μ < 0 and μ > 0, and find that the gravitino mass is generically heavier than about 2 TeV for both cases due to the Higgs mass low bound 123 GeV. In particular, we identify a region of parameter space with the electroweak fine-tuning as small as Δ EW ~ 24-32 (3-4%). In the viable parameter space which is consistent with all the current constraints, the mass ranges for gluino, the first two-generation squarks and sleptons are respectively [3, 18] TeV, [3, 16] TeV, and [2, 7] TeV. For the third-generation sfermions, the light stop satisfying 5 σ WMAP bounds via neutralino-stop coannihilation has mass from 0.5 to 1.2 TeV, and the light stau can be as light as 800 GeV. We also show various coannihilation and resonance scenarios through which the observed dark matter relic density is achieved. Interestingly, the certain portions of parameter space has excellent t- b- τ and b- τ Yukawa coupling unification. Three regions of parameter space are highlighted as well where the dominant component of the lightest neutralino is a bino, wino or higgsino. We discuss various scenarios in which such solutions may avoid recent astrophysical bounds in case if they satisfy or above observed relic density bounds. Prospects of finding higgsino-like neutralino in direct and indirect searches are also studied. And we display six tables of benchmark points depicting various interesting features of our model. Note that the lightest neutralino can be heavy up to 2.8 TeV, and there exists a natural region of parameter space from low-energy fine-tuning definition with heavy gluino and first two-generation squarks/sleptons, we point out that the 33 TeV and 100 TeV proton-proton colliders
Numerical simulation of wave propagation in a realistic model of the human external ear.
Fadaei, Mohaddeseh; Abouali, Omid; Emdad, Homayoun; Faramarzi, Mohammad; Ahmadi, Goodarz
2015-01-01
In this study, a numerical investigation is performed to evaluate the effects of high-pressure sinusoidal and blast wave's propagation around and inside of a human external ear. A series of computed tomography images are used to reconstruct a realistic three-dimensional (3D) model of a human ear canal and the auricle. The airflow field is then computed by solving the governing differential equations in the time domain using a computational fluid dynamics software. An unsteady algorithm is used to obtain the high-pressure wave propagation throughout the ear canal which is validated against the available analytical and numerical data in literature. The effects of frequency, wave shape, and the auricle on pressure distribution are then evaluated and discussed. The results clearly indicate that the frequency plays a key role on pressure distribution within the ear canal. At 4 kHz frequency, the pressure magnitude is much more amplified within the ear canal than the frequencies of 2 and 6 kHz, for the incident wave angle of 90° investigated in this study, attributable to the '4-kHz notch' in patients with noise-induced hearing loss. According to the results, the pressure distribution patterns at the ear canal are very similar for both sinusoidal pressure waveform with the frequency of 2 kHz and blast wave. The ratio of the peak pressure value at the eardrum to that at the canal entrance increases from about 8% to 30% as the peak pressure value of the blast wave increases from 5 to 100 kPa for the incident wave angle of 90° investigated in this study. Furthermore, incorporation of the auricle to the ear canal model is associated with centerline pressure magnitudes of about 50% and 7% more than those of the ear canal model without the auricle throughout the ear canal for sinusoidal and blast waves, respectively, without any significant effect on pressure distribution pattern along the ear canal for the incident wave angle of 90° investigated in this study.
NASA Astrophysics Data System (ADS)
Gerya, Taras; Burov, Evgueni
2015-04-01
-branch junction formation and evolution by using high-resolution 3D numerical mechanical experiments that take into account realistic thermo-rheological structure and rheology of the lithosphere. We find that two major types of quadruple and triple junctions are formed under bi-directional or multidirectional far-field stress field: (i) plate rifting junctions are formed by the initial plate fragmentation and can be subsequently re-arranged into (ii) oceanic spreading junctions controlled by the new oceanic crust accretion. In particular, we document initial formation and destabilization of quadruple R-R-R-R junctions as initial plate rifting structures under bi-directional extension. In most cases, quadruple plate rifting junctions rapidly (typically within 1-2 Myr) evolve towards formation of two diverging triple oceanic spreading junctions connected by a linear spreading center lengthening with time. This configuration remains stable over long time scales. However, under certain conditions, quadruple junctions may also remain relatively stable. Asymmetric stretching results in various configurations, for example formation of "T-junctions" with trans-extensional components and combination of fast and slow spreading ridges. Combined with plume impingement, this scenario evolves in realistic patterns closely resembling observed plate dynamics. In particular, opening of the Red Sea and of the Afar rift system find a logical explanation within a single model. Numerical experiments also suggest that several existing oceanic spreading junctions form as the result of plate motions rearrangements after which only one of two plates spreading along the ridge become subjected to bi-directional spreading.
Acceleration modeling of moderate to large earthquakes based on realistic fault models
NASA Astrophysics Data System (ADS)
Arvidsson, R.; Toral, J.
2003-04-01
Strong motion is affected by distance to the earthquake, local crustal structure, focal mechanism, azimuth to the source. However, the faulting process is also of importance such as development of rupture, i.e., directivity, slip distribution on the fault, extent of fault, rupture velocity. We have modelled these parameters for earthquakes that occurred in three tectonic zones close to the Panama Canal. We included in the modeling directivity, distributed slip, discrete faulting, fault depth and expected focal mechanism. The distributed slip is based on previous fault models that we produced from the region of other earthquakes. Such previous examples show that maximum intensities in some cases coincides with areas of high slip on the fault. Our acceleration modeling also gives similar values to the few observations that have been made for moderate to small earthquakes in the range M=5-6.2. The modeling indicates that events located in the Caribbean might cause strong motion in the lower frequency spectra where high frequency Rayleigh waves dominates.
New supersymmetric index of heterotic compactifications with torsion
NASA Astrophysics Data System (ADS)
Israël, Dan; Sarkis, Matthieu
2015-12-01
We compute the new supersymmetric index of a large class of N=2 heterotic compactifications with torsion, corresponding to principal two-torus bundles over warped K3 surfaces with H-flux. Starting from a UV description as a (0,2) gauged linear sigma-model with torsion, we use supersymmetric localization techniques to provide an explicit expression of the index as a sum over the Jeffrey-Kirwan residues of the one-loop determinant. We finally propose a geometrical formula that gives the new supersymmetric index in terms of bundle data, regardless of any particular choice of underlying two-dimensional theory.
1982-05-01
CR-82-0i22-1 Reports Control Symbol OSD. 1366 41-~41,•) 1, ANALYSIS OF MULTIPLE SOURCE OBSCURANTS ON THE REALISTIC BATTLEFIELD (AMSORB) VOLLME I...PERIOD COVERED ANALYSIS O)F MULTIPLE SOURCE OBSCURANTS ON THE FnlRpr REALISIIC BATTLEFIELD (AMSORB)______________ VOLUME I - MATHEMATICAL MODELS AND...ROUTINES 102 4.1 Mixitng-Layer Analysis Routine 102 4.2 Battlefield Source Characteristics Routine 118 4.3 Dispersion Model Routines and Meteorological
Marques, José P; Bowtell, R W
2008-07-01
This paper assesses the reliability of the infinite cylinder model used previously in the literature to simulate blood oxygenation level dependent (BOLD) signal changes. A three-dimensional finite element method was applied to a realistic model of the cortical vasculature, and the results compared with those generated from a simple model of the vasculature as a set of independent, randomly oriented, infinite cylinders. The realistic model is based on scanning electron microscopy measurements of the terminal vascular bed in the superficial cortex of the rat. Good agreement is found between the two models with regard to the extravascular R(2)* and R(2) dependence on the cerebral blood volume and blood oxygenation fraction. Using the realistic model, it is also possible to gain further understanding of the relative importance of intravascular and extravascular BOLD contrast. A simple parameterisation of the dependence of the relaxation rates on relative cerebral blood volume and blood-tissue susceptibility difference was carried out, allowing discussion of the variation in the form of the haemodynamic response with field strength.
Aspects of a supersymmetric Brans-Dicke theory
Catena, Riccardo
2007-02-15
We consider a locally supersymmetric theory where the Planck mass is replaced by a dynamical superfield. This model can be thought of as the minimal supersymmetric extension of the Brans-Dicke theory (MSBD). The motivation that underlies this analysis is the research of possible connections between dark energy models based on Brans-Dicke-like theories and supersymmetric dark matter scenarios. We find that the phenomenology associated with the MSBD model is very different compared to the one of the original Brans-Dicke theory: the gravitational sector does not couple to the matter sector in a universal metric way. This feature could make the minimal supersymmetric extension of the BD idea phenomenologically inconsistent.
Hallez, Hans; Vanrumste, Bart; Van Hese, Peter; Delputte, Steven; Lemahieu, Ignace
2008-04-07
To improve the EEG source localization in the brain, the conductivities used in the head model play a very important role. In this study, we focus on the modeling of the anisotropic conductivity of the white matter. The anisotropic conductivity profile can be derived from diffusion weighted magnetic resonance images (DW-MRI). However, deriving these anisotropic conductivities from diffusion weighted MR images of the white matter is not straightforward. In the literature, two methods can be found for calculating the conductivity from the diffusion weighted images. One method uses a fixed value for the ratio of the conductivity in different directions, while the other method uses a conductivity profile obtained from a linear scaling of the diffusion ellipsoid. We propose a model which can be used to derive the conductivity profile from the diffusion tensor images. This model is based on the variable anisotropic ratio throughout the white matter and is a combination of the linear relationship as stated in the literature, with a constraint on the magnitude of the conductivity tensor (also known as the volume constraint). This approach is stated in the paper as approach A. In our study we want to investigate dipole estimation differences due to using a more simplified model for white matter anisotropy (approach B), while the electrode potentials are derived using a head model with a more realistic approach for the white matter anisotropy (approach A). We used a realistic head model, in which the forward problem was solved using a finite difference method that can incorporate anisotropic conductivities. As error measures we considered the dipole location error and the dipole orientation error. The results show that the dipole location errors are all below 10 mm and have an average of 4 mm in gray matter regions. The dipole orientation errors ranged up to 66.4 degrees, and had a mean of, on average, 11.6 degrees in gray matter regions. In a qualitative manner, the results
TIME3D-IGGCAS: A New Three-Dimension Theoretical Ionospheric Model in realistic geomagnetic fields
NASA Astrophysics Data System (ADS)
Ren, Zhipeng; Liu, Libo; Huijun Le, lake709.; Wan, Weixing
Based on the previous work, a new global three-dimension theoretical ionospheric model in realistic geomagnetic fields is developed, named Three-Dimension Theoretical Ionospheric Model of the Earth in the Institute of Geology and Geophysics, Chinese Academy of Sciences (TIME3D-IGGCAS). This new model covers the whole ionosphere and plasmasphere. It self-consistently solves the equations of mass continuity, motion and energy of electron and ions to give out the time-dependent three-dimensional structures of the main ionospheric and plasmaspheric parameters in realistic geomagnetic fields, including ion number densities of O+, H+, He+, NO+, O2+ , N2+ and electron; electron and ion temperature; and ion velocity vectors. TIME3D-IGGCAS can also self-consistently run as the module of ionosphere-plasmasphere of GCITEM-IGGCAS (Global Coupled Ionosphere-Thermosphere-Electrodynamics Model developed at Institute of Geology and Geophysics, Chinese Academy of Sciences). We carry out simulations in March Equinox and in June Solstice, and compare the simulated results with that from IRI empirical model. TIME3D-IGGCAS can well reproduce the main ionospheric features in all simulations. We also simulate the ionospheric differences between different kinds of geomagnetic fields. The results suggest that the geomagnetic field configuration obviously affect the ionospheric plasma density, and the differences between NmF2 in realistic geomagnetic fields and that in tilted dipole fields can be larger than 60%.
Magnetic fluid hyperthermia modeling based on phantom measurements and realistic breast model.
Miaskowski, Arkadiusz; Sawicki, Bartosz
2013-07-01
Magnetic fluid hyperthermia (MFH) is a minimally invasive procedure that destroys cancer cells. It is based on a superparamagnetic heat phenomenon and consists in feeding a ferrofluid into a tumor, and then applying an external electromagnetic field, which leads to apoptosis. The strength of the magnetic field, optimal dose of the ferrofluid, the volume of the tumor and the safety standards have to be taken into consideration when MFH treatment is planned. In this study, we have presented the novel complementary investigation based both on the experiments and numerical methodology connected with female breast cancer. We have conducted experiments on simplified female breast phantoms with numerical analysis and then we transferred the results on an anatomically-like breast model.
NASA Astrophysics Data System (ADS)
Pierrard, V.; Poedts, S.; Lazar, M.
2014-12-01
Direct in-situ measurements of the velocity distributions of plasma particles in the solar wind reveal two distinct components: a Maxwellian (thermal) core, and a less dense but hotter halo in the high-energy (suprathermal) tails of the distribution, which are well-described by Kappa power-laws. Despite these evidences, the present attempts to parameterize the observed anisotropy and the resulting plasma wave instabilities are limited to idealized models of the distributions. These are, for instance, simplified models which ignore the suprathermal populations, or minimize the role of the core, assuming this component is cold, and model only the suprathermal tails with a Kappa distribution function. It is worthwhile to asses to which extent these models are relevant in realistic situations. Here, we present a comparative analysis with more realistic approaches, which combine a Maxwellian core, and one or two Kappa distributed components (the halo and the field-aligned strahl in the fast wind). A comparison is provided for the particular case of the cyclotron instabilities, which enables us to emphasize the effects produced by the thermal spread of plasma particles from the core, and extend approaching complex situations frequently observed in the solar wind, when both the core and halo populations are anisotropic. Correlated with the radial profile of Kappa components in the heliosphere, these effects help us to build a realistic picture on the role played by these instabilities in major processes like heating and energy dissipation in the solar wind.