Motion in Brane World Models: The Bazanski Approach
Kahil, M.E.
2007-11-20
Recently, path equations have been obtained for charged and spinning objects in brane world models, using a modified Bazanski Lagrangian. In this study, path deviation equations of extended objects are derived. The significance of moving extended objects in brane world models is examined. Motion in non-symmetric brane world models is also considered.
Fermions in 5D brane world models
NASA Astrophysics Data System (ADS)
Smolyakov, Mikhail
2016-10-01
In the present manuscript the fermion fields in the background of 5D brane world models with compact extra dimension are examined. It is shown that the only case that allows one to perform the Kaluza-Klein decomposition in a mathematically consistent way without unnatural fine-tunings and possible pathologies, is the one which does not admit localization of the zero mode. The report is based on the results presented in [1].
Simple brane-world inflationary models — An update
NASA Astrophysics Data System (ADS)
Okada, Nobuchika; Okada, Satomi
2016-05-01
In the light of the Planck 2015 results, we update simple inflationary models based on the quadratic, quartic, Higgs and Coleman-Weinberg potentials in the context of the Randall-Sundrum brane-world cosmology. Brane-world cosmological effect alters the inflationary predictions of the spectral index (ns) and the tensor-to-scalar ratio (r) from those obtained in the standard cosmology. In particular, the tensor-to-scalar ratio is enhanced in the presence of the 5th dimension. In order to maintain the consistency with the Planck 2015 results for the inflationary predictions in the standard cosmology, we find a lower bound on the five-dimensional Planck mass (M5). On the other hand, the inflationary predictions laying outside of the Planck allowed region can be pushed into the allowed region by the brane-world cosmological effect with a suitable choice of M5.
Fermions in five-dimensional brane world models
NASA Astrophysics Data System (ADS)
Smolyakov, Mikhail N.
2016-06-01
In the present paper the fermion fields, living in the background of five-dimensional warped brane world models with compact extra dimension, are thoroughly examined. The Kaluza-Klein decomposition and isolation of the physical degrees of freedom is performed for those five-dimensional fermion field Lagrangians, which admit such a decomposition to be performed in a mathematically consistent way and provide a physically reasonable four-dimensional effective theory. It is also shown that for the majority of five-dimensional fermion field Lagrangians there are no (at least rather obvious) ways to perform the Kaluza-Klein decomposition consistently. Moreover, in these cases one may expect the appearance of various pathologies in the four-dimensional effective theory. Among the cases, for which the Kaluza-Klein decomposition can be performed in a mathematically consistent way, the case, which reproduces the Standard Model by the zero Kaluza-Klein modes most closely regardless of the size of the extra dimension, is examined in detail in the background of the Randall-Sundrum model.
Bouhmadi-Lopez, Mariam; Ferrera, Antonio E-mail: a.ferrera.pardo@gmail.com
2008-10-15
We construct a new brane-world model composed of a bulk with a dilatonic field, plus a brane with brane tension coupled to the dilaton, cold dark matter and an induced gravity term. It is possible to show that, depending on the nature of the coupling between the brane tension and the dilaton, this model can describe the late time acceleration of the brane expansion (for the normal branch) as it moves within the bulk. The acceleration is produced together with a mimicry of the crossing of the cosmological constant line (w = -1) on the brane, although this crossing of the phantom divide is obtained without invoking any phantom matter either on the brane or in the bulk. The role of dark energy is played by the brane tension, which reaches a maximum positive value along the cosmological expansion of the brane. It is precisely at that maximum that the crossing of the phantom divide takes place. We also show that these results remain valid when the induced gravity term on the brane is switched off.
NASA Astrophysics Data System (ADS)
Yi, Piljin
2005-12-01
We consider reheating processes at the end of string theory inflation involving unstable D-brane systems. Nucleosynthesis restricts how much of reheating energy may be present in the nonstandard matter sector, such as gravitons and gravitinos, introducing some constraints on reheating process. In string theory setting, these may not be avoided ad hoc by fine-tuning and provide a useful tool in weeding out unrealistic scenarios. In this talk, we how the energy gets deposited into various light degrees of freedom in open and closed strings sectors. We show that a viable reheating is possible in a single throat case of KKLMMT type inflation model. Depending on details of the geometry, however, a potential problem with long-lived KK relic is present. For multi-throat case, this problem of KK relic is typically more severe and generic.
Brane-world cosmology with black strings
NASA Astrophysics Data System (ADS)
Gergely, László Á.
2006-07-01
We consider the simplest scenario when black strings/cigars penetrate the cosmological brane. As a result, the brane has a Swiss-cheese structure, with Schwarzschild black holes immersed in a Friedmann-Lemaître-Robertson-Walker brane. There is no dark radiation in the model, the cosmological regions of the brane are characterized by a cosmological constant Λ and flat spatial sections. Regardless of the value of Λ, these brane-world universes forever expand and forever decelerate. The totality of source terms in the modified Einstein equation sum up to a dust, establishing a formal equivalence with the general relativistic Einstein-Straus model. However in this brane-world scenario with black strings the evolution of the cosmological fluid strongly depends on Λ. For Λ≤0 it has positive energy density ρ and negative pressure p and at late times it behaves as in the Einstein-Straus model. For (not too high) positive values of Λ the cosmological evolution begins with positive ρ and negative p, but this is followed by an epoch with both ρ and p positive. Eventually, ρ becomes negative, while p stays positive. A similar evolution is present for high positive values of Λ, however in this case the evolution ends in a pressure singularity, accompanied by a regular behavior of the cosmic acceleration. This is a novel type of singularity appearing in brane-worlds.
Brane-World Cosmology and Varying G
NASA Astrophysics Data System (ADS)
Amarilla, Leonardo; Vucetich, Héctor
We consider a brane-world cosmological model coupled to a bulk scalar field. Since the brane tension turns out to be proportional to Newton's coupling G, in such a model a time variation of G naturally occurs. By resorting to available bounds on the variation of G, the parameters of the model are constrained. The constraints coming from nucleosynthesis and CMB result to be the severest ones.
Cross sections for production of closed superstrings at high energy colliders in brane world models
Chialva, Diego; Iengo, Roberto; Russo, Jorge G.
2005-05-15
In brane world string models with large extra dimensions, there are processes where fermion and antifermion (or two gluons) can annihilate producing a light particle (e.g. gluon) carrying transverse momentum and a Kaluza-Klein graviton or an excited closed string that propagates in the extra dimensions. In high energy colliders, this process gives a missing-momentum signature. We compute the total cross section for this process within the context of type II superstring theory in the presence of a D-brane. This includes all missing-energy sources for this string-theory model up to s=8M{sub s}{sup 2}, and it can be used to put new limits on the string scale M{sub s}.
Effective theory approach to brane world black holes
McFadden, Paul L.; Turok, Neil
2005-04-15
We derive static spherically symmetric vacuum solutions of the low-energy effective action for the two brane Randall-Sundrum model. The solutions with nontrivial radion belong to a one-parameter family describing traversable wormholes between the branes and a black hole, and were first discovered in the context of Einstein gravity with a conformally coupled scalar field. From a brane world perspective, a distinctive feature of all the solutions with nontrivial radion is a brane intersection about which the bulk geometry is conical but the induced metrics on the branes are regular. Contrary to earlier claims in the literature, we show these solutions are stable under monopole perturbations.
Asymmetric Swiss-cheese brane-worlds
NASA Astrophysics Data System (ADS)
Gergely, László Á.; Képíró, Ibolya
2007-07-01
We study a brane-world cosmological scenario with local inhomogeneities represented by black holes. The brane is asymmetrically embedded into the bulk. The black strings/cigars penetrating the Friedmann brane generate a Swiss-cheese-type structure. This universe forever expands and decelerates, as its general relativistic analogue. The evolution of the cosmological fluid, however, can proceed along four branches, two allowed to have positive energy density, and one of them having the symmetric embedding limit. On this branch a future pressure singularity can arise for either (a) a difference in the cosmological constants of the cosmological and black hole brane regions or (b) a difference in the left and right bulk cosmological constants. While behaviour (a) can be avoided by a redefinition of the fluid variables, (b) establishes a critical value of the asymmetry over which the pressure singularity occurs. We introduce the pressure singularity censorship which bounds the degree of asymmetry in the bulk cosmological constant. We also show as a model-independent generic feature that the asymmetry source term due to the bulk cosmological constant increases in the early universe. In order to obey the nucleosynthesis constraints, the brane tension should be constrained therefore both from below and from above. With the maximal degree of asymmetry obeying the pressure singularity censorship, the higher limit is ten times the lower limit. The degree of asymmetry allowed by present cosmological observations is, however, much less, pushing the upper limit to infinity.
Phantomlike behavior in a brane-world model with curvature effects
Bouhmadi-Lopez, Mariam; Moniz, Paulo Vargas
2008-10-15
Recent observational evidence seems to allow the possibility that our Universe may currently be under a dark energy effect of a phantom nature. A suitable effective phantom fluid behavior can emerge in brane cosmology; in particular, within the normal non-self-accelerating Dvali-Gabadadze-Porrati branch, without any exotic matter and due to curvature effects from induced gravity. The phantomlike behavior is based in defining an effective energy density that grows as the brane expands. This effective description breaks down at some point in the past when the effective energy density becomes negative and the effective equation of state parameter blows up. In this paper we investigate if the phantomlike regime can be enlarged by the inclusion of a Gauss-Bonnet (GB) term into the bulk. The motivation is that such a GB component would model additional curvature effects on the brane setting. More precisely, our aim is to determine if the GB term, dominating and modifying the early behavior of the brane universe, may eventually extend the regime of validity of the phantom mimicry on the brane. However, we show that the opposite occurs: the GB effect seems instead to induce a breakdown of the phantomlike behavior at an even smaller redshift.
Gravity on codimension 2 brane worlds
Navarro, Ignacio; Santiago, Jose; /Durham U., IPPP /Fermilab
2004-11-01
The authors compute the matching conditions for a general thick codimension 2 brane, a necessary previous step towards the investigation of gravitational phenomena in co-dimension 2 braneworlds. They show that, provided the brane is weakly curved, they are specified by the integral in the extra dimensions of the brane energy-momentum, independently of its detailed internal structure. These general matching conditions can then be used as boundary conditions for the bulk solution. By evaluating Einstein equations at the brane boundary they are able to write an evolution equation for the induced metric on the brane depending only on physical brane parameters and the bulk energy-momentum tensor. They particularize to a cosmological metric and show that a realistic cosmology can be obtained in the simplest case of having just a non-zero cosmological constant in the bulk. They point out several parallelisms between this case and the codimension 1 brane worlds in an AdS space.
Conformal symmetry of brane world effective actions
McFadden, Paul L.; Turok, Neil
2005-01-15
A simple derivation of the low-energy effective action for brane worlds is given, highlighting the role of conformal invariance. We show how to improve the effective action for a positive- and negative-tension brane pair using the AdS/CFT correspondence.
de Sitter and double asymmetric brane worlds
Guerrero, Rommel; Rodriguez, R. Omar; Torrealba, Rafael
2005-12-15
Asymmetric brane worlds with dS expansion and static double kink topology are obtained from a recently proposed method and their properties are analyzed. These domain walls interpolate between two spacetimes with different cosmological constants. In the dynamic case, the vacua correspond to dS and AdS geometry, unlike the static case where they correspond to AdS background. We show that it is possible to confine gravity on such branes. In particular, the double-brane world hosts two different walls, so that the gravity is localized on one of them.
Davis, Stephen C.; Brechet, Sylvain
2005-05-15
The bubble nucleation rate for a first order phase transition occurring on a brane world is calculated. Both the Coleman-de Luccia thin wall instanton and the Hawking-Moss instanton are considered. The results are compared with the corresponding nucleation rates for standard four-dimensional gravity.
Branes in Poisson sigma models
Falceto, Fernando
2010-07-28
In this review we discuss possible boundary conditions (branes) for the Poisson sigma model. We show how to carry out the perturbative quantization in the presence of a general pre-Poisson brane and how this is related to the deformation quantization of Poisson structures. We conclude with an open problem: the perturbative quantization of the system when the boundary has several connected components and we use a different pre-Poisson brane in every component.
Classical and quantum aspects of brane-world cosmology
Cordero, Ruben; Rojas, Efrain
2011-10-14
We give a brief overview of several models in brane-world cosmology. In particular, we focus on the asymmetric DGP and Regge-Teiltelboim models. We present the associated equations of motion governing the dynamics of the brane and their corresponding Friedmann-like equations. In order to develop the quantum Regge-Teiltelboim type cosmology we construct its Ostrogradski Hamiltonian formalism which naturally leads to the corresponding Wheeler-DeWitt equation. In addition, we comment on possible generalizations for these models including second order derivative geometrical terms.
Topics in brane world and quantum field theory
NASA Astrophysics Data System (ADS)
Corradini, Olindo
In the first part of the thesis we study various issues in the Brane World scenario with particular emphasis on gravity and the cosmological constant problem. First, we study localization of gravity on smooth domain-wall solutions of gravity coupled to a scalar field. In this context we discuss how the aforementioned localization is affected by including higher curvature terms in the theory, pointing out among other things that, general combinations of such terms lead to delocalization of gravity with the only exception of the Gauss-Bonnet combination (and its higher dimensional counterparts). We then find a solitonic 3-brane solution in 6D bulk in the Einstein-Hilbert-Gauss-Bonnet theory of gravity. Near to the brane the metric is that for a product of the 4D flat Minkowski space with a 2D wedge whose deficit angle is proportional to the brane tension. Consistency tests imposed on such backgrounds appear to require the localized matter on the brane to be conformal. We then move onto infinite volume extra dimension Brane World scenarios where we study gravity in a codimension-2 model, generalizing the work of Dvali, Gabadadze and Porrati to tensionful branes. We point out that, in the presence of the bulk Gauss-Bonnet combination, the Einstein-Hilbert term is induced on the brane already at the classical level. Consistency tests are presented here as well. To conclude we discuss, using String Theory, an interesting class of large-N gauge theories which have vanishing energy density even though these theories are non-covariant and non-supersymmetric. In the second part of the thesis we study a formulation of Quantum Mechanical Path Integrals in curved space. Such Path Integrals present superficial divergences which need to be regulated. We perform a three-loop calculation in mode regularization as a nontrivial check of the non-covariant counterterms required by such scheme. We discover that dimensional regularization can be successfully adopted to evaluate the
Abundance of Asymmetric Dark Matter in Brane World Cosmology
NASA Astrophysics Data System (ADS)
Abdusattar, Haximjan; Iminniyaz, Hoernisa
2016-09-01
Relic abundance of asymmetric Dark Matter particles in brane world cosmological scenario is investigated in this article. Hubble expansion rate is enhanced in brane world cosmology and it affects the relic abundance of asymmetric Dark Matter particles. We analyze how the relic abundance of asymmetric Dark Matter is changed in this model. We show that in such kind of nonstandard cosmological scenario, indirect detection of asymmetric Dark Matter is possible if the cross section is small enough which let the anti-particle abundance kept in the same amount with the particle. We show the indirect detection signal constraints can be used to such model only when the cross section and the 5-dimensional Planck mass scale are in appropriate values. Supported by the National Natural Science Foundation of China under Grant No. 11365022
Gauge field localization on brane worlds
Guerrero, Rommel; Rodriguez, R. Omar; Melfo, Alejandra; Pantoja, Nelson
2010-04-15
We consider the effects of spacetime curvature and brane thickness on the localization of gauge fields on a brane via kinetic terms induced by localized fermions. We find that in a warped geometry with an infinitely thin brane, both the infrared and the ultraviolet behavior of the electromagnetic propagator are affected, providing a more stringent bound on the brane's tension than that coming from the requirement of four-dimensional gravity on the brane. On the other hand, for a thick wall in a flat spacetime, where the fermions are localized by means of a Yukawa coupling, we find that four-dimensional electromagnetism is recovered in a region bounded from above by the same critical distance appearing in the thin case, but also from below by a new scale related to the brane's thickness and the electromagnetic couplings. This imposes very stringent bounds on the brane's thickness which seem to invalidate the localization mechanism for this case.
Branes and integrable lattice models
NASA Astrophysics Data System (ADS)
Yagi, Junya
2017-01-01
This is a brief review of my work on the correspondence between four-dimensional 𝒩 = 1 supersymmetric field theories realized by brane tilings and two-dimensional integrable lattice models. I explain how to construct integrable lattice models from extended operators in partially topological quantum field theories, and elucidate the correspondence as an application of this construction.
Effective contact interactions in a stabilized RS1 brane world model
Boos, E. E. Bunichev, V. E. Smolyakov, M. N. Volobuev, I. P.
2010-06-15
We consider the effective Lagrangian due to the exchange of heavy Kaluza-Klein (KK) tensor graviton and scalar radion states in a stabilized Randall-Sundrum model (RS1) and compute explicitly the corresponding effective coupling constants. The Drell-Yan lepton pair production at the Tevatron and the LHC is analyzed in two situations, when the first KK resonance is too heavy to be directly detected at the colliders, and when the first KK resonance is visible but other states are still too heavy. In the first case the effective Lagrangian reduces to a contact interaction of Standard Model (SM) particles, whereas in the second case it includes a coupling of SM particles to the first KK mode and a contact interaction due to the exchange of all the heavier modes. It is shown that in both cases the contribution from the invisible KK tower leads to a modification of final particles distributions. In particular, for the second case a nontrivial interference between the first KK mode and the rest KK tower takes place. Expected 95% C.L. limits for model parameters for the Tevatron and the LHC are given. The numerical results are obtained by means of the CompHEP code, in which all new effective interactions are implemented providing a tool for simulation of corresponding events and a more detailed analysis.
The Einstein equations on the 3-brane world
NASA Astrophysics Data System (ADS)
Shiromizu, Tetsuya; Maeda, Kei-Ichi; Sasaki, Misao
2000-07-01
We carefully investigate the gravitational equations of the brane world, in which all the matter forces except gravity are confined on the 3-brane in a 5-dimensional spacetime with Z2 symmetry. We derive the effective gravitational equations on the brane, which reduce to the conventional Einstein equations in the low energy limit. From our general argument we conclude that the first Randall-Sundrum-type theory predicts that the brane with a negative tension is an antigravity world and hence should be excluded from the physical point of view. Their second-type theory where the brane has a positive tension provides the correct signature of gravity. In this latter case, if the bulk spacetime is exactly anti-de Sitter spacetime, generically the matter on the brane is required to be spatially homogeneous because of the Bianchi identities. By allowing deviations from anti-de Sitter spacetime in the bulk, the situation will be relaxed and the Bianchi identities give just the relation between the Weyl tensor and the energy momentum tensor. In the present brane world scenario, the effective Einstein equations cease to be valid during an era when the cosmological constant on the brane is not well defined, such as in the case of the matter dominated by the potential energy of the scalar field.
Signals from the brane-world black hole
Shen Jianyong; Wang Bin; Su Rukeng
2006-08-15
We have studied the wave dynamics and the Hawking radiation for a scalar field as well as a brane-localized gravitational field in the background of a brane-world black hole with a tidal charge containing information on the extra dimension. Comparing with four-dimensional black holes, we have observed the signature of the tidal charge which presents the signals of the extra dimension both in the wave dynamics and the Hawking radiation.
Generalized complex geometry, generalized branes and the Hitchin sigma model
NASA Astrophysics Data System (ADS)
Zucchini, Roberto
2005-03-01
Hitchin's generalized complex geometry has been shown to be relevant in compactifications of superstring theory with fluxes and is expected to lead to a deeper understanding of mirror symmetry. Gualtieri's notion of generalized complex submanifold seems to be a natural candidate for the description of branes in this context. Recently, we introduced a Batalin-Vilkovisky field theoretic realization of generalized complex geometry, the Hitchin sigma model, extending the well known Poisson sigma model. In this paper, exploiting Gualtieri's formalism, we incorporate branes into the model. A detailed study of the boundary conditions obeyed by the world sheet fields is provided. Finally, it is found that, when branes are present, the classical Batalin-Vilkovisky cohomology contains an extra sector that is related non trivially to a novel cohomology associated with the branes as generalized complex submanifolds.
Zeta functions in brane world cosmology
NASA Astrophysics Data System (ADS)
Flachi, Antonino; Knapman, Alan; Naylor, Wade; Sasaki, Misao
2004-12-01
We present a calculation of the zeta function and of the functional determinant for a Laplace-type differential operator, corresponding to a scalar field in a higher-dimensional deSitter brane background, which consists of a higher-dimensional anti deSitter bulk spacetime bounded by a deSitter section, representing a brane. Contrary to the existing examples, which all make use of conformal transformations, we evaluate the zeta function working directly with the higher-dimensional wave operator. We also consider a generic mass term and coupling to curvature, generalizing previous results. The massless, conformally coupled case is obtained as a limit of the general result and compared with known calculations. In the limit of large anti deSitter radius, the zeta determinant for the ball is recovered in perfect agreement with known expressions, providing an interesting check of our result and an alternative way of obtaining the ball determinant.
Gravity and antigravity in a brane world with metastable gravitons
NASA Astrophysics Data System (ADS)
Gregory, R.; Rubakov, V. A.; Sibiryakov, S. M.
2000-09-01
In the framework of a five-dimensional three-brane model with quasi-localized gravitons we evaluate metric perturbations induced on the positive tension brane by matter residing thereon. We find that at intermediate distances, the effective four-dimensional theory coincides, up to small corrections, with General Relativity. This is in accord with Csaki, Erlich and Hollowood and in contrast to Dvali, Gabadadze and Porrati. We show, however, that at ultra-large distances this effective four-dimensional theory becomes dramatically different: conventional tensor gravity changes into scalar anti-gravity.
Farakos, K.; Koutsoumbas, G.; Pasipoularides, P.
2007-09-15
Brane world models with a nonminimally coupled bulk scalar field have been studied recently. In this paper we consider metric fluctuations around an arbitrary gravity-scalar background solution, and we show that the corresponding spectrum includes a localized zero mode which strongly depends on the profile of the background scalar field. For a special class of solutions, with a warp factor of the RS form, we solve the linearized Einstein equations, for a pointlike mass source on the brane, by using the brane bending formalism. We see that general relativity on the brane is recovered only if we impose restrictions on the parameter space of the models under consideration.
On Realistic Brane Worlds from Type i Strings
NASA Astrophysics Data System (ADS)
Aldazabal, Gerardo; IbÁñez, Luis E.; Quevedo, Fernando
We review recent progress in constructing realistic brane models from type I string vacua. Explicit models with three families of the standard model gauge group and its l-right generalizations are presented with supersymmetry broken at the string scale of order Ms ~ 1010-12
Casimir force in brane worlds: Coinciding results from Green's and zeta function approaches
Linares, Roman; Morales-Tecotl, Hugo A.; Pedraza, Omar
2010-06-15
Casimir force encodes the structure of the field modes as vacuum fluctuations and so it is sensitive to the extra dimensions of brane worlds. Now, in flat spacetimes of arbitrary dimension the two standard approaches to the Casimir force, Green's function, and zeta function yield the same result, but for brane world models this was only assumed. In this work we show that both approaches yield the same Casimir force in the case of universal extra dimensions and Randall-Sundrum scenarios with one and two branes added by p compact dimensions. Essentially, the details of the mode eigenfunctions that enter the Casimir force in the Green's function approach get removed due to their orthogonality relations with a measure involving the right hypervolume of the plates, and this leaves just the contribution coming from the zeta function approach. The present analysis corrects previous results showing a difference between the two approaches for the single brane Randall-Sundrum; this was due to an erroneous hypervolume of the plates introduced by the authors when using the Green's function. For all the models we discuss here, the resulting Casimir force can be neatly expressed in terms of two four-dimensional Casimir force contributions: one for the massless mode and the other for a tower of massive modes associated with the extra dimensions.
Coisotropic D8-branes and model-building
NASA Astrophysics Data System (ADS)
Font, Anamaría; Ibáñez, Luis E.; Marchesano, Fernando
2006-09-01
Up to now chiral type IIA vacua have been mostly based on intersecting D6-branes wrapping special Lagrangian 3-cycles on a CY3 manifold. We argue that there are additional BPS D-branes which have so far been neglected, and which seem to have interesting model-building features. They are coisotropic D8-branes, in the sense of Kapustin and Orlov. The D8-branes wrap 5-dimensional submanifolds of the CY3 which are trivial in homology, but contain a worldvolume flux that induces D6-brane charge on them. This induced D6-brane charge not only renders the D8-brane BPS, but also creates D = 4 chirality when two D8-branes intersect. We discuss in detail the case of a type IIA T6/(Bbb Z2 × Bbb Z2) orientifold, where we provide explicit examples of coisotropic D8-branes. We study the chiral spectrum, SUSY conditions, and effective field theory of different systems of D8-branes in this orientifold, and show how the magnetic fluxes generate a superpotential for untwisted Kähler moduli. Finally, using both D6-branes and coisotropic D8-branes we construct new examples of MSSM-like type IIA vacua.
Notes on the two-brane model with variable tension
Abdalla, M. C. B.; Hoff da Silva, J. M. Hoff; Rocha, R. da
2009-08-15
Motivated by possible extensions of the braneworld models with two branes, we investigate some consequences of a variable brane tension, using the well established results on consistency conditions. By a slight modification of the usual stress-tensor used in order to derive the braneworld sum rules, we find some important constraints obeyed by time-dependent brane tensions. In particular, it is shown that the tensions of two Randall-Sundrum-like branes obeying, at the same time, an Eoetvoes law, aggravate the fine-tuning problem. Also, it is shown that if the hidden brane tension obeys an Eoetvoes law, then the visible brane has a mixed behavior allowing a bouncinglike period at early times while it is dominated by an Eoetvoes law now. To finalize, we discuss some qualitative characteristics, which may arise in the scope of dynamical brane tensions, as anisotropic background and branons production.
Brane model with two asymptotic regions
NASA Astrophysics Data System (ADS)
Lubo, Musongela
2005-02-01
Some brane models rely on a generalization of the Melvin magnetic universe including a complex scalar field among the sources. We argue that the geometric interpretation of Kip. S. Thorne of this geometry restricts the kind of potential a complex scalar field can display to keep the same asymptotic behavior. While a finite energy is not obtained for a Mexican hat potential in this interpretation, this is the case for a potential displaying a broken phase and an unbroken one. We use for technical simplicity and illustrative purposes an ad hoc potential which however shares some features with those obtained in some supergravity models. We construct a sixth dimensional cylindrically symmetric solution which has two asymptotic regions: the Melvin-like metric on one side and a flat space displaying a conical singularity on the other. The causal structure of the configuration is discussed. Unfortunately, gravity is not localized on the brane.
Brane model with two asymptotic regions
Lubo, Musongela
2005-02-15
Some brane models rely on a generalization of the Melvin magnetic universe including a complex scalar field among the sources. We argue that the geometric interpretation of Kip. S. Thorne of this geometry restricts the kind of potential a complex scalar field can display to keep the same asymptotic behavior. While a finite energy is not obtained for a Mexican hat potential in this interpretation, this is the case for a potential displaying a broken phase and an unbroken one. We use for technical simplicity and illustrative purposes an ad hoc potential which however shares some features with those obtained in some supergravity models. We construct a sixth dimensional cylindrically symmetric solution which has two asymptotic regions: the Melvin-like metric on one side and a flat space displaying a conical singularity on the other. The causal structure of the configuration is discussed. Unfortunately, gravity is not localized on the brane.
Casimir force for a scalar field in warped brane worlds
Linares, Roman; Morales-Tecotl, Hugo A.; Pedraza, Omar
2008-03-15
In looking for imprints of extra dimensions in braneworld models one usually builds these so that they are compatible with known low energy physics and thus focuses on high energy effects. Nevertheless, just as submillimeter Newton's law tests probe the mode structure of gravity other low energy tests might apply to matter. As a model example, in this work we determine the 4D Casimir force corresponding to a scalar field subject to Dirichlet boundary conditions on two parallel planes lying within the single brane of a Randall-Sundrum scenario extended by one compact extra dimension. Using the Green's function method such a force picks the contribution of each field mode as if it acted individually but with a weight given by the square of the mode wave functions on the brane. In the low energy regime one regains the standard 4D Casimir force that is associated to a zero mode in the massless case or to a quasilocalized or resonant mode in the massive one while the effect of the extra dimensions gets encoded as an additional term.
Brane-world stars with a solid crust and vacuum exterior
NASA Astrophysics Data System (ADS)
Ovalle, Jorge; Gergely, László Á.; Casadio, Roberto
2015-02-01
The minimal geometric deformation approach is employed to show the existence of brane-world stellar distributions with a vacuum Schwarzschild exterior, thus without energy leaking from the exterior of the brane-world star into the extra dimension. The interior satisfies all the elementary criteria of physical acceptability for a stellar solution, namely, it is regular at the origin, the pressure and density are positive and decrease monotonically with increasing radius, and all energy conditions are fulfilled. A very thin solid crust with negative radial pressure separates the interior from the exterior, having a thickness Δ inversely proportional to both the brane tension σ and the radius R of the star, i.e. {{Δ }-1}˜ Rσ . This brane-world star with Schwarzschild exterior would appear only thermally radiating to a distant observer and be fully compatible with the stringent constraints imposed on stellar parameters by observations of gravitational lensing, orbital evolutions or properties of accretion disks.
Wightman function and vacuum fluctuations in higher dimensional brane models
Saharian, Aram A.
2006-02-15
The Wightman function and the vacuum expectation value of the field square are evaluated for a massive scalar field with a general curvature coupling parameter subject to Robin boundary conditions on two codimension-one parallel branes located on a (D+1)-dimensional background spacetime AdS{sub D{sub 1}}{sub +1}x{sigma} with a warped internal space {sigma}. The general case of different Robin coefficients on separate branes is considered. The application of the generalized Abel-Plana formula for the series over zeros of combinations of cylinder functions allows us to manifestly extract the part due to the bulk without boundaries. Unlike the purely anti-de Sitter (AdS) bulk, the vacuum expectation value of the field square induced by a single brane, in addition to the distance from the brane, depends also on the position of the brane in the bulk. The brane induced part in this expectation value vanishes when the brane position tends to the AdS horizon or the AdS boundary. The asymptotic behavior of the vacuum densities near the branes and at large distances is investigated. The contribution of Kaluza-Klein modes along {sigma} is discussed in various limiting cases. In the limit when the curvature radius for the AdS spacetime tends to infinity, we derive the results for two parallel Robin plates on the background spacetime R{sup (D{sub 1},1)}x{sigma}. For strong gravitational fields corresponding to large values of the AdS energy scale, both the single brane and interference parts of the expectation values integrated over the internal space are exponentially suppressed. As an example the case {sigma}=S{sup 1} is considered, corresponding to the AdS{sub D+1} bulk with one compactified dimension. An application to the higher dimensional generalization of the Randall-Sundrum brane model with arbitrary mass terms on the branes is discussed.
De Sitter brane-world, localization of gravity, and the cosmological constant
Neupane, Ishwaree P.
2011-04-15
Cosmological models with a de Sitter 3-brane embedded in a 5-dimensional de Sitter spacetime (dS{sub 5}) give rise to a finite 4D Planck mass similar to that in Randall-Sundrum (RS) brane-world models in anti-de Sitter 5-dimensional spacetime(AdS{sub 5}). Yet, there arise a few important differences as compared to the results with a flat 3-brane or 4D Minkowski spacetime. For example, the mass reduction formula (MRF) M{sub Pl}{sup 2}=M{sub (5)}{sup 3}l{sub AdS} as well as the relationship M{sub Pl}{sup 2}=M{sub Pl(4+n)}{sup n+2}L{sup n} (with L being the average size or the radius of the n extra dimensions) expected in models of product-space (or Kaluza-Klein) compactifications get modified in cosmological backgrounds. In an expanding universe, a physically relevant MRF encodes information upon the 4-dimensional Hubble expansion parameter, in addition to the length and mass parameters L, M{sub Pl}, and M{sub Pl(4+n)}. If a bulk cosmological constant is present in the solution, then the reduction formula is further modified. With these new insights, we show that the localization of a massless 4D graviton as well as the mass hierarchy between M{sub Pl} and M{sub Pl(4+n)} can be explained in cosmological brane-world models. A notable advantage of having a 5D de Sitter bulk is that in this case the zero-mass wave function is normalizable, which is not necessarily the case if the bulk spacetime is anti-de Sitter. In spacetime dimensions D{>=}7, however, the bulk cosmological constant {Lambda}{sub b} can take either sign ({Lambda}{sub b}<0, =0, or >0). The D=6 case is rather inconclusive, in which case {Lambda}{sub b} may be introduced together with 2-form gauge field (or flux). We obtain some interesting classical gravity solutions that compactify higher-dimensional spacetime to produce a Robertson-Walker universe with de Sitter-type expansion plus one extra noncompact direction. We also show that such models can admit both an effective 4-dimensional Newton constant
Intersecting branes and Nambu-Jona-Lasinio model
Dhar, Avinash; Nag, Partha
2009-06-15
We discuss chiral symmetry breaking in the intersecting brane model of Sakai and Sugimoto at weak coupling for a generic value of separation L between the flavor D8 and anti-D8-branes. For any finite value of the radius R of the circle around which the color D4-branes wrap, a nonlocal Nambu-Jona-Lasinio-type short-range interaction couples the flavor branes and antibranes. We argue that chiral symmetry is broken in this model only above a certain critical value of the four-dimensional 't Hooft coupling and confirm this through numerical calculations of solutions to the gap equation. We also numerically investigate chiral symmetry breaking in the limit R{yields}{infinity} keeping L fixed, but find that simple ways of implementing this limit do not lead to a consistent picture of chiral symmetry breaking in the noncompact version of the nonlocal Nambu-Jona-Lasinio model.
Stability of the graviton Bose-Einstein condensate in the brane-world
NASA Astrophysics Data System (ADS)
Casadio, Roberto; da Rocha, Roldão
2016-12-01
We consider a solution of the effective four-dimensional Einstein equations, obtained from the general relativistic Schwarzschild metric through the principle of Minimal Geometric Deformation (MGD). Since the brane tension can, in general, introduce new singularities on a relativistic Eötvös brane model in the MGD framework, we require the absence of observed singularities, in order to constrain the brane tension. We then study the corresponding Bose-Einstein condensate (BEC) gravitational system and determine the critical stability region of BEC MGD stellar configurations. Finally, the critical stellar densities are shown to be related with critical points of the information entropy.
Brane-inspired models in gravitation and cosmology
NASA Astrophysics Data System (ADS)
Gal'tsov, Dmitri
We discuss some recent development in gravitation and cosmology related to the concept of branes. These lectures include: a brief review of braneworld scenarios with an emphasis on the black hole problem, soliton and black hole solutions of the gravitating non-Abelian Born-Infeld (NBI) model, NBI homogeneous and isotropic cosmology, brane NBI cosmology, the issue of Yang-Mills chaos in the context of the NBI dynamics.
Cosmological constraints on parameters of one-brane models with extra dimension
Iofa, Mikhail Z.
2009-11-01
We study some aspects of cosmologies in 5D models with one infinite extra dimension. Matter is confined to the brane, gravity extends to the bulk. Models with positive and negative tension of the brane are considered. Cosmological evolution of the 4D world is described by warped solutions of the generalized Friedmann equation. Cosmological solutions on the brane are obtained with the input of the present-time observational cosmological parameters. We estimate the age of the Universe and abundance of {sup 4}He produced in primordial nucleosynthesis in different models. Using these estimates we find constraints on dimensionless combinations of the 5D gravitational scale, scale of the warp factor and coupling at the 4D curvature term in the action.
Noncommutative brane-world, (Anti) de Sitter vacua and extra dimensions
NASA Astrophysics Data System (ADS)
Kar, Supriya
2006-10-01
We investigate a curved brane-world, inspired by a noncommutative D3-brane, in a type IIB string theory. We obtain, an axially symmetric and a spherically symmetric, (anti) de Sitter black holes in 4D. The event horizons of these black holes possess a constant curvature and may be seen to be governed by different topologies. The extremal geometries are explored, using the noncommutative scaling in the theory, to reassure the attractor behavior at the black hole event horizon. The emerging two dimensional, semi-classical, black hole is analyzed to provide evidence for the extra dimensions in a curved brane-world. It is argued that the gauge nonlinearity in the theory may be redefined by a potential in a moduli space. As a result, D = 11 and D = 12 dimensional geometries may be obtained at the stable extrema of the potential.
Casimir force for a scalar field in a single brane world
Linares, R.; Morales-Tecotl, H. A.; Pedraza, O.
2010-02-10
Vacuum force is an interesting low energy test for brane worlds due to its dependence on field's modes and its role in submillimeter gravity experiments. In this contribution we obtain the scalar field vacuum force between two parallel plates lying in the brane of a Randall-Sundrum scenario extended by p compact dimensions (RSII-{sub p}). We obtain the force using the Green's function technique and we compare our results with the ones obtained by using the zeta function regularization method. As a result we obtain agreement in the expression for the force independently of the method used, thus we solve a previous discrepancy between the two approaches.
Particle Physics of Brane Worlds and Extra Dimensions
NASA Astrophysics Data System (ADS)
Raychaudhuri, Sreerup; Sridhar, K.
2016-06-01
Preface; 1. Dimensional dreams; 2. The Standard Model and beyond; 3. The birth of compact dimensions; 4. String theory: a review; 5. Effective theories; 6. Large extra dimensions; 7. Visible towers of invisible gravitons; 8. Making black holes; 9. Universal extra dimensions; 10. Warped compactifications; 11. Graviton resonances; 12. Stability of warped Worlds; 13. Exploring the bulk; 14. Epilogue; Appendix A. General relativity in a nutshell; Appendix B. Testing the inverse square law; Index.
Frolov, Valeri P.; Mukohyama, Shinji
2011-02-15
The aim of this paper is to demonstrate that in models with large extra dimensions under special conditions one can extract information from the interior of 4D black holes. For this purpose we study an induced geometry on a test brane in the background of a higher-dimensional static black string or a black brane. We show that, at the intersection surface of the test brane and the bulk black string or brane, the induced metric has an event horizon, so that the test brane contains a black hole. We call it a brane hole. When the test brane moves with a constant velocity V with respect to the bulk black object, it also has a brane hole, but its gravitational radius r{sub e} is greater than the size of the bulk black string or brane r{sub 0} by the factor (1-V{sup 2}){sup -1}. We show that bulk ''photon'' emitted in the region between r{sub 0} and r{sub e} can meet the test brane again at a point outside r{sub e}. From the point of view of observers on the test brane, the events of emission and capture of the bulk photon are connected by a spacelike curve in the induced geometry. This shows an example in which extra dimensions can be used to extract information from the interior of a lower-dimensional black object. Instead of the bulk black string or brane, one can also consider a bulk geometry without a horizon. We show that nevertheless the induced geometry on the moving test brane can include a brane hole. In such a case the extra dimensions can be used to extract information from the complete region of the brane-hole interior. We discuss thermodynamic properties of brane holes and interesting questions which arise when such an extra-dimensional channel for the information mining exists.
Micro-orbits in a many-brane model and deviations from Newton's 1/r^2 law
NASA Astrophysics Data System (ADS)
Donini, A.; Marimón, S. G.
2016-12-01
We consider a five-dimensional model with geometry M = M_4 × S_1, with compactification radius R. The Standard Model particles are localized on a brane located at y=0, with identical branes localized at different points in the extra dimension. Objects located on our brane can orbit around objects located on a brane at a distance d=y/R, with an orbit and a period significantly different from the standard Newtonian ones. We study the kinematical properties of the orbits, finding that it is possible to distinguish one motion from the other in a large region of the initial conditions parameter space. This is a warm-up to study if a SM-like mass distribution on one (or more) distant brane(s) may represent a possible dark matter candidate. After using the same technique to the study of orbits of objects lying on the same brane (d=0), we apply this method to the detection of generic deviations from the inverse-square Newton law. We propose a possible experimental setup to look for departures from Newtonian motion in the micro-world, finding that an order of magnitude improvement on present bounds can be attained at the 95% CL under reasonable assumptions.
D3-Brane Model Building and the Supertrace Rule.
Bena, Iosif; Graña, Mariana; Kuperstein, Stanislav; Ntokos, Praxitelis; Petrini, Michela
2016-04-08
A common way to obtain standard-model-like Lagrangians in string theory is to place D3-branes inside flux compactifications. The bosonic and fermionic masses and couplings of the resulting gauge theory are determined by the ten-dimensional metric and the fluxes, respectively, and the breaking of supersymmetry is soft. However, not any soft-supersymmetry-breaking Lagrangian can be obtained this way since the string theory equations of motion impose certain relations between the soft couplings. We show that for D3-branes in background fluxes, these relations imply that the sums of the squares of the boson and of the fermion masses are equal and that, furthermore, one- and two-loop quantum corrections do not spoil this equality. This makes the use of D3-branes for constructing computationally controllable models for physics beyond the standard model problematic.
Stability of Dark Energy Models on the Brane Universes
NASA Astrophysics Data System (ADS)
Saadat, Hassan
2013-08-01
In this paper the equation of state formalism for the dark energy models on the brane considered and stability of theory investigated. We consider four different cases of the Little Rip, Asymptotic de Sitter, Asymptotic breakdown, and Big Freeze singularity models and find that the only stable model is Asymptotic de Sitter case. In other cases we get negative value of squared sound speed.
Phenomenological Lagrangians, gauge models and branes
NASA Astrophysics Data System (ADS)
Zheltukhin, A. A.
2017-03-01
Phenomenological Lagrangians for physical systems with spontaneously broken symmetries are reformulated in terms of gauge field theory. Description of the Dirac p-branes in terms of the Yang-Mills- Cartan gauge multiplets interacting with gravity, is proved to be equivalent to their description as a closed dynamical system with the symmetry ISO(1, D - 1) spontaneously broken to ISO(1, p) × SO( D - p - 1).
Black hole as a point radiator and recoil effect on the brane world.
Frolov, Valeri; Stojković, Dejan
2002-10-07
A small black hole attached to a brane in a higher-dimensional space emitting quanta into the bulk may leave the brane as a result of a recoil. We construct a field theory model in which such a black hole is described as a massive scalar particle with internal degrees of freedom. In this model, the probability of transition between the different internal levels is identical to the probability of thermal emission calculated for the Schwarzschild black hole. The discussed recoil effect implies that the thermal emission of the black holes, which might be created by interaction of high energy particles in colliders, could be terminated and the energy nonconservation can be observed in the brane experiments.
Comments on SUSY Inflation Models on the Brane
NASA Astrophysics Data System (ADS)
Lee, Lu-Yun; Cheung, Kingman; Lin, Chia-Min
In this paper we consider a class of inflation models on the brane where the dominant part of the inflaton scalar potential does not depend on the inflaton field value during inflation. In particular, we consider supernatural inflation, its hilltop version, A-term inflation, and supersymmetric (SUSY) D- and F-term hybrid inflation on the brane. We show that the parameter space can be broadened, the inflation scale generally can be lowered, and still possible to have the spectral index ns = 0.96.
NASA Astrophysics Data System (ADS)
Ebert, Dietmar; Plefka, Jan; Rodigast, Andreas
2009-02-01
We study the question of a modification of the running gauge coupling of Yang-Mills theories due to quantum gravitational effects in a compact large extra dimensional brane world scenario with a low energy quantum gravity scale. The ADD scenario is applied for a D = d+δ dimensional space-time in which gravitons freely propagate, whereas the non-abelian gauge fields are confined to a d-dimensional brane. The extra dimensions are taken to be toroidal and the transverse fluctuation modes (branons) of the brane are taken into account. On this basis we have calculated the one-loop corrections due to virtual Kaluza-Klein graviton and branon modes for the gluon two- and three-point functions in an effective field theory treatment. Applying momentum cut-off regularization we find that for a d = 4 brane the leading gravitational divergencies cancel irrespective of the number of extra dimensions δ, generalizing previous results in the absence of extra-dimensions. Hence, again the Yang-Mills β-function receives no gravitational corrections at one-loop. This is no longer true in a `universal' extra dimensional scenario with a d > 4 dimensional brane. Moreover, the subleading power-law gravitational divergencies induce higher-dimensional counterterms, which we establish in our scheme. Interestingly, for d = 4 these gravitationally induced counterterms are of the form recently considered in non-abelian Lee-Wick extensions of the standard model—now with a possible mass scale in the TeV range due to the presence of large extra dimensions.
Minimal left-right symmetric intersecting D-brane model
NASA Astrophysics Data System (ADS)
Anchordoqui, Luis A.; Antoniadis, Ignatios; Goldberg, Haim; Huang, Xing; Lüst, Dieter; Taylor, Tomasz R.
2017-01-01
We investigate left-right symmetric extensions of the standard model based on open strings ending on D-branes, with gauge bosons due to strings attached to stacks of D-branes and chiral matter due to strings stretching between intersecting D-branes. The left-handed and right-handed fermions transform as doublets under S p (1 )L and S p (1 )R, and so their masses must be generated by the introduction of Higgs fields in a bifundamental (2 ,2 ) representation under the two S p (1 ) gauge groups. For such D-brane configurations the left-right symmetry must be broken by Higgs fields in the doublet representation of S p (1 )R and therefore Majorana mass terms are suppressed by some higher physics scale. The left-handed and right-handed neutrinos pair up to form Dirac fermions which control the decay widths of the right-handed W' boson to yield comparable branching fractions into dilepton and dijet channels. Using the most recent searches at LHC13 Run II with 2016 data we constrain the (gR,mW') parameter space. Our analysis indicates that independent of the coupling strength gR, gauge bosons with masses mW'≳3.5 TeV are not ruled out. As the LHC is just beginning to probe the TeV scale, significant room for W' discovery remains.
Some phenomenology of intersecting D-brane models
Kane, Gordon L.; Kumar, Piyush; Lykken, Joseph D.; Wang, Ting T.; /Michigan U., MCTP
2004-11-01
We present some phenomenology of a new class of intersecting D-brane models. Soft SUSY breaking terms for these models are calculated in the complex structure (u)-moduli dominant SUSY breaking approach (in type IIA). In this case, the dependence of the soft terms on the Yukawas and Wilson lines drops out. These soft terms have a different pattern compared to the usual heterotic string models. Phenomenological implications for dark matter are discussed.
Model to localize gauge and tensor fields on thick branes
NASA Astrophysics Data System (ADS)
Chumbes, A. E. R.; Hoff da Silva, J. M.; Hott, M. B.
2012-04-01
It is shown that the introduction of a suitable function in the higher-dimensional gauge field action may be used in order to achieve gauge bosons localization on a thick brane. The model is constructed upon analogies to the effective coupling of neutral scalar field to electromagnetic field and to the Friedberg-Lee model for hadrons. After that we move forward studying the localization of the Kalb-Ramond field via this procedure.
On higher rank coisotropic A-branes
NASA Astrophysics Data System (ADS)
Herbst, Manfred
2012-02-01
This article is devoted to a world sheet analysis of A-type D-branes in N=(2,2) supersymmetric non-linear sigma models. In addition to the familiar Lagrangian submanifolds with flat connection we reproduce the rank one A-branes of Kapustin and Orlov, which are supported on coisotropic submanifolds. The main focus is however on gauge fields of higher rank and on tachyon profiles on brane-antibrane pairs. This will lead to the notion of a complex of coisotropic A-branes. A particular role is played by the noncommutative geometry on the brane world volume. It ensures that brane-antibrane pairs localize again on coisotropic submanifolds.
Possibility of catastrophic black hole growth in the warped brane-world scenario at the LHC
Casadio, Roberto; Fabi, Sergio; Harms, Benjamin
2009-10-15
In this paper, we present the results of our analysis of the growth and decay of black holes possibly produced at the Large Hadron Collider, based on our previous study of black holes in the context of the warped brane-world scenario. The black hole mass accretion and decay is obtained as a function of time, and the maximum black hole mass are obtained as a function of a critical mass parameter. The latter occurs in our expression for the luminosity and is related to the size of extra-dimensional corrections to Newton's law. Based on this analysis, we argue against the possibility of catastrophic black hole growth at the LHC.
D-branes in Massive IIA and Solitons in Chern-Simons Theory
Brodie, John H
2001-07-25
We investigate D2-branes and D4-branes parallel to D8-branes. The low energy world volume theory on the branes is non-supersymmetric Chern-Simons theory. We identify the fundamental strings as the anyons of the 2+1 Chern-Simons theory and the D0-branes as solitons. The Chern-Simons theory with a boundary is modeled using NS 5-branes with ending D6-branes. The brane set-up provides for a graphical description of anomaly inflow. We also model the 4+1 Chern-Simons theory using branes and conjecture that D4-branes with a boundary describes a supersymmetric version of Kaplan's theory of chiral fermions.
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.
How a Randall-Sundrum Brane-World Effective Potential Influences Inflation Physics
Beckwith, A. W.
2007-01-30
In string theory, even when there are ten to the thousand power vacuum states, does inflation produce overwhelmingly one preferred type of vacuum state? We respond affirmatively to questions whether existence of graviton production is confirmable using present detector methodology. We use an explicit Randall-Sundrum brane-world effective potential as congruent with an inflationary quadratic potential start. This occurs after Bogomolnyi inequality eliminates need for ad hoc assumption of axion wall mass high temperature related disappearing. Graviton production has explicit links with a five-dimensional brane-world negative cosmological constant and a four-dimensional positive valued cosmological constant, whose temperature dependence permits an early universe graviton production activity burst. We show how di quarks, wave functions, and various forms tie into the Wheeler-De Witt equation. This permits investigating a discretized quantum bounce and a possible link to the initial phases of present universe's evolution with a prior universe's collapse to the bounce point--the initial starting point to inflationary expansion. This opens a possibility of realistically investigating gravitons as part of a space propulsion system and dealing with problems from a beam of gravity waves, which would create a g-force because the geodestic structure is near field. It can be applied to existing and to new space propulsion concepts.
Two-branes with variable tension model and the effective Newtonian constant
Hoff da Silva, J. M.
2011-03-15
It is shown that, in the two brane time variation model framework, if the hidden brane tension varies according to the phenomenological Eoetvoes law, the visible brane tension behavior is such that its time derivative is negative in the past and positive after a specific time of cosmological evolution. This behavior is interpreted in terms of a useful mechanical system analog and its relation with the variation of the Newtonian (effective) gravitational ''constant'' is explored.
Brane world corrections to the scalar vacuum force in the Randall-Sundrum II-p scenario
Linares, Roman; Morales-Tecotl, Hugo A.; Pedraza, Omar
2008-09-15
Vacuum force is an interesting low energy test for brane worlds due to its dependence on field's modes and its role in submillimeter gravity experiments. In this work, we generalize a previous model example: the scalar field vacuum force between two parallel plates lying in the brane of a Randall-Sundrum scenario extended by p compact dimensions (RSII-p). Upon use of Green's function technique, for the massless scalar field, the 4D force is obtained from a zero mode while leading order corrections due to the noncompact dimension turn out attractive and depend on the separation between plates as l{sup -(6+p)}. For the massive scalar field, a quasilocalized mode yields the 4D force with attractive corrections behaving like l{sup -(10+p)}. Corrections are negligible with respect to 4D force for anti-de Sitter (AdS{sub (5+p)}) radius much less than {approx}10{sup -6} m. In the massless case we also determined, numerically, the corrections due to compact dimensions. To avoid conflict with experimental data we get R{<=}0.4 {mu}m, 0.3 {mu}m for the cases p=1, 2, respectively. Although the p=0 case is not physically viable due to the different behavior in regard to localization for the massless scalar and electromagnetic fields it yields a useful comparison between the dimensional regularization and Green's function techniques as we describe in the discussion.
Lepton flavour violation in RS models with a brane- or nearly brane-localized Higgs
NASA Astrophysics Data System (ADS)
Beneke, M.; Moch, P.; Rohrwild, J.
2016-05-01
We perform a comprehensive study of charged lepton flavour violation in Randall-Sundrum (RS) models in a fully 5D quantum-field-theoretical framework. We consider the RS model with minimal field content and a "custodially protected" extension as well as three implementations of the IR-brane localized Higgs field, including the non-decoupling effect of the KK excitations of a narrow bulk Higgs. Our calculation provides the first complete result for the flavour-violating electromagnetic dipole operator in Randall-Sundrum models. It contains three contributions with different dependence on the magnitude of the anarchic 5D Yukawa matrix, which can all be important in certain parameter regions. We study the typical range for the branching fractions of μ → eγ, μ → 3 e, μN → eN as well as τ → μγ, τ → 3 μ and the electron electric dipole moment by a numerical scan in both the minimal and the custodial RS model. The combination of μ → eγ and μN → eN currently provides the most stringent constraint on the parameter space of the model. A typical lower limit on the KK scale T is around 2 TeV in the minimal model (up to 4 TeV in the bulk Higgs case with large Yukawa couplings), and around 4 TeV in the custodially protected model, which corresponds to a mass of about 10 TeV for the first KK excitations, far beyond the lower limit from the non-observation of direct production at the LHC.
Brane-world and loop cosmology from a gravity-matter coupling perspective
NASA Astrophysics Data System (ADS)
Olmo, Gonzalo J.; Rubiera-Garcia, D.
2015-01-01
We show that the effective brane-world and the loop quantum cosmology background expansion histories can be reproduced from a modified gravity perspective in terms of an f (R) gravity action plus a g (R) term non-minimally coupled with the matter Lagrangian. The reconstruction algorithm that we provide depends on a free function of the matter density that must be specified in each case and allows to obtain analytical solutions always. In the simplest cases, the function f (R) is quadratic in the Ricci scalar, R, whereas g (R) is linear. Our approach is compared with recent results in the literature. We show that working in the Palatini formalism there is no need to impose any constraint that keeps the equations second-order, which is a key requirement for the successful implementation of the reconstruction algorithm.
Probing topologically charged black holes on brane worlds in f({R}) bulk
NASA Astrophysics Data System (ADS)
Kuerten, André M.; da Rocha, Roldão
2016-07-01
The perihelion precession, the deflection of light and the radar echo delay are classical tests of General Relativity here used to probe brane-world topologically charged black holes in a f(R) bulk. Moreover, such tests are used to constrain the parameter that arises from the Shiromizu-Maeda-Sasaki procedure applied to a f(R) bulk. Observational data constrain the possible values of the tidal charge parameter and the effective cosmological constant in this context. We show that the observational/experimental data for both perihelion precession and radar echo delay make the black hole parameters to be more strict than the ones for the DMPR black hole. Moreover, the deflection of light constrains the tidal charge parameter similarly as the DMPR black holes, due to a peculiarity in the equation of motion.
Higher-dimensional bulk wormholes and their manifestations in brane worlds
Rodrigo, Enrico
2006-11-15
There is nothing to prevent a higher-dimensional anti-de Sitter bulk spacetime from containing various other branes in addition to hosting our universe, presumed to be a positive-tension 3-brane. In particular, it could contain closed, microscopic branes that form the boundary surfaces of void bubbles and thus violate the null energy condition in the bulk. The possible existence of such micro branes can be investigated by considering the properties of the ground state of a pseudo-Wheeler-DeWitt equation describing brane quantum dynamics in minisuperspace. If they exist, a concentration of these micro branes could act as a fluid of exotic matter able to support macroscopic wormholes connecting otherwise-distant regions of the bulk. Were the brane constituting our universe to expand into a region of the bulk containing such higher-dimensional macroscopic wormholes, they would likely manifest themselves in our brane as wormholes of normal dimensionality, whose spontaneous appearance and general dynamics would seem inexplicably peculiar. This encounter could also result in the formation of baby universes of a particular type.
Bulk Casimir densities and vacuum interaction forces in higher dimensional brane models
Saharian, Aram A.
2006-03-15
Vacuum expectation value of the energy-momentum tensor and the vacuum interaction forces are evaluated for a massive scalar field with general curvature coupling parameter satisfying Robin boundary conditions on two codimension one parallel branes embedded in (D+1)-dimensional background spacetime AdS{sub D{sub 1}}{sub +1}x{sigma} with a warped internal space {sigma}. The vacuum energy-momentum tensor is presented as a sum of boundary-free, single brane-induced, and interference parts. The latter is finite everywhere including the points on the branes and is exponentially small for large interbrane distances. Unlike to the purely anti-de Sitter (AdS) bulk, the part induced by a single brane, in addition to the distance from the brane, depends also on the position of the brane in the bulk. The asymptotic behavior of this part is investigated for the points near the brane and for the position of the brane close to the AdS horizon and AdS boundary. The contribution of Kaluza-Klein modes along {sigma} is discussed in various limiting cases. The vacuum forces acting on the branes are presented as a sum of the self-action and interaction terms. The first one contains well-known surface divergences and needs a further renormalization. The interaction forces between the branes are finite for all nonzero interbrane distances and are investigated as functions of the brane positions and the length scale of the internal space. We show that there is a region in the space of parameters in which these forces are repulsive for small distances and attractive for large distances. As an example, the case {sigma}=S{sup D{sub 2}} is considered. An application to the higher dimensional generalization of the Randall-Sundrum brane model with arbitrary mass terms on the branes is discussed. Taking the limit with infinite curvature radius for the AdS bulk, from the general formulas we derive the results for two parallel Robin plates on background of R{sup (D{sub 1},1)}x{sigma} spacetime.
Revolving D-branes and spontaneous gauge-symmetry breaking
NASA Astrophysics Data System (ADS)
Iso, Satoshi; Kitazawa, Noriaki
2015-12-01
We propose a new mechanism of spontaneous gauge-symmetry breaking in the world-volume theory of revolving D-branes around a fixed point of orbifolds. In this paper, we consider a simple model of the T^6/Z_3 orbifold on which we put D3-branes, D7-branes, and their anti-branes. The configuration breaks supersymmetry, but the Ramond-Ramond tadpole cancellation conditions are satisfied. A set of three D3-branes at an orbifold fixed point can separate from the point, but, when they move perpendicular to the anti-D7-branes put on the fixed point, they are pulled back due to an attractive interaction between the D3- and anti-D7-branes. In order to stabilize the separation of the D3-branes at nonzero distance, we consider revolution of the D3-branes around the fixed point. Then the gauge symmetry on the D3-branes is spontaneously broken, and the rank of the gauge group is reduced. The distance can be set at will by appropriately choosing the angular momentum of the revolving D3-branes, which should be determined by the initial condition of the cosmological evolution of the D-brane configurations. The distance corresponds to the vacuum expectation values of brane moduli fields in the world-volume theory and, if it is written as M/M_s^2 in terms of the string scale M_s, the scale of gauge-symmetry breaking is given by M. Angular momentum conservation of revolving D3-branes assures the stability of the scale M against M_s.
From the currency rate quotations onto strings and brane world scenarios
NASA Astrophysics Data System (ADS)
Horváth, D.; Pincak, R.
2012-11-01
In the paper, we study the projections of the real exchange rate dynamics onto the string-like topology. Our approach is inspired by the contemporary movements in the string theory. The string map of data is defined here by the boundary conditions, characteristic length, real valued and the method of redistribution of information. As a practical matter, this map represents the detrending and data standardization procedure. We introduced maps onto 1-end-point and 2-end-point open strings that satisfy the Dirichlet and Neumann boundary conditions. The questions of the choice of extra-dimensions, symmetries, duality and ways to the partial compactification are discussed. Subsequently, we pass to higher dimensional and more complex objects. The 2D-Brane was suggested which incorporated bid-ask spreads. Polarization by the spread was considered which admitted analyzing arbitrage opportunities on the market where transaction costs are taken into account. The model of the rotating string which naturally yields calculation of angular momentum is suitable for tracking of several currency pairs. The systematic way which allows one suggest more structured maps suitable for a simultaneous study of several currency pairs was analyzed by means of the Gâteaux generalized differential calculus. The effect of the string and brane maps on test data was studied by comparing their mean statistical characteristics. The study revealed notable differences between topologies. We review the dependence on the characteristic string length, mean fluctuations and properties of the intra-string statistics. The study explores the coupling of the string amplitude and volatility. The possible utilizations of the string theory approach in financial markets are slight.
Gibbons-Hawking boundary terms and junction conditions for higher-order brane gravity models
Balcerzak, Adam; Dabrowski, Mariusz P. E-mail: mpdabfz@wmf.univ.szczecin.pl
2009-01-15
We derive the most general junction conditions for the fourth-order brane gravity constructed of arbitrary functions of curvature invariants. We reduce these fourth-order theories to second order theories at the expense of introducing new scalar and tensor fields - the scalaron and the tensoron. In order to obtain junction conditions we apply the method of generalized Gibbons-Hawking boundary terms which are appended to the appropriate actions. After assuming the continuity of the scalaron and the tensoron on the brane, we recover junction conditions for such general brane universe models previously obtained by different methods. The derived junction conditions can serve studying the cosmological implications of the higher-order brane gravity models.
Cosmic constraint to DGP brane model: Geometrical and dynamical perspectives
Xu Lixin; Wang Yuting
2010-08-15
In this paper, the Dvali-Gabadadze-Porrati (DGP) brane model is confronted by current cosmic observational data sets from geometrical and dynamical perspectives. On the geometrical side, the recently released Union2 557 of type Ia supernovae (SN Ia), the baryon acoustic oscillation from the Sloan Digital Sky Survey and the Two Degree Galaxy Redshift Survey (transverse and radial to line-of-sight data points), the cosmic microwave background measurement given by the seven-year Wilkinson Microwave Anisotropy Probe observations [shift parameters R, l{sub a}(z{sub *}) and redshift at the last scatter surface z{sub *}], ages of high redshifts galaxies, i.e., the lookback time and the high redshift gamma ray bursts are used. On the dynamical side, data points about the growth function of matter linear perturbations are used. Using the same data set combination, we also constrain the flat {Lambda}CDM model as a comparison. The results show that current geometrical and dynamical observational data sets much favor the flat {Lambda}CDM model and the departure from it is above 4{sigma}(6{sigma}) for the spatially flat DGP model with (without) SN systematic errors. The consistence of growth function data points is checked in terms of a relative departure of redshift-distance relation.
World-sheet duality for D-branes with travelling waves
NASA Astrophysics Data System (ADS)
Bachas, Constantin P.; Gaberdiel, Matthias R.
2004-03-01
We study D-branes with plane waves of arbitrary profiles as examples of time-dependent backgrounds in string theory. We show how to reproduce the quantum mechanical (one-to-one) open-string S-matrix starting from the closed-string boundary state for the D-branes, thereby establishing the channel duality of this calculation. The required Wick rotation to a lorentzian worldsheet singles out as `prefered' time coordinate the open-string light-cone time.
No Swiss-cheese universe on the brane
NASA Astrophysics Data System (ADS)
Gergely, László Á.
2005-04-01
We study the possibility of brane-world generalization of the Einstein-Straus Swiss-cheese cosmological model. We find that the modifications induced by the brane-world scenario are excessively restrictive. At a first glance only the motion of the boundary is modified and the fluid in the exterior region is allowed to have pressure. The general relativistic Einstein-Straus model emerges in the low density limit. However by imposing that the central mass in the Schwarzschild voids is constant, a combination of the junction conditions and modified cosmological evolution leads to the conclusion that the brane is flat. Thus no generic Swiss-cheese universe can exist on the brane. The conclusion is not altered by the introduction of a cosmological constant in the FLRW regions. This shows that although allowed in the low density limit, the Einstein-Straus universe cannot emerge from cosmological evolution in the brane-world scenario.
Dynamics of scalar-tensor cosmology from a Randall-Sundrum two-brane model
Jaerv, Laur; Kuusk, Piret; Saal, Margus
2007-01-15
We consider a Randall-Sundrum two-brane cosmological model in the low energy gradient expansion approximation by Kanno and Soda. It is a scalar-tensor theory with a specific coupling function and a specific potential. Upon introducing the Friedmann-Lemaitre-Robertson-WalkerFLRW metric and perfect fluid matter on both branes in the Jordan frame, the effective dynamical equation for the A-brane (our Universe) scale factor decouples from the scalar field and B-brane matter leaving only a nonvanishing integration constant (the dark radiation term). We find exact solutions for the A-brane scale factor for four types of matter: cosmological constant, radiation, dust, and cosmological constant plus radiation. We perform a complementary analysis of the dynamics of the scalar field (radion) using phase space methods and examine convergence towards the limit of general relativity. In particular, we find that radion stabilizes at a certain finite value for suitable negative matter densities on the B-brane. Observational constraints from solar system experiments (PPN) and primordial nucleosynthesis (BBN) are also briefly discussed.
Super-Lie n-algebra extensions, higher WZW models and super-p-branes with tensor multiplet fields
NASA Astrophysics Data System (ADS)
Fiorenza, Domenico; Sati, Hisham; Schreiber, Urs
2015-12-01
We formalize higher-dimensional and higher gauge WZW-type sigma-model local prequantum field theory, and discuss its rationalized/perturbative description in (super-)Lie n-algebra homotopy theory (the true home of the "FDA"-language used in the supergravity literature). We show generally how the intersection laws for such higher WZW-type σ-model branes (open brane ending on background brane) are encoded precisely in (super-)L∞-extension theory and how the resulting "extended (super-)space-times" formalize spacetimes containing σ-model brane condensates. As an application we prove in Lie n-algebra homotopy theory that the complete super-p-brane spectrum of superstring/M-theory is realized this way, including the pure σ-model branes (the "old brane scan") but also the branes with tensor multiplet worldvolume fields, notably the D-branes and the M5-brane. For instance the degree-0 piece of the higher symmetry algebra of 11-dimensional (11D) spacetime with an M2-brane condensate turns out to be the "M-theory super-Lie algebra". We also observe that in this formulation there is a simple formal proof of the fact that type IIA spacetime with a D0-brane condensate is the 11D sugra/M-theory spacetime, and of (prequantum) S-duality for type IIB string theory. Finally we give the non-perturbative description of all this by higher WZW-type σ-models on higher super-orbispaces with higher WZW terms in stacky differential cohomology.
Hashimoto, Koji; Ho, Pei-Ming; Wang, John E
2003-04-11
We derive effective actions for "spacelike branes" (S-branes) and find a solution describing the formation of fundamental strings in the rolling tachyon background. The S-brane action is a Dirac-Born-Infeld action for Euclidean world volumes defined in the context of time-dependent tachyon condensation of non-BPS (Bogomol'nyi-Prasad-Sommerfield) branes. It includes gauge fields and, in particular, a scalar field associated with translation along the time direction. We show that the BIon spike solutions constructed in this system correspond to the production of a confined electric flux tube (a fundamental string) at late time of the rolling tachyon.
Brane models with a Ricci-coupled scalar field
Bogdanos, C.; Dimitriadis, A.; Tamvakis, K.
2006-08-15
We consider the problem of a scalar field, nonminimally coupled to gravity through a -{xi}{phi}{sup 2}R term, in the presence of a brane. Exact solutions, for a wide range of values of the coupling parameter {xi}, for both {phi}-dependent and {phi}-independent brane tension, are derived and their behavior is studied. In the case of a Randall-Sundrum geometry, a class of the resulting scalar field solutions exhibits a folded-kink profile. We go beyond the Randall-Sundrum geometry studying general warp factor solutions in the presence of a kink scalar. Analytic and numerical results are provided for the case of a brane or for smooth geometries, where the scalar field acts as a thick brane. It is shown that finite geometries with warp factors that asymptotically decrease exponentially are realizable for a wide range of parameter values. We also study graviton localization in our setup and find that the localizing potential for gravitons with the characteristic volcanolike profile develops a local maximum located at the origin for high values of the coupling {xi}.
Intersecting S-branes and an anisotropic models of dark energy
Orlov, Dmitry G.
2008-10-10
We consider an anisotropic S-brane (space-like hyperbrane) solutions in application to cosmological model. The gravity-dilaton-antisymmetric form field initial model is compactified of extra space and we get four dimensional space (space of three dimensional S-brane plus time coordinate). Dynamic of obtained model depends from the dynamic of compactified space. In all cases of extra space in such cosmological models the primordial inflationary phase was obtained. Focus attention to the question of an anisotropy of space and an improving a number of e-folding.
Multiresonance modes in sine-Gordon brane models
NASA Astrophysics Data System (ADS)
Cruz, W. T.; Maluf, R. V.; Dantas, D. M.; Almeida, C. A. S.
2016-12-01
In this work, we study the localization of the vector gauge field in two five-dimensional braneworlds generated by scalar fields coupled to gravity. The sine-Gordon like potentials are employed to produce different thick brane setups. A zero mode localized is obtained, and we show the existence of reverberations with the wave solutions indicating a quasi-localized massive mode. More interesting results are achieved when we propose a double sine-Gordon potential to the scalar field. The resulting thick brane shows a more detailed topology with the presence of an internal structure composed by two kinks. The massive spectrum of the gauge field is revalued on this scenario revealing the existence of various resonant modes. Furthermore, we compute the corrections to Coulomb law coming from these massive KK vector modes in these thick scenarios, which is concluded that the dilaton parameter regulates these corrections.
Regarding the radion in Randall-Sundrum models with brane curvature
NASA Astrophysics Data System (ADS)
Dillon, Barry M.; George, Damien P.; McDonald, Kristian L.
2016-09-01
In Randall-Sundrum models, one typically expects the radion to be the lightest new "gravity" state, as it is dual to a composite pseudo-Goldstone boson associated with conformal symmetry breaking in the IR. Here, we investigate the effects of localized brane curvature on the properties of the radion in Goldberger-Wise stabilized Randall-Sundrum models. We point out that both the radion mass and coupling to brane matter are sensitive to the brane curvature. Radion/Higgs kinetic mixing, via an IR-localized nonminimal coupling to the Higgs, is also investigated, in relation to the ghostlike radion that can occur for O (10 ) values of the IR curvature (as required to significantly suppress the first Kaluza-Klein graviton mass). We also discuss a class of IR-localized terms involving the radion. Basic comments regarding the dual four-dimensional theory are offered.
NASA Astrophysics Data System (ADS)
Bazeia, D.; Lima, Elisama E. M.; Losano, L.
2017-02-01
This work reports on models described by two real scalar fields coupled with gravity in the five-dimensional spacetime, with a warped geometry involving one infinite extra dimension. Through a mechanism that smoothly changes a thick brane into a hybrid brane, one investigates the appearance of hybrid branes hosting internal structure, characterized by the splitting on the energy density and the volcano potential, induced by the parameter which controls interactions between the two scalar fields. In particular, we investigate distinct symmetric and asymmetric hybrid brane scenarios.
Quantum self-consistency of AdS×Σ brane models
NASA Astrophysics Data System (ADS)
Flachi, Antonino; Pujolàs, Oriol
2003-07-01
Continuing our previous work, we consider a class of higher dimensional brane models with the topology of AdSD1+1×Σ, where Σ is a one-parameter compact manifold and two branes of codimension one are located at the orbifold fixed points. We consider a setup where such a solution arises from Einstein-Yang-Mills theory and evaluate the one-loop effective potential induced by gauge fields and by a generic bulk scalar field. We show that this type of brane model resolves the gauge hierarchy between the Planck and electroweak scales through redshift effects due to the warp factor a=e-πkr. The value of a is then fixed by minimizing the effective potential. We find that, as in the Randall-Sundrum case, the gauge field contribution to the effective potential stabilizes the hierarchy without fine-tuning as long as the Laplacian ΔΣ on Σ has a zero eigenvalue. Scalar fields can stabilize the hierarchy depending on the mass and the nonminimal coupling. We also address the quantum self-consistency of the solution, showing that the classical brane solution is not spoiled by quantum effects.
Extended Holography: Double-Trace Deformation and Brane-Induced Gravity Models
NASA Astrophysics Data System (ADS)
Barvinsky, A. O.
2017-03-01
We put forward a conjecture that for a special class of models - models of the double-trace deformation and brane-induced gravity types - the principle of holographic dualitiy can be extended beyond conformal invariance and anti-de Sitter (AdS) isometry. Such an extension is based on a special relation between functional determinants of the operators acting in the bulk and on the boundary.
Higgs-gluon coupling in warped extra dimensional models with brane kinetic terms
NASA Astrophysics Data System (ADS)
Dey, Ujjal Kumar; Ray, Tirtha Sankar
2016-01-01
Warped models with the Higgs confined to the weak brane and the gauge and matter fields accessing the AdS5 bulk provide a viable setting to address the gauge hierarchy problem. Brane kinetic terms for the bulk fields are known to ease some of the tensions of these models with precision electroweak observables and flavor constraints. We study the loop-driven Higgs coupling to the gluons that are relevant to the Higgs program at the LHC, in this scenario. We demonstrate a partial cancellation in the contribution of the fermionic Kaluza-Klein (KK) towers within such framework relatively independent of the 5D parameters. The entire dependence of this coupling on the new physics arises from the mixing between the Standard Model states and the KK excitations. We find that the present precision in measurement of these couplings can lead to a constraint on the KK scale up to 1.2 TeV at 95% confidence level.
A Deconstruction Lattice Description of the D1/D5 Brane World-Volume Gauge Theory
Giedt, Joel
2011-01-01
I genermore » alize the deconstruction lattice formulation of Endres and Kaplan to two-dimensional super-QCD with eight supercharges, denoted by (4,4), and bifundamental matter. I specialize to a particularly interesting (4,4) gauge theory, with gauge group U ( N c ) × U ( N f ) , and U ( N f ) being weakly gauged. It describes the infrared limit of the D1/D5 brane system, which has been studied extensively as an example of the AdS 3 /CFT 2 correspondence. The construction here preserves two supercharges exactly and has a lattice structure quite similar to that which has previously appeared in the deconstruction approach, that is, site, link, and diagonal fields with both the Bose and Fermi statistics. I remark on possible applications of the lattice theory that would test the AdS 3 /CFT 2 correspondence, particularly one that would exploit the recent worldsheet instanton analysis of Chen and Tong.« less
Multidimensional Gravitational Models: Fluxbrane and S-Brane Solutions with Polynomials
NASA Astrophysics Data System (ADS)
Ivashchuk, V. D.; Melnikov, V. N.
2007-06-01
Main results in obtaining exact solutions for multidimensional models and their application to solving main problems of modern cosmology and black hole physics are described. Some new results on composite fluxbrane and S-brane solutions for a wide class of intersection rules are presented. These solutions are defined on a product manifold R* × M1 × ... × Mn which contains n Ricci-flat spaces M1,...,Mn with 1-dimensional R* and M1. They are defined up to a set of functions obeying non-linear differential equations equivalent to Toda-type equations with certain boundary conditions imposed. Exact solutions corresponding to configurations with two branes and intersections related to simple Lie algebras C2 and G2 are obtained. In these cases the functions Hs(z), s = 1, 2, are polynomials of degrees: (3, 4) and (6, 10), respectively, in agreement with a conjecture suggested earlier. Examples of simple S-brane solutions describing an accelerated expansion of a certain factor-space are given explicitely.
NASA Astrophysics Data System (ADS)
Sahni, Varun
2016-07-01
The Phantom brane is based on the normal branch of the DGP braneworld. It possesses a phantom-like equation of state at late times, but no big-rip future singularity. In this braneworld, the cosmological constant is dynamically screened at late times. Consequently it provides a good fit to SDSS DR11 measurements of H(z) at high redshifts. We obtain a closed system of equations for scalar perturbations on the brane. Perturbations of radiation, matter and the Weyl fluid are self-consistently evolved until the present epoch. We find that the late time growth of density perturbations on the brane proceeds at a faster rate than in ΛCDM. Additionally, the gravitational potentials φ, Ψ evolve differently on the brane than in ΛCDM, for which φ = Ψ. On the Brane, by contrast, the ratio φ/Ψ exceeds unity during the late matter dominated epoch (z ≤ 50). These features emerge as smoking gun tests of phantom brane cosmology and allow predictions of this scenario to be tested against observations of galaxy clustering and large scale structure. The phantom brane also displays a pole in its equation of state, which provides a key test of this dark energy model.
Inflation from Intersecting Branes
Leblond, Louis
2007-11-20
We propose a new scenario for D-term inflation which appears quite straightforwardly in the open string sector of intersecting brane models. We take the inflaton to be a chiral field in a bifundamental representation of the hidden sector and we argue that a sufficiently flat potential can be brane engineered. This type of model generically predicts a near gaussian red spectrum with negligible tensor modes.
Chern-Simons supersymmetric branes
NASA Astrophysics Data System (ADS)
Mora, Pablo
2001-01-01
The purpose of this paper is to continue the study of the class of models proposed in a previous letter. The model corresponds to a system of branes of diverse dimensionalities with Chern-Simons actions for a supergroup, embedded in a background described also by a Chern-Simons action. The model treats the background and the branes on an equal footing, providing a "brane-target space democracy". Here we suggest some possible extensions of the original model, and discuss its equations of motion, as well as the issue of currents and charges carried by the branes. We also discuss the relationship with M-theory and Superstring theory.
McGreevy, John Austen; /Stanford U., Phys. Dept.
2005-07-06
This thesis is a study of D-branes in string compactifications. In this context, D-branes are relevant as an important component of the nonperturbative spectrum, as an incisive probe of these backgrounds, and as a natural stringy tool for localizing gauge interactions. In the first part of the thesis, we discuss half-BPS D-branes in compactifications of type II string theory on Calabi-Yau threefolds. The results we describe for these objects are pertinent both in their role as stringy brane-worlds, and in their role as solitonic objects. In particular, we determine couplings of these branes to the moduli determining the closed-string geometry, both perturbatively and non-perturbatively in the worldsheet expansion. We provide a local model for transitions in moduli space where the BPS spectrum jumps, and discuss the extension of mirror symmetry between Calabi-Yau manifolds to the case when D-branes are present. The next section is an interlude which provides some applications of D-branes to other curved backgrounds of string theory. In particular, we discuss a surprising phenomenon in which fundamental strings moving through background Ramond-Ramond fields dissolve into large spherical D3-branes. This mechanism is used to explain a previously-mysterious fact discovered via the AdS-CFT correspondence. Next, we make a connection between type IIA string vacua of the type discussed in the first section and M-theory compactifications on manifolds of G{sub 2} holonomy. Finally we discuss constructions of string vacua which do not have large radius limits. In the final part of the thesis, we develop techniques for studying the worldsheets of open strings ending on the curved D-branes studied in the first section. More precisely, we formulate a large class of massive two-dimensional gauge theories coupled to boundary matter, which flow in the infrared to the relevant boundary conformal field theories. Along with many other applications, these techniques are used to describe
Lehners, Jean-Luc
2007-11-20
In a braneworld description of our universe, we must allow for the possibility of having dynamical branes around the time of the big bang. Some properties of such domain walls in motion are discussed here, for example the ability of negative-tension domain walls to bounce off spacetime singularities and the consequences for cosmological perturbations. In this context, we will also review a colliding branes solution of heterotic M-theory that has been proposed as a model for early universe cosmology.
First-order formalism for flat branes in generalized N-field models
NASA Astrophysics Data System (ADS)
Bazeia, D.; Lobão, A. S., Jr.; Losano, L.; Menezes, R.
2013-08-01
This work deals with braneworld scenarios obtained from N real scalar fields, whose dynamics is generalized to include higher-order power in the derivative of the fields. For the scalar fields being driven by nonstandard dynamics, we show how a first-order formalism can be obtained for a flat brane in the presence of several fields. We then illustrate our findings, investigating distinct potentials with one and two fields, and obtaining stable standard and compact solutions in the braneworld theory. In particular, we have found different models describing the very same warp factor.
Spherically symmetric thick branes cosmological evolution
NASA Astrophysics Data System (ADS)
Bernardini, A. E.; Cavalcanti, R. T.; da Rocha, Roldão
2015-01-01
Spherically symmetric time-dependent solutions for the 5D system of a scalar field canonically coupled to gravity are obtained and identified as an extension of recent results obtained by Ahmed et al. (JHEP 1404:061. arXiv:1312.3576 [hep-th], 2014). The corresponding cosmology of models with regularized branes generated by such a 5D scalar field scenario is also investigated. It has been shown that the anisotropic evolution of the warp factor and consequently the Hubble like parameter are both driven by the radial coordinate on the brane, which leads to an emergent thick brane-world scenario with spherically symmetric time dependent warp factor. Meanwhile, the separability of variables depending on fifth dimension, , which is exhibited by the equations of motion, allows one to recover the extra dimensional profiles obtained in Ahmed et al. (2014), namely the extra dimensional part of the scale (warp) factor and the scalar field dependence on . Therefore, our results are mainly concerned with the time dependence of a spherically symmetric warp factor. Besides evincing possibilities for obtaining asymmetric stable brane-world scenarios, the extra dimensional profiles here obtained can also be reduced to those ones investigated in Ahmed et al. (2014).
Flavor condensates in brane models and dark energy
Mavromatos, Nick E.; Sarkar, Sarben; Tarantino, Walter
2009-10-15
In the context of a microscopic model of string-inspired foam, in which foamy structures are provided by brany pointlike defects (D-particles) in space-time, we discuss flavor mixing as a result of flavor nonpreserving interactions of (low-energy) fermionic stringy matter excitations with the defects. Such interactions involve splitting and capture of the matter string state by the defect, and subsequent re-emission. As a result of charge conservation, only electrically neutral matter can interact with the D-particles. Quantum fluctuations of the D-particles induce a nontrivial space-time background; in some circumstances, this could be akin to a cosmological Friedman-Robertson-Walker expanding-universe, with weak (but nonzero) particle production. Furthermore, the D-particle medium can induce an Mikheyev-Smirnov-Wolfenstein-type effect. We have argued previously, in the context of bosons, that the so-called flavor vacuum is the appropriate state to be used, at least for low-energy excitations, with energies/momenta up to a dynamically determined cutoff scale. Given the intriguing mass scale provided by neutrino flavor mass differences from the point of view of dark energy, we evaluate the flavor-vacuum expectation value (condensate) of the stress-energy tensor of the 1/2-spin fields with mixing in an effective-low-energy quantum field theory in this foam-induced curved space-time. We demonstrate, at late epochs of the Universe, that the fermionic vacuum condensate behaves as a fluid with negative pressure and positive energy; however, the equation of state has w{sub fermion}>-1/3 and so the contribution of the fermion-fluid flavor vacuum alone could not yield accelerating universes. Such contributions to the vacuum energy should be considered as (algebraically) additive to the flavored boson contributions, evaluated in our previous works; this should be considered as natural from (broken) target-space supersymmetry that characterizes realistic superstring
750 GeV diphoton excesses in a realistic D-brane model
NASA Astrophysics Data System (ADS)
Li, Tianjun; Maxin, James A.; Mayes, Van E.; Nanopoulos, Dimitri V.
2016-07-01
We study the diphoton excesses near 750 GeV recently reported by the ATLAS and CMS collaborations within the context of a phenomenologically interesting intersecting/magnetized D-brane model on a toroidal orientifold. It is shown that the model contains a Standard Model singlet scalar as well as vector-like quarks and leptons. In addition, it is shown that the singlet scalar has Yukawa couplings with vector-like quarks and leptons such that it may be produced in proton-proton collisions via gluon fusion as well as decay to diphotons through loops involving the vector-like quarks. Moreover, the required vector-like quarks and leptons may appear in complete S U (5 ) multiplets so that gauge coupling unification may be maintained. Finally, it is shown that the diphoton signal may be accommodated within the model.
Rajaraman, Arvind
2003-06-02
We suggest a duality invariant formula for the entropy and temperature of nonextreme black holes in supersymmetric string theory. The entropy is given in terms of the duality invariant parameter of the deviation from extremality and 56 SU(8) covariant central charges. It interpolates between the entropies of Schwarzschild solution and extremal solutions with various amount of unbroken supersymmetries and therefore serves for classification of black holes in supersymmetric string theories. We introduce the second auxiliary 56 via E(7) symmetric constraint. The symmetric and antisymmetric combinations of these two multiplets are related via moduli to the corresponding two fundamental representations of E(7): brane and anti-brane ''numbers.'' Using the CPT as well as C symmetry of the entropy formula and duality one can explain the mysterious simplicity of the non-extreme black hole area formula in terms of branes and anti-branes.
NASA Astrophysics Data System (ADS)
Budhwani, Karim Ismail
The tremendous quality of life impact notwithstanding, cardiovascular diseases and Cancer add up to over US$ 700bn each year in financial costs alone. Aging and population growth are expected to further expand the problem space while drug research and development remain expensive. However, preclinical costs can be substantially mitigated by substituting animal models with in vitro devices that accurately model human cardiovascular transport. Here we present a novel physiologically relevant lab-on-a-brane that simulates in vivo pressure, flow, strain, and shear waveforms associated with normal and pathological conditions in large and small blood vessels for studying molecular transport across the endothelial monolayer. The device builds upon previously demonstrated integrated microfluidic loop design by: (a) introducing nanoscale pores in the substrate membrane to enable transmembrane molecular transport, (b) transforming the substrate membrane into a nanofibrous matrix for 3D smooth muscle cell (SMC) tissue culture, (c) integrating electrospinning fabrication methods, (d) engineering an invertible sandwich cell culture device architecture, and (e) devising a healthy co-culture mechanism for human arterial endothelial cell (HAEC) monolayer and multiple layers of human smooth muscle cells (HSMC) to accurately mimic arterial anatomy. Structural and mechanical characterization was conducted using confocal microscopy, SEM, stress/strain analysis, and infrared spectroscopy. Transport was characterized using FITC-Dextran hydraulic permeability protocol. Structure and transport characterization successfully demonstrate device viability as a physiologically relevant arterial mimic for testing transendothelial transport. Thus, our lab-on-a-brane provides a highly effective and efficient, yet considerably inexpensive, physiologically relevant alternative for pharmacokinetic evaluation; possibly reducing animals used in pre-clinical testing, clinical trials cost from false
D-branes in Cosmological Backgrounds
NASA Astrophysics Data System (ADS)
Hikida, Yasuaki
2005-12-01
We investigate D-branes in cosmological models. In particuler, we examine Misner space, which can be constructed as a Lorentzian orbifold. This space includes big crunch/big bang singularity and closed time-like curves. We compute annulas amplitudes for open strings on D0-brane and D1-brane and find imaginary part of the amplitudes. The imaginary parts are interpreted as the rate of open string pair creation on D0-brane and as the emission rate of closed strings from D1-brane. We also compute 2-->2 scattering amplitude of open strings and examine its divergence structure.
Brane Effective Actions, Kappa-Symmetry and Applications
NASA Astrophysics Data System (ADS)
Simón, Joan
2012-12-01
This is a review on brane effective actions, their symmetries and some of their applications. Its first part covers the Green-Schwarz formulation of single M- and D-brane effective actions focusing on kinematical aspects: the identification of their degrees of freedom, the importance of world volume diffeomorphisms and kappa symmetry to achieve manifest spacetime covariance and supersymmetry, and the explicit construction of such actions in arbitrary on-shell supergravity backgrounds. Its second part deals with applications. First, the use of kappa symmetry to determine supersymmetric world volume solitons. This includes their explicit construction in flat and curved backgrounds, their interpretation as Bogomol’nyi-Prasad-Sommerfield (BPS) states carrying (topological) charges in the supersymmetry algebra and the connection between supersymmetry and Hamiltonian BPS bounds. When available, I emphasise the use of these solitons as constituents in microscopic models of black holes. Second, the use of probe approximations to infer about the non-trivial dynamics of strongly-coupled gauge theories using the anti de Sitter/conformal field theory (AdS/CFT) correspondence. This includes expectation values of Wilson loop operators, spectrum information and the general use of D-brane probes to approximate the dynamics of systems with small number of degrees of freedom interacting with larger systems allowing a dual gravitational description. Its final part briefly discusses effective actions for N D-branes and M2-branes. This includes both Super-Yang-Mills theories, their higher-order corrections and partial results in covariantising these couplings to curved backgrounds, and the more recent supersymmetric Chern-Simons matter theories describing M2-branes using field theory, brane constructions and 3-algebra considerations.
Shortcuts in cosmological branes
NASA Astrophysics Data System (ADS)
Abdalla, Elcio; Casali, Adenauer G.; Cuadros-Melgar, Bertha
2004-02-01
We consider a dynamical membrane world in a space-time with scalar bulk matter described by domain walls, as well as a dynamical membrane world in empty Anti de Sitter space-time. Using the solutions to Einstein equations and boundary conditions we investigate the possibility of having shortcuts for gravitons leaving the membrane and returning subsequently. In comparison with photons following a geodesic inside the brane we verify that shortcuts exist. For some Universes they are small, but sometimes are quite effective. In the case of matter branes, we argue that at times just before nucleosynthesis the effect is sufficiently large to provide corrections to the inflationary scenario, especially as concerning the horizon problem. This work has been supported by Fundca~o de Amparo à Pesquisa do Estado de Sa~o Paulo (FAPESP) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brazil.
Casimir energies and special dimensions in a toy model for branes
NASA Astrophysics Data System (ADS)
Cohen, Isaac
1988-12-01
We consider a generalization to branes of the old action for the strings without reparamentrization invariance. These actions admit natural supplementary mass-shell conditions. By regularizing the Casimir energies we calculate the special dimensions at which these toy branes show vector massless states in its spectrum. They all turn out to be non-integers. On sabbatical leave from Departamento de Física, Facultad de Ciencias, Universidad Central de Venezuela, Apartado Postal 66961, Caracas 1061A, Venezuela.
Towards geometric D6-brane model building on non-factorisable toroidal ℤ 4-orbifolds
NASA Astrophysics Data System (ADS)
Berasaluce-González, Mikel; Honecker, Gabriele; Seifert, Alexander
2016-08-01
We present a geometric approach to D-brane model building on the non-factorisable torus backgrounds of T 6/ ℤ 4, which are A 3 × A 3 and A 3 × A 1 × B 2. Based on the counting of `short' supersymmetric three-cycles per complex structure vev, the number of physically inequivalent lattice orientations with respect to the anti-holomorphic involution ℛ of the Type IIA/Ωℛ orientifold can be reduced to three for the A 3 × A 3 lattice and four for the A 3 × A 1 × B 2 lattice. While four independent three-cycles on A 3 × A 3 cannot accommodate phenomenologically interesting global models with a chiral spectrum, the eight-dimensional space of three-cycles on A 3 × A 1 × B 2 is rich enough to provide for particle physics models, with several globally consistent two- and four-generation Pati-Salam models presented here.
Anomalies and graded coisotropic branes
NASA Astrophysics Data System (ADS)
Li, Yi
2006-03-01
We compute the anomaly of the axial U(1) current in the A-model on a Calabi-Yau manifold, in the presence of coisotropic branes discovered by Kapustin and Orlov. Our results relate the anomaly-free condition to a recently proposed definition of graded coisotropic branes in Calabi-Yau manifolds. More specifically, we find that a coisotropic brane is anomaly-free if and only if it is gradable. We also comment on a different grading for coisotropic submanifolds introduced recently by Oh.
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
NASA Technical Reports Server (NTRS)
Janson, Siegfried
2017-01-01
A Brane Craft is a membrane spacecraft with solar cells, command and control electronics, communications systems, antennas, propulsion systems, attitude and proximity sensors, and shape control actuators as thin film structures manufactured on 10 micron thick plastic sheets. This revolutionary spacecraft design can have a thickness of tens of microns with a surface area of square meters to maximize area-to-mass ratios for exceptionally low-mass spacecraft. Communications satellites, solar power satellites, solar electric propulsion stages, and solar sails can benefit from Brane Craft design. It also enables new missions that require low-mass spacecraft with exceptionally high delta-V. Active removal of orbital debris from Earth orbit is the target application for this study.
Why do we live in a 4D world: Can cosmology, black holes and branes give an answer?
NASA Astrophysics Data System (ADS)
Zloshchastiev, Konstantin G.
2006-07-01
We derive the general form of the cosmological scalar field potential which is compatible both with the existence of black holes and p-branes related to string/M theory and with multidimensional inflationary cosmology. It is shown that the scalar potential alters non-trivially from dimension to dimension yet always obeys one single equation where the number of spacetime dimensions is a free parameter. Using this equation we formulate an eigenvalue problem for the dimensionality parameter. It turns out that in the low-energy regime of sub-Planckian values of the inflaton field, i.e., when the Universe has cooled and expanded sufficiently enough, the value four arises as the largest admissible (eigen)value of this parameter.
Cosmological evolution of a D-brane
Li Huiquan
2011-03-15
We study the cosmological evolution of a single BPS D-brane coupled to gravity in the absence of potential. When such a D-brane moves in the bulk with nonvanishing velocity, it tends to slow down to zero velocity via mechanisms like gravitational wave leakage to the bulk, losing its kinetic energy to fuel the expansion of the Universe on the D-brane. If the initial velocity of the D-brane is high enough, the Universe on the D-brane undergoes a dustlike stage at early times and an acceleration stage at late times, realizing the original Chaplygin gas model. When the D-brane velocity is initially zero, the D-brane will always remain fixed at some position in the bulk, with the brane tension over the Plank mass squared as a cosmological constant. It is further shown that this kind of fixed brane universe can arise as defects from tachyon inflation on a non-Bogomol'nyi-Prasad-Sommerfeld D-brane with one dimension higher.
Operation of the World Master in the World Modeling System
1987-10-01
This research note describes the operation of the World Master process of the World Modeling System. It is intended to be an aid to maintainers of ... the World Master, and implementors of additional simulated physical properties of the world . The World Master is the core of the World Modeling System
NASA Astrophysics Data System (ADS)
Ivashchuk, V. D.; Melnikov, V. N.
2006-02-01
A family of generalized S-brane solutions with orthogonal intersection rules and n Ricciflat factor spaces in the theory with several scalar fields, antisymmetric forms and multiple scalar potential is considered. Two subclasses of solutions with power-law and exponential behaviour of scale factors are singled out. These subclasses contain sub-families of solutions with accelerated expansion of certain factor spaces. The solutions depend on charge densities of branes, their dimensions and intersections, dilatonic couplings and the number of dilatonic fields. Certain examples of solutions with exponential dependence of one scale factor and constant scale factors of "internal" spaces (e.g. "Freund-Rubin" type solutions) are also considered.
A note on intersections of S-branes with p-branes
Deger, Nihat Sadik
2007-06-15
We first investigate intersections of an S-brane with a single p-brane and show that in addition to the already known solutions, it is possible to place the S-brane so that the radial part of the p-brane is not included in its world volume. This leads to a new set of solutions. Second, we consider intersections of an S-brane with a supersymmetric Dp{sub 1}-Dp{sub 2} intersection and find the list of allowed solutions for both positions of the S-brane. Among them there are D1-D5-S1 and D1-D5-S5 intersections which might be appropriate for studying time dependent AdS/CFT correspondence.
Kleihaus, Burkhard; Kunz, Jutta; Senkbeil, Daniel; Radu, Eugen
2011-05-15
We consider black holes localized on the brane in the Randall-Sundrum infinite braneworld model. These configurations are static and charged with respect to a spherically symmetric, electric Maxwell field living on the brane. We start by attempting to construct vacuum black holes, in which case our conclusions are in agreement with those of Yoshino [J. High Energy Phys. 01 (2009) 068]. Although approximate solutions appear to exist for sufficiently small brane tension, these are likely only numerical artifacts. The qualitative features of the configurations in the presence of a brane U(1) electric field are similar to those in the vacuum case. In particular, we find a systematic unnatural behavior of the metric functions in the asymptotic region in the vicinity of the anti-de Sitter horizon. Our results are most naturally interpreted as evidence for the nonexistence of static, nonextremal charged black holes on the brane. In contrast, extremal black holes are more likely to exist on the brane. We determine their near-horizon form by employing both analytical and numerical methods. For any bulk dimension d>4, we find good agreement between the properties of large extremal black holes and the predictions of general relativity, with calculable subleading corrections.
Fermion localization on a split brane
Chumbes, A. E. R.; Vasquez, A. E. O.; Hott, M. B.
2011-05-15
In this work we analyze the localization of fermions on a brane embedded in five-dimensional, warped and nonwarped, space-time. In both cases we use the same nonlinear theoretical model with a nonpolynomial potential featuring a self-interacting scalar field whose minimum energy solution is a soliton (a kink) which can be continuously deformed into a two-kink. Thus a single brane splits into two branes. The behavior of spin 1/2 fermions wave functions on the split brane depends on the coupling of fermions to the scalar field and on the geometry of the space-time.
Rapid world modelling for robotics
Littile, C.Q.; Wilson, C.W.
1996-04-01
The ability to use an interactive world model, whether it is for robotics simulation or most other virtual graphical environments, relies on the users ability to create an accurate world model. Typically this is a tedious process, requiring many hours to create 3-D CAD models of the surfaces within a workspace. The goal of this ongoing project is to develop usable methods to rapidly build world models of real world workspaces. This brings structure to an unstructured environment and allows graphical based robotics control to be accomplished in a reasonable time frame when traditional CAD modelling is not enough. To accomplish this, 3D range sensors are deployed to capture surface data within the workspace. This data is then transformed into surface maps, or models. A 3D world model of the workspace is built quickly and accurately, without ever having to put people in the environment.
Brane Inflation: From Superstring to Cosmic Strings
Tye, S.-H. Henry
2004-12-10
Brane inflation, where branes move towards each other in the brane world, has been shown to be quite natural in superstring theory. Inflation ends when branes collide and heat the universe, initiating the hot big bang. Cosmic strings (but not domain walls or monopoles) are copiously produced during the brane collision. Using the COBE data on the temperature anisotropy in the cosmic microwave background, the cosmic string tension {mu} is estimated to be around 10 -6 > G{mu} > 10-11, while the present observational bound is 7 x 10 -7 > G{mu}. This implies that the anisotropy that seeds structure formation comes mostly from inflation, but with a small component (< 10%) from cosmic string effects. This cosmic string effect should be testable in the near future via gravitational lensing, the cosmic microwave background radiation, and/or gravitational wave detectors like LIGO II/VIRGO.
Perturbations of nested branes with induced gravity
Sbisà, Fulvio; Koyama, Kazuya E-mail: kazuya.koyama@port.ac.uk
2014-06-01
We study the behaviour of weak gravitational fields in models where a 4D brane is embedded inside a 5D brane equipped with induced gravity, which in turn is embedded in a 6D spacetime. We consider a specific regularization of the branes internal structures where the 5D brane can be considered thin with respect to the 4D one. We find exact solutions corresponding to pure tension source configurations on the thick 4D brane, and study perturbations at first order around these background solutions. To perform the perturbative analysis, we adopt a bulk-based approach and we express the equations in terms of gauge invariant and master variables using a 4D scalar-vector-tensor decomposition. We then propose an ansatz on the behaviour of the perturbation fields when the thickness of the 4D brane goes to zero, which corresponds to configurations where gravity remains finite everywhere in the thin limit of the 4D brane. We study the equations of motion using this ansatz, and show that they give rise to a consistent set of differential equations in the thin limit, from which the details of the internal structure of the 4D brane disappear. We conclude that the thin limit of the ''ribbon'' 4D brane inside the (already thin) 5D brane is well defined (at least when considering first order perturbations around pure tension configurations), and that the gravitational field on the 4D brane remains finite in the thin limit. We comment on the crucial role of the induced gravity term on the 5D brane.
Full linear perturbations and localization of gravity on f( R, T) brane
NASA Astrophysics Data System (ADS)
Gu, Bao-Min; Zhang, Yu-Peng; Yu, Hao; Liu, Yu-Xiao
2017-02-01
We study the thick brane world system constructed in the recently proposed f( R, T) theories of gravity, with R the Ricci scalar and T the trace of the energy-momentum tensor. We try to get the analytic background solutions and discuss the full linear perturbations, especially the scalar perturbations. We compare how the brane world model is modified with that of general relativity coupled to a canonical scalar field. It is found that some more interesting background solutions are allowed, and only the scalar perturbation mode is modified. There is no tachyon state existing in this model and only the massless tensor mode can be localized on the brane, which recovers the effective four-dimensional gravity. These conclusions hold provided that two constraints on the original formalism of the action are satisfied.
Many-body treatment of white dwarf and neutron stars on the brane
Azam, Mofazzal; Sami, M.
2005-07-15
Brane-world models suggest modification of Newton's law of gravity on the 3-brane at submillimeter scales. The brane-world induced corrections are in higher powers of inverse distance and appear as additional terms with the Newtonian potential. The average interparticle distance in white dwarf and neutron stars is 10{sup -10} cms and 10{sup -13} cms, respectively, and therefore, the effect of submillimeter corrections needs to be investigated. We show, by carrying out simple many-body calculations, that the mass and mass-radius relationship of the white dwarf and neutron stars are not effected by submillimeter corrections. However, our analysis shows that the correction terms in the effective theory give rise to force akin to surface tension in normal liquids.
Horowitz, Gary; Lawrence, Albion; Silverstein, Eva; /SLAC /Stanford U., Phys. Dept. /Santa Barbara, KITP
2010-08-26
We study a simple model of a black hole in AdS and obtain a holographic description of the region inside the horizon. A key role is played by the dynamics of the scalar fields in the dual gauge theory. This leads to a proposal for a dual description of D-branes falling through the horizon of any AdS black hole. The proposal uses a field-dependent time reparameterization in the field theory. We relate this reparametrization to various gauge invariances of the theory. Finally, we speculate on information loss and the black hole singularity in this context.
NASA Astrophysics Data System (ADS)
Rasanen, Syksy
The thesis consists of three research papers and an introduction which provides background and also contains some new observations not included in the papers. In the thesis I consider certain questions in the new field of brane cosmology. The basic idea of brane cosmology is that the visible universe is a four- dimensional slice in higher-dimensional spacetime. I give a self-contained introduction to the field, starting from the Randall-Sundrum model and proceeding to the general case of brane gravity and cosmology in the case of one extra dimension. I emphasise the main result of studies of brane gravity: it is possible to obtain approximately four-dimensional gravity independent of the size of the extra dimension, in contrast to set-ups where the observers are not localised in the extra dimension. I proceed to examine a new and promising brave cosmology set-up, the ekpyrotic scenario, in detail. The ekpyrotic scenario aims to be a comprehensive model of the primordial universe and has been presented as an alternative to the prominent scenarios, inflation and pre-big bang. I give an overview of these three scenarios of the primordial universe. I then present the starting point of the ekpyrotic scenario and the construction of the four-dimensional effective theory. After briefly discussing the internal problems of the four-dimensional effective theory, I proceed to the far more serious problems of the four- dimensional construction itself. I conclude that the four-dimensional effective theory does not give a correct description even at a qualitative level. I then discuss some problems faced by the five-dimensional approach, and comment on the spin-off known as the “cyclic model of the universe”. I conclude that the ekpyrotic scenario is a welcome new idea but that most work done thus far is not solid. Careful analysis in the five-dimensional setting is needed to promote the scenario from an interesting concept to a working model with testable predictions.
M5-branes on S 2 × M 4: Nahm's equations and 4d topological sigma-models
NASA Astrophysics Data System (ADS)
Assel, Benjamin; Schäfer-Nameki, Sakura; Wong, Jin-Mann
2016-09-01
We study the 6d N = (0 , 2) superconformal field theory, which describes multiple M5-branes, on the product space S 2 × M 4, and suggest a correspondence between a 2d N = (0 , 2) half-twisted gauge theory on S 2 and a topological sigma-model on the four-manifold M 4. To set up this correspondence, we determine in this paper the dimensional reduction of the 6d N = (0 , 2) theory on a two-sphere and derive that the four-dimensional theory is a sigma-model into the moduli space of solutions to Nahm's equations, or equivalently the moduli space of k-centered SU(2) monopoles, where k is the number of M5-branes. We proceed in three steps: we reduce the 6d abelian theory to a 5d Super-Yang-Mills theory on I × M 4, with I an interval, then non-abelianize the 5d theory and finally reduce this to 4d. In the special case, when M 4 is a Hyper-Kähler manifold, we show that the dimensional reduction gives rise to a topological sigma-model based on tri-holomorphic maps. Deriving the theory on a general M 4 requires knowledge of the metric of the target space. For k = 2 the target space is the Atiyah-Hitchin manifold and we twist the theory to obtain a topological sigma-model, which has both scalar fields and self-dual two-forms.
Induced cosmological constant and other features of asymmetric brane embedding
Shtanov, Yuri; Sahni, Varun; Shafieloo, Arman; Toporensky, Alexey E-mail: varun@iucaa.ernet.in E-mail: lesha@xray.sai.msu.ru
2009-04-15
We investigate the cosmological properties of an 'induced gravity' brane scenario in the absence of mirror symmetry with respect to the brane. We find that brane evolution can proceed along one of four distinct branches. By contrast, when mirror symmetry is imposed, only two branches exist, one of which represents the self-accelerating brane, while the other is the so-called normal branch. This model incorporates many of the well-known possibilities of brane cosmology including phantom acceleration (w < -1), self-acceleration, transient acceleration, quiescent singularities, and cosmic mimicry. Significantly, the absence of mirror symmetry also provides an interesting way of inducing a sufficiently small cosmological constant on the brane. A small (positive) {Lambda}-term in this case is induced by a small asymmetry in the values of bulk fundamental constants on the two sides of the brane.
Non-geometric five-branes in heterotic supergravity
NASA Astrophysics Data System (ADS)
Sasaki, Shin; Yata, Masaya
2016-11-01
We study T-duality chains of five-branes in heterotic supergravity where the first order α'-corrections are present. By performing the α'-corrected T-duality transformations of the heterotic NS5-brane solutions, we obtain the KK5-brane and the exotic 5 2 2 -brane solutions associated with the symmetric, the neutral and the gauge NS5-branes. We find that the Yang-Mills gauge field in these solutions satisfies the self-duality condition in the three- and two-dimensional transverse spaces to the brane world-volumes. The O(2 , 2) monodromy structures of the 5 2 2 -brane solutions are investigated by the α'-corrected generalized metric. Our analysis shows that the symmetric 5 2 2 -brane solution, which satisfies the standard embedding condition, is a T-fold and it exhibits the non-geometric nature. We also find that the neutral 5 2 2 -brane solution is a T-fold at least at O({α}^') . On the other hand, the gauge 5 2 2 -brane solution is not a T-fold but show unusual structures of space-time.
BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension
NASA Astrophysics Data System (ADS)
Dai, De-Chang; Starkman, Glenn; Stojkovic, Dejan; Issever, Cigdem; Rizvi, Eram; Tseng, Jeff
2008-04-01
We present a comprehensive black-hole event generator, BlackMax, which simulates the experimental signatures of microscopic and Planckian black-hole production and evolution at the LHC in the context of brane world models with low-scale quantum gravity. The generator is based on phenomenologically realistic models free of serious problems that plague low-scale gravity, thus offering more realistic predictions for hadron-hadron colliders. The generator includes all of the black-hole gray-body factors known to date and incorporates the effects of black-hole rotation, splitting between the fermions, nonzero brane tension, and black-hole recoil due to Hawking radiation (although not all simultaneously). The generator can be interfaced with Herwig and Pythia. The main code can be downloaded from http://www-pnp.physics.ox.ac.uk/~issever/BlackMax/blackmax.html.
BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension
Dai Dechang; Starkman, Glenn; Stojkovic, Dejan; Issever, Cigdem; Tseng, Jeff; Rizvi, Eram
2008-04-01
We present a comprehensive black-hole event generator, BlackMax, which simulates the experimental signatures of microscopic and Planckian black-hole production and evolution at the LHC in the context of brane world models with low-scale quantum gravity. The generator is based on phenomenologically realistic models free of serious problems that plague low-scale gravity, thus offering more realistic predictions for hadron-hadron colliders. The generator includes all of the black-hole gray-body factors known to date and incorporates the effects of black-hole rotation, splitting between the fermions, nonzero brane tension, and black-hole recoil due to Hawking radiation (although not all simultaneously). The generator can be interfaced with Herwig and Pythia. The main code can be downloaded from http://www-pnp.physics.ox.ac.uk/{approx}issever/BlackMax/blackmax.html.
Quasinormal ringing on the brane
NASA Astrophysics Data System (ADS)
Chung, Hyeyoun; Randall, Lisa; Rodriguez, Maria J.; Varela, Oscar
2016-12-01
While the linear behavior of gravity in braneworld models is well understood, much less is known about full nonlinear gravitational effects. Even when they agree at the linear level, these could be expected to distinguish braneworlds from a lower-dimensional theory with no brane. Black holes are a good testing ground for such studies, as they are nonlinear solutions that would be expected to reflect the background geometry. In particular, we assess the role of black hole quasinormal modes (QNMs) in gravitational experiments devised to be sensitive to the existence of the brane, in a lower-dimensional setting where we have analytical control. We compute QNMs of brane-localized black holes and find that they follow the entropy of the corresponding black hole. This observation allows us to conclude that, surprisingly, the scattering problem we consider, at least in some regimes, does not distinguish between nonlinear gravitational effects of black holes in AdS space with a brane and black holes in a spacetime of one lower dimension.
NASA Astrophysics Data System (ADS)
Anderson, Lara B.; Heckman, Jonathan J.; Katz, Sheldon
2014-05-01
T-branes are a non-abelian generalization of intersecting branes in which the matrix of normal deformations is nilpotent along some subspace. In this paper we study the geometric remnant of this open string data for six-dimensional F-theory vacua. We show that in the dual M-theory / IIA compactification on a smooth Calabi-Yau threefold X smth, the geometric remnant of T-brane data translates to periods of the three-form potential valued in the intermediate Jacobian of X smth. Starting from a smoothing of a singular Calabi-Yau, we show how to track this data in singular limits using the theory of limiting mixed Hodge structures, which in turn directly points to an emergent Hitchin-like system coupled to defects. We argue that the physical data of an F-theory compactification on a singular threefold involves specifying both a geometry as well as the remnant of three-form potential moduli and flux which is localized on the discriminant. We give examples of T-branes in compact F-theory models with heterotic duals, and comment on the extension of our results to four-dimensional vacua.
Brane resolution through fibration
NASA Astrophysics Data System (ADS)
Vázquez-Poritz, Justin F.; Zhang, Zhibai
2012-11-01
We consider p-branes with one or more circular directions fibered over the transverse space. The fibration, in conjunction with the transverse space having a blown-up cycle, enables these p-brane solutions to be completely regular. Some such circularly wrapped D3-brane solutions describe flows from SU(N)3 N=2 theory, F0 theory, as well as an infinite family of superconformal quiver gauge theories, down to three-dimensional field theories. We discuss the operators that are turned on away from the UV fixed points. Similarly, there are wrapped M2-brane solutions which describe smooth flows from known three-dimensional supersymmetric Chern-Simons matter theories, such as Aharony-Bergman-Jafferis-Maldacena theory. We also consider p-brane solutions on gravitational instantons, and discuss various ways in which U-duality can be applied to yield other nonsingular solutions.
Classical Renormalization of Codimension-two Brane Couplings
Rham, Claudia de
2007-11-20
The curvature on codimension-two and higher branes is not regular for arbitrary matter sources. Nevertheless, the low-energy theory for an observer on such a brane should be well-defined and independent to any regularization procedure. This is achieved via appropriate classical renormalization of the brane couplings, and leads to a natural hierarchy between standard model couplings and couplings to gravity.
The gravity of dark vortices: effective field theory for branes and strings carrying localized flux
NASA Astrophysics Data System (ADS)
Burgess, C. P.; Diener, R.; Williams, M.
2015-11-01
A Nielsen-Olesen vortex usually sits in an environment that expels the flux that is confined to the vortex, so flux is not present both inside and outside. We construct vortices for which this is not true, where the flux carried by the vortex also permeates the `bulk' far from the vortex. The idea is to mix the vortex's internal gauge flux with an external flux using off-diagonal kinetic mixing. Such `dark' vortices could play a phenomenological role in models with both cosmic strings and a dark gauge sector. When coupled to gravity they also provide explicit ultra-violet completions for codimension-two brane-localized flux, which arises in extra-dimensional models when the same flux that stabilizes extra-dimensional size is also localized on space-filling branes situated around the extra dimensions. We derive simple formulae for observables such as defect angle, tension, localized flux and on-vortex curvature when coupled to gravity, and show how all of these are insensitive to much of the microscopic details of the solutions, and are instead largely dictated by low-energy quantities. We derive the required effective description in terms of a world-sheet brane action, and derive the matching conditions for its couplings. We consider the case where the dimensions transverse to the bulk compactify, and determine how the on- and off-vortex curvatures and other bulk features depend on the vortex properties. We find that the brane-localized flux does not gravitate, but just renormalizes the tension in a magnetic-field independent way. The existence of an explicit UV completion puts the effective description of these models on a more precise footing, verifying that brane-localized flux can be consistent with sensible UV physics and resolving some apparent paradoxes that can arise with a naive (but commonly used) delta-function treatment of the brane's localization within the bulk.
NASA Astrophysics Data System (ADS)
Roberts, Mark D.
2015-10-01
Solutions are found to field equations constructed from the Pauli, Bach and Gauss-Bonnet quadratic tensors to the Kasner and Kasner brane spacetimes in up to five dimensions. A double Kasner space is shown to have a vacuum solution. Brane solutions in which the bulk components of the Einstein tensor vanish are also looked at and for four-branes a solution similar to radiation Robertson-Walker spacetime is found. Matter trapping of a test scalar field and a test perfect fluid are investigated using energy conditions.
Cosmological and spherically symmetric solutions with intersecting p-branes
NASA Astrophysics Data System (ADS)
Ivashchuk, V. D.; Melnikov, V. N.
1999-12-01
Multidimensional model describing the cosmological evolution and/or spherically symmetric configuration with n+1 Einstein spaces in the theory with several scalar fields and forms is considered. When electro-magnetic composite p-brane ansatz is adopted, n ``internal'' spaces are Ricci-flat, one space M0 has a nonzero curvature, and all p-branes do not ``live'' in M0, a class of exact solutions is obtained if certain block-orthogonality relations on p-brane vectors are imposed. A subclass of spherically symmetric solutions (containing nonextremal p-brane black holes) is considered. Post-Newtonian parameters are calculated.
Comments on D-brane dynamics near NS5-branes
NASA Astrophysics Data System (ADS)
Sahakyan, David A.
2004-10-01
We study the properties of a D-brane in the presence of k NS5 branes. The Dirac-Born-Infeld action describing the dynamics of this D-brane is very similar to that of a non-BPS D-brane in ten dimensions. As the D-brane approaches the fivebranes, its equation of state approaches that of a pressureless fluid. In non-BPS D-brane case this is considered as an evidence for the decay of the D-brane into ``tachyon matter''. We show that in our case similar behavior is the consequence of the motion of the D-brane. In particular in the rest frame of the moving D-brane the equation of state is that of a usual D-brane, for which the pressure is equal to the energy density. We also compute the total cross-section for the decay of the D-brane into closed string modes and show that the emitted energy has a power like divergence for D0, D1 and D2 branes, while converges for higher dimensional D-branes. We also speculate on the possibility that the infalling D-brane describes a decaying defect in six dimensional Little String Theory.
MODELING WORLD BIOENERGY CROP POTENTIAL
NASA Astrophysics Data System (ADS)
Hagiwara, Kensuke; Hanasaki, Naota; Kanae, Shinjiro
Bioenergy is regarded as clean energy due to its characteristics and expected to be a new support of world energy de¬mand, but there are few integrated assessments of the potential of bioenergy considering sustainable land use. We esti¬mated the global bioenergy potential with an integrated global water resources model, the H08. It can simulate the crop yields on global-scale at a spatial resolution of 0.50.5. Seven major crops in the world were considered; namely, maize, sugar beet, sugar cane, soybean, rapeseed, rice, and wheat, of which the first 5 are commonly used to produce biofuel now. Three different land-cover types were chosen as potential area for cultivation of biofuel-producing crop: fallow land, grassland, and portion of forests (excluding areas sensitive for biodiversity such as frontier forest). We attempted to estimate the maximum global bioenergy potential and it was estimated to be 1120EJ. Bioenergy potential depends on land-use limitations for the protection of bio-diversity and security of food. In another condition which assumed more land-use limitations, bioenergy potential was estimated to be 70-233EJ.
Koivisto, Tomi; Wills, Danielle; Zavala, Ivonne E-mail: d.e.wills@durham.ac.uk
2014-06-01
Disformally coupled cosmologies arise from Dirac-Born-Infeld actions in Type II string theories, when matter resides on a moving hidden sector D-brane. Since such matter interacts only very weakly with the standard model particles, this scenario can provide a natural origin for the dark sector of the universe with a clear geometrical interpretation: dark energy is identified with the scalar field associated to the D-brane's position as it moves in the internal space, acting as quintessence, while dark matter is identified with the matter living on the D-brane, which can be modelled by a perfect fluid. The coupling functions are determined by the (warped) extra-dimensional geometry, and are thus constrained by the theory. The resulting cosmologies are studied using both dynamical system analysis and numerics. From the dynamical system point of view, one free parameter controls the cosmological dynamics, given by the ratio of the warp factor and the potential energy scales. The disformal coupling allows for new scaling solutions that can describe accelerating cosmologies alleviating the coincidence problem of dark energy. In addition, this scenario may ameliorate the fine-tuning problem of dark energy, whose small value may be attained dynamically, without requiring the mass of the dark energy field to be unnaturally low.
Thermodynamics of anisotropic branes
NASA Astrophysics Data System (ADS)
Ávila, Daniel; Fernández, Daniel; Patiño, Leonardo; Trancanelli, Diego
2016-11-01
We study the thermodynamics of flavor D7-branes embedded in an anisotropic black brane solution of type IIB supergravity. The flavor branes undergo a phase transition between a `Minkowski embedding', in which they lie outside of the horizon, and a `black hole embedding', in which they fall into the horizon. This transition depends on the black hole temperature, its degree of anisotropy, and the mass of the flavor degrees of freedom. It happens either at a critical temperature or at a critical anisotropy. A general lesson we learn from this analysis is that the anisotropy, in this particular realization, induces similar effects as the temperature. In particular, increasing the anisotropy bends the branes more and more into the horizon. Moreover, we observe that the transition becomes smoother for higher anisotropies.
NASA Astrophysics Data System (ADS)
Bachlechner, Thomas C.; McAllister, Liam
2013-10-01
We study the dynamics of ultrarelativistic D-branes. The dominant phenomenon is bremsstrahlung: mild acceleration induced by closed string interactions triggers extremely rapid energy loss through radiation of massless closed strings. After characterizing bremsstrahlung from a general k-dimensional extended object in a D-dimensional spacetime, we incorporate effects specific to D-branes, including velocity-dependent forces and open string pair creation. We then show that dissipation due to bremsstrahlung can substantially alter the dynamics in DBI inflation.
Duality cascade in brane inflation
Bean, Rachel; Chen Xingang; Hailu, Girma; Henry Tye, S-H; Xu Jiajun E-mail: xgchen@mit.edu E-mail: tye@lepp.cornell.edu
2008-03-15
We show that brane inflation is very sensitive to tiny sharp features in extra dimensions, including those in the potential and in the warp factor. This can show up as observational signatures in the power spectrum and/or non-Gaussianities of the cosmic microwave background radiation (CMBR). One general example of such sharp features is a succession of small steps in a warped throat, caused by Seiberg duality cascade using gauge/gravity duality. We study the cosmological observational consequences of these steps in brane inflation. Since the steps come in a series, the prediction of other steps and their properties can be tested by future data and analysis. It is also possible that the steps are too close to be resolved in the power spectrum, in which case they may show up only in the non-Gaussianity of the CMB temperature fluctuations and/or EE polarization. We study two cases. In the slow-roll scenario, where steps appear in the inflaton potential, the sensitivity of brane inflation to the height and width of the steps is increased by several orders of magnitude compared to that in previously studied large field models. In the IR DBI scenario, where steps appear in the warp factor, we find that the glitches in the power spectrum caused by these sharp features are generally small or even unobservable, but associated distinctive non-Gaussianity can be large. Together with its large negative running of the power spectrum index, this scenario clearly illustrates how rich and different a brane inflationary scenario can be when compared to generic slow-roll inflation. Such distinctive stringy features may provide a powerful probe of superstring theory.
D-branes in Type IIB plane wave background
Lee, Bum-Hoon
2007-01-12
We classify and summarize the intersecting supersymmetric D-branes in the type IIB plane wave background, based on the Green-Schwarz superstring formulation. Many new configurations appears if we turn on the electric or magnetic background fields or boost the D-branes. Applications to the phenomelogical models are left for further study.
Perturbations on and off de Sitter brane in anti-de Sitter bulk
NASA Astrophysics Data System (ADS)
Libanov, M.; Rubakov, V.
2016-09-01
Motivated by holographic models of a (pseudo)conformal Universe, we carry out a complete analysis of linearized metric perturbations in the time-dependent two-brane setup of the Lykken-Randall type. We present the equations of motion for the scalar, vector and tensor perturbations and identify light modes in the spectrum, which are scalar radion and transverse-traceless graviton. We show that there are no other modes in the discrete part of the spectrum. We pay special attention to properties of light modes and show, in particular, that the radion has red power spectrum at late times, as anticipated on holographic grounds. Unlike the graviton, the radion survives in the single-brane limit, when one of the branes is sent to the adS boundary. These properties imply that potentially observable features characteristic of the 4d (pseudo)conformal cosmology, such as statistical anisotropy and specific shapes of non-Gaussianity, are inherent also in holographic conformal models as well as in brane world inflation.
Emergence and expansion of cosmic space as due to M0-branes
NASA Astrophysics Data System (ADS)
Sepehri, Alireza; Setare, Mohammad Reza; Capozziello, Salvatore
2015-12-01
Recently, Padmanabhan (arXiv:1206.4916 [hep-th]) discussed that the difference between the number of degrees of freedom on the boundary surface and the number of degrees of freedom in a bulk region causes the accelerated expansion of the universe. The main question arising is: what is the origin of this inequality between the surface degrees of freedom and the bulk degrees of freedom? We answer this question in M-theory. In our model, first M0-branes are compactified on one circle and N D0-branes are created. Then N D0-branes join each other, grow, and form one D5-branes. Next, the D5-brane is compactified on two circles and our universe's D3-brane, two D1-branes and some extra energies are produced. After that, one of the D1-branes, which is closer to the universe's brane, gives its energy into it, and this leads to an increase in the difference between the numbers of degrees of freedom and the occurring inflation era. With the disappearance of this D1-brane, the number of degrees of freedom of boundary surface and bulk region become equal and inflation ends. At this stage, extra energies that are produced due to the compactification cause an expansion of the universe and deceleration epoch. Finally, another D1-brane dissolves in our universe's brane, leads to an inequality between degrees of freedom, and there occurs a new phase of acceleration.
Common world model for unmanned systems
NASA Astrophysics Data System (ADS)
Dean, Robert Michael S.
2013-05-01
The Robotic Collaborative Technology Alliance (RCTA) seeks to provide adaptive robot capabilities which move beyond traditional metric algorithms to include cognitive capabilities. Key to this effort is the Common World Model, which moves beyond the state-of-the-art by representing the world using metric, semantic, and symbolic information. It joins these layers of information to define objects in the world. These objects may be reasoned upon jointly using traditional geometric, symbolic cognitive algorithms and new computational nodes formed by the combination of these disciplines. The Common World Model must understand how these objects relate to each other. Our world model includes the concept of Self-Information about the robot. By encoding current capability, component status, task execution state, and histories we track information which enables the robot to reason and adapt its performance using Meta-Cognition and Machine Learning principles. The world model includes models of how aspects of the environment behave, which enable prediction of future world states. To manage complexity, we adopted a phased implementation approach to the world model. We discuss the design of "Phase 1" of this world model, and interfaces by tracing perception data through the system from the source to the meta-cognitive layers provided by ACT-R and SS-RICS. We close with lessons learned from implementation and how the design relates to Open Architecture.
Fragmentation of spinning branes
NASA Astrophysics Data System (ADS)
Yamada, D.
2008-07-01
The near-horizon geometries of spinning D3-, M2- and M5-branes are examined by the probes immersed in a co-rotating frame. It is found that the geometries become unstable at critical values of the spin angular velocity by emitting the branes. We show that this instability corresponds to the metastability of the black hole systems and different from the known (local) thermodynamic instability. For the D3 case, the instability found here is in complete agreement with the known metastability of the \\mathcal{N}=4 super-Yang Mills theory with R-symmetry chemical potentials.
Brane inflation and the overshoot problem
NASA Astrophysics Data System (ADS)
Bird, Simeon; Peiris, Hiranya V.; Baumann, Daniel
2009-07-01
We investigate recent claims that brane inflation solves the overshoot problem through a combination of microphysical restrictions on the phase space of initial conditions and the existence of the Dirac-Born-Infeld attractor in regimes where the slow-roll attractor does not apply. Carrying out a comprehensive analysis of the parameter space allowed by the latest advances in brane inflation model-building, we find that these restrictions are insufficient to solve the overshoot problem. The vast majority of the phase space of initial conditions is still dominated by overshoot trajectories. We present an analytic proof that the brane-inflationary attractor must be close to the slow-roll limit, and update the predictions for observables such as non-Gaussianity, cosmic string tension, and tensor modes.
Gauge Field Localization on Deformed Branes
NASA Astrophysics Data System (ADS)
Tofighi, A.; Moazzen, M.; Farokhtabar, A.
2016-02-01
In this paper, we utilise the Chumbes-Holf da Silva-Hott (CHH) mechanism to investigate the issue of gauge field localization on a deformed brane constructed with one scalar field, which can be coupled to gravity minimally or non-minimally. The study of deformed defects is important because they contain internal structures which may have implications in braneworld models. With the CHH mechanism, we find that the massless zero mode of gauge field, in the case of minimal or non-minimal coupling is localized on the brane. Moreover, in the case of non-minimal coupling, it is shown that, when the non-minimal coupling constant is larger than its critical value, then the zero mode is localized on each sub brane.
Graviton Kaluza-Klein modes in nonflat branes with stabilized modulus
NASA Astrophysics Data System (ADS)
Paul, Tanmoy; SenGupta, Soumitra
2016-04-01
We consider a generalized two brane Randall-Sundrum model where the branes are endowed with nonzero cosmological constant. In this scenario, we re-examine the modulus stabilization mechanism and the nature of Kaluza-Klein (KK) graviton modes. Our result reveals that while the KK mode graviton masses may change significantly with the brane cosmological constant, the Goldberger-Wise stabilization mechanism, which assumes a negligible backreaction on the background metric, continues to hold even when the branes have a large cosmological constant. The possibility of having a global minimum for the modulus is also discussed. Our results also include an analysis for the radion mass in this nonflat brane scenario.
Brane-localized Kinetic Terms in the Randall-Sundrum Model
Rizzo, Thomas G.
2002-12-20
We examine the effects of boundary kinetic terms in the Randall-Sundrum model with gauge fields in the bulk. We derive the resulting gauge Kaluza-Klein (KK) state wavefunctions and their corresponding masses, as well as the KK gauge field couplings to boundary fermions, and find that they are modified in the presence of the boundary terms. In particular, for natural choices of the parameters, these fermionic couplings can be substantially suppressed compared to those in the conventional Randall-Sundrum scenario. This results in a significant relaxation of the bound on the lightest gauge KK mass obtained from precision electroweak data; we demonstrate that this bound can be as low as m{sub 1} {approx}> 5 TeV. Due to the relationship between the lightest gauge KK state and the electroweak scale in this model, this weakened constraint allows for the electroweak scale to be near a TeV in this minimal extension of the Randall-Sundrum model with bulk gauge fields, as opposed to the conventional scenario.
NASA Astrophysics Data System (ADS)
Ashour, Amani; Faizal, Mir; Ali, Ahmed Farag; Hammad, Fayçal
2016-05-01
In this work, we investigate the thermodynamics of black p-branes (BB) in the context of Gravity's Rainbow. We investigate this using rainbow functions that have been motivated from loop quantum gravity and κ -Minkowski non-commutative spacetime. Then for the sake of comparison, we examine a couple of other rainbow functions that have also appeared in the literature. We show that, for consistency, Gravity's Rainbow imposes a constraint on the minimum mass of the BB, a constraint that we interpret here as implying the existence of a black p-brane remnant. This interpretation is supported by the computation of the black p-brane's heat capacity that shows that the latter vanishes when the Schwarzschild radius takes on a value that is bigger than its extremal limit. We found that the same conclusion is reached for the third version of rainbow functions treated here but not with the second one for which only standard black p-brane thermodynamics is recovered.
The spectrum of FZZT branes beyond the planar limit
NASA Astrophysics Data System (ADS)
Atkin, Max R.; Wheater, John F.
2011-02-01
Minimal string theory has a number of FZZT brane boundary states; one for each Cardy state of the minimal model. It was conjectured by Seiberg and Shih that all branes in a minimal string theory could be expressed as a linear combination of the brane associated to the identity operator of the minimal model with complex shifts in the boundary cosmological constant. Subsequently it was found that this identification of FZZT branes does not hold exactly for some cylinder amplitudes but was spoiled by terms that are associated with vanishing worldsheet area and are therefore non-universal. In this paper we investigate this claim systematically, using both Liouville and matrix model methods, beyond the planar limit. We find that the aforementioned identification of FZZT branes is spoiled by terms that do not admit an interpretation as non-universal terms. Furthermore, the spoiling terms as computed using the matrix model are found to be in agreement with those coming from Liouville theory, which also suggests that these terms have universal meaning. Finally, we also investigate the identification of FZZT branes by replacing the boundary state with a sum of local operators. We find in this case that the brane associated with the identity operator appears to be special as it is the only one to correctly reproduce the correlation numbers for bulk operators on the torus.
World Energy Projection System Plus Model Documentation: Electricity Model
2017-01-01
This report documents the objectives, analytical approach and development of the World Energy Projection System Plus (WEPS ) World Electricity Model. It also catalogues and describes critical assumptions, computational methodology, parameter estimation techniques, and model source code.
World Energy Projection System Plus Model Documentation: Industrial Model
2016-01-01
This report documents the objectives, analytical approach and development of the World Energy Projection System Plus (WEPS ) World Industrial Model (WIM). It also catalogues and describes critical assumptions, computational methodology, parameter estimation techniques, and model source code.
Graviton resonances on deformed branes
NASA Astrophysics Data System (ADS)
Cruz, W. T.; Gomes, A. R.; Almeida, C. A. S.
2011-11-01
Plane-wave solutions of Schrödinger-like equations obtained from the metric perturbations in 5D braneworld scenarios can present resonant modes. The search for those structures is important because they can provide us with massive modes with not suppressed couplings with the membrane. We propose in this paper the study of graviton Kaluza-Klein spectrum in a special kind of membrane that possesses internal structure. The interest in the study of these deformed defects is due to the fact that they have a richer internal structure that has implications in the matter energy density along the extra dimensions and this produces a space-time background whose curvature has a splitting, if compared to the usual kink-like models. Such models arise from (4, 1)-branes constructed with one scalar field coupled with gravity where we find two-kink solutions from deformations of a phi4 potential. The main objective of this work is to observe the effects of deformation process in the resonant modes as well as in the coupling between the graviton massive modes and the brane.
Smith, David; Nomura, Yasunori; Weiner, Neal
2001-04-04
We present a five-dimensional supersymmetric SU(5) theory in which the gauge symmetry is broken maximally (i.e. at the 5D Planck scale M{sub *}) on the same 4D brane where chiral matter is localized. Masses of the lightest Kaluza-Klein modes for the colored Higgs and X and Y gauge fields are determined by the compactification scale of the fifth dimension, M{sub C} {approx} 10{sup 15} GeV, rather than by M{sub *}. These fields' wave functions are repelled from the GUT-breaking brane, so that proton decay rates are suppressed below experimental limits. Above the compactification scale, the differences between the standard model gauge couplings evolve logarithmically, so that ordinary logarithmic gauge coupling unification is preserved. The maximal breaking of the grand unified group can also lead to other effects, such as O(1) deviations from SU(5) predictions of Yukawa couplings, even in models utilizing the Froggatt-Nielsen mechanism.
World energy projection system: Model documentation
NASA Astrophysics Data System (ADS)
1992-06-01
The World Energy Project System (WEPS) is an accounting framework that incorporates projects from independently documented models and assumptions about the future energy intensity of economic activity (ratios of total energy consumption divided by gross domestic product) and about the rate of incremental energy requirements met by hydropower, geothermal, coal, and natural gas to produce projections of world energy consumption published annually by the Energy Information Administration (EIA) in the International Energy Outlook (IEO). Two independently documented models presented in Figure 1, the Oil Market Simulation (OMS) model and the World Integrated Nuclear Evaluation System (WINES), provide projections of oil and nuclear power consumption published in the IEO. Output from a third independently documented model, and the International Coal Trade Model (ICTM), is not published in the IEO but is used in WEPS as a supply check on projections of world coal consumption produced by WEPS and published in the IEO. A WEPS model of natural gas production documented in this report provides the same type of implicit supply check on the WEPS projections of world natural gas consumption published in the IEO. Two additional models are included in Figure 1, the OPEC Capacity model and the Non-OPEC Oil Production model. These WEPS models provide inputs to the OMS model and are documented in this report.
Spatially homogeneous rotating world models.
NASA Technical Reports Server (NTRS)
Ozsvath, I.
1971-01-01
The mathematical problem encountered when looking for the simplest expanding and rotating model of the universe without the compactness condition for the space sections is formulated. The Lagrangian function is derived for four different rotating universes simultaneously. These models correspond in a certain sense to Godel's (1950) ?symmetric case.'
A new approach to the classical and quantum dynamics of branes
NASA Astrophysics Data System (ADS)
Pavšič, Matej
2016-07-01
It is shown that the Dirac-Nambu-Goto brane can be described as a point particle in an infinite-dimensional brane space with a particular metric. This suggests a generalization to brane spaces with arbitrary metric, including the “flat” metric. Then quantization of such a system is straightforward: it is just like quantization of a bunch of noninteracting particles. This leads us to a system of a continuous set of scalar fields. For a particular choice of the metric in the space of fields we find that the classical Dirac-Nambu-Goto brane theory arises as an effective theory of such an underlying quantum field theory. Quantization of branes is important for the brane world scenarios, and thus for “quantum gravity.”
Apostolopoulos, P.S.; Brouzakis, N.; Saridakis, E.N.; Tetradis, N.
2005-08-15
We discuss features of the brane cosmological evolution that arise through the presence of matter in the bulk. As these deviations from the conventional evolution are not associated with some observable matter component on the brane, we characterize them as mirage effects. We review an example of expansion that can be attributed to mirage nonrelativistic matter (mirage cold dark matter) on the brane. The real source of the evolution is an anisotropic bulk fluid with negative pressure along the extra dimension. We also study the general problem of exchange of real nonrelativistic matter between the brane and the bulk, and discuss the related mirage effects. Finally, we derive the brane cosmological evolution within a bulk that contains a global monopole (hedgehog) configuration. This background induces a mirage curvature term in the effective Friedmann equation, which can cause a brane universe with positive spatial curvature to expand forever.
Inhomogeneous exact solution in brane gravity and its applications
NASA Astrophysics Data System (ADS)
Heydari-Fard, Malihe; Heydari-Fard, Mohaddese
2017-02-01
Considering an inhomogeneous brane embedded in a five dimensional constant curvature bulk, we find the non-static and spherically symmetric exact solutions of the Einstein equations on the brane. With different choices of the parameters, one interesting case/solution is studied. We show that an inhomogeneous brane model can explain the accelerated expansion of the universe at large distance scales and also the galaxy rotation curves of spiral galaxies without assuming the existence of dark matter or new modified theories at the galactic scales.
Light-cone M5 and multiple M2-branes
NASA Astrophysics Data System (ADS)
Bandos, Igor A.; Townsend, Paul K.
2008-12-01
We present the light-cone gauge fixed Lagrangian for the M5-brane; it has a residual 'exotic' gauge invariance with the group of 5-volume preserving diffeomorphisms, SDiff5, as gauge group. For an M5-brane of topology \\bb{R}^2\\times M_3 , for closed 3-manifold M3, we find an infinite tension limit that yields an SO(8)-invariant (1 + 2)-dimensional field theory with 'exotic' SDiff3 gauge invariance. We show that this field theory is the Carrollian limit of the Nambu bracket realization of the 'BLG' model for multiple M2-branes.
A compact codimension-two braneworld with precisely one brane
Akerblom, Nikolas; Cornelissen, Gunther
2010-06-15
Building on earlier work on football-shaped extra dimensions, we construct a compact codimension-two braneworld with precisely one brane. The two extra dimensions topologically represent a 2-torus which is stabilized by a bulk cosmological constant and magnetic flux. The torus has positive constant curvature almost everywhere, except for a single conical singularity at the location of the brane. In contradistinction to the football-shaped case, there is no fine-tuning required for the brane tension. We also present some plausibility arguments why the model should not suffer from serious stability issues.
Fermion localization and resonances on two-field thick branes
Almeida, C. A. S.; Casana, R.; Ferreira, M. M. Jr.; Gomes, A. R.
2009-06-15
We consider (4, 1)-dimensional branes constructed with two scalar fields {phi} and {chi} coupled to a Dirac spinor field by means of a general Yukawa coupling. The equation of motion for the coefficients of the chiral decomposition of the spinor in curved spacetime leads to a Schroedinger-like equation whose solutions allow to obtain the masses of the fermionic modes. The simplest Yukawa coupling {psi}{phi}{chi}{psi} is considered for the Bloch brane model and fermion localization is studied. We found resonances for both chiralities and related their appearance to branes with internal structure.
NASA Astrophysics Data System (ADS)
Sepehri, Alireza
2016-07-01
Recently, some authors (Cruz and Rojas, 2013 [1]) have constructed a Born-Infeld type action which may be written in terms of the Lovelock brane Lagrangians for a given dimension p. We reconsider their model in M-theory and study the process of birth and growth of nonlinear spinor and bosonic gravity during the construction of Mp-branes. Then, by application of this idea to BIonic system, we construct a BIonic superconductor in the background of nonlinear gravity. In this model, first, M0-branes link to each other and build an M5-brane and an anti-M5-brane connected by an M2-brane. M0-branes are zero dimensional objects that only scalars are attached to them. By constructing higher dimensional branes from M0-branes, gauge fields are produced. Also, if M0-branes don't link to each other completely, the symmetry of system is broken and fermions are created. The curvature produced by fermions has the opposite sign the curvature produced by gauge fields. Fermions on M5-branes and M2 plays the role of bridge between them. By passing time, M2 dissolves in M5's and nonlinear bosonic and spinor gravities are produced. By closing M5-branes towards each other, coupling of two identical fermions on two branes to each other causes that the square mass of their system becomes negative and some tachyonic states are created. For removing these tachyons, M5-branes compact, the sign of gravity between branes reverses, anti-gravity is produced which causes that branes and identical fermions get away from each other. This is the reason for the emergence of Pauli exclusion principle in Bionic system. Also, the spinor gravity vanishes and its energy builds a new M2 between M5-branes. We obtain the resistivity in this system and find that its value decreases by closing M5 branes to each other and shrinks to zero at colliding point of branes. This idea has different applications. For example, in cosmology, universes are located on M5-branes and M2-brane has the role of bridge between
NASA Astrophysics Data System (ADS)
Kallosh, Renata; Rajaraman, Arvind
1996-11-01
We suggest a duality-invariant formula for the entropy and temperature of nonextreme black holes in supersymmetric string theory. The entropy is given in terms of the duality-invariant parameter of the deviation from extremality and 56 SU(8) covariant central charges. It interpolates between the entropies of Schwarzschild solution and extremal solutions with various amount of unbroken supersymmetries, and therefore, serves for classification of black holes in supersymmetric string theories. We introduce the second auxiliary 56 via an E(7) symmetric constraint. The symmetric and antisymmetric combinations of these two multiplets are related via moduli to the corresponding two fundamental representations of E(7): brane and antibrane ``numbers.'' Using the CPT as well as C symmetry of the entropy formula and duality one can explain the mysterious simplicity of the nonextreme black hole area formula in terms of branes and antibranes.
Kallosh, R.; Rajaraman, A.
1996-11-01
We suggest a duality-invariant formula for the entropy and temperature of nonextreme black holes in supersymmetric string theory. The entropy is given in terms of the duality-invariant parameter of the deviation from extremality and 56 SU(8) covariant central charges. It interpolates between the entropies of Schwarzschild solution and extremal solutions with various amount of unbroken supersymmetries, and therefore, serves for classification of black holes in supersymmetric string theories. We introduce the second auxiliary 56 via an E(7) symmetric constraint. The symmetric and antisymmetric combinations of these two multiplets are related via moduli to the corresponding two fundamental representations of E(7): brane and antibrane {open_quote}{open_quote}numbers.{close_quote}{close_quote} Using the {ital CPT} as well as {ital C} symmetry of the entropy formula and duality one can explain the mysterious simplicity of the nonextreme black hole area formula in terms of branes and antibranes. {copyright} {ital 1996 The American Physical Society.}
Hamiltonian Approach To Dp-Brane Noncommutativity
NASA Astrophysics Data System (ADS)
Nikolic, B.; Sazdovic, B.
2010-07-01
In this article we investigate Dp-brane noncommutativity using Hamiltonian approach. We consider separately open bosonic string and type IIB superstring which endpoints are attached to the Dp-brane. From requirement that Hamiltonian, as the time translation generator, has well defined derivatives in the coordinates and momenta, we obtain boundary conditions directly in the canonical form. Boundary conditions are treated as canonical constraints. Solving them we obtain initial coordinates in terms of the effective ones as well as effective momenta. Presence of momenta implies noncommutativity of the initial coordinates. Effective theory, defined as initial one on the solution of boundary conditions, is its Ω even projection, where Ω is world-sheet parity transformation Ω:σ→-σ. The effective background fields are expressed in terms of Ω even and squares of the Ω odd initial background fields.
Wronskians, dualities and FZZT-Cardy branes
NASA Astrophysics Data System (ADS)
Chan, Chuan-Tsung; Irie, Hirotaka; Niedner, Benjamin; Yeh, Chi-Hsien
2016-09-01
The resolvent operator plays a central role in matrix models. For instance, with utilizing the loop equation, all of the perturbative amplitudes including correlators, the free-energy and those of instanton corrections can be obtained from the spectral curve of the resolvent operator. However, at the level of non-perturbative completion, the resolvent operator is generally not sufficient to recover all the information from the loop equations. Therefore it is necessary to find a sufficient set of operators which provide the missing non-perturbative information. In this paper, we study generalized Wronskians of the Baker-Akhiezer systems as a manifestation of these new degrees of freedom. In particular, we derive their isomonodromy systems and then extend several spectral dualities to these systems. In addition, we discuss how these Wronskian operators are naturally aligned on the Kac table. Since they are consistent with the Seiberg-Shih relation, we propose that these new degrees of freedom can be identified as FZZT-Cardy branes in Liouville theory. This means that FZZT-Cardy branes are the bound states of elemental FZZT branes (i.e. the twisted fermions) rather than the bound states of principal FZZT-brane (i.e. the resolvent operator).
A delicate universe: compactification obstacles to D-brane inflation.
Baumann, Daniel; Dymarsky, Anatoly; Klebanov, Igor R; McAllister, Liam; Steinhardt, Paul J
2007-10-05
We investigate whether explicit models of warped D-brane inflation are possible in string compactifications. To this end, we study the potential for D3-brane motion in a warped conifold that includes holomorphically embedded D7-branes involved in moduli stabilization. The presence of the D7-branes significantly modifies the inflaton potential. We construct an example based on a very simple and symmetric embedding due to Kuperstein, z1= const, in which it is possible to fine-tune the potential so that slow-roll inflation can occur. The resulting model is rather delicate: inflation occurs in the vicinity of an inflection point, and the cosmological predictions are extremely sensitive to the precise shape of the potential.
Emergence and oscillation of cosmic space by joining M1-branes
NASA Astrophysics Data System (ADS)
Sepehri, Alireza; Rahaman, Farook; Capozziello, Salvatore; Ali, Ahmed Farag; Pradhan, Anirudh
2016-05-01
Recently, it has been proposed by Padmanabhan that the difference between the number of degrees of freedom on the boundary surface and the number of degrees of freedom in a bulk region leads to the expansion of the universe. Now, a natural question arises; how could this model explain the oscillation of the universe between contraction and expansion branches? We try to address this issue in the framework of a BIonic system. In this model, M0-branes join to each other and give rise to a pair of M1-anti- M1-branes. The fields which live on these branes play the roles of massive gravitons that cause the emergence of a wormhole between them and formation of a BIon system. This wormhole dissolves into M1-branes and causes a divergence between the number of degrees of freedom on the boundary surface of M1 and the bulk leading to an expansion of M1-branes. When M1-branes become close to each other, the square energy of their system becomes negative and some tachyonic states emerge. To remove these states, M1-branes become compact, the sign of compacted gravity changes, causing anti-gravity to arise: in this case, branes get away from each other. By articulating M1-BIons, an M3-brane and an anti- M3-brane are created and connected by three wormholes forming an M3-BIon. This new system behaves like the initial system and by closing branes to each other, they become compact and, by getting away from each other, they open. Our universe is located on one of these M3-branes and, by compactifying the M3-brane, it contracts and, by opening it, it expands.
Brane surgery: energy conditions, traversable wormholes, and voids
NASA Astrophysics Data System (ADS)
Barceló1, C.; Visser, M.
2000-09-01
Branes are ubiquitous elements of any low-energy limit of string theory. We point out that negative tension branes violate all the standard energy conditions of the higher-dimensional spacetime they are embedded in; this opens the door to very peculiar solutions of the higher-dimensional Einstein equations. Building upon the (/3+1)-dimensional implementation of fundamental string theory, we illustrate the possibilities by considering a toy model consisting of a (/2+1)-dimensional brane propagating through our observable (/3+1)-dimensional universe. Developing a notion of ``brane surgery'', based on the Israel-Lanczos-Sen ``thin shell'' formalism of general relativity, we analyze the dynamics and find traversable wormholes, closed baby universes, voids (holes in the spacetime manifold), and an evasion (not a violation) of both the singularity theorems and the positive mass theorem. These features appear generic to any brane model that permits negative tension branes: This includes the Randall-Sundrum models and their variants.
Large field inflation from D-branes
NASA Astrophysics Data System (ADS)
Escobar, Dagoberto; Landete, Aitor; Marchesano, Fernando; Regalado, Diego
2016-04-01
We propose new large field inflation scenarios built on the framework of F-term axion monodromy. Our setup is based on string compactifications where D-branes create potentials for closed string axions via F-terms. Because the source of the axion potential is different from the standard sources of moduli stabilization, it is possible to lower the inflaton mass as compared to other massive scalars. We discuss a particular class of models based on type IIA flux compactifications with D6-branes. In the small field regime they describe supergravity models of quadratic chaotic inflation with a stabilizer field. In the large field regime the inflaton potential displays a flattening effect due to Planck suppressed corrections, allowing us to easily fit the cosmological parameters of the model within current experimental bounds.
Rapid world modelling from a mobile platform
Barry, R.E.; Jones, J.P.; Little, C.Q.; Wilson, C.W.
1997-04-01
The ability to successfully use and interact with a computerized world model is dependent on the ability to create an accurate world model. The goal of this project was to develop a prototype system to remotely deploy sensors into a workspace, collect surface information, and rapidly build an accurate world model of that workspace. A key consideration was that the workspace areas are typically hazardous environments, where it is difficult or impossible for humans to enter. Therefore, the system needed to be fully remote, with no external connections. To accomplish this goal, an electric, mobile platform with battery power sufficient for both the platform and sensor electronics was procured and 3D range sensors were deployed on the platform to capture surface data within the workspace. A radio Ethernet connection was used to provide communications to the vehicle and all on-board electronics. Video from on-board cameras was also transmitted to the base station and used to teleoperate the vehicle. Range data generated by the on-board 3D sensors was transformed into surface maps, or models. Registering the sensor location to a consistent reference frame as the platform moved through the workspace allowed construction of a detailed 3D world model of the extended workspace.
Magnetic Branes from Generalized 't Hooft Tensor
NASA Astrophysics Data System (ADS)
Duan, Yi-Shi; Wu, Shao-Feng
't Hooft-Polykov magnetic monopole regularly realizes the Dirac magnetic monopole in terms of a two-rank tensor, the so-called 't Hooft tensor in 3D space. Based on the Chern kernel method, we propose the arbitrary rank 't Hooft tensors, which universally determine the quantized low energy boundaries of generalized Georgi-Glashow models under asymptotic conditions. Furthermore, the dual magnetic branes theory is built up in terms of ϕ-mapping theory.
World Energy Projection System Plus Model Documentation: Main Model
2016-01-01
This report documents the objectives, analytical approach and development of the World Energy Projection System Plus (WEPS ) Main Model. It also catalogues and describes critical assumptions, computational methodology, parameter estimation techniques, and model source code.
World Energy Projection System Plus Model Documentation: Greenhouse Gases Model
2011-01-01
This report documents the objectives, analytical approach and development of the World Energy Projection System Plus (WEPS ) Greenhouse Gases Model. It also catalogues and describes critical assumptions, computational methodology, parameter estimation techniques, and model source code.
World Energy Projection System Plus Model Documentation: Refinery Model
2016-01-01
This report documents the objectives, analytical approach and development of the World Energy Projection System Plus (WEPS ) Refinery Model. It also catalogues and describes critical assumptions, computational methodology, parameter estimation techniques, and model source code.
World Energy Projection System Plus Model Documentation: Coal Model
2011-01-01
This report documents the objectives, analytical approach and development of the World Energy Projection System Plus (WEPS ) Coal Model. It also catalogues and describes critical assumptions, computational methodology, parameter estimation techniques, and model source code.
World Energy Projection System Plus Model Documentation: Residential Model
2016-01-01
This report documents the objectives, analytical approach and development of the World Energy Projection System Plus (WEPS ) Residential Model. It also catalogues and describes critical assumptions, computational methodology, parameter estimation techniques, and model source code.
World Energy Projection System Plus Model Documentation: Transportation Model
2011-01-01
This report documents the objectives, analytical approach and development of the World Energy Projection System Plus (WEPS ) International Transportation model. It also catalogues and describes critical assumptions, computational methodology, parameter estimation techniques, and model source code.
World Energy Projection System Plus Model Documentation: District Heat Model
2017-01-01
This report documents the objectives, analytical approach and development of the World Energy Projection System Plus (WEPS ) District Heat Model. It also catalogues and describes critical assumptions, computational methodology, parameter estimation techniques, and model source code.
World Energy Projection System Plus Model Documentation: Natural Gas Model
2011-01-01
This report documents the objectives, analytical approach and development of the World Energy Projection System Plus (WEPS ) Natural Gas Model. It also catalogues and describes critical assumptions, computational methodology, parameter estimation techniques, and model source code.
NASA Astrophysics Data System (ADS)
Clark, T. E.; ter Veldhuis, T.
2016-11-01
Coset methods are used to determine the action of a co-dimension one brane (domain wall) embedded in (d + 1)-dimensional AdS space in the Carroll limit in which the speed of light goes to zero. The action is invariant under the non-linearly realized symmetries of the AdS-Carroll spacetime. The Nambu-Goldstone field exhibits a static spatial distribution for the brane with a time varying momentum density related to the brane's spatial shape as well as the AdS-C geometry. The AdS-C vector field dual theory is obtained.
Localization and mass spectra of various matter fields on scalar-tensor brane
Xie, Qun-Ying; Zhao, Zhen-Hua; Zhong, Yi; Yang, Jie; Zhou, Xiang-Nan
2015-03-10
Recently, a new scalar-tensor braneworld model was presented in [http://dx.doi.org/10.1103/PhysRevD.86.127502]. It not only solves the gauge hierarchy problem but also reproduces a correct Friedmann-like equation on the brane. In this new model, there are two different brane solutions, for which the mass spectra of gravity on the brane are the same. In this paper, we investigate localization and mass spectra of various bulk matter fields (i.e., scalar, vector, Kalb-Ramond, and fermion fields) on the brane. It is shown that the zero modes of all the matter fields can be localized on the positive tension brane under some conditions, and the mass spectra of each kind of bulk matter field for the two brane solutions are different except for some special cases, which implies that the two brane solutions are not physically equivalent. When the coupling constants between the dilaton and bulk matter fields take special values, the mass spectra for both solutions are the same, and the scalar and vector zero modes are localized on the negative tension brane, while the KR zero mode is still localized on the positive tension brane.
AdS5 solutions from M5-branes on Riemann surface and D6-branes sources
NASA Astrophysics Data System (ADS)
Bah, Ibrahima
2015-09-01
We describe the gravity duals of four-dimensional N=1 superconformal field theories obtained by wrapping M5-branes on a punctured Riemann surface. The internal geometry, normal to the AdS 5 factor, generically preserves two U(1)s, with generators ( J +, J -), that are fibered over the Riemann surface. The metric is governed by a single potential that satisfies a version of the Monge-Ampère equation. The spectrum of N=1 punctures is given by the set of supersymmetric sources of the potential that are localized on the Riemann surface and lead to regular metrics near a puncture. We use this system to study a class of punctures where the geometry near the sources corresponds to M-theory description of D6-branes. These carry a natural ( p, q) label associated to the circle dual to the killing vector pJ + + qJ - which shrinks near the source. In the generic case the world volume of the D6-branes is AdS 5 × S 2 and they locally preserve N=2 supersymmetry. When p = - q, the shrinking circle is dual to a flavor U(1). The metric in this case is non-degenerate only when there are co-dimension one sources obtained by smearing M5-branes that wrap the AdS 5 factor and the circle dual the superconformal R-symmetry. The D6-branes are extended along the AdS 5 and on cups that end on the co-dimension one branes. In the special case when the shrinking circle is dual to the R-symmetry, the D6-branes are extended along the AdS 5 and wrap an auxiliary Riemann surface with an arbitrary genus. When the Riemann surface is compact with constant curvature, the system is governed by a Monge-Ampère equation.
Fluid/gravity correspondence and the CFM black brane solutions
NASA Astrophysics Data System (ADS)
Casadio, R.; Cavalcanti, R. T.; da Rocha, Roldão
2016-10-01
We consider the lower bound for the shear viscosity-to-entropy density ratio, obtained from the fluid/gravity correspondence, in order to constrain the post-Newtonian parameter of brane-world metrics. In particular, we analyse the Casadio-Fabbri-Mazzacurati (CFM) effective solutions for the gravity side of the correspondence and argue that including higher-order terms in the hydrodynamic expansion can lead to a full agreement with the experimental bounds, for the Eddington-Robertson-Schiff post-Newtonian parameter in the CFM metrics. This lends further support to the physical relevance of the viscosity-to-entropy ratio lower bound and fluid/gravity correspondence. Hence we show that CFM black branes are, effectively, Schwarzschild black branes.
Brane Inflation, Solitons and Cosmological Solutions: I
Chen, P.
2005-01-25
In this paper we study various cosmological solutions for a D3/D7 system directly from M-theory with fluxes and M2-branes. In M-theory, these solutions exist only if we incorporate higher derivative corrections from the curvatures as well as G-fluxes. We take these corrections into account and study a number of toy cosmologies, including one with a novel background for the D3/D7 system whose supergravity solution can be completely determined. Our new background preserves all the good properties of the original model and opens up avenues to investigate cosmological effects from wrapped branes and brane-antibrane annihilation, to name a few. We also discuss in some detail semilocal defects with higher global symmetries, for example exceptional ones, that occur in a slightly different regime of our D3/D7 model. We show that the D3/D7 system does have the required ingredients to realize these configurations as non-topological solitons of the theory. These constructions also allow us to give a physical meaning to the existence of certain underlying homogeneous quaternionic Kahler manifolds.
Validating agent based models through virtual worlds.
Lakkaraju, Kiran; Whetzel, Jonathan H.; Lee, Jina; Bier, Asmeret Brooke; Cardona-Rivera, Rogelio E.; Bernstein, Jeremy Ray Rhythm
2014-01-01
As the US continues its vigilance against distributed, embedded threats, understanding the political and social structure of these groups becomes paramount for predicting and dis- rupting their attacks. Agent-based models (ABMs) serve as a powerful tool to study these groups. While the popularity of social network tools (e.g., Facebook, Twitter) has provided extensive communication data, there is a lack of ne-grained behavioral data with which to inform and validate existing ABMs. Virtual worlds, in particular massively multiplayer online games (MMOG), where large numbers of people interact within a complex environ- ment for long periods of time provide an alternative source of data. These environments provide a rich social environment where players engage in a variety of activities observed between real-world groups: collaborating and/or competing with other groups, conducting battles for scarce resources, and trading in a market economy. Strategies employed by player groups surprisingly re ect those seen in present-day con icts, where players use diplomacy or espionage as their means for accomplishing their goals. In this project, we propose to address the need for ne-grained behavioral data by acquiring and analyzing game data a commercial MMOG, referred to within this report as Game X. The goals of this research were: (1) devising toolsets for analyzing virtual world data to better inform the rules that govern a social ABM and (2) exploring how virtual worlds could serve as a source of data to validate ABMs established for analogous real-world phenomena. During this research, we studied certain patterns of group behavior to compliment social modeling e orts where a signi cant lack of detailed examples of observed phenomena exists. This report outlines our work examining group behaviors that underly what we have termed the Expression-To-Action (E2A) problem: determining the changes in social contact that lead individuals/groups to engage in a particular behavior
Holographic Systematics of D-brane Inflation
Baumann, Daniel; Dymarsky, Anatoly; Kachru, Shamit; Klebanov, Igor R.; McAllister, Liam; /Cornell U., Phys. Dept.
2008-11-05
We provide a systematic treatment of possible corrections to the inflaton potential for D-brane inflation in the warped deformed conifold. We consider the D3-brane potential in the presence of the most general possible corrections to the throat geometry sourced by coupling to the bulk of a compact Calabi-Yau space. This corresponds to the potential on the Coulomb branch of the dual gauge theory, in the presence of arbitrary perturbations of the Lagrangian. The leading contributions arise from perturbations by the most relevant operators that do not destroy the throat geometry. We find a generic contribution from a non-chiral operator of dimension {Delta} = 2 associated with a global symmetry current, resulting in a negative contribution to the inflaton mass-squared. If the Calabi-Yau preserves certain discrete symmetries, this is the dominant correction to the inflaton potential, and fine-tuning of the inflaton mass is possible. In the absence of such discrete symmetries, the dominant contribution comes from a chiral operator with {Delta} = 3/2, corresponding to a {phi}{sup 3/2} term in the inflaton potential. The resulting inflationary models are phenomenologically identical to the inflection point scenarios arising from specific D7-brane embeddings, but occur under far more general circumstances. Our strategy extends immediately to other warped geometries, given sufficient knowledge of the Kaluza-Klein spectrum.
Cai Ronggen; Li Tong; Li Xueqian; Wang Xun
2007-11-15
Motivated by the alpha-magnetic-spectrometer (AMS) project, we assume that after the big bang or inflation epoch, antimatter was repelled onto one brane which is separated from our brane where all the observational matter resides. It is suggested that CP may be spontaneously broken, the two branes would correspond to ground states for matter and antimatter, respectively. Generally a complex scalar field which is responsible for the spontaneous CP violation, exists in the space between the branes. The matter and antimatter on the two branes attract each other via gravitational force, meanwhile the scalar field causes a Casimir effect to result in a repulsive force against the gravitation. We find that the Casimir force is much stronger than the gravitational force, as long as the separation of the two branes is small. Thus at early epoch after the big bang, the two branes were closer and then have been separated by the Casimir repulsive force from each other. The trend will continue until the separation is sufficiently large and then the gravitational force observed in our four-space would obviously deviate from the Newton's universal gravitational law. We suppose that there is a potential barrier at the brane boundary, which is similar to the surface tension for a water membrane. The barrier prevents the matter (antimatter) particles from entering the space between two branes and jump from one brane to another. However, by the quantum tunneling, a sizable antimatter flux may come to our brane and be observed by the AMS. In this work by considering two possible models, i.e. the naive flat space-time and Randall-Sundrum models, and using the observational data on the visible matter in our universe as inputs, we derive the antimatter flux which comes to our detector in the nonrelativistic approximation and make a rough numerical estimate of possible numbers of antihelium at AMS.
Sp-branes: integrable multidimensional cosmologies
NASA Astrophysics Data System (ADS)
Baukh, V.; Zhuk, A.
2006-10-01
We investigate time-dependent solutions (Sp-brane solutions) for product manifolds consisting of factor spaces where only one of them is of a non-Ricci-flat type. Our model contains a minimally coupled free scalar field and form field (flux) as matter sources. We discuss the possibility of generating late-time acceleration of the Universe. For these models, we investigate the variation with time of the effective four-dimensional fundamental 'constants'. We show that experimental bounds for the fundamental constant variations apply strong restrictions to the considered models.
Modelling ecological systems in a changing world.
Evans, Matthew R
2012-01-19
The world is changing at an unprecedented rate. In such a situation, we need to understand the nature of the change and to make predictions about the way in which it might affect systems of interest; often we may also wish to understand what might be done to mitigate the predicted effects. In ecology, we usually make such predictions (or forecasts) by making use of mathematical models that describe the system and projecting them into the future, under changed conditions. Approaches emphasizing the desirability of simple models with analytical tractability and those that use assumed causal relationships derived statistically from data currently dominate ecological modelling. Although such models are excellent at describing the way in which a system has behaved, they are poor at predicting its future state, especially in novel conditions. In order to address questions about the impact of environmental change, and to understand what, if any, action might be taken to ameliorate it, ecologists need to develop the ability to project models into novel, future conditions. This will require the development of models based on understanding the processes that result in a system behaving the way it does, rather than relying on a description of the system, as a whole, remaining valid indefinitely.
Microscopic entropy of nondilatonic branes: A 2D approach
NASA Astrophysics Data System (ADS)
Cadoni, Mariano; Serra, Nicola
2004-12-01
We investigate nondilatonic p-branes in the near-extremal, near-horizon regime. A two-dimensional gravity model, obtained from dimensional reduction, gives an effective description of the brane. We show that the AdSp+2/CFTp+1 correspondence at finite temperature admits an effective description in terms of a AdS2/CFT1 duality endowed with a scalar field, which breaks the conformal symmetry and generates a nonvanishing central charge. The entropy of the CFT1 is computed using Cardy formula. Fixing in a natural way a free, dimensionless, parameter introduced in the model by a renormalization procedure, we find exact agreement between the CFT1 entropy and the Bekenstein-Hawking entropy of the brane.
Ostrogradski Hamiltonian approach for geodetic brane gravity
Cordero, Ruben; Molgado, Alberto
2010-12-07
We present an alternative Hamiltonian description of a branelike universe immersed in a flat background spacetime. This model is named geodetic brane gravity. We set up the Regge-Teitelboim model to describe our Universe where such field theory is originally thought as a second order derivative theory. We refer to an Ostrogradski Hamiltonian formalism to prepare the system to its quantization. This approach comprize the manage of both first- and second-class constraints and the counting of degrees of freedom follows accordingly.
NASA Astrophysics Data System (ADS)
Pejhan, Hamed; Rahbardehghan, Surena
2016-09-01
In a previous work [S. Rahbardehghan and H. Pejhan, Phys. Lett. B 750, 627 (2015)], we considered a simple brane-world model: a single four-dimensional brane embedded in a five-dimensional de Sitter (dS) space-time. Then, by including a conformally coupled scalar field in the bulk, we studied the induced Casimir energy-momentum tensor. Technically, the Krein-Gupta-Bleuler quantization scheme as a covariant and renormalizable quantum field theory in dS space was used to perform the calculations. In the present paper, we generalize this study to a less idealized, but physically motivated, scenario; namely, we consider Friedmann-Robertson-Walker (FRW) space-time which behaves asymptotically as a dS space-time. More precisely, we evaluate a Casimir energy-momentum tensor for a system with two D -dimensional curved branes on background of D +1 -dimensional FRW space-time with negative spatial curvature and a conformally coupled bulk scalar field that satisfied the Dirichlet boundary condition on the branes.
Degenerate and critical Bloch branes
Souza Dutra, A. de; Amaro de Faria, A. C. Jr.; Hott, M.
2008-08-15
In the last few years a number of works reported the appearance of thick branes with internal structure, induced by the parameter which controls the interaction between two scalar fields coupled to gravity in (4,1) dimensions in warped space-time with one extra dimension. Here we show that one can implement the control over the brane thickness without needing to change the potential parameter. On the contrary, this is going to be done by means of the variation of a parameter associated with the domain wall degeneracy. We also report the existence of novel and qualitatively different solutions for a critical value of the degeneracy parameter, which could be called critical Bloch branes.
Fermion localization on thick branes
Melfo, Alejandra; Pantoja, Nelson; Tempo, Jose David
2006-02-15
We consider chiral fermion confinement in scalar thick branes, which are known to localize gravity, coupled through a Yukawa term. The conditions for the confinement and their behavior in the thin-wall limit are found for various different BPS branes, including double walls and branes interpolating between different AdS{sub 5} spacetimes. We show that only one massless chiral mode is localized in all these walls, whenever the wall thickness is keep finite. We also show that, independently of wall's thickness, chiral fermionic modes cannot be localized in dS{sub 4} walls embedded in a M{sub 5} spacetime. Finally, massive fermions in double wall spacetimes are also investigated. We find that, besides the massless chiral mode localization, these double walls support quasilocalized massive modes of both chiralities.
NASA Astrophysics Data System (ADS)
Kofinas, Georgios; Irakleidou, Maria
2014-03-01
We raise on theoretical grounds the question of the physical relevance of Israel matching conditions and their generalizations to higher codimensions, the standard cornerstone of the braneworld and other membrane scenarios. Our reasoning is based on the incapability of the conventional matching conditions to accept the Nambu-Goto probe limit, the inconsistency of codimension-2 and -3 classical defects for D=4 and the probable inconsistency of high enough codimensional defects for any D since there is no high enough Lovelock density to support them. We propose alternative matching conditions which seem to overcome the previous puzzles. Instead of varying the brane-bulk action with respect to the bulk metric at the brane position, we vary with respect to the brane embedding fields so that the gravitational backreaction is included ("gravitating Nambu-Goto matching conditions"). Here, we consider in detail the case of a codimension-2 brane in 6-dim Einstein-Gauss-Bonnet gravity, prove its consistency for an axially symmetric cosmological configuration and show that the theory possesses richer structure compared to the standard theory. The cosmologies found have the Friedmann behavior and extra correction terms. For a radiation brane one solution avoids a cosmological singularity and undergoes accelerated expansion near the minimum scale factor. In the presence of an induced gravity term, there naturally appears in the theory the effective cosmological constant scale λ /(M64rc2), which for a brane tension λ ˜M64 (e.g. TeV4) and rc˜H0-1 gives the observed value of the cosmological constant.
World Energy Projection System model documentation
Hutzler, M.J.; Anderson, A.T.
1997-09-01
The World Energy Projection System (WEPS) was developed by the Office of Integrated Analysis and Forecasting within the Energy Information Administration (EIA), the independent statistical and analytical agency of the US Department of Energy. WEPS is an integrated set of personal computer based spreadsheets containing data compilations, assumption specifications, descriptive analysis procedures, and projection models. The WEPS accounting framework incorporates projections from independently documented models and assumptions about the future energy intensity of economic activity (ratios of total energy consumption divided by gross domestic product GDP), and about the rate of incremental energy requirements met by natural gas, coal, and renewable energy sources (hydroelectricity, geothermal, solar, wind, biomass, and other renewable resources). Projections produced by WEPS are published in the annual report, International Energy Outlook. This report documents the structure and procedures incorporated in the 1998 version of the WEPS model. It has been written to provide an overview of the structure of the system and technical details about the operation of each component of the model for persons who wish to know how WEPS projections are produced by EIA.
NASA Astrophysics Data System (ADS)
Koivisto, Tomi Sebastian; Wills, Danielle Elizabeth
2013-10-01
A novel generalization of the Dirac-Born-Infeld string scenario is described. It is shown that matter residing on the moving brane is dark and has the so-called disformal coupling to gravity. This gives rise to cosmologies where dark matter stems from the oscillations of the open strings along the brane and the transverse oscillations result in dark energy. Furthermore, due to a new screening mechanism that conceals the fifth force from local experiments, one may even entertain the possibility that the visible sector is also moving along the extra dimensions.
Lifshitz hydrodynamics from Lifshitz black branes with linear momentum
NASA Astrophysics Data System (ADS)
Hartong, Jelle; Obers, Niels A.; Sanchioni, Marco
2016-10-01
We construct a new class of 4-dimensional z = 2 Lifshitz black branes that have a non-zero linear momentum. These are solutions of an Einstein-Proca-dilaton model that can be obtained by Scherk-Schwarz circle reduction of AdS5 gravity coupled to a free real scalar field. The boundary of a bulk Lifshitz space-time is a Newton-Cartan geometry. We show that the fluid dual to the moving Lifshitz black brane leads to a novel form of Lifshitz hydrodynamics on a Newton-Cartan space-time. Since the linear momentum of the black brane cannot be obtained by a boost transformation the velocity of the fluid or rather, by boundary rotational invariance, its magnitude plays the role of a chemical potential. The conjugate dual variable is mass density. The Lifshitz perfect fluid can be thought of as arising from a Schrödinger perfect fluid with broken particle number symmetry.
D-branes and coherent topological charge structure in QCD
NASA Astrophysics Data System (ADS)
Thacker, Hank
2006-12-01
Monte Carlo studies of pure glue SU(3) gauge theory using the overlap-based topological charge operator have revealed a laminar structure in the QCD vacuum consisting of extended, thin, co- herent, locally 3-dimensional sheets of topological charge embedded in 4D space, with opposite sign sheets interleaved. Studies of localization properties of Dirac eigenmodes have also shown evidence for the delocalization of low-lying modes on effectively 3-dimensional surfaces. In this talk, I review some theoretical ideas which suggest the possibility of 3-dimensionally coherent topological charge structure in 4-dimensional gauge theory and provide a possible interpretation of the observed structure. I begin with Luscher's "Wilson bag" integral over the 3-index Chern- Simons tensor. The analogy with a Wilson loop as a charged world line in 2-dimensional CP N-1 sigma models suggests that the Wilson bag surface represents the world volume of a physical membrane. The large-N chiral Lagrangian arguments of Witten also indicate the existence of multiple "k-vacuum" states with discontinuous transitions between k-vacua at θ = odd multi- ples of π. The domain walls between these vacua have the properties of a Wilson bag surface. Finally, I review the AdS/CFT duality view of θ dependence in QCD. The dual realtionship be- tween topological charge in gauge theory and Ramond-Ramond charge in type IIA string theory suggests that the coherent topological charge sheets observed on the lattice are the holographic image of wrapped D6 branes.
Branes in Extended Spacetime: Brane Worldvolume Theory Based on Duality Symmetry.
Sakatani, Yuho; Uehara, Shozo
2016-11-04
We propose a novel approach to the brane worldvolume theory based on the geometry of extended field theories: double field theory and exceptional field theory. We demonstrate the effectiveness of this approach by showing that one can reproduce the conventional bosonic string and membrane actions, and the M5-brane action in the weak-field approximation. At a glance, the proposed 5-brane action without approximation looks different from the known M5-brane actions, but it is consistent with the known nonlinear self-duality relation, and it may provide a new formulation of a single M5-brane action. Actions for exotic branes are also discussed.
D0- and D1-branes with κ- and κ+ extended symmetry
NASA Astrophysics Data System (ADS)
Moshe, Moshe; Sakai, Norisuke
2000-10-01
D0-brane (D-particle) and D1-brane actions possess first and second class constraints that result in local κ symmetry. The κ symmetry of the D-particle and the D1-brane is extended here into a larger symmetry (κ- and κ+) in a larger phase space by turning second class constraints into first class constraints. Different gauge fixings of these symmetries result in different presentations of these systems while a ``unitary'' gauge fixing of the new κ+ symmetry retrieves the original action with κ-=κ symmetry. For a D1-brane our extended phase space makes all constraints into first class constraints in the case of a vanishing world sheet electric field [namely, (0,1) string].
Sensory processing and world modeling for an active ranging device
NASA Technical Reports Server (NTRS)
Hong, Tsai-Hong; Wu, Angela Y.
1991-01-01
In this project, we studied world modeling and sensory processing for laser range data. World Model data representation and operation were defined. Sensory processing algorithms for point processing and linear feature detection were designed and implemented. The interface between world modeling and sensory processing in the Servo and Primitive levels was investigated and implemented. In the primitive level, linear features detectors for edges were also implemented, analyzed and compared. The existing world model representations is surveyed. Also presented is the design and implementation of the Y-frame model, a hierarchical world model. The interfaces between the world model module and the sensory processing module are discussed as well as the linear feature detectors that were designed and implemented.
World Energy Projection System Plus Model Documentation: Commercial Model
2016-01-01
The Commercial Model of the World Energy Projection System Plus (WEPS ) is an energy demand modeling system of the world commercial end?use sector at a regional level. This report describes the version of the Commercial Model that was used to produce the commercial sector projections published in the International Energy Outlook 2016 (IEO2016). The Commercial Model is one of 13 components of the WEPS system. The WEPS is a modular system, consisting of a number of separate energy models that are communicate and work with each other through an integrated system model. The model components are each developed independently, but are designed with well?defined protocols for system communication and interactivity. The WEPS modeling system uses a shared database (the “restart” file) that allows all the models to communicate with each other when they are run in sequence over a number of iterations. The overall WEPS system uses an iterative solution technique that forces convergence of consumption and supply pressures to solve for an equilibrium price.
Improvements in Empirical Modelling of the World-Wide Ionosphere
1986-10-31
OF THE WORLD -’WIDE IONOSPHIERE.I Prof. Kurt Suchy Inst. f. Theor. Physik 11...ELEMENT NO. NO. NO ACCESSION NO 62101F 4643 08 11. TITLE (Andude Secu ty Clauiflcation) IMPROVEMENTS IN EMPIRICAL MODELLING OF THE WORLD -WIDE IONOSPHERE 1...THE FIGURES 53 - 57 ’ " " i " I ’ Q !NMI- P ’ I IMPROVE MENTS IN EMPIRICAL MODELLING OF THE WORLD -WIDE IONOSPHERE 1. INTRODUCTION Numerical Models
Zero branes on a compact orbifold
NASA Astrophysics Data System (ADS)
Ramgoolam, Sanjaye; Waldram, Daniel
1998-07-01
The non-commutative algebra which defines the theory of zero-branes on T4/Z2 allows a unified description of moduli spaces associated with zero-branes, two-branes and four-branes on the orbifold space. Bundles on a dual space hat T4/Z2 play an important role in this description. We discuss these moduli spaces in the context of dualities of K3 compactifications, and in terms of properties of instantons on T4. Zero-branes on the degenerate limits of the compact orbifold lead to fixed points with six-dimensional scale but not conformal invariance. We identify some of these in terms of the ADS dual of the (0,2) theory at large N, giving evidence for an interesting picture of ``where the branes live'' in ADS.
Cosmology from quantum potential in brane-anti-brane system
NASA Astrophysics Data System (ADS)
Sepehri, Alireza
2015-09-01
Recently, some authors removed the big-bang singularity and predicted an infinite age of our universe. In this paper, we show that the same result can be obtained in string theory and M-theory; however, the shape of universe changes in different epochs. In our mechanism, first, N fundamental string decay to N D0-anti-D0-brane. Then, D0-branes join each other, grow and form a six-dimensional brane-antibrane system. This system is unstable, broken and at present the form of four-dimensional universes, one anti-universe in addition to one wormhole are produced. Thus, there isn't any big-bang in cosmology and the universe is a fundamental string at the beginning. Also, the total age of universe contains two parts, one is related to initial age and the other corresponds to the present age of universe (ttot =tinitial +tpresent). On the other hand, the initial age of universe includes two parts, the age of fundamental string and the time of transition (tinitial =ttransition +tf-string). We observe that only in the case of (tf-string → ∞), the scale factor of universe is zero and as a result, the total age of universe is infinity.
Spinflation and Cycling Branes in Warped Throats
Easson, Damien A.
2007-11-20
The implications of brane motion in angular directions of Calabi-Yau flux compactifications is discussed from the point of view of an observer living on the worldvolume of such a brane and from the point of view of an observer living elsewhere in the three non-compact dimensions. The brane observer experiences cosmological bounces and cyclic behavior induced by centrifugal angular momentum barriers. Observers living elsewhere in the compactification experience marginally prolonged periods of inflation due to large angular momentum.
Localizing gravity on exotic thick 3-branes
Castillo-Felisola, Oscar; Melfo, Alejandra; Pantoja, Nelson; Ramirez, Alba
2004-11-15
We consider localization of gravity on thick branes with a nontrivial structure. Double walls that generalize the thick Randall-Sundrum solution, and asymmetric walls that arise from a Z{sub 2} symmetric scalar potential, are considered. We present a new asymmetric solution: a thick brane interpolating between two AdS{sub 5} spacetimes with different cosmological constants, which can be derived from a 'fake supergravity' superpotential, and show that it is possible to confine gravity on such branes.
Cosmological dynamics of brane f(R) gravity
Haghani, Zahra; Sepangi, Hamid Reza; Shahidi, Shahab E-mail: hr-sepangi@sbu.ac.ir
2012-02-01
The cosmological dynamics of a brane world scenario where the bulk action is taken as a generic function of the Ricci scalar is considered in a framework where the use of the Z{sub 2} symmetry and Israel junction conditions are relaxed. The corresponding cosmological solutions for some specific forms of f(R) are obtained and shown to be in the form of exponential as well as power law for a vacuum brane space-time. It is shown that the existence of matter dominated epoch for a bulk action in the form of a power law for R can only be obtained in the presence of ordinary matter. Using phase space analysis, we show that the universe must start from an unstable matter dominated epoch and eventually falls into a stable accelerated expanding phase.
Supersymmetric Intersecting Branes on the Type IIA T6/Bbb Z4 Orientifold
NASA Astrophysics Data System (ADS)
Blumenhagen, Ralph; Görlich, Lars; Ott, Tassilo
2003-01-01
We study supersymmetric intersecting D6-branes wrapping 3-cycles in the Type IIA T6/Z4 orientifold background. As a new feature, the 3-cycles in this orbifold space arise both from the untwisted and the Z2 twisted sectors. We present an integral basis for the homology lattice, H3(M,Z), in terms of fractional 3-cycles, for which the intersection form involves the Cartan matrix of E8. We show that these fractional D6-branes can be used to construct supersymmetric brane configurations realizing a three generation Pati-Salam model. Via brane recombination processes preserving supersymmetry, this GUT model can be broken down to a standard-like model.
Black branes in flux compactifications
Torroba, Gonzalo; Wang, Huajia
2013-10-01
We construct charged black branes in type IIA flux compactifications that are dual to (2 + 1)-dimensional field theories at finite density. The internal space is a general Calabi-Yau manifold with fluxes, with internal dimensions much smaller than the AdS radius. Gauge fields descend from the 3-form RR potential evaluated on harmonic forms of the Calabi-Yau, and Kaluza-Klein modes decouple. Black branes are described by a four-dimensional effective field theory that includes only a few light fields and is valid over a parametrically large range of scales. This effective theory determines the low energy dynamics, stability and thermodynamic properties. Tools from flux compactifications are also used to construct holographic CFTs with no relevant scalar operators, that can lead to symmetric phases of condensed matter systems stable to very low temperatures. The general formalism is illustrated with simple examples such as toroidal compactifications and manifolds with a single size modulus. We initiate the classification of holographic phases of matter described by flux compactifications, which include generalized Reissner-Nordstrom branes, nonsupersymmetric AdS_{2}×R^{2} and hyperscaling violating solutions.
Marginal fluctuations as instantons on M2/D2-branes
NASA Astrophysics Data System (ADS)
Naghdi, M.
2014-03-01
We introduce some (anti-) M/D-branes through turning on the corresponding field strengths of the 11- and 10-dimensional supergravity theories over spaces, where we use and for the internal spaces. Indeed, when we add M2/D2-branes on the same directions with the near horizon branes of the Aharony-Bergman-Jafferis-Maldacena model, all symmetries and supersymmetries are preserved trivially. In this case, we obtain a localized object just in the horizon. This normalizable bulk massless scalar mode is a singlet of and , and it agrees with a marginal boundary operator of the conformal dimension of . However, after performing a special conformal transformation, we see that the solution is localized in the Euclideanized space and is attributable to the included anti-M2/D2-branes, which are also necessary to ensure that there is no back-reaction. The resultant theory now breaks all supersymmetries to , while the other symmetries are so preserved. The dual boundary operator is then set up from the skew-whiffing of the representations and for the supercharges and scalars, respectively, while the fermions remain fixed in of the original theory. Besides, we also address another alternate bulk to boundary matching procedure through turning on one of the gauge fields of the full gauge group along the same lines with a similar situation to the one faced in the AdS/CFT correspondence. The latter approach covers the difficulty already faced with in the bulk-boundary matching procedure for as well.
Teleparallel loop quantum cosmology in a system of intersecting branes
NASA Astrophysics Data System (ADS)
Sepehri, Alireza; Pradhan, Anirudh; Beesham, Aroonkumar; de Haro, Jaume
2016-09-01
Recently, some authors have removed the big bang singularity in teleparallel Loop Quantum Cosmology (LQC) and have shown that the universe may undergo a number of oscillations. We investigate the origin of this type of teleparallel theory in a system of intersecting branes in M-theory in which the angle between them changes with time. This system is constructed by two intersecting anti-D8-branes, one compacted D4-brane and a D3-brane. These branes are built by joining M0-branes which develop in decaying fundamental strings. The compacted D4-brane is located between two intersecting anti-D8 branes and glues to one of them. Our universe is located on the D3 brane which wraps around the D4 brane from one end and sticks to one of the anti-D8 branes from the other one. In this system, there are three types of fields, corresponding to compacted D4 branes, intersecting branes and D3-branes. These fields interact with each other and make the angle between branes oscillate. By decreasing this angle, the intersecting anti-D8 branes approach each other, the D4 brane rolls, the D3 brane wraps around the D4 brane, and the universe contracts. By separating the intersecting branes and increasing the angle, the D4 brane rolls in the opposite direction, the D3 brane separates from it and the expansion branch begins. Also, the interaction between branes in this system gives us the exact form of the relevant Lagrangian for teleparallel LQC.
From local to global in F-theory model building
NASA Astrophysics Data System (ADS)
Andreas, Björn; Curio, Gottfried
2010-09-01
When locally engineering F-theory models some D7-branes for the gauge group factors are specified and matter is localized on the intersection curves of the compact parts of the world-volumes. In this note, we discuss to what extent one can draw conclusions about F-theory models by just restricting the attention locally to a particular seven-brane. Globally, the possible D7-branes are not independent from each other and the (compact part of the) D7-brane can have unavoidable intrinsic singularities. Many special intersecting loci which were not chosen by hand occur inevitably, notably codimension-three loci which are not intersections of matter curves. We describe these complications specifically in a global SU(5) model and also their impact on the tadpole cancellation condition.
Standard 4D gravity on a brane in six-dimensional flux compactifications
Peloso, Marco; Sorbo, Lorenzo; Tasinato, Gianmassimo
2006-05-15
We consider a six-dimensional space-time, in which two of the dimensions are compactified by a flux. Matter can be localized on a codimension one brane coupled to the bulk gauge field and wrapped around an axis of symmetry of the internal space. By studying the linear perturbations around this background, we show that the gravitational interaction between sources on the brane is described by Einstein 4D gravity at large distances. Our model provides a consistent setup for the study of gravity in the rugby (or football) compactification, without having to deal with the complications of a deltalike, codimension two brane. To our knowledge, this is the first complete study of gravity in a realistic brane model with two extra dimensions, in which the mechanism of stabilization of the extra space is fully taken into account.
Common world model for unmanned systems: Phase 2
NASA Astrophysics Data System (ADS)
Dean, Robert M. S.; Oh, Jean; Vinokurov, Jerry
2014-06-01
The Robotics Collaborative Technology Alliance (RCTA) seeks to provide adaptive robot capabilities which move beyond traditional metric algorithms to include cognitive capabilities. Key to this effort is the Common World Model, which moves beyond the state-of-the-art by representing the world using semantic and symbolic as well as metric information. It joins these layers of information to define objects in the world. These objects may be reasoned upon jointly using traditional geometric, symbolic cognitive algorithms and new computational nodes formed by the combination of these disciplines to address Symbol Grounding and Uncertainty. The Common World Model must understand how these objects relate to each other. It includes the concept of Self-Information about the robot. By encoding current capability, component status, task execution state, and their histories we track information which enables the robot to reason and adapt its performance using Meta-Cognition and Machine Learning principles. The world model also includes models of how entities in the environment behave which enable prediction of future world states. To manage complexity, we have adopted a phased implementation approach. Phase 1, published in these proceedings in 2013 [1], presented the approach for linking metric with symbolic information and interfaces for traditional planners and cognitive reasoning. Here we discuss the design of "Phase 2" of this world model, which extends the Phase 1 design API, data structures, and reviews the use of the Common World Model as part of a semantic navigation use case.
Not Available
1994-04-11
This manual is intended primarily for use as a reference by analysts applying the WORLD model to regional studies. It also provides overview information on WORLD features of potential interest to managers and analysts. Broadly, the manual covers WORLD model features in progressively increasing detail. Section 2 provides an overview of the WORLD model, how it has evolved, what its design goals are, what it produces, and where it can be taken with further enhancements. Section 3 reviews model management covering data sources, managing over-optimization, calibration and seasonality, check-points for case construction and common errors. Section 4 describes in detail the WORLD system, including: data and program systems in overview; details of mainframe and PC program control and files;model generation, size management, debugging and error analysis; use with different optimizers; and reporting and results analysis. Section 5 provides a detailed description of every WORLD model data table, covering model controls, case and technology data. Section 6 goes into the details of WORLD matrix structure. It provides an overview, describes how regional definitions are controlled and defines the naming conventions for-all model rows, columns, right-hand sides, and bounds. It also includes a discussion of the formulation of product blending and specifications in WORLD. Several Appendices supplement the main sections.
Meta-Stable Vacua and D-Branes at the Conifold
Argurio, Riccardo; Bertolini, Matteo; Kachru, Shamit
2008-07-28
We study gauge theories arising on D-branes on quotients of the conifold. They exhibit meta-stable SUSY breaking along the lines of the model by Intriligator, Seiberg and Shih. We propose a candidate for the extrapolation to large't Hooft coupling of the meta-stable state. It involves anti D3-branes in a smooth gravity dual of a cascading gauge theory.
[The Bariloche model: a Latin American world model].
Johr, W A
1981-01-01
At the beginning of the 1970s, a research team under the direction of Amilcar O. Herrera was constituted within the Bariloche Foundation of Buenos Aires. Its task was to write a counterreport to the research work initiated by the Club of Rome, carried out under the direction of Dennis L. Meadows, and published with the title "The Limits to Growth." The 1st of 2 main parts of our study provides an extensive abstract of the basic arguments of the Bariloche Team. Its report begins by shaping the framework (socialist) of the proposed New Society which, it is claimed, would have the responsibility of satisfying the basic needs of all human beings in all parts of the world. With the aid of a projection model, comprising a period up to the year 2060, the authors attempt to answer the question of the extent to which the 4 world regions of the model can, under the conditions of the New Society, satisfy the basic needs of the population. In the 2nd critical part of our study, the main arguments of the Bariloche Team are examined. Regarding the proposed New Society, our criticism is that important questions remain unanswered; e.g., the question of the structure of the governmental organization of the New Society, and the important problem of coordinating the different enterprises of the entire economy. In spite of this and other shortcomings, however, we recognize that the Bariloche Report is an interesting and original approach attacking and trying to solve problems which are of the utmost importance for the world. (author's)
Dimensional reduction for D3-brane moduli
NASA Astrophysics Data System (ADS)
Cownden, Brad; Frey, Andrew R.; Marsh, M. C. David; Underwood, Bret
2016-12-01
Warped string compactifications are central to many attempts to stabilize moduli and connect string theory with cosmology and particle phenomenology. We present a first-principles derivation of the low-energy 4D effective theory from dimensional reduction of a D3-brane in a warped Calabi-Yau compactification of type IIB string theory with imaginary self-dual 3-form flux, including effects of D3-brane motion beyond the probe approximation, and find the metric on the moduli space of brane positions, the universal volume modulus, and axions descending from the 4-form potential. As D3-branes may be considered as carrying either electric or magnetic charges for the self-dual 5-form field strength, we present calculations in both duality frames. Our results are consistent with, but extend significantly, earlier results on the low-energy effective theory arising from D3-branes in string compactifications.
The goldstino brane, the constrained superfields and matter in {N}=1 supergravity
NASA Astrophysics Data System (ADS)
Bandos, Igor; Heller, Markus; Kuzenko, Sergei M.; Martucci, Luca; Sorokin, Dmitri
2016-11-01
We show that different (brane and constrained superfield) descriptions for the Volkov-Akulov goldstino coupled to {N}=1 , D = 4 supergravity with matter produce similar wide classes of models with spontaneously broken local supersymmetry and discuss the relation between the different formulations. As with the formulations with irreducible constrained superfields, the geometric goldstino brane approach has the advantage of being manifestly off-shell supersymmetric without the need to introduce auxiliary fields. It provides an explicit solution of the nilpotent superfield constraints and avoids issues with non-Gaussian integration of auxiliary fields. We describe general couplings of the supersymmetry breaking sector, including the goldstino and other non-supersymmetric matter, to supergravity and matter supermultiplets. Among various examples, we discuss a goldstino brane contribution to the gravitino mass term and the supersymmetrization of the anti-D3-brane contribution to the effective theory of type IIB warped flux compactifications.
D-branes and extended characters in SL(2,R)/U(1)
NASA Astrophysics Data System (ADS)
Fotopoulos, Angelos; Niarchos, Vasilis; Prezas, Nikolaos
2005-03-01
We present a detailed study of D-branes in the axially gauged SL(2/U(1) coset conformal field theory for integer level k. Our analysis is based on the modular bootstrap approach and utilizes the extended SL(2,R)/U(1) characters and the embedding of the parafermionic coset algebra in the N=2 superconformal algebra. We propose three basic classes of boundary states corresponding to D0-, D1- and D2-branes. We verify that these boundary states satisfy the Cardy consistency conditions and discuss their physical properties. The D0- and D1-branes agree with those found in earlier work by Ribault and Schomerus using different methods (descent from the Euclidean AdS model). The D2-branes are new. They are not, in general, space-filling but extend from the asymptotic circle at infinity up to a minimum distance ρ⩾0 from the tip of the cigar.
Tensor gauge field localization in branes
Tahim, M. O.; Cruz, W. T.; Almeida, C. A. S.
2009-04-15
In this work we study localization of a Kalb-Ramond tensorial gauge field on a membrane described by real scalar fields. The membrane is embedded in an AdS-type five-dimensional bulk space, which mimics a Randall-Sundrum scenario. First, we consider a membrane described by only a single real scalar field. In that scenario we find that there is no localized tensorial zero mode. When we take into account branes described by two real scalar fields with internal structures, we obtain again a nonlocalized zero mode for a Kalb-Ramond tensorial gauge field. After modifying our model of one single scalar field by coupling the dilaton to the Kalb-Ramond field, we find that this result is changed. Furthermore, we analyze Kaluza-Klein massive modes and resonance structures.
A Conceptual Model of the World of Work.
ERIC Educational Resources Information Center
VanRooy, William H.
The conceptual model described in this paper resulted from the need to organize a body of knowledge related to the world of work which would enable curriculum developers to prepare accurate, realistic instructional materials. The world of work is described by applying Malinowski's scientific study of the structural components of culture. It is…
Where does curvaton reside? Differences between bulk and brane frames
NASA Astrophysics Data System (ADS)
Larrouturou, François; Mukohyama, Shinji; Namba, Ryo; Watanabe, Yota
2017-03-01
Some classes of inflationary models naturally introduce two distinct metrics/frames, and their equivalence in terms of observables has often been put in question. D-brane inflation proposes candidates for an inflaton embedded in the string theory and possesses descriptions on the brane and bulk metrics/frames, which are connected by a conformal/disformal transformation that depends on the inflaton and its derivatives. It has been shown that curvature perturbations generated by the inflaton are identical in both frames, meaning that observables such as the spectrum of cosmic microwave background (CMB) anisotropies are independent of whether matter fields—including those in the standard model of particle physics—minimally couple to the brane or the bulk metric/frame. This is true despite the fact that the observables are eventually measured by the matter fields and that the total action including the matter fields is different in the two cases. In contrast, in curvaton scenarios, the observables depend on the frame to which the curvaton minimally couples. Among all inflationary scenarios, we focus on two models motivated by the KKLMMT fine-tuning problem: a slow-roll inflation with an inflection-point potential and a model of a rapidly rolling inflaton that conformally couples to gravity. In the first model, the difference between the frames in which the curvaton resides is encoded in the spectral index of the curvature perturbations, depicting the nature of the frame transformation. In the second model, the curvaton on the brane induces a spectral index significantly different from that in the bulk and is even falsified by the observations. This work thus demonstrates that two frames connected by a conformal/disformal transformation lead to different physical observables such as CMB anisotropies in curvaton models.
A Real-World Network Modeling Project
2014-02-12
flows, mini- mum cost flows, multi-commodity flows, stochastic models, and perhaps multi-objective models. The students can then think about their...few questions of the homework assignment ask the students to compute the optimal escape route for the drug lord, and look at it on a map to see if it...results. The homework assignments then ask the students to adjust the model so that the drug smuggler is not computing the shortest escape route , but
An econometric model of the world copper industry
Lewanika, M.W.
1989-01-01
This model of the world copper economy is fitted to 1960-1984 annual data. Here, unlike in previous models, an attempt is made to depart from the tendency to force the same functional form to represent individual country supply curves. The methodology utilized in constructing this model allows for individual countries to have supply curves that differ in functional form. The model consists of five categories - Western world consumption, Western world primary supply, Western world secondary supply, change in inventory, and net exports to the Centrally Planned Economies. Consumption, secondary supply, and change in inventory are each estimated by one equation aggregating the Western world. Primary supply is the sum of the supply equations for primary copper estimated for seven major producing countries and the Rest of the world. The seven countries are Chile, the United States, Canada, Zambia, Zaire, Peru, and Australia. The model is used to examine the copper industry in the coming decade under various scenarios. The copper market is found to be characterized by low short-run and slightly higher long-run price elasticities except in the case of the Rest of the World whose short-run elasticity is 1.52.
Codimension-2 Brane Black Holes
NASA Astrophysics Data System (ADS)
Zamorano, Nelson; Arias, Cesar; Ordenes, Ariel; Guzman, Francisco
2012-03-01
We analyze the geometry associated to a six dimensional solution of the Einstein's equations. It describes a Schwarzschild de-Sitter black hole on a 3-brane, surrounded by a two dimensional compact bulk. A four dimensional effective cosmological constant and a Planck mass are matched to their six dimensional counterpart. Deviation from Newton's law are computed in both of the solutions found. To learn about the geometry of the bulk, we study the geodesics in this sector. At least, in our opinion, there are some features of these solutions that makes worth to pursue this analysis. The singularity associated to the warped bulk is controlled by the mass M of the black hole. It vanishes if we set M=0. In the same context, it makes an interesting problem to study the Gregory-Laflamme instability in this context [1]. Another feature is the rugby ball type of geometry exhibited by these solutions [2]. They end up in two conical singularities at its respective poles. The branes are located precisely at the poles. Besides, a Wick's rotation generates a connection between different solutions. [4pt] [1] R. Gregory and R. Laflamme, Phys. Rev Lett., 70,2837 (1993)[0pt] [2] S. M. Carroll and M. M. Guica, arXiv:hep-th/0302067
Near-horizon brane-scan revived
NASA Astrophysics Data System (ADS)
Duff, M. J.
2009-03-01
In 1987 two versions of the brane-scan of D-dimensional super p-branes were put forward. The first pinpointed those (p,D) slots consistent with kappa-symmetric Green-Schwarz type actions; the second generalized the membrane at the end of the universe idea to all those superconformal groups describing p-branes on the boundary of AdS×S. Although the second version predicted D3- and M5-branes in addition to those of the first, it came unstuck because the 1/2 BPS solitonic branes failed to exhibit the required symmetry enhancement in the near-horizon limit, except in the non-dilatonic cases (p=2,D=11), (p=3,D=10) and (p=5,D=11). Just recently, however, it has been argued that the fundamental D=10 heterotic string does indeed display a near-horizon enhancement to OSp(8|2) as predicted by the brane-scan, provided α corrections are taken into account. If this logic could be extended to the other strings and branes, it would resolve this 21-year-old paradox and provide a wealth of new AdS/CFT dualities, which we tabulate.
Rapid prototype modeling in a multimodality world
NASA Astrophysics Data System (ADS)
Bidaut, Luc; Madewell, John; Yasko, Alan
2006-03-01
Introduction: Rapid prototype modeling (RPM) has been used in medicine principally for bones - that are easily extracted from CT data sets - for planning orthopaedic, plastic or maxillo-facial interventions, and/or for designing custom prostheses and implants. Based on newly available technology, highly valuable multimodality approaches can now be applied to RPM, particularly for complex musculo-skeletal (MSK) tumors where multimodality often transcends CT alone. Methods: CT data sets are acquired for primary evaluation of MSK tumors in parallel with other modalities (e.g., MR, PET, SPECT). In our approach, CT is first segmented to provide bony anatomy for RPM and all other data sets are then registered to the CT reference. Parametric information relevant to the tumor's characterization is then extracted from the multimodality space and merged with the CT anatomy to produce a hybrid RPM-ready model. This model - that also accommodates digital multimodality visualization - is then produced on the latest generation of 3D printers, which permits both shapes and colors. Results: Multimodality models of complex MSK tumors have been physically produced on modern RPM equipment. This new approach has been found to be a clear improvement over the previously disconnected physical RPM and digital multimodality visualization. Conclusions: New technical developments keep opening doors to sophisticated medical applications that can directly impact the quality of patient care. Although this early work still deals with bones as base models for RPM, its use to encompass soft tissues is already envisioned for future approaches.
Black holes and wormholes in AdS branes
Molina, C.; Neves, J. C. S.
2010-08-15
In this work we have derived a class of geometries which describe black holes and wormholes in Randall-Sundrum-type brane models, focusing mainly on asymptotically anti-de Sitter backgrounds. We show that by continuously deforming the usual four-dimensional vacuum background, a specific family of solutions is obtained. Maximal extensions of the solutions are presented, and their causal structures are discussed.
Metastable supersymmetry breaking and dynamical vacuum selection in intersecting brane systems
NASA Astrophysics Data System (ADS)
Royston, Andrew B.
In this thesis we study metastable supersymmetry breaking and dynamical vacuum selection in intersecting brane systems that are known to be useful for realizing supersymmetric gauge theories in string theory. Metastable supersymmetry breaking configurations of D-branes and NS5-branes in string theory often owe their existence to classical gravitational interactions between the branes. We show that in the effective theory of the light fields, these interactions give rise to a non-canonical Kahler potential and other D-terms. String theory provides a UV completion in which these non-renormalizable terms can be computed. We use these observations to clarify the relation between the phase structure of ISS-type models and their brane realizations. We then study dynamical vacuum selection in a system of D-branes localized near an intersection of Neveu-Schwarz fivebranes that is known to exhibit a rich landscape of supersymmetric and (metastable) supersymmetry breaking vacua. We show that early universe cosmology, in the form of excited fivebranes relaxing via Hawking radiation, drives the system to a particular long-lived supersymmetry breaking ground state.
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…
The Singularity Problem in Brane Cosmology
NASA Astrophysics Data System (ADS)
Antoniadis, Ignatios; Cotsakis, Spiros
2017-02-01
We review results about the development and asymptotic nature of singularities in `brane-bulk' systems. These arise for warped metrics obeying the 5-dimensional Einstein equations with fluid-like sources, and including a brane 4-metric that is either Minkowski or de Sitter or Anti-de Sitter. We characterize all singular Minkowski brane solutions, and look for regular solutions with nonzero curvature. We briefly comment on matching solutions, energy conditions and finite Planck mass criteria for admissibility, and we briefly discuss the connection of these results to ambient theory.
Branes, instantons, and Taub-NUT spaces
NASA Astrophysics Data System (ADS)
Witten, Edward
2009-06-01
ALE and Taub-NUT (or ALF) hyper-Kahler four-manifolds can be naturally constructed as hyper-Kahler quotients. In the ALE case, this construction has long been understood in terms of D-branes; here we give a D-brane derivation in the Taub-NUT case. Likewise, instantons on ALE spaces and on Taub-NUT spaces have ADHM-like constructions related to hyper-Kahler quotients. Here we refine the analysis in the Taub-NUT case by making use of a D-brane probe.
Brane f(R) gravity and the dark side of the universe
Borzou, A.; Sepangi, H. R.; Shahidi, S.; Yousefi, R.
2009-10-27
We consider a brane world scenario in which the bulk action is assumed to have the form of a generic function of the Ricci scalar f(R) and derive the resulting Einstein field equation on the brane. In a constant curvature bulk a conserved geometric quantity appears in the field equations which can be associated with matter. We present spherically symmetric solutions which account for galaxy rotation curves in a specific form. Then cosmological solutions by assuming a specific form for f(R) are derived which can explain an accelerated expanding universe.
Quantum billiards with branes on product of Einstein spaces
NASA Astrophysics Data System (ADS)
Ivashchuk, V. D.
2016-05-01
We consider a gravitational model in dimension D with several forms, l scalar fields and a Λ -term. We study cosmological-type block-diagonal metrics defined on a product of an 1-dimensional interval and n oriented Einstein spaces. As an electromagnetic composite brane ansatz is adopted and certain restrictions on the branes are imposed the conformally covariant Wheeler-DeWitt (WDW) equation for the model is studied. Under certain restrictions, asymptotic solutions to the WDW equation are found in the limit of the formation of the billiard walls. These solutions reduce the problem to the so-called quantum billiard in (n + l -1)-dimensional hyperbolic space. Several examples of quantum billiards in the model with electric and magnetic branes, e.g. corresponding to hyperbolic Kac-Moody algebras, are considered. In the case n=2 we find a set of basis asymptotic solutions to the WDW equation and derive asymptotic solutions for the metric in the classical case.
Reheating the D-brane universe via instant preheating
Panda, Sudhakar; Sami, M.; Thongkool, I.
2010-05-15
We investigate a possibility of reheating in a scenario of D-brane inflation in a warped deformed conifold background which includes perturbative corrections to throat geometry sourced by a chiral operator of dimension 3/2 in the conformal field theory. The effective D-brane potential, in this case, belongs to the class of nonoscillatory models of inflation for which the conventional reheating mechanism does not work. We find that gravitational particle production is inefficient and leads to reheating temperature of the order of 10{sup 8} GeV. We show that instant preheating is quite suitable to the present scenario and can easily reheat the universe to a temperature which is higher by about 3 orders of magnitude than its counterpart associated with gravitational particle production. The reheating temperature is shown to be insensitive to a particular choice of inflationary parameters suitable to observations.
Induced matter brane gravity and Einstein static universe
Heydarzade, Y.; Darabi, F. E-mail: f.darabi@azaruniv.edu
2015-04-01
We investigate stability of the Einstein static universe against the scalar, vector and tensor perturbations in the context of induced matter brane gravity. It is shown that in the framework of this model, the Einstein static universe has a positive spatial curvature. In contrast to the classical general relativity, it is found that a stable Einstein static universe against the scalar perturbations does exist provided that the variation of time dependent geometrical equation of state parameter is proportional to the minus of the variation of the scale factor, δ ω{sub g}(t) = −Cδ a(t). We obtain neutral stability against the vector perturbations, and the stability against the tensor perturbations is guaranteed due to the positivity of the spatial curvature of the Einstein static universe in induced matter brane gravity.
Nonminimal kinetic coupled gravity: Inflation on the warped DGP brane
NASA Astrophysics Data System (ADS)
Darabi, F.; Parsiya, A.; Atazadeh, K.
2016-03-01
We consider the nonminimally kinetic coupled version of DGP brane model, where the kinetic term of the scalar field is coupled to the metric and Einstein tensor on the brane by a coupling constant ζ. We obtain the corresponding field equations, using the Friedmann-Robertson-Walker metric and the perfect fluid, and study the inflationary scenario to confront the numerical analysis of six typical scalar field potentials with the current observational results. We find that among the suggested potentials and coupling constants, subject to the e-folding N = 60, the potentials V (ϕ) = σϕ, V (ϕ) = σϕ2 and V (ϕ) = σϕ3 provide the best fits with both Planck+WP+highL data and Planck+WP+highL+BICEP2 data.
Constrained superfields from an anti-D3-brane in KKLT
NASA Astrophysics Data System (ADS)
Vercnocke, Bert; Wrase, Timm
2016-08-01
The KKLT construction of dS vacua [1] relies on an uplift term that arises from an anti-D3-brane. It was argued by Kachru, Pearson and Verlinde [2] that this anti-D3-brane is an excited state in a supersymmetric theory since it can decay to a supersymmetric ground state. Hence the anti-D3-brane breaks supersymmetry spontaneously and one should be able to package all the world-volume fields on the anti-D3-brane into a four dimensional {N} = 1 supersymmetric action. Here we extend previous results and identify the constrained superfields that correspond to all the degrees of freedom on the anti-D3-brane. In particular, we show explicitly that the four 4D worldvolume spinors give rise to constrained chiral multiplets S and Y i , i = 1 , 2 , 3 that satisfy S 2 = SY i = 0. We also conjecture (and provide evidence in a forthcoming publication) that the vector field A μ and the three scalars ϕ i give rise to a field strength multiplet W α and three chiral multiplets H i that satisfy the constraints S{W}_{α }={overline{D}}_{overset{\\cdot }{α }}(S{overline{H}}^i)=0 . This is the first time that such constrained multiplets appear in string theory constructions.
Algebraic approach to small-world network models
NASA Astrophysics Data System (ADS)
Rudolph-Lilith, Michelle; Muller, Lyle E.
2014-01-01
We introduce an analytic model for directed Watts-Strogatz small-world graphs and deduce an algebraic expression of its defining adjacency matrix. The latter is then used to calculate the small-world digraph's asymmetry index and clustering coefficient in an analytically exact fashion, valid nonasymptotically for all graph sizes. The proposed approach is general and can be applied to all algebraically well-defined graph-theoretical measures, thus allowing for an analytical investigation of finite-size small-world graphs.
The geometry of branes and extended superspaces
NASA Astrophysics Data System (ADS)
Chryssomalakos, C.; de Azcárraga, J. A.; Izquierdo, J. M.; Pérez Bueno, J. C.
We argue that a description of supersymmetric extended objects from a unified geometric point of view requires an enlargement of superspace. To this aim we study in a systematic way how superspace groups and algebras arise from Grassmann spinors when these are assumed to be the only primary entities. In the process, we recover generalized space-time superalgebras and extensions of supersymmetry found earlier. The enlargement of ordinary superspace with new parameters gives rise to extended superspace groups, on which manifestly supersymmetric actions may be constructed for various types of p-branes, including D-branes (given by Chevalley-Eilenberg cocycles) with their Born-Infeld fields. This results in a field/extended superspace democracy for superbranes: all brane fields appear as pull-backs from a suitable target superspace. Our approach also clarifies some facts concerning the origin of the central charges for the different p-branes.
Holographic thermalization from nonrelativistic branes
NASA Astrophysics Data System (ADS)
Roychowdhury, Dibakar
2016-05-01
In this paper, based on the fundamental principles of gauge/gravity duality and considering a global quench, we probe the physics of thermalization for certain special classes of strongly coupled nonrelativistic quantum field theories that are dual to an asymptotically Schrödinger D p brane space time. In our analysis, we note that during the prelocal stages of the thermal equilibrium the entanglement entropy has a faster growth in time compared to its relativistic cousin. However, it shows a linear growth during the postlocal stages of thermal equilibrium where the so-called tsunami velocity associated with the linear growth of the entanglement entropy saturates to that of its value corresponding to the relativistic scenario. Finally, we explore the saturation region and it turns out that one must constraint certain parameters of the theory in a specific way in order to have discontinuous transitions at the point of saturation.
The joint US/UK 1990 epoch world magnetic model
NASA Technical Reports Server (NTRS)
Quinn, John M.; Coleman, Rachel J.; Peck, Michael R.; Lauber, Stephen E.
1991-01-01
A detailed summary of the data used, analyses performed, modeling techniques employed, and results obtained in the course of the 1990 Epoch World Magnetic Modeling effort are given. Also, use and limitations of the GEOMAG algorithm are presented. Charts and tables related to the 1990 World Magnetic Model (WMM-90) for the Earth's main field and secular variation in Mercator and polar stereographic projections are presented along with useful tables of several magnetic field components and their secular variation on a 5-degree worldwide grid.
On the Cn/Zm fractional branes
NASA Astrophysics Data System (ADS)
Karp, Robert L.
2009-02-01
We construct several geometric representatives for the Cn/Zm fractional branes on either a partially or the completely resolved orbifold. In the process we use large radius and conifold-type monodromies and provide a strong consistency check. In particular, for C3/Z5 we give three different sets of geometric representatives. We also find the explicit Seiberg duality which connects our fractional branes to the ones given by the McKay correspondence.
Spiked instantons from intersecting D-branes
NASA Astrophysics Data System (ADS)
Nekrasov, Nikita; Prabhakar, Naveen S.
2017-01-01
The moduli space of spiked instantons that arises in the context of the BPS/CFT correspondence [22] is realised as the moduli space of classical vacua, i.e. low-energy open string field configurations, of a certain stack of intersecting D1-branes and D5-branes in Type IIB string theory. The presence of a constant B-field induces an interesting dynamics involving the tachyon condensation.
Dynamical intersecting brane solutions of supergravity
Uzawa, Kunihito
2010-02-10
We present dynamical intersecting brane solutions in higher-dimensional gravitational theory coupled to dilaton and several forms. Assuming the forms of metric, form fields, and dilaton field, we can give the dynamical intersecting brane solutions. The dynamical solutions can be always obtained by replacing the constant modulus h{sub 0} in the warp factor for supersymmetric solutions by a linear function h{sub 0}(t) of the time coordinates t.
Rotating black holes on codimension 2 branes
Kiley, Derrick
2007-12-15
It has recently been demonstrated that certain types of nontensional stress-energy can live on tensional codimension-2 branes, including gravitational shockwaves and small Schwarzschild black holes. In this paper we generalize the earlier Schwarzschild results, and construct the exact gravitational fields of small rotating black holes on a codimension-2 brane. We focus on the phenomenologically interesting case of a three-brane embedded in a spacetime with two compactified extra dimensions. For a nonzero tension on the brane, we verify that these solutions also show the ''lightning rod'' effect found in the Schwarzschild solutions, the net effect of which is to rescale the fundamental Planck mass. This allows for larger black hole parameters, such as the event horizon, angular momentum, and lifetime than would be naively expected for a tensionless brane. It is also found that a black hole with angular momentum pointing purely along the brane directions has a smaller horizon angular velocity than the corresponding tensionless case, while a hole with bulk components of angular momentum has a larger angular velocity.
Brane induced gravity: Ghosts and naturalness
NASA Astrophysics Data System (ADS)
Eglseer, Ludwig; Niedermann, Florian; Schneider, Robert
2015-10-01
Linear stability of brane induced gravity in two codimensions on a static pure tension background is investigated. The brane is regularized as a ring of finite circumference in extra space. By explicitly calculating the vacuum persistence amplitude of the corresponding quantum theory, we show that the parameter space is divided into two regions—one corresponding to a stable Minkowski vacuum on the brane and one being plagued by ghost instabilities. This analytical result affirms a recent nonlinear, but mainly numerical analysis. The main result is that the ghost is absent for a sufficiently large brane tension, in perfect agreement with a value expected from a natural effective field theory point of view. Unfortunately, the linearly stable parameter regime is either ruled out phenomenologically or becomes unstable for nontrivial cosmologies. We argue that supercritical brane backgrounds constitute the remaining window of opportunity. In the special case of a tensionless brane, we find that the ghost exists for all phenomenologically relevant values of the induced gravity scale. Regarding this case, there are contradicting results in the literature, and we are able to fully resolve this controversy by explicitly uncovering the errors made in the "no-ghost" analysis. Finally, a Hamiltonian analysis generalizes the ghost result to more than two codimensions.
Precise lower bound on Monster brane boundary entropy
NASA Astrophysics Data System (ADS)
Friedan, Daniel; Konechny, Anatoly; Schmidt-Colinet, Cornelius
2013-07-01
In this paper we develop further the linear functional method of deriving lower bounds on the boundary entropy of conformal boundary conditions in 1+1 dimensional conformal field theories (CFTs). We show here how to use detailed knowledge of the bulk CFT spectrum. Applying the method to the Monster CFT with c = overline{c} = 24 we derive a lower bound s > -3.02×10-19 on the boundary entropy s = ln g, and find compelling evidence that the optimal bound is s ≥ 0. We show that all g=1 branes must have the same low-lying boundary spectrum, which matches the spectrum of the known g=1 branes, suggesting that the known examples comprise all possible g=1 branes, and also suggesting that the bound s ≥ 0 holds not just for critical boundary conditions but for all boundary conditions in the Monster CFT. The same analysis applied to a second bulk CFT — a certain c = 2 Gaussian model — yields a less strict bound, suggesting that the precise linear functional bound on s for the Monster CFT is exceptional.
Anti-de Sitter D-branes in curved backgrounds
NASA Astrophysics Data System (ADS)
Huang, Wung-Hong
2005-07-01
We investigate the properties of the AdS D1-branes which are the bound states of a curved D1-brane with n fundamental strings (F1) in the AdS3 spacetime, and the AdS D2-branes which are the axially symmetric bound states of a curved D2-brane with m D0-branes and n fundamental strings in the AdS3 × S3 spacetime. We see that, while the AdS D1-branes asymptotically approach to the event horizon of the AdS3 spacetime the AdS D2-branes will end on it. As the near horizon geometry of the F1/NS5 becomes the spacetime of AdS3 × S3 × T4 with NS-NS three form turned on, we furthermore investigate the corresponding AdS D-branes in the NS5-branes and macroscopic F-strings backgrounds, as an attempt to understand the origin of the AdS D-branes. From the found DBI solutions we see that in the F-strings background, both of the AdS D1-branes and AdS D2-branes will asymptotically approach to the position with a finite distance away from the F-strings. However, the AdS D2-branes therein could also end on the F-strings once it carries sufficient D0-branes charges. We also see that there does not exist any stable AdS D-branes in the NS5-branes backgrounds. We present physical arguments to explain these results, which could help us in understanding the intriguing mechanics of the formation of the AdS D-branes.
Rapid world modeling: Fitting range data to geometric primitives
Feddema, J.; Little, C.
1996-12-31
For the past seven years, Sandia National Laboratories has been active in the development of robotic systems to help remediate DOE`s waste sites and decommissioned facilities. Some of these facilities have high levels of radioactivity which prevent manual clean-up. Tele-operated and autonomous robotic systems have been envisioned as the only suitable means of removing the radioactive elements. World modeling is defined as the process of creating a numerical geometric model of a real world environment or workspace. This model is often used in robotics to plan robot motions which perform a task while avoiding obstacles. In many applications where the world model does not exist ahead of time, structured lighting, laser range finders, and even acoustical sensors have been used to create three dimensional maps of the environment. These maps consist of thousands of range points which are difficult to handle and interpret. This paper presents a least squares technique for fitting range data to planar and quadric surfaces, including cylinders and ellipsoids. Once fit to these primitive surfaces, the amount of data associated with a surface is greatly reduced up to three orders of magnitude, thus allowing for more rapid handling and analysis of world data.
Making Connections to the "Real World": A Model Building Lesson
ERIC Educational Resources Information Center
Horibe, Shusaku; Underwood, Bret
2009-01-01
Classroom activities that include the process of model building, in which students build simplified physical representations of a system, have the potential to help students make meaningful connections between physics and the real world. We describe a lesson designed with this intent for an introductory college classroom that engages students in…
A Dynamic Theory of World Press Motivation: An Integrative Model.
ERIC Educational Resources Information Center
Schillinger, Elisabeth
Addressing the dynamic and integrative nature of the world's press systems, this paper presents a comprehensive press theory and accompanying model. Three "primary motives"--survival, ideology, and market--are posited as determinants of press systems, using the nation state as the unit of analysis. The premises of the paper are: (1)…
Investment planning model of the world petrochemical industry
Manouchehri Adib, P.
1985-01-01
The world petrochemical industry is faced with an overcapacity in traditionally producing areas such as the United States, Western Europe, and Japan. At the same time, an increasing amount of new capacities are either planned or almost complete in energy-rich regions such as Canada, Latin America, Eastern Europe, the Middle East and Africa, and the Far East and Oceania. Such a conflicting move may add significantly to the existing problems of the world petrochemical industry. A multi-period, multi-region, multi-product, multi-process linear programming model is developed to analyze investment decisions under selected scenarios. Embodied in the model are detailed technical information about processes and products as well as economic information on different regions. Based on this theoretical model for the world petrochemical industry, both a static and a dynamic model are developed. The static model covers nine regions, thirty-one products, and a five-year period, 1988 to 1992, while the dynamic model includes eight regions, eleven products, and three five-year periods, 1988 to 2002. A variety of different cases are examined including one in which product demand is decreased. Two other cases considered are (1) stricter import policies by traditional producers and (2) adjustment in base-year capacity to include possible new productive units added before 1988.
Mirage cosmology with an unstable probe D3-brane
Jeong, Dong Hyeok; Kim, Jin Young
2005-10-15
We consider the mirage cosmology by an unstable probe brane whose action is represented by Dirac-Born-Infeld action with tachyon. We study how the presence of tachyon affects the evolution of the brane inflation. At the early stage of the brane inflation, the tachyon kinetic term can play an important role in curing the superluminal expansion in mirage cosmology.
Exciting gauge field and gravitons in brane-antibrane annihilation.
Mazumdar, Anupam; Stoica, Horace
2009-03-06
In this Letter we point out the inevitability of an explosive production of gauge field and gravity wave during an open string tachyon condensation in a cosmological setting, in an effective field theory model. We will be particularly studying a toy model of brane-antibrane inflation in a warped throat where inflation ends via tachyon condensation. We point out that a tachyonic instability helps fragmenting the homogeneous tachyon and excites gauge field and contributes to the stress-energy tensor which also feeds into the gravity waves.
BCS instability and finite temperature corrections to tachyon mass in intersecting D1-branes
NASA Astrophysics Data System (ADS)
Chowdhury, Sudipto Paul; Sarkar, Swarnendu; Sathiapalan, B.
2014-09-01
A holographic description of BCS superconductivity is given in [1]. This model was constructed by insertion of a pair of D8-branes on a D4-background. The spectrum of intersecting D8-branes has tachyonic modes indicating an instability which is identified with the BCS instability in superconductors. Our aim is to study the stability of the intersecting branes under finite temperature effects. Many of the technical aspects of this problem are captured by a simpler problem of two intersecting D1-branes on flat background. In the simplified set-up we compute the one-loop finite temperature corrections to the tree-level tachyon mass-squared-squared using the frame-work of SU(2) Yang-Mills theory in (1 + 1)-dimensions. We show that the one-loop two-point functions are ultraviolet finite due to cancellation of ultraviolet divergence between the amplitudes containing bosons and fermions in the loop. The amplitudes are found to be infrared divergent due to the presence of massless fields in the loops. We compute the finite temperature mass-squared correction to all the massless fields and use these temperature dependent masses-squared to compute the tachyonic mass-squared correction. We show numerically the existence of a transition temperature at which the effective mass-squared of the tree-level tachyons becomes zero, thereby stabilizing the brane configuration.
Cosmology from quantum potential in a system of oscillating branes
NASA Astrophysics Data System (ADS)
Sepehri, Alireza
2016-11-01
Recently, some authors proposed a new mechanism which gets rid of the Big Bang singularity and shows that the age of the universe is infinite. In this paper, we will confirm their results and predict that the universe may expand and contract many N fundamental strings decay to N M0-anti-M0-branes. Then, M0-branes join each other and build a M8-anti-M8 system. This system is unstable, broken and two anti-M4-branes, a compactified M4-brane, a M3-brane in addition to one M0-brane are produced. The M3-brane wraps around the compactified M4-brane and both of them oscillate between two anti-M4-branes. Our universe is located on the M3-brane and interacts with other branes by exchanging the M0-brane and some scalars in transverse directions. By wrapping of M3-brane, the contraction epoch of universe starts and some higher order of derivatives of scalar fields in the relevant action of branes are produced which are responsible for generating the generalized uncertainty principle (GUP). By oscillating the compactified M4-M3-brane and approaching one of anti-M4-branes, one end of M3-brane glues to the anti-M4-brane and other end remains sticking and wrapping around M4-brane. Then, by getting away of the M4-M3 system, M4 rolls, wrapped M3 opens and expansion epoch of universe begins. By closing the M4 to anti-M4, the mass of some scalars become negative and they make a transition to tachyonic phase. To remove these states, M4 rebounds, rolls and M3 wraps around it again. At this stage, expansion branch ends and universe enters a contraction epoch again. This process is repeated many times and universe expands and contracts due to oscillation of branes. We obtain the scale factor of universe in this system and find that its values only at t →-∞ shrinks to zero. Thus, in our method, the Big Bang is replaced by the fundamental string and the age of universe is predicted to be infinite. Also, when tachyonic states disappear at the beginning of expansion branch, some extra
On RR couplings and bulk singularity structures of non-BPS branes
NASA Astrophysics Data System (ADS)
Hatefi, Ehsan
2016-09-01
We compute the five point world sheet scattering amplitude of a symmetric closed string Ramond-Ramond, a transverse scalar field, a world volume gauge field and a real tachyon in both world volume and transverse directions of brane in type IIA and IIB superstring theory. We provide the complete analysis of
NASA Astrophysics Data System (ADS)
Kilinc, M.; Beringer, J.; Hutley, L.; Kurioka, K.; Wood, S.; D'Argent, N.; Martin, D.; McHugh, I.; Tapper, N.; McGuire, D.
2009-04-01
Natural forests store vast amounts of carbon in the terrestrial biosphere, and play an important role in the global carbon cycle. Given the significance of natural forests, there is a lack of carbon accounting of primary forests that are undisturbed by human activities. One reason for this lack of interest stems from ecological orthodoxy that suggests that primary forests should be close to dynamic equilibrium, in that Net Ecosystem Production (NEP) approaches zero. However, recent results from the northern hemisphere and tropics, using eddy covariance flux towers, indicate that primary forests are a greater sink than first thought. The role of evergreen primary forests in Australian carbon balance studies remain uncertain and hence may function differently to their deciduous counterparts in the Northern Hemisphere. In order to address the lack of baseline carbon accounts, an undisturbed, 300 year old Mountain Ash (Eucalyptus regnans) ecosystem, located in the Central Highlands of Victoria (Australia) was selected as a permanent study site to investigate carbon and water budgets over diurnal, seasonal and annual cycles. Mountain Ash trees are the world's tallest angiosperms (flowering plants), and one of the largest carbon reservoirs in the biosphere, with an estimated 1900 tC ha-1. A 110 m tall micrometeorological tower that includes eddy covariance instrumentation was installed in August 2005. An independent biometric approach quantifying the annual net gain or loss of carbon was also made within close proximity to the flux tower. Analysis of NEP in 2006 suggests that the ecosystem acted as a carbon sink of 2.5 tC ha-1 yr-1. Woody and soil biomass increment for the same year was estimated to be 2.8 tC ha-1yr-1, in which nearly half of the biomass production was partitioned into the aboveground woody tissue. These results indicate that temperate primary forests act as carbon sinks, and are able to maintain their carbon sink status due to their uneven stand
Thermodynamics of Lovelock-Lifshitz black branes
Dehghani, M. H.; Mann, R. B.
2010-09-15
We investigate the thermodynamics of Lovelock-Lifshitz black branes. We begin by introducing the finite action of third order Lovelock gravity in the presence of a massive vector field for a flat boundary, and use it to compute the energy density of these black branes. Using the field equations, we find a conserved quantity along the r coordinate that relates the metric parameters at the horizon and at infinity. Remarkably, though the subleading large-r behavior of Lovelock-Lifshitz black branes differs substantively from their Einsteinian Lifshitz counterparts, we find that the relationship between the energy density, temperature, and entropy density is unchanged from Einsteinian gravity. Using the first law of thermodynamics to obtain the relationship between entropy and temperature, we find that it too is the same as the Einsteinian case, apart from a constant of integration that depends on the Lovelock coefficients.
Branes and the Kraft-Procesi transition
NASA Astrophysics Data System (ADS)
Cabrera, Santiago; Hanany, Amihay
2016-11-01
The Coulomb and Higgs branches of certain 3 d N=4 gauge theories can be understood as closures of nilpotent orbits. Recently, a new theorem by Namikawa suggests that this is the simplest possible case, thus giving this class a special role. In this note we use branes to reproduce the mathematical work by Kraft and Procesi. It studies the classification of all nilpotent orbits for classical groups and it characterizes an inclusion relation via minimal singularities. We show how these minimal singularities arise naturally in the Type IIB superstring embedding of the 3 d A-type theories. The Higgs mechanism can be used to remove the minimal singularity, corresponding to a transition in the brane configuration that induces a new effective 3 d theory. This reproduces the Kraft-Procesi results, endowing the family of gauge theories with a new underlying structure. We provide an efficient procedure for computing such brane transitions.
A small-world network model of facial emotion recognition.
Takehara, Takuma; Ochiai, Fumio; Suzuki, Naoto
2016-01-01
Various models have been proposed to increase understanding of the cognitive basis of facial emotions. Despite those efforts, interactions between facial emotions have received minimal attention. If collective behaviours relating to each facial emotion in the comprehensive cognitive system could be assumed, specific facial emotion relationship patterns might emerge. In this study, we demonstrate that the frameworks of complex networks can effectively capture those patterns. We generate 81 facial emotion images (6 prototypes and 75 morphs) and then ask participants to rate degrees of similarity in 3240 facial emotion pairs in a paired comparison task. A facial emotion network constructed on the basis of similarity clearly forms a small-world network, which features an extremely short average network distance and close connectivity. Further, even if two facial emotions have opposing valences, they are connected within only two steps. In addition, we show that intermediary morphs are crucial for maintaining full network integration, whereas prototypes are not at all important. These results suggest the existence of collective behaviours in the cognitive systems of facial emotions and also describe why people can efficiently recognize facial emotions in terms of information transmission and propagation. For comparison, we construct three simulated networks--one based on the categorical model, one based on the dimensional model, and one random network. The results reveal that small-world connectivity in facial emotion networks is apparently different from those networks, suggesting that a small-world network is the most suitable model for capturing the cognitive basis of facial emotions.
The joint US/UK EPOCH world magnetic model 1995
NASA Astrophysics Data System (ADS)
Quinn, John M.; Coleman, Rachel J.; Shiel, Donald L.
1995-04-01
This report contains a detailed summary of the data used, analyses performed, modeling techniques employed, and results obtained during the course of the 1995 Epoch World Magnetic Modeling effort. This report also contains the GEOMAG algorithm and describes its uses and limitations. Charts derived from the WMM-95 model and the GEOMAG algorithm for both the Main geomagnetic field components and their Secular Variations are presented on Mercator and polar stereographic projections. Additionally, the numerical values of the Main geomagnetic field components and their Secular Variations are tabulated on a 5-degree worldwide grid.
Derived Categories and Zero-Brane Stability
Lawrence, Albion
2001-07-25
We define a particular class of topological field theories associated to open strings and prove the resulting D-branes and open strings form the bounded derived category of coherent sheaves. This derivation is a variant of some ideas proposed recently by Douglas. We then argue that any 0-brane on any Calabi-Yau threefold must become unstable along some path in the Kahler moduli space. As a byproduct of this analysis we see how the derived category can be invariant under a birational transformation.
Brane decay and an initial spacelike singularity.
Kawai, Shinsuke; Keski-Vakkuri, Esko; Leigh, Robert G; Nowling, Sean
2006-01-27
We present a novel string theory scenario where matter in a spacetime originates from a decaying brane at the origin of time. The decay could be considered as a big-bang-like event at X0=0. The closed string interpretation is a time-dependent spacetime with a semi-infinite time direction, with the initial energy of the brane converted into energy flux from the origin. The open string interpretation can be viewed as a string theoretic nonsingular initial condition.
Developing mathematical models of neurobehavioral performance for the "real world".
Dean, Dennis A; Fletcher, Adam; Hursh, Steven R; Klerman, Elizabeth B
2007-06-01
Work-related operations requiring extended wake durations, night, or rotating shifts negatively affect worker neurobehavioral performance and health. These types of work schedules are required in many industries, including the military, transportation, and health care. These industries are increasingly using or considering the use of mathematical models of neurobehavioral performance as a means to predict the neurobehavioral deficits due to these operational demands, to develop interventions that decrease these deficits, and to provide additional information to augment existing decision-making processes. Recent advances in mathematical modeling have allowed its application to real-world problems. Developing application-specific expertise is necessary to successfully apply mathematical models, in part because development of new algorithms and methods linking the models to the applications may be required. During a symposium, "Modeling Human Neurobehavioral Performance II: Towards Operational Readiness," at the 2006 SIAM-SMB Conference on the Life Sciences, examples of the process of applying mathematical models, including model construction, model validation, or developing model-based interventions, were presented. The specific applications considered included refining a mathematical model of sleep/wake patterns of airline flight crew, validating a mathematical model using railroad operations data, and adapting a mathematical model to develop appropriate countermeasure recommendations based on known constraints. As mathematical models and their associated analytical methods continue to transition into operational settings, such additional development will be required. However, major progress has been made in using mathematical model outputs to inform those individuals making schedule decisions for their workers.
Open M2-branes with flux and the modified Basu-Harvey equation
NASA Astrophysics Data System (ADS)
Chu, Chong-Sun; Sehmbi, Gurdeep S.
2011-04-01
The supersymmetric actions of closed multiple M2 branes with flux for the Bagger-Lambert (BL) and ABJM theories have been constructed recently by Lambert and Richmond (2009 J. High Energy Phys. JHEP10(2009)084). In this paper, we extend the construction to the case of open M2-branes with flux and derive the boundary conditions. This allows us to derive the modified Basu-Harvey equation in the presence of flux. As an example, we consider the Lorentzian BL model. A new feature of the fuzzy funnel solution describing a D2-D4 intersection is obtained as a result of the flux.
The beta distribution: A statistical model for world cloud cover
NASA Technical Reports Server (NTRS)
Falls, L. W.
1973-01-01
Much work has been performed in developing empirical global cloud cover models. This investigation was made to determine an underlying theoretical statistical distribution to represent worldwide cloud cover. The beta distribution with probability density function is given to represent the variability of this random variable. It is shown that the beta distribution possesses the versatile statistical characteristics necessary to assume the wide variety of shapes exhibited by cloud cover. A total of 160 representative empirical cloud cover distributions were investigated and the conclusion was reached that this study provides sufficient statical evidence to accept the beta probability distribution as the underlying model for world cloud cover.
Phenomenology of D-brane inflation with general speed of sound
Peiris, Hiranya; Baumann, Daniel; Friedman, Brett; Cooray, Asantha
2007-11-15
A characteristic of D-brane inflation is that fluctuations in the inflaton field can propagate at a speed significantly less than the speed of light. This yields observable effects that are distinct from those of single-field slow-roll inflation, such as a modification of the inflationary consistency relation and a potentially large level of non-Gaussianities. We present a numerical algorithm that extends the inflationary flow formalism to models with general speed of sound. For an ensemble of D-brane-inflation models parametrized by the Hubble parameter and the speed of sound as polynomial functions of the inflaton field, we give qualitative predictions for the key inflationary observables. We discuss various consistency relations for D-brane inflation, and compare the qualitative shapes of the warp factors we derive from the numerical models with analytical warp factors considered in the literature. Finally, we derive and apply a generalized microphysical bound on the inflaton field variation during brane inflation. While a large number of models are consistent with current cosmological constraints, almost all of these models violate the compactification constraint on the field range in four-dimensional Planck units. If the field range bound is to hold, then models with a detectable level of non-Gaussianity predict a blue scalar spectral index, and a tensor component that is far below the detection limit of any future experiment.
Holographic cosmology from a system of M2-M5 branes
NASA Astrophysics Data System (ADS)
Sepehri, Alireza; Faizal, Mir; Setare, Mohammad Reza; Ali, Ahmed Farag
2016-05-01
In this paper, we analyze the holographic cosmology using a M2-M5 brane configuration. In this configuration, a M2-brane will be placed in between a M5-brane and an anti-M5-brane. The M2-brane will act as a channel for energy to flow from an anti-M5-brane to a M5-brane, and this will increase the degrees of freedom on the M5-brane causing inflation. The inflation will end when the M5-brane and anti-M5-brane get separated. However, at a later stage the distance between the M5-brane and the anti-M5-bran can reduce and this will cause the formation of tachyonic states. These tachyonic states will again open a bridge between the M5-branes and the anti-M5-branes, which will cause further acceleration of the universe.
Holographic cosmology from a system of M2–M5 branes
Sepehri, Alireza; Faizal, Mir; Setare, Mohammad Reza; Ali, Ahmed Farag
2016-05-15
In this paper, we analyze the holographic cosmology using a M2–M5 brane configuration. In this configuration, a M2-brane will be placed in between a M5-brane and an anti-M5-brane. The M2-brane will act as a channel for energy to flow from an anti-M5-brane to a M5-brane, and this will increase the degrees of freedom on the M5-brane causing inflation. The inflation will end when the M5-brane and anti-M5-brane get separated. However, at a later stage the distance between the M5-brane and the anti-M5-bran can reduce and this will cause the formation of tachyonic states. These tachyonic states will again open a bridge between the M5-branes and the anti-M5-branes, which will cause further acceleration of the universe.
3-D world modeling for an autonomous robot
Goldstein, M.; Pin, F.G.; Weisbin, C.R.
1987-08-01
This paper presents a methodology for a concise representation of the 3-D world model for a mobile robot, using range data. The process starts with the segmentation of the scene into ''objects'' that are given a unique label, based on principles of range continuity. Then the external surface of each object is partitioned into homogeneous surface patches. Contours of surface patches in 3-D space are identified by estimating the normal and curvature associated with each pixel. The resulting surface patches are then classified as planar, convex or concave. Since the world model uses a volumetric representation for the 3-D environment, planar surfaces are represented by thin volumetric polyhedra. Spherical and cylindrical surfaces are extracted and represented by appropriate volumetric primitives. All other surfaces are represented using the boolean union of spherical volumes (as described in a separate paper by the same authors). The result is a general, concise representation of the external 3-D world, which allows for efficient and robust 3-D object recognition. 20 refs., 14 figs.
Documentation of the AMIP models on the World Wide Web
Phillips, T.J.
1995-08-01
The intercomparison of atmospheric general circulation model (AGCM) experiments of a similar type has become an increasingly popular methodology for assessing the strengths and weaknesses of climate simulations. In such endeavors, attempts to attribute differences among the simulations to specific model properties require, as a minimum prerequisite, the accurate and comprehensive documentation of these features. Regrettably however, atmospheric model documentation typically is fragmentary and scattered across numerous publications. It is also often inaccurate, in the sense that the pace of model development and the proliferation of new model versions usually outstrip their recorded descriptions. More often than not, the detailed configuration of a model for a particular experiment also is undocumented. In addition, there may be much unevenness in the descriptions of different facets of models. This incompleteness usually is replicated in published results of an intercomparison experiment, in that participating models` features often are summarized only perfunctorily. Summary documentation of the numerics, dynamics, and physics of models participating in the Atmospheric Model Intercomparison Project (AMIP) is now available on the Internet`s World Wide Web. This paper describes the principal attributes of the electronic model documentation and provides instructions on how to access it.
Mesonic quasinormal modes of the Sakai-Sugimoto model at high temperature
Evans, Nick; Threlfall, Ed
2008-06-15
We examine the mesonic thermal spectrum of the Sakai-Sugimoto model of holographic QCD by finding the quasinormal frequencies of the supergravity dual. If flavor is added using D8-D8 branes there exist embeddings where the D-brane world volume contains a black hole. For these embeddings (the high-temperature phase of the Sakai-Sugimoto model) we determine the quasinormal spectra of scalar and vector mesons arising from the world volume Dirac-Born-Infeld (DBI) action of the D-brane. We stress the importance of a coordinate change that makes the infalling quasinormal modes regular at the horizon allowing a simple numerical shooting technique. Finally we examine the effect of finite spatial momentum on quasinormal spectra.
Quasinormal modes of near extremal black branes
NASA Astrophysics Data System (ADS)
Starinets, Andrei O.
2002-12-01
We find quasinormal modes of near extremal black branes by solving a singular boundary value problem for the Heun equation. The corresponding eigenvalues determine the dispersion law for the collective excitations in the dual strongly coupled N=4 supersymmetric Yang-Mills theory at finite temperature.
Primordial spikes from wrapped brane inflation
Kobayashi, Takeshi; Yokoyama, Jun'ichi E-mail: yokoyama@resceu.s.u-tokyo.ac.jp
2013-02-01
Cosmic inflation driven by branes wrapping the extra dimensions involves Kaluza-Klein (KK) degrees of freedom in addition to the zero-mode position of the brane which plays the role of the inflaton. As the wrapped brane passes by localized sources or features along its inflationary trajectory in the extra dimensional space, the KK modes along the wrapped direction are excited and start to oscillate during inflation. We show that the oscillating KK modes induce parametric resonance for the curvature perturbations, generating sharp signals in the perturbation spectrum. The effective four dimensional picture is a theory where the inflaton couples to the heavy KK modes. The Nambu-Goto action of the brane sources couplings between the inflaton kinetic terms and the KK modes, which trigger significant resonant amplification of the curvature perturbations. We find that the strong resonant effects are localized to narrow wave number ranges, producing spikes in the perturbation spectrum. Investigation of such resonant signals opens up the possibility of probing the extra dimensional space through cosmological observations.
First law of p-brane thermodynamics
Rogatko, Marek
2009-08-15
We study the physical process version and the equilibrium state version of the first law of thermodynamics for a charged p-brane. The general setting for our investigations is (n+p+1)-dimensional Einstein dilaton gravity with (p+2) strength form fields.
Collective excitations of massive flavor branes
NASA Astrophysics Data System (ADS)
Itsios, Georgios; Jokela, Niko; Ramallo, Alfonso V.
2016-08-01
We study the intersections of two sets of D-branes of different dimensionalities. This configuration is dual to a supersymmetric gauge theory with flavor hypermultiplets in the fundamental representation of the gauge group which live on the defect of the unflavored theory determined by the directions common to the two types of branes. One set of branes is dual to the color degrees of freedom, while the other set adds flavor to the system. We work in the quenched approximation, i.e., where the flavor branes are considered as probes, and focus specifically on the case in which the quarks are massive. We study the thermodynamics and the speeds of first and zero sound at zero temperature and non-vanishing chemical potential. We show that the system undergoes a quantum phase transition when the chemical potential approaches its minimal value and we obtain the corresponding non-relativistic critical exponents that characterize its critical behavior. In the case of (2 + 1)-dimensional intersections, we further study alternative quantization and the zero sound of the resulting anyonic fluid. We finally extend these results to non-zero temperature and magnetic field and compute the diffusion constant in the hydrodynamic regime. The numerical results we find match the predictions by the Einstein relation.
Cosmological constant, near brane behavior and singularities
NASA Astrophysics Data System (ADS)
Gautason, Fridrik Freyr; Junghans, Daniel; Zagermann, Marco
2013-09-01
We show that the classical cosmological constant in type II flux compactifications can be written as a sum of terms from the action of localized sources plus a specific contribution from non-trivial background fluxes. Exploiting two global scaling symmetries of the classical supergravity action, we find that the flux contribution can in many interesting cases be set to zero such that the cosmological constant is fully determined by the boundary conditions of the fields in the near-source region. This generalizes and makes more explicit previous arguments in the literature. We then discuss the problem of putting -branes at the tip of the Klebanov-Strassler throat glued to a compact space in type IIB string theory so as to engineer a de Sitter solution. Our result for the cosmological constant and a simple global argument indicate that inserting a fully localized and backreacting -brane into such a background yields a singular energy density for the NSNS and RR 3-form field strengths at the -brane. This argument does not rely on partial smearing of the -brane or a linearization of field equations, but on a few general assumptions that we also discuss carefully.
From soft walls to infrared branes
Gersdorff, Gero von
2010-10-15
Five-dimensional warped spaces with soft walls are generalizations of the standard Randall-Sundrum compactifications, where instead of an infrared brane one has a curvature singularity (with vanishing warp factor) at finite proper distance in the bulk. We project the physics near the singularity onto a hypersurface located a small distance away from it in the bulk. This results in a completely equivalent description of the soft wall in terms of an effective infrared brane, hiding any singular point. We perform explicitly this calculation for two classes of soft wall backgrounds used in the literature. The procedure has several advantages. It separates in a clean way the physics of the soft wall from the physics of the five-dimensional bulk, facilitating a more direct comparison with standard two-brane warped compactifications. Moreover, consistent soft walls show a sort of universal behavior near the singularity which is reflected in the effective brane Lagrangian. Thirdly, for many purposes, a good approximation is obtained by assuming the bulk background away from the singularity to be the usual Randall-Sundrum metric, thus making the soft wall backgrounds better analytically tractable. We check the validity of this procedure by calculating the spectrum of bulk fields and comparing it to the exact result, finding very good agreement.
The visual system’s internal model of the world
Lee, Tai Sing
2015-01-01
The Bayesian paradigm has provided a useful conceptual theory for understanding perceptual computation in the brain. While the detailed neural mechanisms of Bayesian inference are not fully understood, recent computational and neurophysiological works have illuminated the underlying computational principles and representational architecture. The fundamental insights are that the visual system is organized as a modular hierarchy to encode an internal model of the world, and that perception is realized by statistical inference based on such internal model. In this paper, I will discuss and analyze the varieties of representational schemes of these internal models and how they might be used to perform learning and inference. I will argue for a unified theoretical framework for relating the internal models to the observed neural phenomena and mechanisms in the visual cortex. PMID:26566294
Kar, Supriya
2006-12-15
We obtain de Sitter (dS) and anti-de Sitter (AdS) generalized Reissner-Nordstrom-like black hole geometries in a curved D{sub 3}-brane framework, underlying a noncommutative gauge theory on the brane world. The noncommutative scaling limit is explored to investigate a possible tunneling of an AdS vacuum in string theory to dS vacuum in its low energy gravity theory. The Hagedorn transition is invoked into its self-dual gauge theory to decouple the gauge nonlinearity from the dS geometry, which in turn is shown to describe a pure dS vacuum.
p-brane dynamics in (N+1)-dimensional FRW universes: A unified framework
Sousa, L.; Avelino, P. P.
2011-05-15
We develop a velocity-dependent one-scale model describing p-brane dynamics in flat homogeneous and isotropic backgrounds in a unified framework. We find the corresponding scaling laws in frictionless and friction-dominated regimes considering both expanding and collapsing phases.
Cancer Models and Real-world Data: Better Together.
Kim, Jane J; Tosteson, Anna Na; Zauber, Ann G; Sprague, Brian L; Stout, Natasha K; Alagoz, Oguzhan; Trentham-Dietz, Amy; Armstrong, Katrina; Pruitt, Sandi L; Rutter, Carolyn M
2016-02-01
Decision-analytic models are increasingly used to inform health policy decisions. These models synthesize available data on disease burden and intervention effectiveness to project estimates of the long-term consequences of care, which are often absent when clinical or policy decisions must be made. While models have been influential in informing US cancer screening guidelines under ideal conditions, incorporating detailed data on real-world screening practice has been limited given the complexity of screening processes and behaviors throughout diverse health delivery systems in the United States. We describe the synergies that exist between decision-analytic models and health care utilization data that are increasingly accessible through research networks that assemble data from the growing number of electronic medical record systems. In particular, we present opportunities to enrich cancer screening models by grounding analyses in real-world data with the goals of projecting the harms and benefits of current screening practices, evaluating the value of existing and new technologies, and identifying the weakest links in the cancer screening process where efforts for improvement may be most productively focused. We highlight the example of the National Cancer Institute-funded consortium Population-based Research Optimizing Screening through Personalized Regimens (PROSPR), a collaboration to harmonize and analyze screening process and outcomes data on breast, colorectal, and cervical cancers across seven research centers. The pairing of models with such data can create more robust models to not only better inform policy but also inform health care systems about best approaches to improve the provision of cancer screening in the United States.
World agriculture and climate change: Current modeling issues
Darwin, R.
1996-12-31
Recent studies suggest that although global increases in temperature and changes in precipitation patterns during the next century will affect world agriculture, farmer adaptations are likely to prevent climate change from jeopardizing world food production. The costs and benefits of global climate change, however, are not equally distributed around the world. Agricultural production may increase in high latitude and alpine areas, but decrease in tropical and some other areas. Also, land use changes that accompany climate-induced shifts in cropland and permanent pasture are likely to raise additional social and environmental issues. Despite these advances, some important aspects of climate change have not been adequately simulated in global models. These include the effects that climate-induced changes in water resources are likely to have on agricultural production, the well-documented beneficial effects of higher concentrations of atmospheric carbon dioxide on plant growth and water use, and the cooling effects of tropospheric emissions of sulfur dioxide. In addition, past research generally relied on equilibrium climates based on a doubling of atmospheric carbon dioxide. Now, however, results from transient climate change experiments are available.
Epidemiology Model on Shortcut and Small World Networks
NASA Astrophysics Data System (ADS)
Shanker, O.; Hogg, Tad
We show that the behavior of an epidemiology model depends sensitively on the shortcut density in the shortcut network. This is consistent with an earlier work on other processes on the shortcut network. We analytically study the reason for the sensitivity. The shortcut network is similar to the small world network, and it has the advantage that the model dependence on the shortcut density can be analytically studied. The model would be relevant to the spread of diseases in human, animal, plant or other populations, to the spread of viruses in computer networks, or to the spread of social contagion in social networks. It would also be relevant in understanding the variations in the load on routers connecting different computer networks, as the network topology gets extended by the addition of new links, and in analyzing the placement of certain special sensors in a sensor network laid out in a non-random way with some shortcut links.
Numerical modelling of floating debris in the world's oceans.
Lebreton, L C-M; Greer, S D; Borrero, J C
2012-03-01
A global ocean circulation model is coupled to a Lagrangian particle tracking model to simulate 30 years of input, transport and accumulation of floating debris in the world ocean. Using both terrestrial and maritime inputs, the modelling results clearly show the formation of five accumulation zones in the subtropical latitudes of the major ocean basins. The relative size and concentration of each clearly illustrate the dominance of the accumulation zones in the northern hemisphere, while smaller seas surrounded by densely populated areas are also shown to have a high concentration of floating debris. We also determine the relative contribution of different source regions to the total amount of material in a particular accumulation zone. This study provides a framework for describing the transport, distribution and accumulation of floating marine debris and can be continuously updated and adapted to assess scenarios reflecting changes in the production and disposal of plastic worldwide.
p-Wave superconductors in D-brane systems
NASA Astrophysics Data System (ADS)
Bu, Yanyan
2012-11-01
In this work we take the intersecting D-brane models to explore some properties of p-wave superconductor at strong coupling. Our studies are focused on four-dimensional spacetime, which is not completely researched as in planar case. Optimistically, the AdS/CFT approach to superconductor, or more precisely superconducting-like phase transition, can give us some intuitions about mysterious high Tc superconductors. Concretely, we use defect D4/D6 and D4/D4 (noncritical) models to carry out comparative investigations. To make the system in the finite temperature bath, we assume that the superconducting phase is in the deconfined and chiral symmetry restoring phase for black D4-brane geometry. For the background fields, we use both analytical and numerical methods to solve the coupled nonlinear equations of motion. Near the phase transition, both methods give the mean filed behavior for the superconducting condensate. We then study gauge field perturbations of the systems to probe the AC conductivity. Similar to previous results, there comes out a gap in low frequency regime and the conductivity gets exponentially small as the condensation is enhanced. In contrast to previous investigations, we also compute the AC conductivity along the x direction, which needs to study a coupled sets of fluctuation modes. This shows us the anisotropic feature of p-wave superconductors.
ERIC Educational Resources Information Center
Falk, Richard A.
The monograph examines the relationship of nuclear power to world order. The major purpose of the document is to stimulate research, education, dialogue, and political action for a just and peaceful world order. The document is presented in five chapters. Chapter I stresses the need for a system of global security to counteract dangers brought…
Vision in Drosophila: seeing the world through a model's eyes.
Paulk, Angelique; Millard, S Sean; van Swinderen, Bruno
2013-01-01
The fruit fly, Drosophila melanogaster, has been used for decades as a genetic model for unraveling mechanisms of development and behavior. In order to efficiently assign gene functions to cellular and behavioral processes, early measures were often necessarily simple. Much of what is known of developmental pathways was based on disrupting highly regular structures, such as patterns of cells in the eye. Similarly, reliable visual behaviors such as phototaxis and motion responses provided a solid foundation for dissecting vision. Researchers have recently begun to examine how this model organism responds to more complex or naturalistic stimuli by designing novel paradigms that more closely mimic visual behavior in the wild. Alongside these advances, the development of brain-recording strategies allied with novel genetic tools has brought about a new era of Drosophila vision research where neuronal activity can be related to behavior in the natural world.
[Cancer screening in Hungary: World Bank supported model programs].
Bodó, M; Döbrössy, L; Liszka, G; Ottó, S; Péter, Z
1997-07-13
Since 1995, a model cancer screening program has been in operation in Hungary, the overall purpose of which is to promote the establishment of effective and efficient screening programs by means of adapting the internationally agreed principles of organized screening to the needs and opportunities in Hungary. The establishment and operation of a national population-based cancer registration system is an other aim of the Program. The model program--financed partly from a loan from the World Bank, partly from local funds provided by the Government of Hungary--is to develop standard procedure for cervical, breast and colorectal screening and to end up with tested recommendations for introduction of organized screening of proved effectiveness, integrated into the health care system, on country-wide service bases in Hungary.
Implementation science in the real world: a streamlined model.
Knapp, Herschel; Anaya, Henry D
2012-01-01
The process of quality improvement may involve enhancing or revising existing practices or the introduction of a novel element. Principles of Implementation Science provide key theories to guide these processes, however, such theories tend to be highly technical in nature and do not provide pragmatic nor streamlined approaches to real-world implementation. This paper presents a concisely comprehensive six step theory-based Implementation Science model that we have successfully used to launch more than two-dozen self-sustaining implementations. In addition, we provide an abbreviated case study in which we used our streamlined theoretical model to successfully guide the development and implementation of an HIV testing/linkage to care campaign in homeless shelter settings in Los Angeles County.
The Big Crunch--Models in Physics Meet the Real World.
ERIC Educational Resources Information Center
Fisher, Brian
2001-01-01
Examines quantitative models in school physics, looking particularly at the degree to which they match the real world. Explores the positive aspects of a mismatch between models and real world conditions. (DDR)
Localization and mass spectrum of q-form fields on branes
NASA Astrophysics Data System (ADS)
Fu, Chun-E.; Zhong, Yuan; Xie, Qun-Ying; Liu, Yu-Xiao
2016-06-01
In this paper, we investigate localization of a bulk massless q-form field on codimension-one branes by using a new Kaluza-Klein (KK) decomposition, for which there are two types of KK modes for the bulk q-form field, the q-form and (q - 1)-form modes. The first modes may be massive or massless while the second ones are all massless. These two types of KK modes satisfy two Schrödinger-like equations. For a five-dimensional brane model with a finite extra dimension, the spectrum of a bulk 3-form field on the brane consists of some massive bound 3-form KK modes as well as some massless bound 2-form ones with different configuration along the extra dimension. These 2-form modes are different from those obtained from a bulk 2-form field. For a five-dimensional degenerated Bloch brane model with an infinite extra dimension, some massive 3-form resonant KK modes and corresponding massless 2-form resonant ones are obtained for a bulk 3-form field.
Perturbations of black p-branes
Abdalla, Elcio; Fernandez Piedra, Owen Pavel; Oliveira, Jeferson de; Molina, C.
2010-03-15
We consider black p-brane solutions of the low-energy string action, computing scalar perturbations. Using standard methods, we derive the wave equations obeyed by the perturbations and treat them analytically and numerically. We have found that tensorial perturbations obtained via a gauge-invariant formalism leads to the same results as scalar perturbations. No instability has been found. Asymptotically, these solutions typically reduce to a AdS{sub (p+2)}xS{sup (8-p)} space which, in the framework of Maldacena's conjecture, can be regarded as a gravitational dual to a conformal field theory defined in a (p+1)-dimensional flat space-time. The results presented open the possibility of a better understanding the AdS/CFT correspondence, as originally formulated in terms of the relation among brane structures and gauge theories.
Transport coefficients of black MQGP -branes
NASA Astrophysics Data System (ADS)
Dhuria, Mansi; Misra, Aalok
2015-01-01
The Strominger-Yau-Zaslow (SYZ) mirror, in the `delocalised limit' of Becker et al. (Nucl Phys B 702:207, 2004), of -branes, fractional -branes and flavour -branes wrapping a non-compact four-cycle in the presence of a black hole (BH) resulting in a non-Kähler resolved warped deformed conifold (NKRWDC) in Mia et al. (Nucl Phys B 839:187, 2010), was carried out in Dhuria and Misra (JHEP 1311:001, 2013) and resulted in black -branes. There are two parts in our paper. In the first we show that in the `MQGP' limit discussed in Dhuria and Misra (JHEP 1311:001, 2013) a finite (and hence expected to be more relevant to QGP), finite and very large , and very small , we have the following. (i) The uplift, if valid globally (like Dasgupta et al., Nucl Phys B 755:21, 2006) for fractional branes in conifolds), asymptotically goes to -branes wrapping a two-cycle (homologously a (large) integer sum of two-spheres) in . (ii) Assuming the deformation parameter to be larger than the resolution parameter, by estimating the five structure torsion () classes we verify that in the large- limit, implying the NKRWDC reduces to a warped Kähler deformed conifold. (iii) The local of Dhuria and Misra (JHEP 1311:001, 2013) in the large- limit satisfies the same conditions as the maximal -invariant special Lagrangian three-cycle of of Ionel and Min-OO (J Math 52(3), 2008), partly justifying use of SYZ-mirror symmetry in the `delocalised limit' of Becker et al. (Nucl Phys B 702:207, 2004) in Dhuria and Misra (JHEP 1311:001, 2013). In the second part of the paper, by either integrating out the angular coordinates of the non-compact four-cycle which a -brane wraps around, using the Ouyang embedding, in the DBI action of a -brane evaluated at infinite radial boundary, or by dimensionally reducing the 11-dimensional EH action to five () dimensions and at the infinite radial boundary, we then calculate in particular the (part of the 'MQGP') limit, a variety of gauge and metric
Naked shell singularities on the brane
Seahra, Sanjeev S.
2005-04-15
By utilizing nonstandard slicings of 5-dimensional Schwarzschild and Schwarzschild-AdS manifolds based on isotropic coordinates, we generate static and spherically-symmetric braneworld spacetimes containing shell-like naked null singularities. For planar slicings, we find that the brane-matter sourcing the solution is a perfect fluid with an exotic equation of state and a pressure singularity where the brane crosses the bulk horizon. From a relativistic point of view, such a singularity is required to maintain matter infinitesimally above the surface of a black hole. From the point of view of the AdS/CFT conjecture, the singular horizon can be seen as one possible quantum correction to a classical black hole geometry. Various generalizations of planar slicings are also considered for a Ricci-flat bulk, and we find that singular horizons and exotic matter distributions are common features.
Controlling reactive behavior with consistent world modeling and reasoning
NASA Astrophysics Data System (ADS)
Bou-Ghannam, Akram A.
1992-03-01
Based on the philosophical view of reflexive behaviors and cognitive modules working in a complementary fashion, this paper proposes a hybrid decomposition of the control architecture for an intelligent, fully autonomous mobile robot. This architecture follows a parallel distributed decomposition and supports a hierarchy of control with lower-level reflexive type behaviors working in parallel with higher-level planning and map building modules. The behavior-based component of the system provides the basic instinctive competences for the robot while the cognitive part performs higher machine intelligence functions such as planning. The interface between the two components utilizes motivated behaviors implemented as part of the behavior-based system. A motivated behavior is one whose response is dictated mainly by the internal state (or the motivation state) of the robot. Thus, the cognitive planning activity can execute its plans by merely setting the motivation state of the robot and letting the behavior-based subsystem worry about the details of plan execution. The goal of such a hybrid architecture is to gain the real-time performance of a behavior-based system without losing the effectiveness of a general purpose world model and planner. We view world models as essential to intelligent interaction with the environment, providing a `bigger picture' for the robot when reactive behaviors encounter difficulty. We describe a live experimental run of our robot under hybrid control in an unknown and unstructured lab environment. This experiment demonstrated the validity of the proposed hybrid control architecture and the sensory knowledge integrator (the underlying model for the map-builder module) for the task of mapping the environment. Results of the emergent robot behavior and different map representations of the environment are presented and discussed.
Geometric phase and gravitational precession of D-branes
Pedder, Chris; Sonner, Julian; Tong, David
2007-12-15
We study Berry's phase in the D0-D4-brane system. When a D0-brane moves in the background of D4-branes, the first excited states undergo a holonomy described by a non-Abelian Berry connection. At weak coupling this is an SU(2) connection over R{sup 5}, known as the Yang monopole. At strong coupling, the holonomy is recast as the classical gravitational precession of a spinning particle. The Berry connection is the spin connection of the near-horizon limit of the D4-branes, which is a continuous deformation of the Yang and anti-Yang monopole.
Exact N=2 supergravity solutions with polarized branes
Bena, Iosif; Ciocarlie, Calin
2004-10-15
We construct several classes of exact supersymmetric supergravity solutions describing D4 branes polarized into NS5 branes and F-strings polarized into D2 branes. These setups belong to the same universality class as the perturbative solutions used by Polchinski and Strassler to describe the string dual of N=1* theories. The D4-NS5 setup can be interpreted as a string dual to a confining 4+1 dimensional theory with 8 supercharges, whose properties we discuss. By T-duality, our solutions give Type IIB supersymmetric backgrounds with polarized branes.
Gravitational couplings on D-brane revisited
NASA Astrophysics Data System (ADS)
Ghodsi, Ahmad; Jafari, Ghadir
2016-11-01
Gravitational couplings in bulk space-time include those terms which are fixed by scattering amplitude of strings and ambiguous terms that are coming from the field redefinitions. These field redefinitions can be fixed in the bulk by ghost-free condition. In this paper we have revised the effective gravitational couplings on D-branes by including the field redefinitions. We find the gravitational effective action up to α '2-order.
Fisher equation for a decaying brane
NASA Astrophysics Data System (ADS)
Ghoshal, Debashis
2011-12-01
We consider the inhomogeneous decay of an unstable D-brane. The dynamical equation that describes this process (in light-cone time) is a variant of the non-linear reaction-diffusion equation that first made its appearance in the pioneering work of (Luther and) Fisher and appears in a variety of natural phenomena. We analyze its travelling front solution using singular perturbation theory.
Chiral vortical effect from the compactified D4-branes with smeared D0-brane charge
NASA Astrophysics Data System (ADS)
Wu, Chao; Chen, Yidian; Huang, Mei
2017-03-01
By using the boundary derivative expansion formalism of fluid/gravity correspondence, we study the chiral vortical effect from the compactified D4-branes with smeared D0-brane charge. This background corresponds to a strongly coupled, nonconformal relativistic fluid with a conserved vector current. The presence of the chiral vortical effect is induced by the addition of a Chern-Simons term in the bulk action. Except that the non-dissipative anomalous viscous coefficient and the sound speed rely only on the chemical potential, most of the other thermal and hydrodynamical quantities of the first order depend both on the temperature and the chemical potential. According to our result, the way that the chiral vortical effect coefficient depends on the chemical potential seems irrelevant with whether the relativistic fluid is conformal or not. Stability analysis shows that this anomalous relativistic fluid is stable and the doping of the smeared D0-brane charge will slow down the sound speed.
Asymmetric Wormholes via Electrically Charged Lightlike Branes
Guendelman, E.; Kaganovich, A.; Nissimov, E.; Pacheva, S.
2010-06-17
We consider a self-consistent Einstein-Maxwell-Kalb-Ramond system in the bulk D = 4 space-time interacting with a variable-tension electrically charged lightlike brane. The latter serves both as a material and charge source for gravity and electromagnetism, as well as it dynamically generates a bulk space varying cosmological constant. We find an asymmetric wormhole solution describing two 'universes' with different spherically symmetric black-hole-type geometries connected through a 'throat' occupied by the lightlike brane. The electrically neutral 'left universe' comprises the exterior region of Schwarzschild-de-Sitter (or pure Schwarzschild) space-time above the inner(Schwarzschild-type) horizon, whereas the electrically charged 'right universe' consists of the exterior Reissner-Nordstroem (or Reissner-Nordstroem-de-Sitter) black hole region beyond the outer Reissner-Nordstroem horizon. All physical parameters of the wormhole are uniquely determined by two free parameters - the electric charge and Kalb-Ramond coupling of the lightlike brane.
Cosmological perturbations across an S-brane
Brandenberger, Robert H.; Kounnas, Costas; Partouche, Hervé; Patil, Subodh P.; Toumbas, Nicolaos E-mail: kounnas@lpt.ens.fr E-mail: subodh.patil@cern.ch
2014-03-01
Space-filling S-branes can mediate a transition between a contracting and an expanding universe in the Einstein frame. Following up on previous work that uncovered such bouncing solutions in the context of weakly coupled thermal configurations of a certain class of type II superstrings, we set up here the formalism in which we can study the evolution of metric fluctuations across such an S-brane. Our work shows that the specific nature of the S-brane, which is sourced by non-trivial massless thermal string states and appears when the universe reaches a maximal critical temperature, allows for a scale invariant spectrum of curvature fluctuations to manifest at late times via a stringy realization of the matter bounce scenario. The finite energy density at the transition from contraction to expansion provides calculational control over the propagation of the curvature perturbations through the bounce, furnishing a working proof of concept that such a stringy universe can result in viable late time cosmology.
Superradiant instability of the Kerr brane
NASA Astrophysics Data System (ADS)
Ishibashi, Akihiro; Pani, Paolo; Gualtieri, Leonardo; Cardoso, Vitor
2015-09-01
We consider linear gravitational perturbations of the Kerr brane, an exact solution of vacuum Einstein's equations in dimensions higher than four and a low-energy solution of string theory. Decomposing the perturbations in tensor harmonics of the trans-verse Ricci-flat space, we show that tensor- and vector-type metric perturbations of the Kerr brane satisfy respectively a massive Klein-Gordon equation and a Proca equation on the four-dimensional Kerr space, where the mass term is proportional to the eigenvalue of the harmonics. Massive bosonic fields trigger a well-known superradiant instability on a Kerr black hole. We thus establish that Kerr branes in dimensions D ≥ 6 are gravi-tationally unstable due to superradiance. These solutions are also unstable against the Gregory-Laflamme instability and we discuss the conditions for either instability to occur and their rather different nature. When the transverse dimensions are compactified and much smaller than the Kerr horizon, only the superradiant instability is present, with a time scale much longer than the dynamical time scale. Our formalism can be also used to discuss other types of higher-dimensional black objects, taking advantage of recent progress in studying linear perturbations of four-dimensional black holes.
Randall-Sundrum brane Universe as a ground state for Chern-Simons gravity
NASA Astrophysics Data System (ADS)
Cordonier-Tello, Fabrizio; Izaurieta, Fernando; Mella, Patricio; Rodríguez, Eduardo
2016-12-01
In stark contrast with the three-dimensional case, higher-dimensional Chern-Simons (CS) theories can have non-topological, propagating degrees of freedom. Finding those vacua that allow for the propagation of linear perturbations, however, proves to be surprisingly challenging. The simplest solutions are somehow ‘hyper-stable’, preventing the construction of realistic, four-dimensional physical models. Here, we show that a Randall-Sundrum (RS) brane Universe can be regarded as a vacuum solution of CS gravity in five-dimensional spacetime, with non vanishing torsion along the dimension perpendicular to the brane. Linearized perturbations around this solution not only exist, but behave as standard gravitational waves on a four-dimensional Minkowski background. In the non-perturbative regime, the solution leads to a four-dimensional ‘cosmological function’ {{Λ }}(x) which depends on the Euler density of the brane. Interestingly, the fact that the solution admits nontrivial linear perturbations seems to be related to an often neglected property of the RS spacetime: that it is a group manifold, or, more precisely, two identical group manifolds glued together along the brane. The gravitational theory is then built around this fact, adding the Lorentz generators and one scalar generator needed to close the algebra. In this way, a conjecture emerges: a spacetime that is also a group manifold can be regarded as the ground state of a CS theory for an appropriate Lie algebra.
Scalar field localization on 3-branes placed at a warped resolved conifold
Silva, J. E. G.; Almeida, C. A. S.
2011-10-15
We have studied the localization of a scalar field on a 3-brane embedded in a six-dimensional warped bulk of the form M{sub 4}xC{sub 2}, where M{sub 4} is a 3-brane and C{sub 2} is a 2-cycle of a six-dimensional resolved conifold C{sub 6} over a T{sup 1,1} space. Since the resolved conifold is singularity-free in r=0 depending on a resolution parameter a, we have analyzed the behavior of the localization of a scalar field when we vary the resolution parameter. On one hand, this enables us to study the effects that a singularity has on the field. On the other hand we can use the resolution parameter as a fine-tuning between the bulk Planck mass and 3-brane Planck mass and so it opens a new perspective to extend the hierarchy problem. Using a linear and a nonlinear warp factor, we have found that the massive and massless modes are trapped to the brane even in the singular cone (a{ne}0). We have also compared the results obtained in this geometry and those obtained in other six-dimensional models, such as stringlike geometry and cigarlike universe geometry.
Effective World Modeling: Multisensor Data Fusion Methodology for Automated Driving
Elfring, Jos; Appeldoorn, Rein; van den Dries, Sjoerd; Kwakkernaat, Maurice
2016-01-01
The number of perception sensors on automated vehicles increases due to the increasing number of advanced driver assistance system functions and their increasing complexity. Furthermore, fail-safe systems require redundancy, thereby increasing the number of sensors even further. A one-size-fits-all multisensor data fusion architecture is not realistic due to the enormous diversity in vehicles, sensors and applications. As an alternative, this work presents a methodology that can be used to effectively come up with an implementation to build a consistent model of a vehicle’s surroundings. The methodology is accompanied by a software architecture. This combination minimizes the effort required to update the multisensor data fusion system whenever sensors or applications are added or replaced. A series of real-world experiments involving different sensors and algorithms demonstrates the methodology and the software architecture. PMID:27727171
Modelling the world in real time: how robots engineer information.
Davison, Andrew J
2003-12-15
Programming robots and other autonomous systems to interact with the world in real time is bringing into sharp focus general questions about representation, inference and understanding. These artificial agents use digital computation to interpret the data gleaned from sensors and produce decisions and actions to guide their future behaviour. In a physical system, however, finite computational resources unavoidably impose the need to approximate and make selective use of the information available to reach prompt deductions. Recent research has led to widespread adoption of the methodology of Bayesian inference, which provides the absolute framework to understand this process fully via modelling as informed, fully acknowledged approximation. The performance of modern systems has improved greatly on the heuristic methods of the early days of artificial intelligence. We discuss the general problem of real-time inference and computation, and draw on examples from recent research in computer vision and robotics: specifically visual tracking and simultaneous localization and mapping.
Modeling falling groundwater tables in major cities of the world
NASA Astrophysics Data System (ADS)
Sutanudjaja, E.; Erkens, G.
2015-12-01
Groundwater use and its over-consumption are one of the major drivers in the hydrology of many major cities in the world, particularly in delta regions. Yet, a global assessment to identify cities with declining groundwater table problems has not been done yet. In this study we used the global hydrological model PCR-GLOBWB (10 km resolution, for 1960-2010). Using this model, we globally calculated groundwater recharge and river discharge/surface water levels, as well as global water demand and abstraction from ground- and surface water resources. The output of PCR-GLOBWB model was then used to force a groundwater MODFLOW-based model simulating spatio-temporal groundwater head dynamics, including groundwater head declines in all major cities - mainly in delta regions - due to escalation in abstraction of groundwater to meet increasing water demand. Using these coupled models, we managed to identify a number of critical cities having groundwater table falling rates above 50 cm/year (average in 2000-2010), such as Barcelona, Houston, Los Angeles, Mexico City, New York, Rome and many large cities in China, Libya, India and Pakistan, as well as in Middle East and Central Asia regions. However, our simulation results overestimate the depletion rates in San Jose, Tokyo, Venice, and other cities where groundwater usages have been aggressively managed and replaced by importing surface water from other places. Moreover, our simulation might underestimate the declining groundwater head trends in some familiar cases, such as Bangkok (12 cm/year), Ho Chi Minh City (34 cm/year), and Jakarta (26 cm/year). The underestimation was due to an over-optimistic model assumption in allocating surface water for satisfying urban water needs. In reality, many big cities, although they are located in wet regions and have abundant surface water availability, still strongly rely on groundwater sources due to inadequate facilities to treat and distribute surface water resources.
Modeling falling groundwater tables in major cities of the world
NASA Astrophysics Data System (ADS)
Sutanudjaja, Edwin; Erkens, Gilles
2016-04-01
Groundwater use and its over-consumption are one of the major drivers in the hydrology of many major cities in the world, particularly in delta regions. Yet, a global assessment to identify cities with declining groundwater table problems has not been done yet. In this study we used the global hydrological model PCR-GLOBWB (10 km resolution, for 1960-2010). Using this model, we globally calculated groundwater recharge and river discharge/surface water levels, as well as global water demand and abstraction from ground- and surface water resources. The output of PCR-GLOBWB model was then used to force a groundwater MODFLOW-based model simulating spatio-temporal groundwater head dynamics, including groundwater head declines in all major cities - mainly in delta regions - due to escalation in abstraction of groundwater to meet increasing water demand. Using these coupled models, we managed to identify a number of critical cities having groundwater table falling rates above 50 cm/year (average in 2000-2010), such as Barcelona, Houston, Los Angeles, Mexico City, New York, Rome and many large cities in China, Libya, India and Pakistan, as well as in Middle East and Central Asia regions. However, our simulation results overestimate the depletion rates in San Jose, Tokyo, Venice, and other cities where groundwater usages have been aggressively managed and replaced by importing surface water from other places. Moreover, our simulation might underestimate the declining groundwater head trends in some familiar cases, such as Bangkok (12 cm/year), Ho Chi Minh City (34 cm/year), and Jakarta (26 cm/year). The underestimation was due to an over-optimistic model assumption in allocating surface water for satisfying urban water needs. In reality, many big cities, although they are located in wet regions and have abundant surface water availability, still strongly rely on groundwater sources due to inadequate facilities to treat and distribute surface water resources.
Monte Carlo modelling of positron transport in real world applications
NASA Astrophysics Data System (ADS)
Marjanović, S.; Banković, A.; Šuvakov, M.; Petrović, Z. Lj
2014-05-01
Due to the unstable nature of positrons and their short lifetime, it is difficult to obtain high positron particle densities. This is why the Monte Carlo simulation technique, as a swarm method, is very suitable for modelling most of the current positron applications involving gaseous and liquid media. The ongoing work on the measurements of cross-sections for positron interactions with atoms and molecules and swarm calculations for positrons in gasses led to the establishment of good cross-section sets for positron interaction with gasses commonly used in real-world applications. Using the standard Monte Carlo technique and codes that can follow both low- (down to thermal energy) and high- (up to keV) energy particles, we are able to model different systems directly applicable to existing experimental setups and techniques. This paper reviews the results on modelling Surko-type positron buffer gas traps, application of the rotating wall technique and simulation of positron tracks in water vapor as a substitute for human tissue, and pinpoints the challenges in and advantages of applying Monte Carlo simulations to these systems.
NASA Astrophysics Data System (ADS)
McLeod, Roger; McLeod, David
2006-03-01
Model a `planar' electron by a closed string of vibrating neutrinos; displacement values are proportional to the speed of light times the square root of the mass. `Spin' supplies required inward spherical fields in three spatial dimensions. Interlocked quark loops model protons or neutrons; ideas like strong and weak forces, or an uncertainty principle, arise. Subtle, longer string-like `vibrating,' quasi-periodic, lighted phenomena we detect are at locations used by some of our Native American forebears, or by the Hopi or Maya -locations indicated by problematic constructions, by `sacred' place-names, or by individuals with `titles' identified as names. Lighted `tubes,' associated with EMF, required by our model for tornado generation, imply breaking the EMF lines will `kill' any tornado. `Kokopelli's hair,' is the place to construct a designated current loop.
A 3D world model builder with a mobile robot
Zhang, Z.; Faugeras, O. )
1992-08-01
This article describes a system to incrementally build a world model with a mobile robot in an unknown environment. The model is, for the moment, segment based. A trinocular stereo system is used to build a local map about the environment. A global map is obtained by integrating a sequence of stereo frames taken when the robot navigates in the environment. The emphasis of this article is on the representation of the uncertainty of 3D segments from stereo and on the integration of segments from multiple views. The proposed representation is simple and very convenient to characterize the uncertainty of segment. A Kalman filter is used to merge matched line segments. An important characteristic of this integration strategy is that a segment observed by the stereo system corresponds only to one part of the segment in space, so the union of the different observations gives a better estimate on the segment in space. The authors have succeeded in integrating 35 stereo frames taken in their robot room.
Hydro-elastic complementarity in black branes at large D
NASA Astrophysics Data System (ADS)
Emparan, Roberto; Izumi, Keisuke; Luna, Raimon; Suzuki, Ryotaku; Tanabe, Kentaro
2016-06-01
We obtain the effective theory for the non-linear dynamics of black branes — both neutral and charged, in asymptotically flat or Anti-deSitter spacetimes — to leading order in the inverse-dimensional expansion. We find that black branes evolve as viscous fluids, but when they settle down they are more naturally viewed as solutions of an elastic soap-bubble theory. The two views are complementary: the same variable is regarded in one case as the energy density of the fluid, in the other as the deformation of the elastic membrane. The large- D theory captures finite-wavelength phenomena beyond the conventional reach of hydrodynamics. For asymptotically flat charged black branes (either Reissner-Nordstrom or p-brane-charged black branes) it yields the non-linear evolution of the Gregory-Laflamme instability at large D and its endpoint at stable non-uniform black branes. For Reissner-Nordstrom AdS black branes we find that sound perturbations do not propagate (have purely imaginary frequency) when their wavelength is below a certain charge-dependent value. We also study the polarization of black branes induced by an external electric field.
Left-right entanglement entropy of D p-branes
NASA Astrophysics Data System (ADS)
Zayas, Leopoldo A. Pando; Quiroz, Norma
2016-11-01
We compute the left-right entanglement entropy for Dp-branes in string theory. We employ the CFT approach to string theory Dp-branes, in particular, its presentation as coherent states of the closed string sector. The entanglement entropy is computed as the von Neumann entropy for a density matrix resulting from integration over the left-moving degrees of freedom. We discuss various crucial ambiguities related to sums over spin structures and argue that different choices capture different physics; however, we advance a themodynamic argument that seems to favor a particular choice of replica. We also consider Dp branes on compact dimensions and verify that the effects of T-duality act covariantly on the Dp brane entanglement entropy. We find that generically the left-right entanglement entropy provides a suitable generalization of boundary entropy and of the D-brane tension.
Discrete Torsion, (Anti) de Sitter D4-Brane and Tunneling
NASA Astrophysics Data System (ADS)
Singh, Abhishek K.; Pandey, P. K.; Singh, Sunita; Kar, Supriya
2014-06-01
We obtain quantum geometries on a vacuum created pair of a (DDbar)3-brane, at a Big Bang singularity, by a local two form on a D4-brane. In fact our analysis is provoked by an established phenomenon leading to a pair creation by a gauge field at a black hole horizon by Stephen Hawking in 1975. Importantly, the five dimensional microscopic black holes are described by an effective non-perturbative curvature underlying a discrete torsion in a second order formalism. In the case for a non-propagating torsion, the effective curvature reduces to Riemannian, which in a low energy limit may describe Einstein vacuum in the formalism. In particular, our analysis suggests that a non-trivial space begin with a hot de Sitter brane-Universe underlying a nucleation of a vacuum pair of (DDbar)-instanton at a Big Bang. A pair of instanton nucleats a D-particle which in turn combines with an anti D-particle to describe a D-string and so on. The nucleation of a pair of higher dimensional pair of brane/anti-brane from a lower dimensional pair may be viewed via an expansion of the brane-Universe upon time. It is in conformity with the conjecture of a branes within a brane presumably in presence of the non-zero modes of two form. Interestingly, we perform a thermal analysis underlying various emergent quantum de Sitter vacua on a D4-brane and argue for the plausible tunneling geometries underlying a thermal equilibrium. It is argued that a de Sitter Schwarzschild undergoes quantum tunneling to an AdS-brane Schwarzschild via Nariai and de Sitter topological black hole.
Energy radiation by cosmic superstrings in brane inflation
Firouzjahi, Hassan
2008-01-15
The dominant method of energy loss by a loop of cosmic D-strings in models of warped brane inflation is studied. It is shown that the energy loss via Ramond-Ramond field radiation can dominate by many orders of magnitude over the energy radiation via gravitational wave emission. The ratio of these two energy loss mechanisms depends on the energy scale of inflation, the mass scale of string theory, and whether it is a single-throat or a multithroat inflationary scenario. This can have important consequences for the detection of cosmic superstrings in the near future. It is argued that the bounds from cosmic microwave background anisotropies and big bang nucleosynthesis are the dominant cosmological sources to constrain the physical parameters of the network of cosmic superstrings, whereas the role of the gravitational wave-based experiments may be secondary.
Localizing global hedgehogs on the brane
Cho, Inyong
2004-10-15
We investigate the localization of 4D topological global defects on the brane embedded in 5D. The defects are induced by 5D scalar fields with a symmetry-breaking potential. Taking an Ansatz which separates the scalar field into the 4D and the extra-D part, we find that the static-hedgehog configuration is accomplished and the defects are formed only in the AdS{sub 4}/AdS{sub 5} background. In the extra dimension, the localization amplitude for the 4D defects is high where the warp factor is high.
Localizing global hedgehogs on the brane
NASA Astrophysics Data System (ADS)
Cho, Inyong
2004-10-01
We investigate the localization of 4D topological global defects on the brane embedded in 5D. The defects are induced by 5D scalar fields with a symmetry-breaking potential. Taking an Ansatz which separates the scalar field into the 4D and the extra-D part, we find that the static-hedgehog configuration is accomplished and the defects are formed only in the AdS4/AdS5 background. In the extra dimension, the localization amplitude for the 4D defects is high where the warp factor is high.
Influence of World and Gravity Model Selection on Surface Interacting Vehicle Simulations
NASA Technical Reports Server (NTRS)
Madden, Michael M.
2007-01-01
A vehicle simulation is surface-interacting if the state of the vehicle (position, velocity, and acceleration) relative to the surface is important. Surface-interacting simulations perform ascent, entry, descent, landing, surface travel, or atmospheric flight. Modeling of gravity is an influential environmental factor for surface-interacting simulations. Gravity is the free-fall acceleration observed from a world-fixed frame that rotates with the world. Thus, gravity is the sum of gravitation and the centrifugal acceleration due to the world s rotation. In surface-interacting simulations, the fidelity of gravity at heights above the surface is more significant than gravity fidelity at locations in inertial space. A surface-interacting simulation cannot treat the gravity model separately from the world model, which simulates the motion and shape of the world. The world model's simulation of the world's rotation, or lack thereof, produces the centrifugal acceleration component of gravity. The world model s reproduction of the world's shape will produce different positions relative to the world center for a given height above the surface. These differences produce variations in the gravitation component of gravity. This paper examines the actual performance of world and gravity/gravitation pairs in a simulation using the Earth.
Modelling world gold prices and USD foreign exchange relationship using multivariate GARCH model
NASA Astrophysics Data System (ADS)
Ping, Pung Yean; Ahmad, Maizah Hura Binti
2014-12-01
World gold price is a popular investment commodity. The series have often been modeled using univariate models. The objective of this paper is to show that there is a co-movement between gold price and USD foreign exchange rate. Using the effect of the USD foreign exchange rate on the gold price, a model that can be used to forecast future gold prices is developed. For this purpose, the current paper proposes a multivariate GARCH (Bivariate GARCH) model. Using daily prices of both series from 01.01.2000 to 05.05.2014, a causal relation between the two series understudied are found and a bivariate GARCH model is produced.
On the 3-form formulation of axion potentials from D-brane instantons
NASA Astrophysics Data System (ADS)
García-Valdecasas, Eduardo; Uranga, Angel
2017-02-01
The study of axion models and quantum corrections to their potential has experienced great progress by phrasing the axion potential in terms of a 3-form field eating up the 2-form field dual to the axion. Such reformulation of the axion potential has been described for axion monodromy models and for axion potentials from non-perturbative gauge dynamics. In this paper we propose a 3-form description of the axion potentials from non-gauge D-brane instantons. Interestingly, the required 3-form field does not arise in the underlying geometry, but rather shows up in the KK compactification in the generalized geometry obtained when the backreaction of the D-brane instanton is taken into account.
Superimposed oscillations in brane inflation
Ávila, Santiago; Martin, Jérôme; Steer, Danièle A. E-mail: jmartin@iap.fr
2014-08-01
In canonical scalar field inflation, the Starobinsky model (with a linear potential but discontinuous slope) is remarkable in that though slow-roll is violated, both the power-spectrum and bi-spectrum can be calculated exactly analytically. The two-point function is characterised by different power on large and small scales, and a burst of small amplitude superimposed oscillations in between. We extend this analysis to Dirac Born Infeld (DBI) inflation, for which generalised slow-roll is violated at the discontinuity and a rapid variation in the speed of sound c{sub S} occurs. In an attempt to characterise the effect of non-linear kinetic terms on the oscillatory features of the primordial power-spectrum, we show that the resulting power spectrum has a shape and features which differ significantly from those of the standard Starobinsky model. In particular, when c{sub S} is small, the power-spectrum now takes very similar scale invariant values on large and small scales, while on intermediate scales it is characterised by much larger amplitude and higher frequency superimposed oscillations. We also show that calculating non-Gaussianities in this model is a complicated but interesting task since all terms in the cubic action now contribute. Investigating whether the superimposed oscillations could fit to the Planck Cosmic Microwave Background (CMB) data (for instance by explaining the large scale Planck anomalies) with, at the same time, small non-Gaussianities remains an intriguing and open possibility.
Constraining the cosmology of the phantom brane using distance measures
NASA Astrophysics Data System (ADS)
Alam, Ujjaini; Bag, Satadru; Sahni, Varun
2017-01-01
The phantom brane has several important distinctive features: (i) Its equation of state is phantomlike, but there is no future "big rip" singularity, and (ii) the effective cosmological constant on the brane is dynamically screened, because of which the expansion rate is smaller than that in Λ CDM at high redshifts. In this paper, we constrain the Phantom braneworld using distance measures such as type-Ia supernovae (SNeIa), baryon acoustic oscillations (BAO), and the compressed cosmic microwave background (CMB) data. We find that the simplest braneworld models provide a good fit to the data. For instance, BAO +SNeIa data can be accommodated by the braneworld for a large region in parameter space 0 ≤Ωℓ≲0.3 at 1 σ . The Hubble parameter can be as high as H0≲78 km s-1 Mpc-1 , and the effective equation of state at present can show phantomlike behavior with w0≲-1.2 at 1 σ . We note a correlation between H0 and w0, with higher values of H0 leading to a lower, and more phantomlike, value of w0. Inclusion of CMB data provides tighter constraints Ωℓ≲0.1 . (Here Ωℓ encodes the ratio of the five- and four-dimensional Planck mass.) The Hubble parameter in this case is more tightly constrained to H0≲71 km s-1 Mpc-1 , and the effective equation of state to w0≲-1.1 . Interestingly, we find that the Universe is allowed to be closed or open, with -0.5 ≲Ωκ≲0.5 , even on including the compressed CMB data. There appears to be some tension in the low and high-z BAO data which may either be resolved by future data, or act as a pointer to interesting new cosmology.
Hierarchies from D-brane instantons in globally defined calabi-yau orientifolds
Cvetič, Mirjam; Weigand, Timo
2008-06-01
We construct the first globally consistent semi-realistic Type I string vacua on an elliptically fibered manifold where the zero modes of the Euclidean D1-instanton sector allow for the generation of non-perturbative Majorana masses of an intermediate scale. In another class of global models, a D1-brane instanton can generate a Polonyi-type superpotential breaking supersymmetry at an exponentially suppressed scale.
Intersecting D 3 -D3 ' -brane system at finite temperature
NASA Astrophysics Data System (ADS)
Cottrell, William; Hanson, James; Hashimoto, Akikazu; Loveridge, Andrew; Pettengill, Duncan
2017-02-01
We analyze the dynamics of the intersecting D 3 -D3 ' -brane system overlapping in 1 +1 dimensions, in a holographic treatment where N D3 branes are manifested as anti-de Sitter Schwartzschild geometry, and the D3 ' brane is treated as a probe. We extract the thermodynamic equation of state from the set of embedding solutions, and analyze the stability at the perturbative and the nonperturbative level. We review a systematic procedure to resolve local instabilities and multivaluedness in the equations of state based on classic ideas of convexity in the microcanonical ensemble. We then identify a runaway behavior which was not noticed previously for this system.
Violation of cosmic censorship in dynamical p -brane systems
NASA Astrophysics Data System (ADS)
Maeda, Kengo; Uzawa, Kunihito
2016-02-01
We study the cosmic censorship of dynamical p -brane systems in a D -dimensional background. This is the generalization of the analysis in the Einstein-Maxwell-dilaton theory, which was discussed by Horne and Horowitz [Phys. Rev. D 48, R5457 (1993)]. We show that a timelike curvature singularity generically appears from an asymptotic region in the time evolution of the p -brane solution. Since we can set regular and smooth initial data in a dynamical M5-brane system in 11-dimensional supergravity, this implies a violation of cosmic censorship.
Gauge theories from D7-branes over vanishing 4-cycles
Franco, Sebastian; Torroba, Gonzalo; /SLAC /Stanford U., Phys. Dept.
2010-12-16
We study quiver gauge theories on D7-branes wrapped over vanishing holomorphic 4-cycles. We investigate how to incorporate O7-planes and/or flavor D7-branes, which are necessary to cancel anomalies. These theories are chiral, preserve four supercharges and exhibit very rich infrared dynamics. Geometric transitions and duality in the presence of O-planes are analyzed. We study the Higgs branch of these quiver theories, showing the emergence of fuzzy internal dimensions. This branch is related to noncommutative instantons on the divisor wrapped by the seven-branes. Our results have a natural application to the recently introduced F(uzz) limit of F-theory.
Graded lagrangians, exotic topological D-branes and enhanced triangulated categories
NASA Astrophysics Data System (ADS)
Lazaroiu, Calin Iuliu
2001-06-01
I point out that (BPS saturated) A-type D-branes in superstring compactification on Calabi-Yau threefolds correspond to graded special lagrangian submanifolds, a particular case of the graded lagrangian submanifolds considered by M. Kontsevich and P. Seidel. Combining this with the categorical formulation of cubic string field theory in the presence of D-branes, I consider a collection of topological D-branes wrapped over the same lagrangian cycle and derive its string field action from first string-theoretic principles. The result is a Script Z-graded version of super-Chern-Simons field theory living on the lagrangian cycle, whose relevant string field is a degree one superconnection in a Script Z-graded superbundle, in the sense previously considered in mathematical work of J.M. Bismutt and J. Lott. This gives a refined (and modified) version of a proposal previously made by C. Vafa. I analyze the vacuum deformations of this theory and relate them to topological D-brane composite formation, upon using the general formalism developed in a previous paper. This allows me to identify a large class of topological D-brane composites (generalized, or ``exotic'' topological D-branes) which do not admit a traditional description. Among these are objects which correspond to the ``covariantly constant sequences of flat bundles'' considered by Bismut and Lott, as well as more general structures, which are related to the enhanced triangulated categories of Bondal and Kapranov. I also give a rough sketch of the relation between this construction and the large radius limit of a certain version of the ``derived category of Fukaya's category''. This paper forms part of a joint project with Prof. S. Popescu, a brief announcement of which can be found in the second part of the note hep-th/0102183. The paralel B-model realization, as well as the relation with the enhanced triangulated categories of Bondal and Kapranov, was recently discussed by D.E. Diaconescu in the paper hep
Intersecting 6-branes from new 7-manifolds with G2 holonomy
NASA Astrophysics Data System (ADS)
Behrndt, Klaus; Dall'Agata, Gianguido; Lüst, Dieter; Mahapatra, Swapna
2002-08-01
We discuss a new family of metrics of 7-manifolds with G2 holonomy, which are Bbb R3 bundles over a quaternionic space. The metrics depend on five parameters and have two abelian isometries. Certain singularities of the G2 manifolds are related to fixed points of these isometries; there are two combinations of Killing vectors that possess co-dimension four fixed points which yield upon compactification only intersecting D6-branes if one also identifies two parameters. Two of the remaining parameters are quantized and we argue that they are related to the number of D6-branes, which appear in three stacks. We perform explicitly the reduction to the type IIA model.
The Policy Relevance of Models in World Politics
1971-10-01
1971, Young, Gran B. "The Perils of Odysseus : On Constructing Theories of International Relations," World Politics Supplement on Theory and Policy in International Relations. 1971. -■--—•■■ —■■■■ -■■-’- ■--
Non-BPS D-brane solutions in six dimensional orbifolds
NASA Astrophysics Data System (ADS)
Lozano, Y.
2000-08-01
Starting with the non-BPS D0-brane solution of IIB/(-1)FLI4 constructed recently by Eyras and Panda we construct via T-duality the non-BPS D2-brane and D1-brane solutions of IIB/(-1)FLI4 and IIA/(-1)FLI4 predicted by Sen. The D2-brane couples magnetically to the vector field of the NS5B-brane living in the twisted sector of the Type IIB orbifold, whereas the D1-brane couples (electrically and magnetically) to the self-dual 2-form potential of the NS5A-brane that is present in the twisted sector of the Type IIA orbifold construction. Finally we discuss the eleven dimensional interpretation of these branes as originating from a non-BPS M1-brane solution of M-theory orientifolded by ΩρI5.
Thick branes from self-gravitating scalar fields
Novikov, Oleg O.; Andrianov, Vladimir A.; Andrianov, Alexander A.
2014-07-23
The formation of a domain wall ('thick brane') induced by scalar matter dynamics and triggered by a thin brane defect is considered in noncompact five-dimensional space-time with warped AdS type geometry. The scalar matter is composed of two fields with softly broken O(2) symmetry and minimal coupling to gravity. The nonperturbative effects in the invariant mass spectrum of light localized scalar states are investigated for different values of the tension of the thin brane defect. Especially interesting is the case of the thin brane with negative tension when the singular barriers form a potential well with two infinitely tall walls and the discrete spectrum of localized states arises completely isolated from the bulk.
Model of the world oil market with an OPEC cartel. [1980 AD to 2040 AD
Alsmiller, R.G. Jr.; Horwedel, J.E.; Marshalla, R.A.; Nesbitt, D.M.; Haas, S.M.
1984-08-01
A world oil market model (WOM) with OPEC treated as a Stackelberg cartel has been developed within the framework of the Generalized Equilibrium Modeling System (GEMS) that is available from Decision Focus, Inc. The US sector of the model is represented by a Liquid Fuels Supply model that was presented previously. The WOM model is described and results obtained with the model for the period 1980 to 2040 are presented. For comparative purposes, results obtained with the model when OPEC is treated as a competitive producer are also presented. By comparing the world oil price as a function of time from the two calculations, the influence that OPEC may have on the oil market by exploiting all of its market power is quantified. The world oil price as obtained with the WOM model is also compared with world oil price projections from a variety of sources. 22 references, 9 figures, 2 tables.
Holography for anisotropic branes with hyperscaling violation
NASA Astrophysics Data System (ADS)
Roychowdhury, Dibakar
2016-01-01
In this paper, based on the principles of Gauge/gavity duality, we explore the field theory description of certain special class of strongly coupled hyperscaling violating QFTs in the presence of scalar deformations near the effective dynamical scale ( r F ) of the theory. In the language of the AdS/CFT duality, the scalar deformations of the above type could be thought of as being sourced due to some massless scalar excitation in the bulk which explicitly break the SO(2) rotational invariance along the spatial directions of the brane. As a consequence of these deformations, it turns out that when we probe such QFTs in terms of its non-local observable like, the entanglement entropy as well as the Wilson operator they indeed receive finite contributions near the effective dynamical scale ( r F ) of the theory.
Note about unstable D-branes with dynamical tension
NASA Astrophysics Data System (ADS)
KlusoÅ, J.
2016-08-01
We propose an action for an unstable Dp-brane with dynamical tension. We show that the equations of motion are equivalent to the equations of motion derived from Dirac-Born-Infeld and Wess-Zumino actions for a non-Bogomol'nyi-Prasad-Sommerfield Dp-brane. We also find the Hamiltonian formulation of this action and analyze the properties of the solutions corresponding to the tachyon vacuum and zero-tension solution.
D-brane superpotentials: Geometric and worldsheet approaches
NASA Astrophysics Data System (ADS)
Baumgartl, Marco; Brunner, Ilka; Soroush, Masoud
2011-02-01
From the worldsheet perspective, the superpotential on a D-brane wrapping internal cycles of a Calabi-Yau manifold is given as a generating functional for disk correlation functions. On the other hand, from the geometric point of view, D-brane superpotentials are captured by certain chain integrals. In this work, we explicitly show for branes wrapping internal two-cycles how these two different approaches are related. More specifically, from the worldsheet point of view, D-branes at the Landau-Ginzburg point have a convenient description in terms of matrix factorizations. We use a formula derived by Kapustin and Li to explicitly evaluate disk correlators for families of D2-branes. On the geometry side, we then construct a three-chain whose period gives rise to the effective superpotential and show that the two expressions coincide. Finally, as an explicit example, we choose a particular compact Calabi-Yau hypersurface and compute the effective D2-brane superpotential in different branches of the open moduli space, in both geometric and worldsheet approaches.
Five-dimensional Nernst branes from special geometry
NASA Astrophysics Data System (ADS)
Dempster, P.; Errington, D.; Gutowski, J.; Mohaupt, T.
2016-11-01
We construct Nernst brane solutions, that is black branes with zero entropy density in the extremal limit, of FI-gauged minimal five-dimensional supergravity coupled to an arbitrary number of vector multiplets. While the scalars take specific constant values and dynamically determine the value of the cosmological constant in terms of the FI-parameters, the metric takes the form of a boosted AdS Schwarzschild black brane. This metric can be brought to the Carter-Novotný-Horský form that has previously been observed to occur in certain limits of boosted D3-branes. By dimensional reduction to four dimensions we recover the four-dimensional Nernst branes of arXiv:1501.07863 and show how the five-dimensional lift resolves all their UV singularities. The dynamics of the compactification circle, which expands both in the UV and in the IR, plays a crucial role. At asymptotic infinity, the curvature singularity of the four-dimensional metric and the run-away behaviour of the four-dimensional scalar combine in such a way that the lifted solution becomes asymptotic to AdS5. Moreover, the existence of a finite chemical potential in four dimensions is related to fact that the compactification circle has a finite minimal value. While it is not clear immediately how to embed our solutions into string theory, we argue that the same type of dictionary as proposed for boosted D3-branes should apply, although with a lower amount of supersymmetry.
Interaction of higher-dimensional rotating black holes with branes
NASA Astrophysics Data System (ADS)
Frolov, Valeri P.; Fursaev, Dmitri V.; Stojkovic, Dejan
2004-07-01
We study interaction of rotating higher-dimensional black holes with a brane in spacetimes with large extra dimensions. We demonstrate that in a general case a rotating black hole attached to a brane can lose bulk components of its angular momenta. A stationary black hole can have only those components of the angular momenta which are connected with Killing vectors generating transformations preserving a position of the brane. In a final stationary state the null Killing vector generating the black hole horizon is tangent to the brane. We discuss first the interaction of a cosmic string and a domain wall with the 4D Kerr black hole. We then prove the general result for slowly rotating higher-dimensional black holes interacting with branes. The characteristic time when a rotating black hole with gravitational radius r0 reaches this final stationary state is T ~ rp-10/(Gσ), where G is the higher-dimensional gravitational coupling constant, σ is the brane tension and p is the number of extra dimensions.
Fine-tuning with brane-localized flux in 6D supergravity
NASA Astrophysics Data System (ADS)
Niedermann, Florian; Schneider, Robert
2016-02-01
There are claims in the literature that the cosmological constant problem could be solved in a braneworld model with two large (micron-sized) supersymmetric extra dimensions. The mechanism relies on two basic ingredients: first, the cosmological constant only curves the compact bulk geometry into a rugby shape while the 4D curvature stays flat. Second, a brane-localized flux term is introduced in order to circumvent Weinberg's fine-tuning argument, which otherwise enters here through a backdoor via the flux quantization condition. In this paper, we show that the latter mechanism does not work in the way it was designed: the only localized flux coupling that guarantees a flat on-brane geometry is one which preserves the scale invariance of the bulk theory. Consequently, Weinberg's argument applies, making a fine-tuning necessary again. The only remaining window of opportunity lies within scale invariance breaking brane couplings, for which the tuning could be avoided. Whether the corresponding 4D curvature could be kept under control and in agreement with the observed value will be answered in our companion paper [1].
A human supervisory approach to rapid world modeling through the use of geometric primitives
Luck, J.; Roberts, R.
1997-08-11
A three-dimensional world model is crucial for many robot-oriented tasks. The most efficient mapping configuration use geometric primitives to model environments, and are easy to store and process. In the past, modeling techniques have been either fully manual or autonomous. Manual methods are extremely time consuming but also highly accurate and flexible. On the other hand autonomous techniques are fast but inflexible and often inaccurate. The method presented in this paper combines the two thereby yielding a highly efficient, flexible, and accurate tool. Our methods enable a human supervisor to quickly construct a fully defined world model from unfiltered and unsegmented real-world range data.
Higgs-radion phenomenology in stabilized RS models
NASA Astrophysics Data System (ADS)
Boos, Eduard; Bunichev, Viacheslav; Keizerov, Sergey; Perfilov, Maxim; Rakhmetov, Eduard; Smolyakov, Mikhail; Svirina, Kseniia; Volobuev, Igor
2016-10-01
An important general prediction of stabilized brane world models is the existence of a bulk scalar radion field, whose lowest Kaluza-Klein (KK) mode is the scalar particle called the radion. This field comes from the fluctuations of the metric in the extra dimension and the radion mass can be smaller than that of all the massive KK modes of the other particles propagating in the multidimensional bulk. Due to its origin, the radion and its KK tower couple to the trace of the energy-momentum tensor of the Standard Model. These fields have the same quantum numbers as the neutral Higgs field and can mix with the latter, if they are coupled. We present a short review of some aspects of Higgs-radion phenomenology in stabilized brane-world models. In particular, we discuss the possibility of explaining the 750 GeV excess by the production of a radion-dominated state.
Storing and Predicting Dynamic Attributes in a World Model Knowledge Store
2009-05-01
Walt Disney 4 ACKNOWLEDGMENTS First I would like to thank my family for their unending support of every endeavor I’ve ever dreamt up. A long...is that the nature of the real world is to exhibit many dynamic characteristics. Historically, most mobile robot systems have assumed the world to...AFRL-RX-TY-TR-2009-4515 STORING AND PREDICTING DYNAMIC ATTRIBUTES IN A WORLD MODEL KNOWLEDGE STORE Daniel A. Kent University of
Storing and Predicting Dynamic Attributes in a World Model Knowledge Store
2007-01-01
myself. “All our dreams can come true… if we have the courage to pursue them.” Walt Disney 4 ACKNOWLEDGMENTS First I would like to thank my...constraints of that world . One of these constraints which have not historically been dealt with is that the nature of the real world is to exhibit many...1 STORING AND PREDICTING DYNAMIC ATTRIBUTES IN A WORLD MODEL KNOWLEDGE STORE By DANIEL ADAM KENT
Holographic model with a Neveu-Schwarz-Neveu-Schwarz field
Seo, Yunseok; Sin, Sang-jin; Xu, Wei-shui
2009-11-15
We consider a holographic model constructed using the D4/D8-D8 brane configuration with a Neveu-Schwarz-Neveu-Schwarz background field. We study some properties of the effective field theory in this intersecting brane construction and calculate the effects of this Neveu-Schwarz-Neveu-Schwarz background field on some underlying dynamics. We also discuss some other general brane configurations.
Time-dependent AdS backgrounds from S-branes
NASA Astrophysics Data System (ADS)
Deger, Nihat Sadik
2016-11-01
We construct time and radial dependent solutions that describe p-branes in chargeless S-brane backgrounds. In particular, there are some new M5- and D3-branes among our solutions which have AdS limits and contain a cosmological singularity as well. We also find a time-dependent version of the dyonic membrane configuration in 11-dimensions by applying a Lunin-Maldacena deformation to our new M5-brane solution.
On-Road Validation of a Simplified Model for Estimating Real-World Fuel Economy: Preprint
Wood, Eric; Gonder, Jeff; Jehlik, Forrest
2017-01-01
On-road fuel economy is known to vary significantly between individual trips in real-world driving conditions. This work introduces a methodology for rapidly simulating a specific vehicle's fuel economy over the wide range of real-world conditions experienced across the country. On-road test data collected using a highly instrumented vehicle is used to refine and validate this modeling approach. Model accuracy relative to on-road data collection is relevant to the estimation of 'off-cycle credits' that compensate for real-world fuel economy benefits that are not observed during certification testing on a chassis dynamometer.
Simulation of the world ocean climate with a massively parallel numerical model
NASA Astrophysics Data System (ADS)
Ushakov, K. V.; Ibrayev, R. A.; Kalmykov, V. V.
2015-07-01
The INM-IO numerical World Ocean model is verified through the calculation of the model ocean climate. The numerical experiment was conducted for a period of 500 years following the CORE-I protocol. We analyze some basic elements of the large-scale ocean circulation and local and integral characteristics of the model solution. The model limitations and ways they are overcome are described. The results generally fit the level of leading models. This experiment is a necessary step preceding the transition to high-resolution diagnostic and prognostic calculations of the state of the World Ocean and its individual basins.
Towards a classification of branes in theories with eight supercharges
NASA Astrophysics Data System (ADS)
Bergshoeff, Eric A.; Riccioni, Fabio; Romano, Luca
2014-05-01
We provide a classification of half-supersymmetric branes in quarter-maximal supergravity theories with scalars parametrising coset manifolds. We show that the results previously obtained for the half-maximal theories give evidence that half-supersymmetric branes correspond to the real longest weights of the representations of the brane charges, where the reality properties of the weights are determined from the Tits-Satake diagrams associated to the global symmetry groups. We show that the resulting brane structure is universal for all theories that can be uplifted to six dimensions. We also show that when viewing these theories as low-energy theories for the suitably compactified heterotic string, the classification we obtain is in perfect agreement with the wrapping rules derived in previous works for the same theory compactified on tori. Finally, we relate the branes to the R-symmetry representations of the central charges and we show that in general the degeneracies of the BPS conditions are twice those of the half-maximal theories and four times those of the maximal ones.
A turbidity current model for real world applications
NASA Astrophysics Data System (ADS)
Macías, Jorge; Castro, Manuel J.; Morales, Tomás
2016-04-01
Traditional turbidity current models suffer from several drawbacks. Among them not preserving freshwater mass, a missing pressure term, or not including terms related to deposition, erosion and entrainment in the momentum equation. In Morales et al.(2009) a new turbidity current model was proposed trying to overcome all these drawbacks. This model takes into account the interaction between the turbidity current and the bottom, considering deposition and erosion effects as well as solid bedload transport of particles at the bed due to the current. Moreover, this model includes the effects of the deposition, erosion and water entrainment into the momentum equation,commonly neglected in this type of models and, finally, in the absence of water entrainment, freshwater mass in the turbidity current is preserved. Despite these improvements, the numerical results obtained by this model when applied to real river systems were not satisfactory due to the simple form of the friction term that was considered. In the present work we propose a different parameterization of this term, where bottom and interface fluid frictions are separately parameterized with more complex expressions. Moreover, the discretization of the deposition/erosion terms is now performed semi-implicitly which guarantees the positivity of the volumetric concentration of sediments in suspension and in the erodible sediment layer at the bed. The numerical simulations obtained with this new turbidity current model (component of HySEA numerical computing platform) greatly improve previous numerical results for simplified geometries as well as for real river systems. Acknowledgements: This research has been partially supported by the Junta de Andalucía research project TESELA (P11-RNM7069) and the Spanish Government Research project DAIFLUID (MTM2012-38383-C02-01) and Universidad de Málaga, Campus de Excelencia Andalucía TECH. References: T. Morales, M. Castro, C. Parés, and E. Fernández-Nieto (2009). On
SUSY in silico: Numerical D-brane bound state spectroscopy
NASA Astrophysics Data System (ADS)
Anous, Tarek
2016-11-01
We numerically construct the supersymmetric and non-supersymmetric wave functions of an N =4 quiver quantum mechanics with two Abelian nodes and a single arrow. This model captures the dynamics of a pair of wrapped D-branes interacting via a single light string mode. A dimensionless parameter ν , which is inversely proportional to the Fayet-Iliopoulos parameter, controls whether the bulk of the wave functions are supported on the Higgs branch or the Coulomb branch. We demonstrate how the supersymmetric and excited states morph as ν is tuned. We also numerically compute the energy gap between the ground state and the first excited states as a function of ν . An expression for the gap, computed on the Coulomb branch, matches nicely with our numerics at large ν but deviates at small ν where the Higgs branch becomes the relevant description of the physics. In the appendix, we provide the Schrödinger equations fully reduced via symmetries which, in principle, allow for the numerical determination of the entire spectrum at any point in moduli space. For the ground states, this numerical determination of the spectrum can be thought of as the first in silico check of various Witten index calculations.
Learning with Artificial Worlds: Computer-Based Modelling in the Curriculum.
ERIC Educational Resources Information Center
Mellar, Harvey, Ed.; And Others
With the advent of the British National Curriculum, computer-based modeling has become an integral part of the school curriculum. This book is about modeling in education and providing children with computer tools to create and explore representations of the world. Members of the London Mental Models Group contributed their research: (1)…
Windows to Other Worlds: Modeling Systems in Transit
NASA Astrophysics Data System (ADS)
Scott, Erin L.
We present light curves and best-fit models of three very different transiting systems: the extended ring system of J1407b, the transiting circumsecondary disk of OGLE-LMC-ECL-11893, and the transiting hot Neptune GJ 436b. We have performed model fits using chi² minimization on the light curves of each of these objects, and present conjectures as to their structures. For J1407, we find an extended flat debris disk of optical depth tau = 3 with four outer rings of optical depths tau1 = 0.1, tau2 = 0.9, tau3 = 0.5, and tau4 = 0.7 (with Ring 1 being the closest in to the main disk and Ring 4 being the farthest out), with the outermost ring extending to 45 RNȯ . The disk is inclined at thetax = 5° along the line of sight and thetay = 10° orthogonal to the line of sight, with the secondary in an orbit of i = 89.964° (0.036° from edge-on, for our assumed period of 9862 days). For OGLE 11893, we find a flat debris disk of uniform optical depth tau = 1.8, with an inner radius of 26.2 RNȯ , an outer radius of 45.8 RNȯ , thetax = 2.0°, theta y = 7.0°, and an orbital inclination of i = 89.38°. For GJ 436 b, we find a planet with radius 4.19+/-0.17 RN⊕ in the photometric g band (4100-5500A), 3.95+/-0.39 RN⊕ in the H band (15000-18000A), and 3.94+/-0.39 RN⊕ in the K band (20000-24000A). The program evolved significantly over the course of its implementation. In addition to implementing the simplex fitting algorithm, I added rings to the debris disk and model the ability to vary the density power lay and dust opacity of the accretion disk, in addition to taking the environmental influences such as Hill radius and silicate dust sublimation radius into account. The program was written first in C++ and later re-written in Python in order to take advantage of a pre-existing planetary transit model (Parviainen, 2015), and can model transit phenomena ranging from eclipsing binaries to circumsecondary disks.
On D-brane -anti D-brane effective actions and their all order bulk singularity structures
NASA Astrophysics Data System (ADS)
Hatefi, Ehsan
2016-04-01
All four point functions of brane anti brane system including their correct all order α' corrections have been addressed. All five point functions of one closed string Ramond-Ramond (RR), two real tachyons and either one gauge field or the scalar field in both symmetric and asymmetric pictures have also been explored. The entire analysis of
Dynamic SU(2) structure from seven-branes
Heidenreich, Ben; McAllister, Liam; Torroba, Gonzalo; /SLAC /Stanford U., Phys. Dept.
2010-12-16
We obtain a family of supersymmetric solutions of type IIB supergravity with dynamic SU(2) structure, which describe the local geometry near a stack of four D7-branes and one O7-plane wrapping a rigid four-cycle. The deformation to a generalized complex geometry is interpreted as a consequence of nonperturbative effects in the seven-brane gauge theory. We formulate the problem for seven-branes wrapping the base of an appropriate del Pezzo cone, and in the near-stack limit in which the four-cycle is flat, we obtain an exact solution in closed form. Our solutions serve to characterize the local geometry of nonperturbatively-stabilized flux compactifications.
Closed timelike curves in asymmetrically warped brane universes
Paes, Heinrich; Pakvasa, Sandip; Dent, James; Weiler, Thomas J.
2009-08-15
In asymmetrically-warped spacetimes different warp factors are assigned to space and to time. We discuss causality properties of these warped brane universes and argue that scenarios with two extra dimensions may allow for timelike curves which can be closed via paths in the extra-dimensional bulk. In particular, necessary and sufficient conditions on the metric for the existence of closed timelike curves are presented. We find a six-dimensional warped metric which satisfies the CTC conditions, and where the null, weak and dominant energy conditions are satisfied on the brane (although only the former remains satisfied in the bulk). Such scenarios are interesting, since they open the possibility of experimentally testing the chronology protection conjecture by manipulating on our brane initial conditions of gravitons or hypothetical gauge-singlet fermions (''sterile neutrinos'') which then propagate in the extra dimensions.
Learning World Models in Environments with Manifest Causal Structure,
1995-05-01
an agent with no prior knowledge than for people because people are told much of what they need to know and do not learn tabula rasa . Many people nd...drafts of this thesis, and for being a great role model. Thanks to Eric Grimson for being much more than an academic advisor. I thank Jonathan Amsterdam...early training of the secretary robot, the trainer plays the role of a babysitter more than that of a teacher. The trainer is available in case of an
Modeling the world in a spreadsheet: Environmental simulation on a microcomputer
Cartwright, T.J.
1993-12-31
This article focuses on the following: Modeling Natural Systems Blowing Smoke; Atmospheric Dispersion of Air Pollution Running Water; The Underground Transport of Pollutants Preserving the Species; Determining Minimum Viable Population Sustainable Yield; Managing the Forest for the Trees Here Comes the Sun; Solar Energy from a Flat-Plate Collector Modeling Social Systems Macroeconomic Policy; Econometrics and the Klein Model Urban Form; The Lowry Model of Population Distribution Affordable Housing; The Bertaud/World Bank Model Traffic on the Roads; Modeling Trip Generation and Trip Distribution Throwing Things Away; A Model for Waste Management Apples and Oranges; and An Environmental Impact Assessment Model Modeling Artificial Systems Life in a Spreadsheet.
Charged rotating black holes on a 3-brane
Aliev, A.N.; Guemruekcueoglu, A.E.
2005-05-15
We study exact stationary and axisymmetric solutions describing charged rotating black holes localized on a 3-brane in the Randall-Sundrum braneworld. The charges of the black holes are considered to be of two types, the first being an induced tidal charge that appears as an imprint of nonlocal gravitational effects from the bulk space and the second is a usual electric charge arising due to a Maxwell field trapped on the brane. We assume a special ansatz for the metric on the brane taking it to be of the Kerr-Schild form and show that the Kerr-Newman solution of ordinary general relativity in which the electric charge is superseded by a tidal charge satisfies a closed system of the effective gravitational field equations on the brane. It turns out that the negative tidal charge may provide a mechanism for spinning up the black hole so that its rotation parameter exceeds its mass. This is not allowed in the framework of general relativity. We also find a new solution that represents a rotating black hole on the brane carrying both charges. We show that for a rapid enough rotation the combined influence of the rotational dynamics and the local bulk effects of the 'squared' energy-momentum tensor on the brane distort the horizon structure of the black hole in such a way that it can be thought of as composed of nonuniformly rotating null circles with growing radii from the equatorial plane to the poles. We finally study the geodesic motion of test particles in the equatorial plane of a rotating black hole with tidal charge. We show that the effects of negative tidal charge tend to increase the horizon radius, as well as the radii of the limiting photon orbit, the innermost bound and the innermost stable circular orbits for both direct and retrograde motions of the particles.
D4 brane probes in gauge/gravity duality
Zhou Yang
2009-03-15
We propose a Dirac-Born-Infeld vertex brane+N{sub c} fundamental strings configuration for a probe baryon in the finite-temperature thermal gauge field via AdS/CFT correspondence. In particular, we investigate properties of this configuration in QCD{sub 4} and warped AdS{sub 6}xS{sup 4}. We find that, in the D4-D8 system, a holographic probe baryon can be described as N{sub c} fundamental strings connecting through a vertex D4 brane wrapped on S{sup 4}. In QCD{sub 4} background, a closed vertex can exist in a confined phase but cannot exist in a deconfined phase. In the low temperature region, the screening effect still exists in the confined phase like a meson, and the vertex D4 brane dominates the baryon mass. The lower energy state corresponds to the vertex brane closer to the radial cutoff position (r=r{sub c}), and the higher energy state corresponds to the vertex brane a little farther away from the cutoff position. The high energy limit of this configuration is just like the unclosed vertex brane configuration in a higher temperature deconfined phase. In warped AdS{sub 6}xS{sup 4} background, a closed vertex can exist in a deconfined phase and the vertex contains a spike, while fundamental strings are relatively short. The screening length should be defined through the distance between the top position of the vertex spike and the boundary.
Geometric K-Homology of Flat D-Branes
NASA Astrophysics Data System (ADS)
Reis, Rui M. G.; Szabo, Richard J.
2006-08-01
We use the Baum-Douglas construction of K-homology to explicitly describe various aspects of D-branes in Type II superstring theory in the absence of background supergravity form fields. We rigorously derive various stability criteria for states of D-branes and show how standard bound state constructions are naturally realized directly in terms of topological K-cycles. We formulate the mechanism of flux stabilization in terms of the K-homology of non-trivial fibre bundles. Along the way we derive a number of new mathematical results in topological K-homology of independent interest.
Comparison of Real World Energy Consumption to Models and Department of Energy Test Procedures
Goetzler, William; Sutherland, Timothy; Kar, Rahul; Foley, Kevin
2011-09-01
This study investigated the real-world energy performance of appliances and equipment as it compared with models and test procedures. The study looked to determine whether the U.S. Department of Energy and industry test procedures actually replicate real world conditions, whether performance degrades over time, and whether installation patterns and procedures differ from the ideal procedures. The study first identified and prioritized appliances to be evaluated. Then, the study determined whether real world energy consumption differed substantially from predictions and also assessed whether performance degrades over time. Finally, the study recommended test procedure modifications and areas for future research.
Lab-on-a-brane: nanofibrous polymer membranes to recreate organ-capillary interfaces
NASA Astrophysics Data System (ADS)
Budhwani, Karim I.; Thomas, Vinoy; Sethu, Palaniappan
2016-03-01
Drug discovery is a complex and time consuming process involving significant basic research and preclinical evaluation prior to testing in patients. Preclinical studies rely extensively on animal models which often fail in human trials. Biomimetic microphysiological systems (MPS) using human cells can be a promising alternative to animal models; where critical interactions between different organ systems are recreated to provide physiologically relevant in vitro human models. Central here are blood-vessel networks, the interface controlling transport of cellular and biomolecular components between the circulating fluid and underlying tissue. Here we present a novel lab-on-a-brane (or lab-on-a-membrane) nanofluidics MPS that combines the elegance of lab-on-a-chip with the more realistic morphology of 3D fibrous tissue-engineering constructs. Our blood-vessel lab-on-a-brane effectively simulates in vivo vessel-tissue interface for evaluating transendothelial transport in various pharmacokinetic and nanomedicine applications. Attributes of our platform include (a) nanoporous barrier interface enabling transmembrane molecular transport, (b) transformation of substrate into nanofibrous 3D tissue matrix, (c) invertible-sandwich architecture, and (d) simple co-culture mechanism for endothelial and smooth muscle layers to accurately mimic arterial anatomy. Structural, mechanical, and transport characterization using scanning electron microscopy, stress/strain analysis, infrared spectroscopy, immunofluorescence, and FITC-Dextran hydraulic permeability confirm viability of this in vitro system. Thus, our lab-on-a-brane provides an effective and efficient, yet considerably inexpensive, physiologically relevant alternative for pharmacokinetic evaluation; possibly reducing animals used in preclinical testing, costs from false starts, and time-to-market. Furthermore, it can be configured in multiple simultaneous arrays for personalized and precision medicine applications and for
Brane-induced Skyrmion on S{sup 3}: Baryonic matter in holographic QCD
Nawa, Kanabu; Suganuma, Hideo; Kojo, Toru
2009-01-15
We study baryonic matter in holographic QCD with D4/D8/D8 multi-D brane system in type IIA superstring theory. The baryon is described as the 'brane-induced Skyrmion', which is a topologically nontrivial chiral soliton in the four-dimensional meson effective action induced by holographic QCD. We employ the ''truncated-resonance model'' approach for the baryon analysis, including pion and {rho} meson fields below the ultraviolet cutoff scale M{sub KK}{approx}1 GeV, to keep the holographic duality with QCD. We describe the baryonic matter in large N{sub c} as single brane-induced Skyrmion on the three-dimensional closed manifold S{sup 3} with finite radius R. The interactions between baryons are simulated by the curvature of the closed manifold S{sup 3}, and the decrease of the size of S{sup 3} represents the increase of the total baryon-number density in the medium in this modeling. We investigate the energy density, the field configuration, the mass and the root-mean-square radius of single baryon on S{sup 3} as the function of its radius R. We find a new picture of 'pion dominance' near the critical density in the baryonic matter, where all the (axial) vector meson fields disappear and only the pion fields survive. We also find the swelling phenomena of the baryons as the precursor of the deconfinement, and propose the mechanism of the swelling in the general context of QCD. The properties of the deconfinement and the chiral symmetry restoration in the baryonic matter are examined by taking the proper order parameters. We also compare our truncated-resonance model with another instanton description of the baryon in holographic QCD, considering the role of cutoff scale M{sub KK}.
Modeling behavior dynamics using computational psychometrics within virtual worlds
Cipresso, Pietro
2015-01-01
In case of fire in a building, how will people behave in the crowd? The behavior of each individual affects the behavior of others and, conversely, each one behaves considering the crowd as a whole and the individual others. In this article, I propose a three-step method to explore a brand new way to study behavior dynamics. The first step relies on the creation of specific situations with standard techniques (such as mental imagery, text, video, and audio) and an advanced technique [Virtual Reality (VR)] to manipulate experimental settings. The second step concerns the measurement of behavior in one, two, or many individuals focusing on parameters extractions to provide information about the behavior dynamics. Finally, the third step, which uses the parameters collected and measured in the previous two steps in order to simulate possible scenarios to forecast through computational models, understand, and explain behavior dynamics at the social level. An experimental study was also included to demonstrate the three-step method and a possible scenario. PMID:26594193
Modeling behavior dynamics using computational psychometrics within virtual worlds.
Cipresso, Pietro
2015-01-01
In case of fire in a building, how will people behave in the crowd? The behavior of each individual affects the behavior of others and, conversely, each one behaves considering the crowd as a whole and the individual others. In this article, I propose a three-step method to explore a brand new way to study behavior dynamics. The first step relies on the creation of specific situations with standard techniques (such as mental imagery, text, video, and audio) and an advanced technique [Virtual Reality (VR)] to manipulate experimental settings. The second step concerns the measurement of behavior in one, two, or many individuals focusing on parameters extractions to provide information about the behavior dynamics. Finally, the third step, which uses the parameters collected and measured in the previous two steps in order to simulate possible scenarios to forecast through computational models, understand, and explain behavior dynamics at the social level. An experimental study was also included to demonstrate the three-step method and a possible scenario.
Coenzyme world model of the origin of life.
Sharov, Alexei A
2016-06-01
The origin of life means the emergence of heritable and evolvable self-reproduction. However the mechanisms of primordial heredity were different from those in contemporary cells. Here I argue that primordial life had no nucleic acids; instead heritable signs were represented by isolated catalytically active self-reproducing molecules, similar to extant coenzymes, which presumably colonized surfaces of oil droplets in water. The model further assumes that coenzyme-like molecules (CLMs) changed surface properties of oil droplets (e.g., by oxidizing terminal carbons), and in this way created and sustained favorable conditions for their own self-reproduction. Such niche-dependent self-reproduction is a necessary condition for cooperation between different kinds of CLMs because they have to coexist in the same oil droplets and either succeed or perish together. Additional kinds of hereditary molecules were acquired via coalescence of oil droplets carrying different kinds of CLMs or via modification of already existing CLMs. Eventually, polymerization of CLMs became controlled by other polymers used as templates; and this kind of template-based synthesis eventually resulted in the emergence of RNA-like replicons. Apparently, oil droplets transformed into the outer membrane of cells via engulfing water, stabilization of the surface, and osmoregulation. In result, the metabolism was internalized allowing cells to accumulate free-floating resources (e.g., animoacids, ATP), which was a necessary condition for the development of protein synthesis. Thus, life originated from simple but already functional molecules, and its gradual evolution towards higher complexity was driven by cooperation and natural selection.
Villa, Daniel L.; Tidwell, Vincent C.; Passell, Howard D.; Roberts, Barry L.
2016-11-01
The World Water and Agriculture Model has been used to simulate water, hydropower, and food sector effects in Egypt, Sudan, and Ethiopia during the filling of the Grand Ethiopian Renaissance Dam reservoir. This unique capability allows tradeoffs to be made between filling policies for the Grand Ethiopian Renaissance Dam reservoir. This Nile River Basin study is presented to illustrate the capacity to use the World Water and Agriculture Model to simulate regional food security issues while keeping a global perspective. The study uses runoff data from the Intergovernmental Panel for Climate Change Coupled Model Inter-comparison Project Phase 5 and information from the literature in order to establish a reasonable set of hydrological initial conditions. Gross Domestic Product and population growth are modelled exogenously based on a composite projection of United Nations and World Bank data. The effects of the Grand Ethiopian Renaissance Dam under various percentages of water withheld are presented.
D-brane categories for orientifolds—the Landau-Ginzburg case
NASA Astrophysics Data System (ADS)
Hori, Kentaro; Walcher, Johannes
2008-04-01
We construct and classify categories of D-branes in orientifolds based on Landau-Ginzburg models and their orbifolds. Consistency of the worldsheet parity action on the matrix factorizations plays the key role. This provides all the requisite data for an orientifold construction after embedding in string theory. One of our main results is a computation of topological field theory correlators on unoriented worldsheets, generalizing the formulas of Vafa and Kapustin-Li for oriented worldsheets, as well as the extension of these results to orbifolds. We also find a doubling of Knörrer periodicity in the orientifold context.
Compact hyperbolic extra dimensions: branes, kaluza-klein modes, and cosmology
Kaloper; March-Russell; Starkman; Trodden
2000-07-31
We reconsider theories with low gravitational (or string) scale M(*) where Newton's constant is generated via new large-volume spatial dimensions, while standard model states are localized to a 3-brane. Utilizing compact hyperbolic manifolds we show that the spectrum of Kaluza-Klein modes is radically altered. This allows the early Universe to evolve normally up to substantial temperatures, and completely negates the astrophysical constraints on M(*). Furthermore, an exponential hierarchy between the usual Planck scale and the true fundamental scale of physics can emerge with only O(1) coefficients. The linear size of the internal space remains small. The proposal has striking testable signatures.
Achieving World-Class Schools: Mastering School Improvement Using a Genetic Model.
ERIC Educational Resources Information Center
Kimmelman, Paul L.; Kroeze, David J.
In providing its program for education reform, this book uses, as an analogy, the genetic model taken from the Human Genome project. In the first part, "Theoretical Underpinnings," the book explains why a genetic model can be used to improve school systems; describes the critical components of a world-class school system; and details the…
Stringy models of modified gravity: space-time defects and structure formation
Mavromatos, Nick E.; Sakellariadou, Mairi; Yusaf, Muhammad Furqaan E-mail: mairi.sakellariadou@kcl.ac.uk
2013-03-01
Starting from microscopic models of space-time foam, based on brane universes propagating in bulk space-times populated by D0-brane defects (''D-particles''), we arrive at effective actions used by a low-energy observer on the brane world to describe his/her observations of the Universe. These actions include, apart from the metric tensor field, also scalar (dilaton) and vector fields, the latter describing the interactions of low-energy matter on the brane world with the recoiling point-like space-time defect (D-particle). The vector field is proportional to the recoil velocity of the D-particle and as such it satisfies a certain constraint. The vector breaks locally Lorentz invariance, which however is assumed to be conserved on average in a space-time foam situation, involving the interaction of matter with populations of D-particle defects. In this paper we clarify the role of fluctuations of the vector field on structure formation and galactic growth. In particular we demonstrate that, already at the end of the radiation era, the (constrained) vector field associated with the recoil of the defects provides the seeds for a growing mode in the evolution of the Universe. Such a growing mode survives during the matter dominated era, provided the variance of the D-particle recoil velocities on the brane is larger than a critical value. We note that in this model, as a result of specific properties of D-brane dynamics in the bulk, there is no issue of overclosing the brane Universe for large defect densities. Thus, in these models, the presence of defects may be associated with large-structure formation. Although our string inspired models do have (conventional, from a particle physics point of view) dark matter components, nevertheless it is interesting that the role of ''extra'' dark matter is also provided by the population of massive defects. This is consistent with the weakly interacting character of the D-particle defects, which predominantly interact only
ERIC Educational Resources Information Center
Mncube, Stephen Sipho, Ed.
This volume presents 10 papers originating with the World University System located at various sites in the Caribbean and the United States which were selected to show the innovative work of that institution between 1976 and 1980. The World University was founded in 1965 in Puerto Rico by John Brann and was based on innovative approaches to…
Approximate world models: Incorporating qualitative and linguistic information into vision systems
Pinhanez, C.S.; Bobick, A.F.
1996-12-31
Approximate world models are coarse descriptions of the elements of a scene, and are intended to be used in the selection and control of vision routines in a vision system. In this paper we present a control architecture in which the approximate models represent the complex relationships among the objects in the world, allowing the vision routines to be situation or context specific. Moreover, because of their reduced accuracy requirements, approximate world models can employ qualitative information such as those provided by linguistic descriptions of the scene. The concept is demonstrated in the development of automatic cameras for a TV studio-SmartCams. Results are shown where SmartCams use vision processing of real imagery and information written in the script of a TV show to achieve TV-quality framing.
Kukona, Anuenue; Tabor, Whitney
2011-01-01
The visual world paradigm presents listeners with a challenging problem: they must integrate two disparate signals, the spoken language and the visual context, in support of action (e.g., complex movements of the eyes across a scene). We present Impulse Processing, a dynamical systems approach to incremental eye movements in the visual world that suggests a framework for integrating language, vision, and action generally. Our approach assumes that impulses driven by the language and the visual context impinge minutely on a dynamical landscape of attractors corresponding to the potential eye-movement behaviors of the system. We test three unique predictions of our approach in an empirical study in the visual world paradigm, and describe an implementation in an artificial neural network. We discuss the Impulse Processing framework in relation to other models of the visual world paradigm. PMID:21609355
D-branes and orientifolds in Calabi-Yau compactifications
NASA Astrophysics Data System (ADS)
Garcia-Raboso, Alberto
We explore the dynamics of nonsupersymmetric D-brane configurations on Calabi-Yau orientifolds with fluxes. We show that supergravity D-terms capture supersymmetry breaking effects predicted by more abstract pi-stability considerations. We also investigate the vacuum structure of such configurations in the presence of fluxes. Based on the shape of the potential, we argue that metastable nonsupersymmetric vacua can be in principle obtained by tuning the values of fluxes. We also develop computational tools for the tree-level superpotential of B-branes in Calabi-Yau orientifolds. Our method is based on a systematic implementation of the orientifold projection in the geometric approach of Aspinwall and Katz. In the process we lay down some ground rules for orientifold projections in the derived category. This dissertation is based on the following articles published in peer-reviewed journals: (1) D.-E. Diaconescu, A. Garcia-Raboso and K. Sinha, A D-brane landscape on Calabi-Yau manifolds, JHEP 0606, 058 (2006), hep-th/0602138. (2) D.-E. Diaconescu, A. Garcia-Raboso, R. L. Karp and K. Sinha, D-brane superpotentials in Calabi-Yau orientifolds, Adv. Theor. Math. Phys. 11, 471 (2007), hep-th/0606180.
Nonlinear electrodynamics and thermodynamic geometry of rotating dilaton black branes
NASA Astrophysics Data System (ADS)
Sheykhi, A.; Naeimipour, F.; Zebarjad, S. M.
2016-07-01
We construct a new class of rotating dilaton solutions in the presence of logarithmic nonlinear electrodynamics. These solutions represent black branes with flat horizon and contain k=[(n-1)/2] rotation parameters in n-dimensional spacetime where [ x] is the integer part of x. We study the causal structure of the spacetime and calculate thermodynamic and conserved quantities and show that these quantities satisfy the first law of thermodynamics on the black brane horizon, { dM}={ TdS}+{{{sum _{i=1}k}}}Ω id{J}i+{ Ud}{Q}. Then, we study geometrical approach towards thermodynamics by choosing an appropriate geometrical metric. We show that the singularity of the Ricci scalar coincides exactly with the phase transition points. We observe that our system encounters two types of phase transitions depending on the metric parameters. For the first one the heat capacity is zero and for the second one the heat capacity diverges. In the first kind of phase transition, the brane has a transition from an unstable non-physical to a stable physical state. In the second type of phase transition the brane moves from a stable to an unstable state. Finally, we comment on the dynamical stability of the obtained solutions under perturbations in four dimensions.
Mass gap for gravity localized on Weyl thick branes
Barbosa-Cendejas, N.; Santos, M. A. Reyes; Herrera-Aguilar, A.; Schubert, C.
2008-06-15
We consider thick brane configurations in a pure geometric Weyl integrable 5D space-time, a non-Riemannian generalization of Kaluza-Klein (KK) theory involving a geometric scalar field. Thus, the 5D theory describes gravity coupled to a self-interacting scalar field which gives rise to the structure of the thick branes. We continue the study of the properties of a previously found family of solutions which is smooth at the position of the brane but involves naked singularities in the fifth dimension. Analyzing their graviton spectrum, we find that a particularly interesting situation arises for a special case in which the 4D graviton is separated from the KK gravitons by a mass gap. The corresponding effective Schroedinger equation has a modified Poeschl-Teller potential and can be solved exactly. Apart from the massless 4D graviton, it contains one massive KK bound state, and the continuum spectrum of delocalized KK modes. We also discuss the mass hierarchy problem, and explicitly compute the corrections to Newton's law in the thin brane limit.
NASA Astrophysics Data System (ADS)
Chakrabarti, Anindya S.
2016-01-01
We present a model of technological evolution due to interaction between multiple countries and the resultant effects on the corresponding macro variables. The world consists of a set of economies where some countries are leaders and some are followers in the technology ladder. All of them potentially gain from technological breakthroughs. Applying Lotka-Volterra (LV) equations to model evolution of the technology frontier, we show that the way technology diffuses creates repercussions in the partner economies. This process captures the spill-over effects on major macro variables seen in the current highly globalized world due to trickle-down effects of technology.
Galindo-Garre, Francisca; Hidalgo, María Dolores; Guilera, Georgina; Pino, Oscar; Rojo, J Emilio; Gómez-Benito, Juana
2015-03-01
The World Health Organization Disability Assessment Schedule II (WHO-DAS II) is a multidimensional instrument developed for measuring disability. It comprises six domains (getting around, self-care, getting along with others, life activities and participation in society). The main purpose of this paper is the evaluation of the psychometric properties for each domain of the WHO-DAS II with parametric and non-parametric Item Response Theory (IRT) models. A secondary objective is to assess whether the WHO-DAS II items within each domain form a hierarchy of invariantly ordered severity indicators of disability. A sample of 352 patients with a schizophrenia spectrum disorder is used in this study. The 36 items WHO-DAS II was administered during the consultation. Partial Credit and Mokken scale models are used to study the psychometric properties of the questionnaire. The psychometric properties of the WHO-DAS II scale are satisfactory for all the domains. However, we identify a few items that do not discriminate satisfactorily between different levels of disability and cannot be invariantly ordered in the scale. In conclusion the WHO-DAS II can be used to assess overall disability in patients with schizophrenia, but some domains are too general to assess functionality in these patients because they contain items that are not applicable to this pathology.
Front waves in the early RNA world: The Schlögl model and the logistic growth model.
Frank, T D
2016-03-07
Front wave solutions of nonlinear reaction-diffusion models describing the spatio-temporal growth of RNA populations in the early RNA world are discussed. A two-variable model for RNA enzymes and enzyme complex molecules as well as single-variable models obtained via adiabatic elimination of the complex molecules are considered. In both models, the focus is on enzyme diffusion in one spatial dimension, assuming that the diffusion of complex molecules can be neglected. It is shown that one of the single-variable models corresponds to a Schlögl model of front propagation. In general, for the single-variable models it is found that front speed corresponds to the minimal speed of traveling fronts. In contrast, the two-variable model exhibits even slower front propagation. Front propagation might be an important factor in competitive evolutionary processes in the early RNA world.
On D-brane -anti D-brane effective actions and their all order bulk singularity structures
Hatefi, Ehsan
2016-04-27
All four point functions of brane anti brane system including their correct all order α{sup ′} corrections have been addressed. All five point functions of one closed string Ramond-Ramond (RR), two real tachyons and either one gauge field or the scalar field in both symmetric and asymmetric pictures have also been explored. The entire analysis of
Using simplifications of reality in the real world: Robust benefits of models for decision making
NASA Astrophysics Data System (ADS)
Hunt, R. J.
2008-12-01
Models are by definition simplifications of reality; the degree and nature of simplification, however, is debated. One view is "the world is 3D, heterogeneous, and transient, thus good models are too" - the more a model directly simulates the complexity of the real world the better it is considered to be. An alternative view is to only use simple models up front because real-world complexity can never be truly known. A third view is construct and calibrate as many models as predictions. A fourth is to build highly parameterized models and either look at an ensemble of results, or use mathematical regularization to identify an optimal most reasonable parameter set and fit. Although each view may have utility for a given decision-making process, there are common threads that perhaps run through all views. First, the model-construction process itself can help the decision-making process because it raises the discussion of opposing parties from one of contrasting professional opinions to discussion of reasonable types and ranges of model inputs and processes. Secondly, no matter what view is used to guide the model building, model predictions for the future might be expected to perform poorly in the future due to unanticipated future changes and stressors to the underlying system simulated. Although this does not reduce the obligation of the modeler to build representative tools for the system, it should serve to temper expectations of model performance. Finally, perhaps the most under-appreciated utility of models is for calculating the reduction in prediction uncertainty resulting from different data collection strategies - an attractive feature separate from the calculation and minimization of absolute prediction uncertainty itself. This type of model output facilitates focusing on efficient use of current and future monitoring resources - something valued by many decision-makers regardless of background, system managed, and societal context.
An Analysis of Results of a High-Resolution World Ocean Circulation Model.
1988-03-01
4 b. Domain and Boundary Conditions .................. 5 c. Resolution ...................................... 7 d. Finite Differencing Schemes...14 B. SPECIFIC EXPERIMENTAL CONDITIONS ....................... 15 1. Robust-Diagnostic Strategy ......................... 15 2. One Degree, Twenty...Center for Atmospheric Research (NCAR)--for his faithful production runs of the world ocean model, on which this thesis is based; and for his
World-Class Higher Education and the Emerging Chinese Model of the University
ERIC Educational Resources Information Center
Li, Jun
2012-01-01
China's recent quest to develop world-class universities is a significant phenomenon within the worldwide transformation of tertiary education. Taking a cultural approach and drawing on empirical findings, this article investigates the emerging Chinese model of the university, considering its key features and contributions to global communities.…
ERIC Educational Resources Information Center
Aksoy, Yilmaz; Bayazit, Ibrahim; Dönmez, S. Merve Kirnap
2015-01-01
This study investigates approaches, strategies and models used by prospective primary school teachers in responding to real-world problems. The research was carried out with 82 participants. Data were collected through written-exam and semi-structured interviews; and they were analysed using content and discourse analysis methods. Most of the…
Solutions on a brane in a bulk spacetime with Kalb–Ramond field
Chakraborty, Sumanta SenGupta, Soumitra
2016-04-15
Effective gravitational field equations on a brane have been derived, when the bulk spacetime is endowed with the second rank antisymmetric Kalb–Ramond field. Since both the graviton and the Kalb–Ramond field are closed string excitations, they can propagate in the bulk. After deriving the effective gravitational field equations on the brane, we solve them for a static spherically symmetric solution. It turns out that the solution so obtained represents a black hole or naked singularity depending on the parameter space of the model. The stability of this model is also discussed. Cosmological solutions to the gravitational field equations have been obtained, where the Kalb–Ramond field is found to behave as normal pressure free matter. For certain specific choices of the parameters in the cosmological solution, the solution exhibits a transition in the behaviour of the scale factor and hence a transition in the expansion history of the universe. The possibility of accelerated expansion of the universe in this scenario is also discussed.
Eddy-resolving 1/10° model of the World Ocean
NASA Astrophysics Data System (ADS)
Ibrayev, R. A.; Khabeev, R. N.; Ushakov, K. V.
2012-02-01
The first results on simulating the intra-annual variability of the World Ocean circulation by use of the eddy-resolving model are considered. For this purpose, a model of the World Ocean with a 1/10° horizontal resolution and 49 vertical levels was developed (a 1/10 × 1/10 × 49 model of the World Ocean). This model is based on the traditional system of three-dimensional equations of the large-scale dynamics of the ocean and boundary conditions with an explicit allowance for water fluxes on the free surface of the ocean. The equations are written in the tripolar coordinate system. The numerical method is based on the separation of the barotropic and baroclinic components of the solution. Discretization in time is implemented using explicit schemes allowing effective parallelization for a large number of processors. The model uses the sub-models of the boundary layer of the atmosphere and the submodel of sea-ice thermodynamics. The model of the World Ocean was developed at the Institute of Numerical Mathematics of the Russian Academy of Sciences (INM RAS) and the P.P. Shirshov Institute of Oceanogy (IO RAS). The formulation of the problem of simulating the intra-annual variability of thermohydrodynamic processes of the World Ocean and the parameterizations that were used are considered. In the numerical experiment, the temporal evolution of the atmospheric effect is determined by the normal annual cycle according to the conditions of the international Coordinated Ocean-Ice Reference Experiment (CORE-I). The calculation was carried out on a multiprocessor computer with distributed memory; 1601 computational cores were used. The presented analysis demonstrates that the obtained results are quite satisfactory when compared to the results that were obtained by other eddy-resolving models of the global ocean. The analysis of the model solution is, to a larger extent, of a descriptive character. A detailed analysis of the results is to be presented in following works
Hybrid Modeling and Diagnosis in the Real World: A Case Study
2002-05-04
mapped to system components case study of an aircraft fuel system, and discuss and parameters. The relations in the model are employed to methodologies for...UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012687 TITLE: Hybrid Modeling and Diagnosis in the Real World : A Case...Study DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: Thirteenth International
The World Organisation for Animal Health and epidemiological modelling: background and objectives.
Willeberg, P; Grubbe, T; Weber, S; Forde-Folle, K; Dubé, C
2011-08-01
The papers in this issue of the Scientific and Technical Review (the Review) examine uses of modelling as a tool to supportthe formulation of disease control policy and applications of models for various aspects of animal disease management. Different issues in model development and several types of models are described. The experience with modelling during the 2001 foot and mouth disease outbreak in the United Kingdom underlines how models might be appropriately applied by decision-makers when preparing for and dealing with animal health emergencies. This paper outlines the involvement of the World Organisation for Animal Health (OIE) in epidemiological modelling since 2005, with emphasis on the outcome of the 2007 questionnaire survey of model usage among Member Countries, the subsequent OIE General Session resolution and the 2008 epidemiological modelling workshop at the Centers for Epidemiology and Animal Health in the United States. Many of the workshop presentations were developed into the papers that are presented in this issue of the Review.
Bulk matters on symmetric and asymmetric de Sitter thick branes
Liu, Yu-Xiao; Zhao, Zhen-Hua; Wei, Shao-Wen; Duan, Yi-Shi E-mail: zhaozhenhua@impcas.ac.cn E-mail: ysduan@lzu.edu.cn
2009-02-15
An asymmetric thick domain wall solution with de Sitter (dS) expansion in five dimensions can be constructed from a symmetric one by using a same scalar (kink) with different potentials. In this paper, by presenting the mass-independent potentials of Kaluza-Klein (KK) modes in the corresponding Schroedinger equations, we investigate the localization and mass spectra of various bulk matter fields on the symmetric and asymmetric dS thick branes. For spin 0 scalars and spin 1 vectors, the potentials of KK modes in the corresponding Schroedinger equations are the modified Poeschl-Teller potentials, and there exist a mass gap and a series of continuous spectrum. It is shown that the spectrum of scalar KK modes on the symmetric dS brane contains only one bound mode (the massless mode). However, for the asymmetric dS brane with a large asymmetric factor, there are two bound scalar KK modes: a zero mode and a massive mode. For spin 1 vectors, the spectra of KK modes on both dS branes consist of a bound massless mode and a set of continuous ones, i.e., the asymmetric factor does not change the number of the bound vector KK modes. For spin 1/2 fermions, two types of kink-fermion couplings are investigated in detail. For the usual Yukawa coupling {eta}barPsi{phi}{Psi}, there exists no mass gap but a continuous gapless spectrum of KK states. For the scalar-fermion coupling {eta}barPsisin({phi}/{phi}{sub 0})cos{sup -{delta}}({phi}/{phi}{sub 0}){Psi} with a positive coupling constant {eta}, there exist some discrete bound KK modes and a series of continuous ones. The total number of bound states increases with the coupling constant {eta}. For the case of the symmetric dS brane and positive {eta}, there are N{sub L}(N{sub L} {>=} 1) left chiral fermion bound states (including zero mode and massive KK modes) and N{sub L}-1 right chiral fermion bound states (including only massive KK modes). For the asymmetric dS brane scenario, the asymmetric factor a reduces the number of the
Interaction of moving branes with background massless and tachyon fields in superstring theory
Rezaei, Z. Kamani, D.
2012-02-15
Using the boundary state formalism, we study a moving Dp-brane in a partially compact space-time in the presence of background fields: the Kalb-Ramond field B{sub {mu}{nu}}, a U(1) gauge field A{sub {alpha}}, and the tachyon field. The boundary state enables us to obtain the interaction amplitude of two branes with the above back-ground fields. The branes are parallel or perpendicular to each other. Because of the presence of background fields, compactification of some space-time directions, motion of the branes, and the arbitrariness of the dimensions of the branes, the system is rather general. Due to the tachyon fields and velocities of the branes, the behavior of the interaction amplitude reveals obvious differences from the conventional behavior.
D-branes in a big bang/big crunch universe: Misner space
NASA Astrophysics Data System (ADS)
Hikida, Yasuaki; Nayak, Rashmi R.; Panigrahi, Kamal L.
2005-09-01
We study D-branes in a two-dimensional lorentzian orbifold Bbb R1,1/Γ with a discrete boost Γ. This space is known as Misner or Milne space, and includes big crunch/big bang singularity. In this space, there are D0-branes in spiral orbits and D1-branes with or without flux on them. In particular, we observe imaginary parts of partition functions, and interpret them as the rates of open string pair creation for D0-branes and emission of winding closed strings for D1-branes. These phenomena occur due to the time-dependence of the background. Open string 2→2 scattering amplitude on a D1-brane is also computed and found to be less singular than closed string case.
Noncommutative Tachyon Kinks as D(p-1)-branes from Unstable Dp-brane
NASA Astrophysics Data System (ADS)
Banerjee, Rabin; Kim, Yoonbai; Kwon, O.-Kab
2005-01-01
We study noncommutative (NC) field theory of a real NC tachyon and NC U(1) gauge field, describing the dynamics of an unstable Dp-brane. For every given set of diagonal component of open string metric G 0 , NC parameter θ0 , and interpolating electric field hat E, we find all possible static NC kinks as exact solutions, in spite of complicated NC terms, which are classified by an array of NC kink-antikink and topological NC kinks. By computing their tensions and charges, those configurations are identified as an array of D0bar D0 and single stable D0 from the unstable D1, respectively. When the interpolating electric field has critical value as G 0 2 = hat E2 , the obtained topological kink becomes a BPS object with nonzero thickness and is identified as BPS D0 in the fluid of fundamental strings. Particularly in the scaling limit of infinite θ0 and vanishing G 0 and hat E, while keeping G 0θ0 = hat Eθ0 = 1, finiteness of the tension of NC kink corresponds to tensionless kink in ordinary effective field theory. An extension to stable D(p-1) from unstable Dp is straightforward for pure electric cases with parallel NC parameter and interpolating two-form field.
Covariant Action for the Super-Five-Brane of {ital M} Theory
Bandos, I.; Nurmagambetov, A.; Sorokin, D.; Lechner, K.; Pasti, P.; Tonin, M.
1997-06-01
We propose a complete, d=6 covariant and kappa-symmetric, action for the M theory five-brane propagating in D=11 supergravity background. This opens a direct way of relating a wide class of super-p -brane solutions of string theory with the five-brane of M theory, which should be useful for studying corresponding dualities and nonperturbative aspects of these theories. {copyright} {ital 1997} {ital The American Physical Society}
Black brane entropy and hydrodynamics: The boost-invariant case
Booth, Ivan; Heller, Michal P.; Spalinski, Michal
2009-12-15
The framework of slowly evolving horizons is generalized to the case of black branes in asymptotically anti-de Sitter spaces in arbitrary dimensions. The results are used to analyze the behavior of both event and apparent horizons in the gravity dual to boost-invariant flow. These considerations are motivated by the fact that at second order in the gradient expansion the hydrodynamic entropy current in the dual Yang-Mills theory appears to contain an ambiguity. This ambiguity, in the case of boost-invariant flow, is linked with a similar freedom on the gravity side. This leads to a phenomenological definition of the entropy of black branes. Some insights on fluid/gravity duality and the definition of entropy in a time-dependent setting are elucidated.
D branes in background fluxes and Nielsen-Olesen instabilities
NASA Astrophysics Data System (ADS)
Russo, Jorge G.
2016-06-01
In quantum field theory, charged particles with spin ≥ 1 may become tachyonic in the present of magnetic fluxes above some critical field, signaling an instability of the vacuum. The phenomenon is generic, in particular, similar instabilities are known to exist in open and closed string theory, where a spinning string state can become tachyonic above a critical field. In compactifications involving RR fluxes F p+2, the quantum states which could become tachyonic by the same Nielsen-Olesen mechanism are D p branes. By constructing an appropriate background with RR magnetic flux that takes into account back-reaction, we identify the possible tachyonic D p brane states and compute the formula for the energy spectrum in a sector. More generally, we argue that in any background RR magnetic flux, there are high spin D p quantum states which become very light at critical fields.
Unstable `black branes' from scaled membranes at large D
NASA Astrophysics Data System (ADS)
Dandekar, Yogesh; Mazumdar, Subhajit; Minwalla, Shiraz; Saha, Arunabha
2016-12-01
It has recently been demonstrated that the dynamics of black holes at large D can be recast as a set of non gravitational membrane equations. These membrane equations admit a simple static solution with shape S D- p-2× R p,1. In this note we study the equations for small fluctuations about this solution in a limit in which amplitude and length scale of the fluctuations are simultaneously scaled to zero as D is taken to infinity. We demonstrate that the resultant nonlinear equations, which capture the Gregory-Laflamme instability and its end point, exactly agree with the effective dynamical `black brane' equations of Emparan Suzuki and Tanabe. Our results thus identify the `black brane' equations as a special limit of the membrane equations and so unify these approaches to large D black hole dynamics.
Obstacle avoidance using predictive vision based on a dynamic 3D world model
NASA Astrophysics Data System (ADS)
Benjamin, D. Paul; Lyons, Damian; Achtemichuk, Tom
2006-10-01
We have designed and implemented a fast predictive vision system for a mobile robot based on the principles of active vision. This vision system is part of a larger project to design a comprehensive cognitive architecture for mobile robotics. The vision system represents the robot's environment with a dynamic 3D world model based on a 3D gaming platform (Ogre3D). This world model contains a virtual copy of the robot and its environment, and outputs graphics showing what the virtual robot "sees" in the virtual world; this is what the real robot expects to see in the real world. The vision system compares this output in real time with the visual data. Any large discrepancies are flagged and sent to the robot's cognitive system, which constructs a plan for focusing on the discrepancies and resolving them, e.g. by updating the position of an object or by recognizing a new object. An object is recognized only once; thereafter its observed data are monitored for consistency with the predictions, greatly reducing the cost of scene understanding. We describe the implementation of this vision system and how the robot uses it to locate and avoid obstacles.
't Hooft operators on an interface and bubbling D5-branes
NASA Astrophysics Data System (ADS)
Nagasaki, Koichi; Yamaguchi, Satoshi
2014-02-01
We consider a brane configuration consisting of a D5-brane, D1-branes and D3-branes. According to the anti-de Sitter/conformal field theory (AdS/CFT) correspondence this system realizes a 't Hooft operator embedded in the interface in the gauge theory side. In the gravity side the near-horizon geometry is AdS5×S5. The D5-brane is treated as a probe in the AdS5×S5 and the D1-branes become the gauge flux on the D5-brane. We examine the condition for preserving an appropriate amount of supersymmetry and derive a set of differential equations which is the sufficient and necessary condition. This supersymmetric configuration shows bubbling behavior. We try to derive the relation between the probe D5-brane and the Young diagram which labels the corresponding 't Hooft operator. We propose the dictionary of the correspondence between the Young diagram and the probe D5-brane configuration.
Couplings between Chern-Simons gravities and 2p-branes
Miskovic, Olivera; Zanelli, Jorge
2009-08-15
The interaction between Chern-Simons (CS) theories and localized external sources (2p-branes) is analyzed. This interaction generalizes the minimal coupling between a point charge (0-brane) and a gauge connection. The external currents that define the 2p branes are covariantly constant (D-2p-1)-forms coupled to (2p-1) CS forms. The general expression for the sources--charged with respect to the corresponding gauge algebra--is presented, focusing on two special cases: 0-branes and (D-3)-branes. In any dimension, 0-branes are constructed as topological defects produced by a surface deficit of (D-2)-sphere in anti-de Sitter space, and they are not constant curvature spaces for D>3. They correspond to dimensionally continued black holes with negative mass. On the other hand, in the case of CS (super) gravities, the (D-3)-branes are naked conical singularities (topological defects) obtained by identification of points with a Killing vector. In 2+1 dimensions, extremal spinning branes of this type are Bogomol'nyi-Prasad-Sommerfield states. Stable (D-3)-branes are shown to exist also in higher dimensions, as well. Classical field equations are also discussed, and in the presence of sources there is a large number of inequivalent and disconnected sectors in solution space.
Open parabosonic string theory between two parallel Dp-branes
Hamam, D.; Belaloui, N.
2012-06-27
We investigate an open parabosonic string theory between two parallel Dp-branes. The spectrum is constructed and the partition function is derived. A common chord between the development of this latter and the degeneracy of the states for each mass level is obtained. The theory is consistent and with no tachyon. The Virasoro algebra is derived and compared to the one of the ordinary case.
Graviton emission from a Gauss-Bonnet brane
Konya, Kenichiro
2007-05-15
We study the emission of gravitons by a homogeneous brane with the Gauss-Bonnet term into an anti-de Sitter five dimensional bulk spacetime. It is found that the graviton emission depends on the curvature scale and the Gauss-Bonnnet coupling and that the amount of emission generally decreases. Therefore nucleosynthesis constraints are easier to satisfy by including the Gauss-Bonnet term.
Joint US/UK Epoch World Magnetic Model 1995. Technical report
Quinn, J.M.; Coleman, R.J.; Shiel, D.L.
1995-04-01
This report contains a detailed summary of the data used, analyses performed, modeling techniques employed, and results obtained during the course of the 1995 Epoch World Magnetic Modeling effort. This report also contains the GEOMAG algorithm and describes its uses and limitations. Charts derived from the WMM-95 model and the GEOMAG algorithm for both the main geomagnetic field components and their secular variations are presented on Mercator and polar stereographic projections. Additionally, the numerical values of the main geomagnetic field components and their secular variations are tabulated on a 5-degree worldwide grid.
A Predictive Logistic Regression Model of World Conflict Using Open Source Data
2015-03-26
model that predicts the future state of the world where nations will either be in a state of “ violent conflict” or “not in violent conflict” based on...state of violent conflict in 2015, seventeen of them are new to conflict since the last published list in 2013. A prediction tool is created to allow...war- game subject matter experts and students to identify future predicted violent conflict and the responsible variables. v Dedication
Franklyn, Melanie; Fildes, Brian; Zhang, Liying; Yang, King; Sparke, Laurie
2005-11-01
Previous studies have shown that both excessive linear and rotational accelerations are the cause of head injuries. Although the head injury criterion has been beneficial as an indicator of head injury risk, it only considers linear acceleration, so there is a need to consider both types of motion in future safety standards. Advanced models of the head/brain complex have recently been developed to gain a better understanding of head injury biomechanics. While these models have been verified against laboratory experimental data, there is a lack of suitable real-world data available for validation. Hence, using two computer models of the head/brain, the objective of the current study was to reconstruct four real-world crashes with known head injury outcomes in a full-vehicle crash laboratory, simulate head/brain responses using kinematics obtained during these reconstructions, and to compare the results predicted by the models against the actual injuries sustained by the occupant. Cases where the occupant sustained no head injuries (AIS 0) and head injuries of severity AIS 4, AIS 5, and multiple head injuries were selected. Data collected from a 9-accelerometer skull were input into the Wayne State University Head Injury Model (WSUHIM) and the NHTSA Simulated Injury Monitor (SIMon). The results demonstrated that both models were able to predict varying injury severities consistent with the difference in AIS injury levels in the real-world cases. The WSUHIM predicted a slightly higher injury threshold than the SIMon, probably due to the finer mesh and different software used for the simulations, and could also determine regions of the brain which had been injured. With further validation, finite element models can be used to establish an injury criterion for each type of brain injury in the future.
Standards in Modeling and Simulation: The Next Ten Years MODSIM World Paper 2010
NASA Technical Reports Server (NTRS)
Collins, Andrew J.; Diallo, Saikou; Sherfey, Solomon R.; Tolk, Andreas; Turnitsa, Charles D.; Petty, Mikel; Wiesel, Eric
2011-01-01
The world has moved on since the introduction of the Distributed Interactive Simulation (DIS) standard in the early 1980s. The cold-war maybe over but there is still a requirement to train for and analyze the next generation of threats that face the free world. With the emergence of new and more powerful computer technology and techniques means that modeling and simulation (M&S) has become an important and growing, part in satisfying this requirement. As an industry grows, the benefits from standardization within that industry grow with it. For example, it is difficult to imagine what the USA would be like without the 110 volts standard for domestic electricity supply. This paper contains an overview of the outcomes from a recent workshop to investigate the possible future of M&S standards within the federal government.
Kukona, Anuenue; Tabor, Whitney
2011-08-01
The Visual World Paradigm (VWP) presents listeners with a challenging problem: They must integrate two disparate signals, the spoken language and the visual context, in support of action (e.g., complex movements of the eyes across a scene). We present Impulse Processing, a dynamical systems approach to incremental eye movements in the visual world that suggests a framework for integrating language, vision, and action generally. Our approach assumes that impulses driven by the language and the visual context impinge minutely on a dynamical landscape of attractors corresponding to the potential eye-movement behaviors of the system. We test three unique predictions of our approach in an empirical study in the VWP, and describe an implementation in an artificial neural network. We discuss the Impulse Processing framework in relation to other models of the VWP.
Modification of the phase structure of black D6 branes in a canonical ensemble and its origin
NASA Astrophysics Data System (ADS)
Lu, J. X.; Ouyang, Jun; Roy, Shibaji
2014-09-01
It is well known that charged black Dp branes of type II string theory share a universal phase structure of van der Waals-Maxwell liquid-gas type except D5 and D6 branes. Interestingly, the phase structure of D5 and D6 branes can be changed to the universal form with the inclusion of particular delocalized charged lower-dimensional branes. For D5 branes, one needs to introduce delocalized D1 branes, and for D6 branes, one needs to introduce delocalized D0 branes to obtain the universal structure. In a previous paper [J. High Energy Phys. 04 (2013) 100], Lu with Wei study the phase structure of black D6 branes with the introduction of delocalized D0 branes in a special case when their charges are equal and the dilaton charge vanishes. In this paper, we look at the phase structure of the black D6/D0 system with the generic values of the parameters, which makes the analysis more involved but the structure more rich. We also provide reasons why the respective modifications of the phase structures to the universal form for the black D5 and D6 branes occur when specific delocalized lower-dimensional branes are introduced.
Kaluza-Klein gravitons are negative energy dust in brane cosmology
Minamitsuji, Masato; Sasaki, Misao; Langlois, David
2005-04-15
We discuss the effect of Kaluza-Klein (KK) modes of bulk metric perturbations on the second Randall-Sundrum (RS II) type brane cosmology, taking the possible backreaction in the bulk and on the brane into account. KK gravitons may be produced via quantum fluctuations during a de Sitter (dS) inflating phase of our brane universe. In an effective 4-dimensional theory in which one integrates out the extra-dimensional dependence in the action, KK gravitons are equivalent to massive gravitons on the brane with masses m>3H/2, where H represents the expansion rate of a dS brane. Thus production of even a tiny amount of KK gravitons may eventually have a significant impact on the late-time brane cosmology. As a first step to quantify the effect of KK gravitons on the brane, we calculate the effective energy density and pressure for a single KK mode. Surprisingly, we find that a KK mode behaves as cosmic dust with a negative energy density on the brane. We note that the bulk energy density of a KK mode is positive definite and there occurs no singular phenomenon in the bulk.
Conservation laws for collisions of branes and shells in general relativity.
Langlois, David; Maeda, Kei-ichi; Wands, David
2002-05-06
We consider the collision of self-gravitating n-branes in a (n+2)-dimensional spacetime. We show that there is a geometrical constraint which can be expressed as a simple sum rule for angles characterizing Lorentz boosts between branes and the intervening spacetime regions. This constraint can then be reinterpreted as either energy or momentum conservation at the collision.
Semantics-Based Composition of Integrated Cardiomyocyte Models Motivated by Real-World Use Cases
Neal, Maxwell L.; Carlson, Brian E.; Thompson, Christopher T.; James, Ryan C.; Kim, Karam G.; Tran, Kenneth; Crampin, Edmund J.; Cook, Daniel L.; Gennari, John H.
2015-01-01
Semantics-based model composition is an approach for generating complex biosimulation models from existing components that relies on capturing the biological meaning of model elements in a machine-readable fashion. This approach allows the user to work at the biological rather than computational level of abstraction and helps minimize the amount of manual effort required for model composition. To support this compositional approach, we have developed the SemGen software, and here report on SemGen’s semantics-based merging capabilities using real-world modeling use cases. We successfully reproduced a large, manually-encoded, multi-model merge: the “Pandit-Hinch-Niederer” (PHN) cardiomyocyte excitation-contraction model, previously developed using CellML. We describe our approach for annotating the three component models used in the PHN composition and for merging them at the biological level of abstraction within SemGen. We demonstrate that we were able to reproduce the original PHN model results in a semi-automated, semantics-based fashion and also rapidly generate a second, novel cardiomyocyte model composed using an alternative, independently-developed tension generation component. We discuss the time-saving features of our compositional approach in the context of these merging exercises, the limitations we encountered, and potential solutions for enhancing the approach. PMID:26716837
The Manhattan Frame Model - Manhattan World Inference in the Space of Surface Normals.
Straub, Julian; Freifeld, Oren; Rosman, Guy; Leonard, John J; Fisher, John W
2017-02-01
Objects and structures within man-made environments typically exhibit a high degree of organization in the form of orthogonal and parallel planes. Traditional approaches utilize these regularities via the restrictive, and rather local, Manhattan World (MW) assumption which posits that every plane is perpendicular to one of the axes of a single coordinate system. The aforementioned regularities are especially evident in the surface normal distribution of a scene where they manifest as orthogonally-coupled clusters. This motivates the introduction of the Manhattan-Frame (MF) model which captures the notion of a MW in the surface normals space, the unit sphere, and two probabilistic MF models over this space. First, for a single MF we propose novel real-time MAP inference algorithms, evaluate their performance and their use in drift-free rotation estimation. Second, to capture the complexity of real-world scenes at a global scale, we extend the MF model to a probabilistic mixture of Manhattan Frames (MMF). For MMF inference we propose a simple MAP inference algorithm and an adaptive Markov-Chain Monte-Carlo sampling algorithm with Metropolis-Hastings split/merge moves that let us infer the unknown number of mixture components. We demonstrate the versatility of the MMF model and inference algorithm across several scales of man-made environments.
Anisotropy in Born-Infeld brane cosmology
Haghani, Zahra; Sepangi, Hamid Reza; Shahidi, Shahab
2011-03-15
The accelerated expansion of the Universe together with its present day isotropy has posed an interesting challenge to the numerous model theories presented over the years to describe them. In this paper, we address the above questions in the context of a braneworld model where the Universe is filled with Born-Infeld matter. We show that in such a model, the Universe evolves from a highly anisotropic state to its present isotropic form, which has entered an accelerated expanding phase.
Seiberg duality for Chern-Simons quivers and D-brane mutations
NASA Astrophysics Data System (ADS)
Closset, Cyril
2012-03-01
Chern-Simons quivers for M2-branes at Calabi-Yau singularities are best understood as the low energy theory of D2-branes on a dual type IIA background. We show how the D2-brane point of view naturally leads to three dimensional Seiberg dualities for Chern-Simons quivers with chiral matter content: They arise from a change of brane basis (or mutation), in complete analogy with the better known Seiberg dualities for D3-brane quivers. This perspective reproduces the known rules for Seiberg dualities in Chern-Simons-Yang-Mills theories with unitary gauge groups. We provide explicit examples of dual theories for the quiver dual to the {Y^{{p,q}}}left( {mathbb{C}{mathbb{P}^{{2}}}} right) geometries. We also comment on the string theory derivation of CS quivers dual to massive type IIA geometries.
Critical load analysis in hazard assessment of metals using a Unit World Model.
Gandhi, Nilima; Bhavsar, Satyendra P; Diamond, Miriam L
2011-09-01
A Unit World approach has been used extensively to rank chemicals for their hazards and to understand differences in chemical behavior. Whereas the fate and effects of an organic chemical in a Unit World Model (UWM) analysis vary systematically according to one variable (fraction of organic carbon), and the chemicals have a singular ranking regardless of environmental characteristics, metals can change their hazard ranking according to freshwater chemistry, notably pH and dissolved organic carbon (DOC). Consequently, developing a UWM approach for metals requires selecting a series of representative freshwater chemistries, based on an understanding of the sensitivity of model results to this chemistry. Here we analyze results from a UWM for metals with the goal of informing the selection of appropriate freshwater chemistries for a UWM. The UWM loosely couples the biotic ligand model (BLM) to a geochemical speciation model (Windermere Humic Adsorption Model [WHAM]) and then to the multi-species fate transport-speciation (Transpec) model. The UWM is applied to estimate the critical load (CL) of cationic metals Cd, Cu, Ni, Pb, and Zn, using three lake chemistries that vary in trophic status, pH, and other parameters. The model results indicated a difference of four orders of magnitude in particle-to-total dissolved partitioning (K(d)) that translated into minimal differences in fate because of the short water residence time used. However, a maximum 300-fold difference was calculated in Cu toxicity among the three chemistries and three aquatic organisms. Critical loads were lowest (greatest hazard) in the oligotrophic water chemistry and highest (least hazard) in the eutrophic water chemistry, despite the highest fraction of free metal ion as a function of total metal occurring in the mesotrophic system, where toxicity was ameliorated by competing cations. Water hardness, DOC, and pH had the greatest influence on CL, because of the influence of these factors on aquatic
Lei, Mia; Acharya, Neha; Kwok Man Lee, Edith; Catherine Holcomb, Emma; Kapoor, Veronica
2017-03-24
The American Mock World Health Organization (AMWHO) is a model for experiential-based learning and student engagement in global health diplomacy. AMWHO was established in 2014 at the University of North Carolina at Chapel Hill with a mission to engage students in health policy by providing a simulation of the World Health Assembly (WHA), the policy-forming body of the World Health Organization that sets norms and transforms the global health agenda. AMWHO conferences are designed to allow students to take their knowledge of global health beyond the classroom and practice their skills in diplomacy by assuming the role of WHA delegates throughout a 3-day weekend. Through the process of developing resolutions like those formed in the WHA, students have the unique opportunity to understand the complexities behind the conflict and compromise that ensues through the lens of a stakeholder. This article describes the structure of the first 2 AMWHO international conferences, analyzes survey results from attendees, and discusses the expansion of the organization into a multi-campus national network. The AMWHO 2014 and 2015 post-conference survey results found that 98% and 90% of participants considered the conference "good" or "better," respectively, and survey responses showed that participants considered the conference "influential" in their careers and indicated that it "allowed a paradigm shift not possible in class."
Bhaumik, Himangsu; Santra, S B
2016-12-01
A dissipative stochastic sandpile model is constructed and studied on small-world networks in one and two dimensions with different shortcut densities ϕ, where ϕ=0 represents regular lattice and ϕ=1 represents random network. The effect of dimension, network topology, and specific dissipation mode (bulk or boundary) on the the steady-state critical properties of nondissipative and dissipative avalanches along with all avalanches are analyzed. Though the distributions of all avalanches and nondissipative avalanches display stochastic scaling at ϕ=0 and mean-field scaling at ϕ=1, the dissipative avalanches display nontrivial critical properties at ϕ=0 and 1 in both one and two dimensions. In the small-world regime (2^{-12}≤ϕ≤0.1), the size distributions of different types of avalanches are found to exhibit more than one power-law scaling with different scaling exponents around a crossover toppling size s_{c}. Stochastic scaling is found to occur for s
NASA Astrophysics Data System (ADS)
Bhaumik, Himangsu; Santra, S. B.
2016-12-01
A dissipative stochastic sandpile model is constructed and studied on small-world networks in one and two dimensions with different shortcut densities ϕ , where ϕ =0 represents regular lattice and ϕ =1 represents random network. The effect of dimension, network topology, and specific dissipation mode (bulk or boundary) on the the steady-state critical properties of nondissipative and dissipative avalanches along with all avalanches are analyzed. Though the distributions of all avalanches and nondissipative avalanches display stochastic scaling at ϕ =0 and mean-field scaling at ϕ =1 , the dissipative avalanches display nontrivial critical properties at ϕ =0 and 1 in both one and two dimensions. In the small-world regime (2-12≤ϕ ≤0.1 ) , the size distributions of different types of avalanches are found to exhibit more than one power-law scaling with different scaling exponents around a crossover toppling size sc. Stochastic scaling is found to occur for s
Modeling a solar-heated anaerobic digester for the developing world using system dynamics
NASA Astrophysics Data System (ADS)
Bentley, Johanna Lynn
Much of the developing world lacks access to a dependable source of energy. Agricultural societies such as Mozambique and Papua New Guinea could sustain a reliable energy source through the microbacterial decomposition of animal and crop waste. Anaerobic digestion produces methane, which can be used directly for heating, cooking, and lighting. Adding a solar component to the digester provides a catalyst for bacteria activity, accelerating digestion and increasing biogas production. Using methane decreases the amount of energy expended by collecting and preparing firewood, eliminates hazardous health effects linked to inhalation of particles, and provides energy close to where it is needed. The purpose of this work is two fold: initial efforts focus on the development and validation of a computer-based system dynamics model that combines elements of the anaerobic digestion process in order to predict methane output; second, the model is flexed to explore how the addition of a solar component increases robustness of the design, examines predicted biogas generation as a function of varying input conditions, and determines how best to configure such systems for use in varying developing world environments. Therefore, the central components of the system: solar insolation, waste feedstock, bacteria population and consumption rates, and biogas production are related both conceptually and mathematically through a serious of equations, conversions, and a causal loop and feedback diagram. Given contextual constraints and initial assumptions for both locations, it was determined that solar insolation and subsequent digester temperature control, amount of waste, and extreme weather patterns had the most significant impact on the system as a whole. Model behavior was both reproducible and comparable to that demonstrated in existing experimental systems. This tool can thus be flexed to fit specific contexts within the developing world to improve the standard of living of many
Ordinal regression models to describe tourist satisfaction with Sintra's world heritage
NASA Astrophysics Data System (ADS)
Mouriño, Helena
2013-10-01
In Tourism Research, ordinal regression models are becoming a very powerful tool in modelling the relationship between an ordinal response variable and a set of explanatory variables. In August and September 2010, we conducted a pioneering Tourist Survey in Sintra, Portugal. The data were obtained by face-to-face interviews at the entrances of the Palaces and Parks of Sintra. The work developed in this paper focus on two main points: tourists' perception of the entrance fees; overall level of satisfaction with this heritage site. For attaining these goals, ordinal regression models were developed. We concluded that tourist's nationality was the only significant variable to describe the perception of the admission fees. Also, Sintra's image among tourists depends not only on their nationality, but also on previous knowledge about Sintra's World Heritage status.
Efficiency of attack strategies on complex model and real-world networks
NASA Astrophysics Data System (ADS)
Bellingeri, Michele; Cassi, Davide; Vincenzi, Simone
2014-11-01
We investigated the efficiency of attack strategies to network nodes when targeting several complex model and real-world networks. We tested 5 attack strategies, 3 of which were introduced in this work for the first time, to attack 3 model networks (Erdos and Renyi, Barabasi and Albert preferential attachment network, and scale-free network configuration models) and 3 real networks (Gnutella peer-to-peer network, email network of the University of Rovira i Virgili, and immunoglobulin interaction network). Nodes were removed sequentially according to the importance criterion defined by the attack strategy, and we used the size of the largest connected component (LCC) as a measure of network damage. We found that the efficiency of attack strategies (fraction of nodes to be deleted for a given reduction of LCC size) depends on the topology of the network, although attacks based on either the number of connections of a node or betweenness centrality were often the most efficient strategies. Sequential deletion of nodes in decreasing order of betweenness centrality was the most efficient attack strategy when targeting real-world networks. The relative efficiency of attack strategies often changed during the sequential removal of nodes, especially for networks with power-law degree distribution.
New world primates as a model of viral-induced astrocytomas.
Houff, S A; London, W T; Zu Rhein, G M; Padgett, B L; Walker, D L; Sever, J L
1983-01-01
Owl and squirrel monkeys are susceptible to the oncogenic effects of JCV. These species of New World monkeys can be safely inoculated intracerebrally. Care must be taken with owl monkeys since they have an inherited clotting abnormality. Incubation times for the development of tumors range from 14 to 30 months. Anorexia was the first clinical sign of tumor development. The clinical course is rapid with death within two to three days. This model provides a means for studying diagnostic, virological, immunological and therapeutic techniques which are applicable to human patients with astrocytomas.
The General Evolving Model for Energy Supply-Demand Network with Local-World
NASA Astrophysics Data System (ADS)
Sun, Mei; Han, Dun; Li, Dandan; Fang, Cuicui
2013-10-01
In this paper, two general bipartite network evolving models for energy supply-demand network with local-world are proposed. The node weight distribution, the "shifting coefficient" and the scaling exponent of two different kinds of nodes are presented by the mean-field theory. The numerical results of the node weight distribution and the edge weight distribution are also investigated. The production's shifted power law (SPL) distribution of coal enterprises and the installed capacity's distribution of power plants in the US are obtained from the empirical analysis. Numerical simulations and empirical results are given to verify the theoretical results.
Intersection democracy for winding branes and stabilization of extra dimensions
NASA Astrophysics Data System (ADS)
Rador, Tonguç
2005-08-01
We show that, in the context of pure Einstein gravity, a democratic principle for intersection possibilities of branes winding around extra dimensions in a given partitioning yield stabilization, while what the observed space follows is matter-like dust evolution. Here democracy is used in the sense that, in a given decimation of extra dimensions, all possible wrappings and hence all possible intersections are allowed. Generally, the necessary and sufficient condition for this is that the dimensionality m of the observed space dimensions obey 3 ⩽ m ⩽ N for N ⩾ 3, where N is the decimation order of the extra dimensions.
Supersymmetric attractors, topological strings, and the M5-brane CFT
NASA Astrophysics Data System (ADS)
Guica, Monica M.
One of the purposes of this thesis is to present the consistent and unifying picture that emerges in string and M-theory with eight supercharges. On one hand, this involves classifying and relating supersymmetric objects that occur in N = 2 compactifications of string and M-theory on a Calabi-Yau manifold. These come in a surprisingly wide variety of four and five-dimensional black holes, black rings and their sometimes very complicated bound states. On the other hand, the topological string also makes its appearance in theories with eight supercharges, and turns out to compute certain black hole degeneracies. We dedicate the introduction and the first chapter to summarizing and reviewing the beautiful relationships between black holes, black rings, their dual conformal field theory and the topological string, and we also outline the remaining puzzles and issues. Some of the black holes in question can be obtained by multiply-wrapping an M-theory M5-brane on a self-intersecting four-cycle in the Calabi-Yau manifold. Their dual microscopic description is known, and consists of a two-dimensional conformal field theory (CFT) which is the low-energy limit of the gauge theory that resides on the worldvolume of the M5 brane. We show that in a certain limit the M5-brane CFT is - perhaps surprisingly - able to reproduce the entropy of a completely different type of black holes, those obtained from wrapped M2-branes, whose microscopic description has not yet been understood. We also argue that certain black hole bound states should also be described by the same CFT, which suggests a unifying description of the various black objects in eight-supercharge supergravity theories. Finally, we describe and present a proof of the so-called OSV conjecture, which states that the mixed partition function of N = 2 four-dimensional BPS black holes equals the modulus square of the type A topological string partition function. We also attempt to use this relationship to better understand
Generalized gravitational entropy of probe branes: flavor entanglement holographically
NASA Astrophysics Data System (ADS)
Karch, Andreas; Uhlemann, Christoph F.
2014-05-01
The notion of generalized gravitational entropy introduced by Lewkowycz and Maldacena allows, via the AdS/CFT correspondence, to calculate CFT entanglement entropies. We adapt the method to the case where flavor branes are present and treated in the probe approximation. This allows to calculate the leading flavor correction to the CFT entanglement entropy from the on-shell action of the probe, while dealing with the backreaction is avoided entirely and from the outset. As an application we give concise derivations for the contribution of massless and massive flavor degrees of freedom to the entanglement entropy in = 4 SYM theory.
Line operators from M-branes on compact Riemann surfaces
NASA Astrophysics Data System (ADS)
Amariti, Antonio; Orlando, Domenico; Reffert, Susanne
2016-12-01
In this paper, we determine the charge lattice of mutually local Wilson and 't Hooft line operators for class S theories living on M5-branes wrapped on compact Riemann surfaces. The main ingredients of our analysis are the fundamental group of the N-cover of the Riemann surface, and a quantum constraint on the six-dimensional theory. The latter plays a central role in excluding some of the possible lattices and imposing consistency conditions on the charges. This construction gives a geometric explanation for the mutual locality among the lines, fixing their charge lattice and the structure of the four-dimensional gauge group.
NASA Astrophysics Data System (ADS)
Washington, Warren M.; Meehl, Gerald A.; Verplank, Lynda; Bettge, Thomas W.
1994-05-01
We have developed an improved version of a world ocean model with the intention of coupling to an atmospheric model. This article documents the simulation capability of this 1° global ocean model, shows improvements over our earlier 5° version, and compares it to features simulated with a 0.5° model. These experiments use a model spin-up methodology whereby the ocean model can subsequently be coupled to an atmospheric model and used for order 100-year coupled model integrations. With present-day computers, 1° is a reasonable compromise in resolution that allows for century-long coupled experiments. The 1° ocean model is derived from a 0.5°-resolution model developed by A. Semtner (Naval Postgraduate School) and R. Chervin (National Center for Atmospheric Research) for studies of the global eddy-resolving world ocean circulation. The 0.5° bottom topography and continental outlines have been altered to be compatible with the 1° resolution, and the Arctic Ocean has been added. We describe the ocean simulation characteristics of the 1° version and compare the result of weakly constraining (three-year time scale) the three-dimensional temperature and salinity fields to the observations below the thermocline (710 m) with the model forced only at the top of the ocean by observed annual mean wind stress, temperature, and salinity. The 1° simulations indicate that major ocean circulation patterns are greatly improved compared to the 5° version and are qualitatively reproduced in comparison to the 0.5° version. Using the annual mean top forcing alone in a 100-year simulation with the 1° version preserves the general features of the major observed temperature and salinity structure with most climate drift occurring mainly beneath the thermocline in the first 50 75 years. Because the thermohaline circulation in the 1° version is relatively weak with annual mean forcing, we demonstrate the importance of the seasonal cycle by performing two sensitivity experiments
Semantic World Modelling and Data Management in a 4d Forest Simulation and Information System
NASA Astrophysics Data System (ADS)
Roßmann, J.; Hoppen, M.; Bücken, A.
2013-08-01
Various types of 3D simulation applications benefit from realistic forest models. They range from flight simulators for entertainment to harvester simulators for training and tree growth simulations for research and planning. Our 4D forest simulation and information system integrates the necessary methods for data extraction, modelling and management. Using modern methods of semantic world modelling, tree data can efficiently be extracted from remote sensing data. The derived forest models contain position, height, crown volume, type and diameter of each tree. This data is modelled using GML-based data models to assure compatibility and exchangeability. A flexible approach for database synchronization is used to manage the data and provide caching, persistence, a central communication hub for change distribution, and a versioning mechanism. Combining various simulation techniques and data versioning, the 4D forest simulation and information system can provide applications with "both directions" of the fourth dimension. Our paper outlines the current state, new developments, and integration of tree extraction, data modelling, and data management. It also shows several applications realized with the system.
Shi, Li; Niu, Xiaoke; Wan, Hong
2015-05-01
The biological networks have been widely reported to present small-world properties. However, the effects of small-world network structure on population's encoding performance remain poorly understood. To address this issue, we applied a small world-based framework to quantify and analyze the response dynamics of cell assemblies recorded from rat primary visual cortex, and further established a population encoding model based on small world-based generalized linear model (SW-GLM). The electrophysiological experimental results show that the small world-based population responses to different topological shapes present significant variation (t test, p < 0.01; effect size: Hedge's g > 0.8), while no significant variation was found for control networks without considering their spatial connectivity (t test, p > 0.05; effect size: Hedge's g < 0.5). Furthermore, the numerical experimental results show that the predicted response under SW-GLM is more accurate and reliable compared to the control model without small-world structure, and the decoding performance is also improved about 10 % by taking the small-world structure into account. The above results suggest the important role of the small-world neural structure in encoding visual information for the neural population by providing electrophysiological and theoretical evidence, respectively. The study helps greatly to well understand the population encoding mechanisms of visual cortex.
Schein, Rebecca; Bruls, Sand; Busch, Vincent; Wilson, Kumanan; Hershfield, Larry; Keelan, Jennifer
2012-01-01
This article explores the factors that contributed to the use of different names for H1N1 by diverse actors in the early stages of the pandemic of 2009 and discusses the implications of inconsistent naming practices for the public's understanding of the virus and the credibility of scientists and health authorities. The authors propose a naming protocol for novel variants modeled after the World Meteorological Association's practice for naming weather events, a model that would enable accurate transmission of technical information among experts and provide a stable name for public use, even in the context of incomplete or changing scientific understanding of the nature of the pathogen.
ERIC Educational Resources Information Center
Prescott, Stephanie, Ed.; And Others
This resource book is designed to assist teachers in implementing California's history-social science framework at the 10th grade level. The models support implementation at the local level and may be used to plan topics and select resources for professional development and preservice education. This document provides a link between the…
Study of long-term characteristics of the INM RAS - IO RAS World Ocean model.
NASA Astrophysics Data System (ADS)
Ushakov, K. V.
2012-04-01
This work is a part of the program for developing a new modern eddy-resolving World Ocean model at the Institute of Numerical Mathematics (INM) and the Institute of Oceanology (IO) of the Russian Academy of Sciences (Ibrayev et al., 2012). The aims of the work are checking the model's characteristics, tuning of the model in conditions of the CORE-I experiment (Griffies et al., 2009), study of the solution's variability and sensitivity to variations of model parameters and external forcing. We show the results of a series of numerical experiments for up to 500 years during which the model ocean circulation reaches a quasi-equilibrium state. The current model configuration uses a three-polar B-type grid, vertical z-coordinates, explicit difference schemes in time (except for vertical viscosity and diffusion) with decomposition of the solution into barotropic and baroclinic components, free ocean surface with explicit description of salt and water fluxes, Boussinesq and hydrostatics approximations. We utilize sea-ice thermodynamics and atmospheric boundary layer submodels. The code is MPI-parallelized according to the regular two-dimensional domain decomposition. The key tuning parameters are horizontal and vertical resolution (1˚ - 0.25˚, 20 - 70 levels), horizontal viscosity and diffusion coefficients, vertical diffusion description method (Munk-Anderson, Gent-McWilliams), equation of state approximation (3 - 25 terms), sea-ice submodel coefficients and short wave radiation penetration parameters. We study the model solution's sensitivity to wind field variations and to surface salinity relaxation to climatological CORE data. The main attention is paid to analysis of the solution in terms of deep circulation of heat and salinity and of vertical velocity field. Some integral and local characteristics are taken into account: cross-sections, global and horizontal means of temperature and salinity fields, kinetic energy, volume transport and separation points of
Influenza H1N1 and the world wide economic crisis--a model of coherence?
Sperling, W; Biermann, T
2009-11-01
A recent published model described the phenomenon of a global panic reaction (GPR) on the stock markets based on two remarkable stock market crashes in the months of January and March [Sperling W, Bleich S, Reulbach U, Black Monday on stock markets throughout the world - a new phenomenon of collective panic disorder? A psychiatric approach. Med Hypotheses; 2008]. This model was completed by a therapeutic approach following typical elements of cognitive behavioural therapy (CBT) [Sperling W, Biermann T, Maler JM, Global panic reaction - a therapeutic approach to a world-wide economic crisis. Med Hypotheses; 2009]. The phenomenon of a global panic reaction due to economic crises seems to have even larger implications on human health as well. It is well known that acute and chronic distress is competent to suppress the immune system by various mechanisms that are discussed in detail. This global panic reaction - that has also been observed in former times - might therefore be responsible for the new variation of recent influenza pandemic coming from Mexico.
Meteorites and the RNA World: A Thermodynamic Model of Nucleobase Synthesis within Planetesimals
NASA Astrophysics Data System (ADS)
Pearce, Ben K. D.; Pudritz, Ralph E.
2016-11-01
The possible meteorite parent body origin of Earth's pregenetic nucleobases is substantiated by the guanine (G), adenine (A), and uracil (U) measured in various meteorites. Cytosine (C) and thymine (T), however, are absent in meteorites, making the emergence of an RNA and later RNA/DNA/protein world problematic. We investigated the meteorite parent body (planetesimal) origin of all nucleobases by computationally modeling 18 reactions that potentially contribute to nucleobase formation in such environments. Out of this list, we identified the two most important reactions for each nucleobase and found that these involve small molecules such as HCN, CO, NH3, and water that ultimately arise from the protoplanetary disks in which planetesimals are built. The primary result of this study is that cytosine is unlikely to persist within meteorite parent bodies due to aqueous deamination. Thymine has a thermodynamically favorable reaction pathway from uracil, formaldehyde, and formic acid but likely did not persist within planetesimals containing H2O2 due to an oxidation reaction with this molecule. Finally, while Fischer-Tropsch (FT) synthesis is found to be the dominant source of nucleobases within our model planetesimal, non-catalytic (NC) synthesis may still be significant under certain chemical conditions (e.g., within CR2 parent bodies). We discuss several major consequences of our results for the origin of the RNA world.
Brane assisted quintessential inflation with transient acceleration
Bento, M. C.; Santos, N. M. C.; Gonzalez Felipe, R.
2008-06-15
A simple model of quintessential inflation with the modified exponential potential e{sup -{alpha}}{sup {phi}}[A+({phi}-{phi}{sub 0}){sup 2}] is analyzed in the braneworld context. Considering reheating via instant preheating, it is shown that the evolution of the scalar field {phi} from inflation to the present epoch is consistent with the observational constraints in a wide region of the parameter space. The model exhibits transient acceleration at late times for 0.96 < or approx. A{alpha}{sup 2} < or approx. 1.26 and 271 < or approx. {phi}{sub 0}{alpha} < or approx. 273, while permanent acceleration is obtained for 2.3x10{sup -8} < or approx. A{alpha}{sup 2} < or approx. 0.98 and 255 < or approx. {phi}{sub 0}{alpha} < or approx. 273. The steep parameter {alpha} is constrained to be in the range 5.3 < or approx. {alpha} < or approx. 10.8.
S-World: A high resolution global soil database for simulation modelling (Invited)
NASA Astrophysics Data System (ADS)
Stoorvogel, J. J.
2013-12-01
There is an increasing call for high resolution soil information at the global level. A good example for such a call is the Global Gridded Crop Model Intercomparison carried out within AgMIP. While local studies can make use of surveying techniques to collect additional techniques this is practically impossible at the global level. It is therefore important to rely on legacy data like the Harmonized World Soil Database. Several efforts do exist that aim at the development of global gridded soil property databases. These estimates of the variation of soil properties can be used to assess e.g., global soil carbon stocks. However, they do not allow for simulation runs with e.g., crop growth simulation models as these models require a description of the entire pedon rather than a few soil properties. This study provides the required quantitative description of pedons at a 1 km resolution for simulation modelling. It uses the Harmonized World Soil Database (HWSD) for the spatial distribution of soil types, the ISRIC-WISE soil profile database to derive information on soil properties per soil type, and a range of co-variables on topography, climate, and land cover to further disaggregate the available data. The methodology aims to take stock of these available data. The soil database is developed in five main steps. Step 1: All 148 soil types are ordered on the basis of their expected topographic position using e.g., drainage, salinization, and pedogenesis. Using the topographic ordering and combining the HWSD with a digital elevation model allows for the spatial disaggregation of the composite soil units. This results in a new soil map with homogeneous soil units. Step 2: The ranges of major soil properties for the topsoil and subsoil of each of the 148 soil types are derived from the ISRIC-WISE soil profile database. Step 3: A model of soil formation is developed that focuses on the basic conceptual question where we are within the range of a particular soil property
Black hole in the expanding universe from intersecting branes
Maeda, Kei-ichi; Nozawa, Masato
2010-02-15
We study physical properties and global structures of a time-dependent, spherically symmetric solution obtained via the dimensional reduction of intersecting M-branes. We find that the spacetime describes a maximally charged black hole which asymptotically tends to the Friedmann-Lemaitre-Robertson-Walker universe filled by a stiff matter. The metric solves the field equations of the Einstein-Maxwell-dilaton system, in which four Abelian gauge fields couple to the dilation with different coupling constants. The spacetime satisfies the dominant energy condition and is characterized by two parameters, Q and {tau}, related to the Maxwell charge and the relative ratio of black-hole horizon radii, respectively. In spite of the nontrivial time dependence of the metric, it turns out that the black-hole event horizon is a Killing horizon. This unexpected symmetry may be ascribed to the fact that the 11-dimensional brane configurations are supersymmetric in the static limit. Finally, combining with laws of the trapping horizon, we discuss the thermodynamic properties of the black hole. It is shown that the horizon possesses a nonvanishing temperature, contrary to the extremal Reissner-Nordstroem solution.
AdS spacetimes from wrapped D3-branes
NASA Astrophysics Data System (ADS)
Gauntlett, Jerome P.; MacConamhna, Oisín A. P.
2007-12-01
We derive a geometrical characterization of a large class of AdS3 and AdS2 supersymmetric spacetimes in type IIB supergravity with non-vanishing five-form flux using G-structures. These are obtained as special cases of a class of supersymmetric spacetimes with an {{\\bb R}}^{1,1} or {{\\bb R}} (time) factor that are associated with D3 branes wrapping calibrated two or three cycles, respectively, in manifolds with SU(2), SU(3), SU(4) and G2 holonomy. We show how two explicit AdS solutions, previously constructed in gauged supergravity, satisfy our more general G-structure conditions. For each explicit solution, we also derive a special holonomy metric which, although singular, has an appropriate calibrated cycle. After analytic continuation, some of the classes of AdS spacetimes give rise to known classes of BPS bubble solutions with {{\\bb R}}\\times {\\it SO}(4)\\times {\\it SO}(4), {{\\bb R}}\\times {\\it SO}(4)\\times U(1) and {{\\bb R}}\\times {\\it SO}(4) symmetry. These have 1/2, 1/4 and 1/8 supersymmetry, respectively. We present a new class of 1/8 BPS geometries with {{\\bb R}}\\times {\\it SU}(2) symmetry, obtained by analytic continuation of the class of AdS spacetimes associated with D3-brane wrapped on associative three cycles.
Fermi surface behavior in the ABJM M2-brane theory
NASA Astrophysics Data System (ADS)
DeWolfe, Oliver; Henriksson, Oscar; Rosen, Christopher
2015-06-01
We calculate fermionic Green's functions for states of the three-dimensional Aharony-Bergman-Jafferis-Maldacena M2-brane theory at large N using the gauge-gravity correspondence. We embed extremal black brane solutions in four-dimensional maximally supersymmetric gauged supergravity, obtain the linearized Dirac equations for each spin-1 /2 mode that cannot mix with a gravitino, and solve these equations with infalling boundary conditions to calculate retarded Green's functions. For generic values of the chemical potentials, we find Fermi surfaces with universally non-Fermi liquid behavior, matching the situation for four-dimensional N =4 super-Yang-Mills. Fermi surface singularities appear and disappear discontinuously at the point where all chemical potentials are equal, reminiscent of a quantum critical point. One limit of parameter space has zero entropy at zero temperature, and fermionic fluctuations are perfectly stable inside an energy region around the Fermi surface. An ambiguity in the quantization of the fermions is resolved by supersymmetry.
Decoupling limit and throat geometry of non-susy D3 brane
NASA Astrophysics Data System (ADS)
Nayek, Kuntal; Roy, Shibaji
2017-03-01
Recently it has been shown by us that, like BPS Dp branes, bulk gravity gets decoupled from the brane even for the non-susy Dp branes of type II string theories indicating a possible extension of AdS/CFT correspondence for the non-supersymmetric case. In that work, the decoupling of gravity on the non-susy Dp branes has been shown numerically for the general case as well as analytically for some special case. Here we discuss the decoupling limit and the throat geometry of the non-susy D3 brane when the charge associated with the brane is very large. We show that in the decoupling limit the throat geometry of the non-susy D3 brane, under appropriate coordinate change, reduces to the Constable-Myers solution and thus confirming that this solution is indeed the holographic dual of a (non-gravitational) gauge theory discussed there. We also show that when one of the parameters of the solution takes a specific value, it reduces, under another coordinate change, to the five-dimensional solution obtained by Csaki and Reece, again confirming its gauge theory interpretation.
NASA Astrophysics Data System (ADS)
Rehfeld, Kira; Trachsel, Mathias; Telford, Richard J.; Laepple, Thomas
2016-12-01
Reconstructions of summer, winter or annual mean temperatures based on the species composition of bio-indicators such as pollen, foraminifera or chironomids are routinely used in climate model-proxy data comparison studies. Most reconstruction algorithms exploit the joint distribution of modern spatial climate and species distribution for the development of the reconstructions. They rely on the space-for-time substitution and the specific assumption that environmental variables other than those reconstructed are not important or that their relationship with the reconstructed variable(s) should be the same in the past as in the modern spatial calibration dataset. Here we test the implications of this "correlative uniformitarianism" assumption on climate reconstructions in an ideal model world, in which climate and vegetation are known at all times. The alternate reality is a climate simulation of the last 6000 years with dynamic vegetation. Transient changes of plant functional types are considered as surrogate pollen counts and allow us to establish, apply and evaluate transfer functions in the modeled world. We find that in our model experiments the transfer function cross validation r2 is of limited use to identify reconstructible climate variables, as it only relies on the modern spatial climate-vegetation relationship. However, ordination approaches that assess the amount of fossil vegetation variance explained by the reconstructions are promising. We furthermore show that correlations between climate variables in the modern climate-vegetation relationship are systematically extended into the reconstructions. Summer temperatures, the most prominent driving variable for modeled vegetation change in the Northern Hemisphere, are accurately reconstructed. However, the amplitude of the model winter and mean annual temperature cooling between the mid-Holocene and present day is overestimated and similar to the summer trend in magnitude. This effect occurs because
Karst water resources in a changing world: Review of hydrological modeling approaches
NASA Astrophysics Data System (ADS)
Hartmann, A.; Goldscheider, N.; Wagener, T.; Lange, J.; Weiler, M.
2014-09-01
Karst regions represent 7-12% of the Earth's continental area, and about one quarter of the global population is completely or partially dependent on drinking water from karst aquifers. Climate simulations project a strong increase in temperature and a decrease of precipitation in many karst regions in the world over the next decades. Despite this potentially bleak future, few studies specifically quantify the impact of climate change on karst water resources. This review provides an introduction to karst, its evolution, and its particular hydrological processes. We explore different conceptual models of karst systems and how they can be translated into numerical models of varying complexity and therefore varying data requirements and depths of process representation. We discuss limitations of current karst models and show that at the present state, we face a challenge in terms of data availability and information content of the available data. We conclude by providing new research directions to develop and evaluate better prediction models to address the most challenging problems of karst water resources management, including opportunities for data collection and for karst model applications at so far unprecedented scales.
Mani, Dalhia; Moody, James
2014-01-01
A central theme of economic sociology has been to highlight the complexity and diversity of real world markets, but many network models of economic social structure ignore this feature and rely instead on stylized one-dimensional characterizations. Here, the authors return to the basic insight of structural diversity in economic sociology. Using the Indian interorganizational ownership network as their case, they discover a composite—or “hybrid”—model of economic networks that combines elements of prior stylized models. The network contains a disconnected periphery conforming closely to a “transactional” model; a semiperiphery characterized by small, dense clusters with sporadic links, as predicted in “small-world” models; and finally a nested core composed of clusters connected via multiple independent paths. The authors then show how a firm’s position within the mesolevel structure is associated with demographic features such as age and industry and differences in the extent to which firms engage in multiplex and high-value exchanges. PMID:25418990
Frequency of RNA–RNA interaction in a model of the RNA World
STRIGGLES, JOHN C.; MARTIN, MATTHEW B.; SCHMIDT, FRANCIS J.
2006-01-01
The RNA World model for prebiotic evolution posits the selection of catalytic/template RNAs from random populations. The mechanisms by which these random populations could be generated de novo are unclear. Non-enzymatic and RNA-catalyzed nucleic acid polymerizations are poorly processive, which means that the resulting short-chain RNA population could contain only limited diversity. Nonreciprocal recombination of smaller RNAs provides an alternative mechanism for the assembly of larger species with concomitantly greater structural diversity; however, the frequency of any specific recombination event in a random RNA population is limited by the low probability of an encounter between any two given molecules. This low probability could be overcome if the molecules capable of productive recombination were redundant, with many nonhomologous but functionally equivalent RNAs being present in a random population. Here we report fluctuation experiments to estimate the redundancy of the set of RNAs in a population of random sequences that are capable of non-Watson-Crick interaction with another RNA. Parallel SELEX experiments showed that at least one in 106 random 20-mers binds to the P5.1 stem–loop of Bacillus subtilis RNase P RNA with affinities equal to that of its naturally occurring partner. This high frequency predicts that a single RNA in an RNA World would encounter multiple interacting RNAs within its lifetime, supporting recombination as a plausible mechanism for prebiotic RNA evolution. The large number of equivalent species implies that the selection of any single interacting species in the RNA World would be a contingent event, i.e., one resulting from historical accident. PMID:16495233
Volcanogenic Massive Sulfide Deposits of the World - Database and Grade and Tonnage Models
Mosier, Dan L.; Berger, Vladimir I.; Singer, Donald A.
2009-01-01
Grade and tonnage models are useful in quantitative mineral-resource assessments. The models and database presented in this report are an update of earlier publications about volcanogenic massive sulfide (VMS) deposits. These VMS deposits include what were formerly classified as kuroko, Cyprus, and Besshi deposits. The update was necessary because of new information about some deposits, changes in information in some deposits, such as grades, tonnages, or ages, revised locations of some deposits, and reclassification of subtypes. In this report we have added new VMS deposits and removed a few incorrectly classified deposits. This global compilation of VMS deposits contains 1,090 deposits; however, it was not our intent to include every known deposit in the world. The data was recently used for mineral-deposit density models (Mosier and others, 2007; Singer, 2008). In this paper, 867 deposits were used to construct revised grade and tonnage models. Our new models are based on a reclassification of deposits based on host lithologies: Felsic, Bimodal-Mafic, and Mafic volcanogenic massive sulfide deposits. Mineral-deposit models are important in exploration planning and quantitative resource assessments for two reasons: (1) grades and tonnages among deposit types vary significantly, and (2) deposits of different types occur in distinct geologic settings that can be identified from geologic maps. Mineral-deposit models combine the diverse geoscience information on geology, mineral occurrences, geophysics, and geochemistry used in resource assessments and mineral exploration. Globally based deposit models allow recognition of important features and demonstrate how common different features are. Well-designed deposit models allow geologists to deduce possible mineral-deposit types in a given geologic environment and economists to determine the possible economic viability of these resources. Thus, mineral-deposit models play a central role in presenting geoscience
Branes as Stable Holomorphic Line Bundles On the Non-Commutative Torus
NASA Astrophysics Data System (ADS)
Grange, Pascal
2004-10-01
It was suggested by A. Kapustin that turning on a B-field, and allowing some discrepancy between the left and and right-moving complex structures, must induce an identification of B-branes with holomorphic line bundles on a non-commutative complex torus. The stability condition for the branes is written as a topological identity of non-commutative gauge theory. This identifies stable B-branes with previously proposed non-commutative instanton equations. Consistency of the non-commutative description with complex geometry is examined, using the non-linearities of the Seiberg-Witten map.
A Model of Continental Growth and Mantle Degassing Comparing Biotic and Abiotic Worlds
NASA Astrophysics Data System (ADS)
Höning, D.; Hansen-Goos, H.; Spohn, T.
2012-12-01
the phase area where the net degassing and continental growth rates are zero. Many of the parameter combinations result in one stable fixed point with a completely dry mantle that lacks continents altogether and a second stable fixed point with a continent coverage and mantle water concentration close to that of the present Earth. In addition, there is an unstable fixed point situated between the two. In general, the abiotic world has a larger zone of attraction for the fixed point with a dry mantle and no continents than the biotic world. Thus a biotic world is found to be more likely to develop continents and a have wet mantle. Furthermore, the biotic model is generally found to have a wetter mantle than an abiotic model with the same continent coverage. Through the effect of water on the mantle rheology, the biotic world would thus tend to be tectonically more active and have a more rapid long-term carbon silicate cycle. References: J. Kim, H. Dong, J. Seabaugh, S. W. Newell, D. D. Eberl, Science 303, 830-832, 2004 N. H. Sleep, D. K. Bird, E. Pope, Annu. Rev. Earth Planet. Sci. 40, 277-300, 2012 M. T. Rosing, D. K. Bird, N. H. Sleep, W. Glassley, F. Albarede, Paleo3 232, 90-113, 2006
Developing the Roots of Modelling Conceptions: "Mathematical Modelling Is the Life of the World"
ERIC Educational Resources Information Center
Brown, Jill Patricia; Stillman, Gloria Ann
2017-01-01
A study conducted with 25 Year 6 primary school students investigated the potential for a short classroom intervention to begin the development of a "Modelling" conception of mathematics on the way to developing a sense of mathematics as a way of thinking about life. The study documents the developmental roots of the cognitive activity,…
Receptor Surface Models in the Classroom: Introducing Molecular Modeling to Students in a 3-D World
ERIC Educational Resources Information Center
Geldenhuys, Werner J.; Hayes, Michael; Van der Schyf, Cornelis J.; Allen, David D.; Malan, Sarel F.
2007-01-01
A simple, novel and generally applicable method to demonstrate structure-activity associations of a group of biologically interesting compounds in relation to receptor binding is described. This method is useful for undergraduates and graduate students in medicinal chemistry and computer modeling programs.
Sarrafzadegan, Nizal; Kelishad, Roya; Rabiei, Katayoun; Abedi, Heidarali; Mohaseli, Khadijeh Fereydoun; Masooleh, Hasan Azaripour; Alavi, Mousa; Heidari, Gholamreza; Ghaffari, Mostafa; O’Loughlin, Jennifer
2012-01-01
Background: Iran is one of the countries that has ratified the World Health Organization Framework Convention of Tobacco Control (WHO-FCTC), and has implemented a series of tobacco control interventions including the Comprehensive Tobacco Control Law. Enforcement of this legislation and assessment of its outcome requires a dedicated evaluation system. This study aimed to develop a generic model to evaluate the implementation of the Comprehensive Tobacco Control Law in Iran that was provided based on WHO-FCTC articles. Materials and Methods: Using a grounded theory approach, qualitative data were collected from 265 subjects in individual interviews and focus group discussions with policymakers who designed the legislation, key stakeholders, and members of the target community. In addition, field observations data in supermarkets/shops, restaurants, teahouses and coffee shops were collected. Data were analyzed in two stages through conceptual theoretical coding. Findings: Overall, 617 open codes were extracted from the data into tables; 72 level-3 codes were retained from the level-2 code series. Using a Model Met paradigm, the relationships between the components of each paradigm were depicted graphically. The evaluation model entailed three levels, namely: short-term results, process evaluation and long-term results. Conclusions: Central concept of the process of evaluation is that enforcing the law influences a variety of internal and environmental factors including legislative changes. These factors will be examined during the process evaluation and context evaluation. The current model can be applicable for providing FCTC evaluation tools across other jurisdictions. PMID:23833621
Bruni, Renato; Cesarone, Francesco; Scozzari, Andrea; Tardella, Fabio
2016-09-01
A large number of portfolio selection models have appeared in the literature since the pioneering work of Markowitz. However, even when computational and empirical results are described, they are often hard to replicate and compare due to the unavailability of the datasets used in the experiments. We provide here several datasets for portfolio selection generated using real-world price values from several major stock markets. The datasets contain weekly return values, adjusted for dividends and for stock splits, which are cleaned from errors as much as possible. The datasets are available in different formats, and can be used as benchmarks for testing the performances of portfolio selection models and for comparing the efficiency of the algorithms used to solve them. We also provide, for these datasets, the portfolios obtained by several selection strategies based on Stochastic Dominance models (see "On Exact and Approximate Stochastic Dominance Strategies for Portfolio Selection" (Bruni et al. [2])). We believe that testing portfolio models on publicly available datasets greatly simplifies the comparison of the different portfolio selection strategies.
WHO WOULD EAT IN A WORLD WITHOUT PHOSPHORUS? A GLOBAL DYNAMIC MODEL
NASA Astrophysics Data System (ADS)
Dumas, M.
2009-12-01
Phosphorus is an indispensable and non-substitutable resource, as agriculture is impossible if soils do not hold adequate amounts of this nutrient. Phosphorus is also considered to be a non-renewable and increasingly scarce resource, as phosphate rock reserves - as one measure of availability amongst others - are estimated to last for 50 to 100 years at current rates of consumption. How would food production decline in different parts of the world in the scenario of a sudden shortage in phosphorus? To answer this question and explore management scenarios, I present a probabilistic model of the structure and dynamics of the global P cycle in the world’s agro-ecosystems. The model proposes an original solution to the challenge of capturing the large-scale aggregate dynamics of multiple micro-scale soil cycling processes. Furthermore, it integrates the essential natural processes with a model of human-managed flows, thereby bringing together several decades of research and measurements from soil science, plant nutrition and long-term agricultural experiments from around the globe. In this paper, I present the model, the first simulation results and the implications for long-term sustainable management of phosphorus and soil fertility.
Routing strategy on a two-dimensional small-world network model.
Li, Ming; Liu, Feng; Ren, Feng-Yuan
2007-06-01
Based on a two-dimensional small-world network model, we propose an efficient routing strategy that enhances the network capacity while keeping the average packet travel time low. We deterministically increase the weight of the links attached to the "congestible nodes" and compute the effective distance of a path by summing up the weight of the links belong to that path. The routing cost of a node is a linear combination of the minimum effective distance from the node to the target and its queue length. The weight assignment reduces the maximum load of the network, while the incorporation of dynamic information further balances the traffic on the network. Simulation results show that the network capacity is much improved compared with the reference strategies, while the average packet travel time is relatively small.
Lane, Justin E
2015-11-01
Agent-based modeling allows researchers to investigate theories of complex social phenomena and subsequently use the model to generate new hypotheses that can then be compared to real-world data. However, computer modeling has been underutilized in regard to the understanding of religious systems, which often require very complex theories with multiple interacting variables (Braxton et al. in Method Theory Study Relig 24(3):267-290, 2012. doi: 10.1163/157006812X635709 ; Lane in J Cogn Sci Relig 1(2):161-180, 2013). This paper presents an example of how computer modeling can be used to explore, test, and further understand religious systems, specifically looking at one prominent theory of religious ritual. The process is continuous: theory building, hypothesis generation, testing against real-world data, and improving the model. In this example, the output of an agent-based model of religious behavior is compared against real-world religious sermons and texts using semantic network analysis. It finds that most religious materials exhibit unique scale-free small-world properties and that a concept's centrality in a religious schema best predicts its frequency of presentation. These results reveal that there adjustments need to be made to existing models of religious ritual systems and provide parameters for future models. The paper ends with a discussion of implications for a new multi-agent model of doctrinal ritual behaviors as well as propositions for further interdisciplinary research concerning the multi-agent modeling of religious ritual behaviors.
Carbonatites of the World, Explored Deposits of Nb and REE - Database and Grade and Tonnage Models
Berger, Vladimir I.; Singer, Donald A.; Orris, Greta J.
2009-01-01
This report is based on published tonnage and grade data on 58 Nb- and rare-earth-element (REE)-bearing carbonatite deposits that are mostly well explored and are partially mined or contain resources of these elements. The deposits represent only a part of the known 527 carbonatites around the world, but they are characterized by reliable quantitative data on ore tonnages and grades of niobium and REE. Grade and tonnage models are an important component of mineral resource assessments. Carbonatites present one of the main natural sources of niobium and rare-earth elements, the economic importance of which grows consistently. A purpose of this report is to update earlier publications. New information about known deposits, as well as data on new deposits published during the last decade, are incorporated in the present paper. The compiled database (appendix 1; linked to right) contains 60 explored Nb- and REE-bearing carbonatite deposits - resources of 55 of these deposits are taken from publications. In the present updated grade-tonnage model we have added 24 deposits comparing with the previous model of Singer (1998). Resources of most deposits are residuum ores in the upper part of carbonatite bodies. Mineral-deposit models are important in exploration planning and quantitative resource assessments for two reasons: (1) grades and tonnages among deposit types vary significantly, and (2) deposits of different types are present in distinct geologic settings that can be identified from geologic maps. Mineral-deposit models combine the diverse geoscience information on geology, mineral occurrences, geophysics, and geochemistry used in resource assessments and mineral exploration. Globally based deposit models allow recognition of important features and demonstrate how common different features are. Well-designed deposit models allow geologists to deduce possible mineral-deposit types in a given geologic environment, and the grade and tonnage models allow economists to
Lenhart, S. |; Protopopescu, V.
1994-09-01
The last years have witnessed a dramatic shift of the world`s military, political, and economic paradigm from a bi-polar competitive gridlock to a more fluid, multi-player environment. This change has necessarily been followed by a re-evaluation of the strategic thinking and by a reassessment of mutual positions, options, and decisions. The essential attributes of the new situation are modeled by a system of nonlinear evolution equations with competitive/cooperative interactions. The mathematical setting is quite general to accommodate models related to military confrontation, arms control, economic competition, political negotiations, etc. Irrespective of the specific details, all these situations share a common denominator, namely the presence of various players with different and often changing interests and goals. The interests, ranging from conflicting to consensual, are defined in a context of interactions between the players that vary from competitive to cooperative. Players with converging interests tend to build up cooperative coalitions while coalitions with diverging interests usually compete among themselves, but this is not an absolute requirement (namely, one may have groups with converging interests and competitive interactions, and vice-versa). Appurtenance to a coalition may change in time according to the shift in one`s perceptions, interests, or obligations. During the time evolution, the players try to modify their strategies as to best achieve their respective goals. An objective functional quantifying the rate of success (payoff) vs. effort (cost) measures the degree of goal attainment for all players involved, thus selecting an optimal strategy based on optimal controls. While the technical details may vary from problem to problem, the general approach described here establishes a standard framework for a host of concrete situations that may arise from tomorrow`s {open_quotes}next competition{close_quotes}.
Modeling of Women's 100-m Dash World Record: Wind-Aided or Not?
NASA Astrophysics Data System (ADS)
Hazelrigg, Conner; Waibel, Bryson; Baker, Blane
2015-11-01
On July 16, 1988, Florence Griffith Joyner (FGJ) shattered the women's 100-m dash world record (WR) with a time of 10.49 s, breaking the previous mark by an astonishing 0.27 s. By all accounts FGJ dominated the race that day, securing her place as the premiere female sprinter of that era, and possibly all time. In the aftermath of such an extraordinary performance, track officials immediately assumed that her posted time was wind aided—that is, attained under tailwind conditions beyond the legal limit of 2.0 m/s for world records. However, wind-measuring devices at the track site showed zero wind conditions during her WR performance. Before and during FGJ's race, other wind-measuring devices indicated speeds exceeding 4.0 m/s at the site of the triple jump runway, located on the same field as the running track. Video clips of flags placed near the starting line of FGJ's race also revealed tailwind conditions. Using available data from that era, the study here incorporates modeling techniques to compute velocity and position as functions of time for no wind and tailwind conditions. Modeling under no wind conditions produces a 100-m time of 10.70 s, a performance clearly attainable by FGJ during this stage of her sprinting career. Incorporating tailwinds of 4.0 m/s into the computations reduces this time by approximately 0.20 s, in close agreement with FGJ's record-breaking performance. These results strongly suggest that tailwinds of order 4 m/s were present during FGJ's world record race even though wind-measuring devices at the track site did not register these speeds. In spite of such strong evidence to support a wind-aided race on July 16, 1988, FGJ remains one of the top female sprinters in history and would likely hold the WR even today, given that she attained a non-wind-aided 100-m time of 10.61 s on the day following her WR performance.
D p-branes, NS5-branes and U-duality from nonabelian (2,0) theory with Lie 3-algebra
NASA Astrophysics Data System (ADS)
Honma, Yoshinori; Ogawa, Morirou; Shiba, Shotaro
2011-04-01
We derive the super Yang-Mills action of D p-branes on a torus T p-4 from the nonabelian (2, 0) theory with Lie 3-algebra [1]. Our realization is based on Lie 3-algebra with pairs of Lorentzian metric generators. The resultant theory then has negative norm modes, but it results in a unitary theory by setting VEV's of these modes. This procedure corresponds to the torus compactification, therefore by taking a transformation which is equivalent to T-duality, the D p-brane action is obtained. We also study type IIA/IIB NS5brane and Kaluza-Klein monopole systems by taking other VEV assignments. Such various compactifications can be realized in the nonabelian (2, 0) theory, since both longitudinal and transverse directions can be compactified, which is different from the BLG theory. We finally discuss U-duality among these branes, and show that most of the moduli parameters in U-duality group are recovered. Especially in D5-brane case, the whole U-duality relation is properly reproduced.
Microinverter Thermal Performance in the Real-World: Measurements and Modeling.
Hossain, Mohammad Akram; Xu, Yifan; Peshek, Timothy J; Ji, Liang; Abramson, Alexis R; French, Roger H
2015-01-01
Real-world performance, durability and reliability of microinverters are critical concerns for microinverter-equipped photovoltaic systems. We conducted a data-driven study of the thermal performance of 24 new microinverters (Enphase M215) connected to 8 different brands of PV modules on dual-axis trackers at the Solar Durability and Lifetime Extension (SDLE) SunFarm at Case Western Reserve University, based on minute by minute power and thermal data from the microinverters and PV modules along with insolation and environmental data from July through October 2013. The analysis shows the strengths of the associations of microinverter temperature with ambient temperature, PV module temperature, irradiance and AC power of the PV systems. The importance of the covariates are rank ordered. A multiple regression model was developed and tested based on stable solar noon-time data, which gives both an overall function that predicts the temperature of microinverters under typical local conditions, and coefficients adjustments reecting refined prediction of the microinverter temperature connected to the 8 brands of PV modules in the study. The model allows for prediction of internal temperature for the Enphase M215 given similar climatic condition and can be expanded to predict microinverter temperature in fixed-rack and roof-top PV systems. This study is foundational in that similar models built on later stage data in the life of a device could reveal potential influencing factors in performance degradation.
Small-world network model of propagation of the AIDS epidemic
NASA Astrophysics Data System (ADS)
Shi, Pengliang; Small, Michael
2004-03-01
Sexual contact and intravenus drug-use are the most common modes of transmission of HIV-AIDS. In this paper, homogenerous and heterogeneous models are proposed to model the dynamics in a system contains Small-World clusters. Four high risk groups: intravenus drug-users (D); homosexuals (H); individuals with multiple-sexual partners (M) and prostitutes (P), are classified using two models. Both networks are embedded among a background (low-risk) population using rich-get-richer preferential attachment. When a network is established, an epidemic is simulated in it by seeding randomly. We compare the two epidemic networks in detail and consider the effect of different levels of control policies in both. This study highlights two main conclusions: (i) set high protection coefficient for a massive-linkage-vertex (i.e. protect the highly connected individuals); and, (ii) a quick removal for the infected massive-linkage-veterx from the network is essential (rapidly quarantine infected individuals). While these conclusions may be intuitive, they indicate a necessary change of public policy toward prostitution in some developing countries such as China and India. An active effort to prevent possible infection from super-spreader is recommended.
Microinverter Thermal Performance in the Real-World: Measurements and Modeling
Hossain, Mohammad Akram; Xu, Yifan; Peshek, Timothy J.; Ji, Liang; Abramson, Alexis R.; French, Roger H.
2015-01-01
Real-world performance, durability and reliability of microinverters are critical concerns for microinverter-equipped photovoltaic systems. We conducted a data-driven study of the thermal performance of 24 new microinverters (Enphase M215) connected to 8 different brands of PV modules on dual-axis trackers at the Solar Durability and Lifetime Extension (SDLE) SunFarm at Case Western Reserve University, based on minute by minute power and thermal data from the microinverters and PV modules along with insolation and environmental data from July through October 2013. The analysis shows the strengths of the associations of microinverter temperature with ambient temperature, PV module temperature, irradiance and AC power of the PV systems. The importance of the covariates are rank ordered. A multiple regression model was developed and tested based on stable solar noon-time data, which gives both an overall function that predicts the temperature of microinverters under typical local conditions, and coefficients adjustments reecting refined prediction of the microinverter temperature connected to the 8 brands of PV modules in the study. The model allows for prediction of internal temperature for the Enphase M215 given similar climatic condition and can be expanded to predict microinverter temperature in fixed-rack and roof-top PV systems. This study is foundational in that similar models built on later stage data in the life of a device could reveal potential influencing factors in performance degradation. PMID:26147339
Autoplan: A self-processing network model for an extended blocks world planning environment
NASA Technical Reports Server (NTRS)
Dautrechy, C. Lynne; Reggia, James A.; Mcfadden, Frank
1990-01-01
Self-processing network models (neural/connectionist models, marker passing/message passing networks, etc.) are currently undergoing intense investigation for a variety of information processing applications. These models are potentially very powerful in that they support a large amount of explicit parallel processing, and they cleanly integrate high level and low level information processing. However they are currently limited by a lack of understanding of how to apply them effectively in many application areas. The formulation of self-processing network methods for dynamic, reactive planning is studied. The long-term goal is to formulate robust, computationally effective information processing methods for the distributed control of semiautonomous exploration systems, e.g., the Mars Rover. The current research effort is focusing on hierarchical plan generation, execution and revision through local operations in an extended blocks world environment. This scenario involves many challenging features that would be encountered in a real planning and control environment: multiple simultaneous goals, parallel as well as sequential action execution, action sequencing determined not only by goals and their interactions but also by limited resources (e.g., three tasks, two acting agents), need to interpret unanticipated events and react appropriately through replanning, etc.
Porphyry copper deposits of the world: database, map, and grade and tonnage models
Singer, Donald A.; Berger, Vladimir Iosifovich; Moring, Barry C.
2005-01-01
Mineral deposit models are important in exploration planning and quantitative resource assessments for two reasons: (1) grades and tonnages among deposit types are significantly different, and (2) many types occur in different geologic settings that can be identified from geologic maps. Mineral deposit models are the keystone in combining the diverse geoscience information on geology, mineral occurrences, geophysics, and geochemistry used in resource assessments and mineral exploration. Too few thoroughly explored mineral deposits are available in most local areas for reliable identification of the important geoscience variables or for robust estimation of undiscovered deposits-thus we need mineral-deposit models. Globally based deposit models allow recognition of important features because the global models demonstrate how common different features are. Well-designed and -constructed deposit models allow geologists to know from observed geologic environments the possible mineral deposit types that might exist, and allow economists to determine the possible economic viability of these resources in the region. Thus, mineral deposit models play the central role in transforming geoscience information to a form useful to policy makers. The foundation of mineral deposit models is information about known deposits-the purpose of this publication is to make this kind of information available in digital form for porphyry copper deposits. This report is an update of an earlier publication about porphyry copper deposits. In this report we have added 84 new porphyry copper deposits and removed 12 deposits. In addition, some errors have been corrected and a number of deposits have had some information, such as grades, tonnages, locations, or ages revised. This publication contains a computer file of information on porphyry copper deposits from around the world. It also presents new grade and tonnage models for porphyry copper deposits and for three subtypes of porphyry copper
Sediment-Hosted Zinc-Lead Deposits of the World - Database and Grade and Tonnage Models
Singer, Donald A.; Berger, Vladimir I.; Moring, Barry C.
2009-01-01
This report provides information on sediment-hosted zinc-lead mineral deposits based on the geologic settings that are observed on regional geologic maps. The foundation of mineral-deposit models is information about known deposits. The purpose of this publication is to make this kind of information available in digital form for sediment-hosted zinc-lead deposits. Mineral-deposit models are important in exploration planning and quantitative resource assessments: Grades and tonnages among deposit types are significantly different, and many types occur in different geologic settings that can be identified from geologic maps. Mineral-deposit models are the keystone in combining the diverse geoscience information on geology, mineral occurrences, geophysics, and geochemistry used in resource assessments and mineral exploration. Too few thoroughly explored mineral deposits are available in most local areas for reliable identification of the important geoscience variables, or for robust estimation of undiscovered deposits - thus, we need mineral-deposit models. Globally based deposit models allow recognition of important features because the global models demonstrate how common different features are. Well-designed and -constructed deposit models allow geologists to know from observed geologic environments the possible mineral-deposit types that might exist, and allow economists to determine the possible economic viability of these resources in the region. Thus, mineral-deposit models play the central role in transforming geoscience information to a form useful to policy makers. This publication contains a computer file of information on sediment-hosted zinc-lead deposits from around the world. It also presents new grade and tonnage models for nine types of these deposits and a file allowing locations of all deposits to be plotted in Google Earth. The data are presented in FileMaker Pro, Excel and text files to make the information available to as many as possible. The
Models with quartic potential of dynamical SUSY breaking in meta-stable vacua
NASA Astrophysics Data System (ADS)
Hirano, Shinji
2007-05-01
We search for models of dynamical SUSY breaking in meta-stable vacua which might have dual string descriptions with a few brane probes. Two models with quartic superpotential are proposed: One of them might be closely related to the dual gauge theory to the flavored Maldacena-Nuñez geometry by Casero, Nuñez, and Paredes with a few additional brane probes corresponding to massive flavors. The other model might be dual to the Klebanov-Strassler geometry with one fractional D3-brane and a few D7-branes as probes.
Hobi, Martina L.; Ginzler, Christian
2012-01-01
Digital surface models (DSMs) are widely used in forest science to model the forest canopy. Stereo pairs of very high resolution satellite and digital aerial images are relatively new and their absolute accuracy for DSM generation is largely unknown. For an assessment of these input data two DSMs based on a WorldView-2 stereo pair and a ADS80 DSM were generated with photogrammetric instruments. Rational polynomial coefficients (RPCs) are defining the orientation of the WorldView-2 satellite images, which can be enhanced with ground control points (GCPs). Thus two WorldView-2 DSMs were distinguished: a WorldView-2 RPCs-only DSM and a WorldView-2 GCP-enhanced RPCs DSM. The accuracy of the three DSMs was estimated with GPS measurements, manual stereo-measurements, and airborne laser scanning data (ALS). With GCP-enhanced RPCs the WorldView-2 image orientation could be optimised to a root mean square error (RMSE) of 0.56 m in planimetry and 0.32 m in height. This improvement in orientation allowed for a vertical median error of −0.24 m for the WorldView-2 GCP-enhanced RPCs DSM in flat terrain. Overall, the DSM based on ADS80 images showed the highest accuracy of the three models with a median error of 0.08 m over bare ground. As the accuracy of a DSM varies with land cover three classes were distinguished: herb and grass, forests, and artificial areas. The study suggested the ADS80 DSM to best model actual surface height in all three land cover classes, with median errors <1.1 m. The WorldView-2 GCP-enhanced RPCs model achieved good accuracy, too, with median errors of −0.43 m for the herb and grass vegetation and −0.26 m for artificial areas. Forested areas emerged as the most difficult land cover type for height modelling; still, with median errors of −1.85 m for the WorldView-2 GCP-enhanced RPCs model and −1.12 m for the ADS80 model, the input data sets evaluated here are quite promising for forest canopy modelling. PMID:22778645
D-brane networks in flux vacua, generalized cycles and calibrations
NASA Astrophysics Data System (ADS)
Evslin, Jarah; Martucci, Luca
2007-07-01
We consider chains of generalized submanifolds, as defined by Gualtieri in the context of generalized complex geometry, and define a boundary operator that acts on them. This allows us to define generalized cycles and the corresponding homology theory. Gauge invariance demands that D-brane networks on flux vacua must wrap these generalized cycles, while deformations of generalized cycles inside of a certain homology class describe physical processes such as the dissolution of D-branes in higher-dimensional D-branes and MMS-like instantonic transitions. We introduce calibrations that identify the supersymmetric D-brane networks, which minimize their energy inside of the corresponding homology class of generalized cycles. Such a calibration is explicitly presented for type II Script N = 1 flux compactifications to four dimensions. In particular networks of walls and strings in compactifications on warped Calabi-Yau's are treated, with explicit examples on a toroidal orientifold vacuum and on the Klebanov-Strassler geometry.
Magnetically-charged black branes and viscosity/entropy ratios
NASA Astrophysics Data System (ADS)
Liu, Hai-Shan; Lü, H.; Pope, C. N.
2016-12-01
We consider asymptotically-AdS n-dimensional black brane solutions in a theory of gravity coupled to a set of N p-form field strengths, in which the field strengths carry magnetic charges. For appropriately chosen charges, the metrics are isotropic in the ( n - 2) transverse directions. However, in general the field strength configurations break the full Euclidean symmetry of the ( n - 2)-dimensional transverse space, and the shear viscosity tensor in the dual theory is no longer isotropic. We study the linearised equations for transverse traceless metric perturbations in these backgrounds, and by employing the Kubo formula we obtain expressions for the ratios η/S of the shear viscosity components divided by the entropy density. We find that the KSS bound on the ratios η/S is generally violated in these solutions. We also extend the discussion by including a dilatonic scalar field in the theory, leading to solutions that are asymptotically Lifshitz with hyperscaling violation.
Analytic black branes in Lifshitz-like backgrounds and thermalization
NASA Astrophysics Data System (ADS)
Aref'eva, Irina Ya.; Golubtsova, Anastasia A.; Gourgoulhon, Eric
2016-09-01
Using black brane solutions in 5d Lifshitz-like backgrounds with arbitrary dynamical exponent ν, we construct the Vaidya geometry, asymptoting to the Lifshitz-like spacetime, which represents a thin shell infalling at the speed of light. We apply the new Lifshitz-Vaidya background to study the thermalization process of the quark-gluon plasma via the thin shell approach previously successfully used in several backgrounds. We find that the thermalization depends on the chosen direction because of the spatial anisotropy. The plasma thermalizes thus faster in the transversal direction than in the longitudinal one. To probe the system described by the Lifshitz-like backgrounds, we also calculate the holographic entanglement entropy for the subsystems delineated along both transversal and longitudinal directions. We show that the entropy has some universality in the behavior for both subsystems. At the same time, we find that certain characteristics strongly depend on the critical exponent ν.
Negative tension branes as stable thin shell wormholes
NASA Astrophysics Data System (ADS)
Kokubu, Takafumi; Harada, Tomohiro
2015-10-01
We investigate negative tension branes as stable thin shell wormholes (TSWs) in Reissner-Nordström-(anti) de Sitter spacetimes in d dimensional Einstein gravity. Imposing Z2 symmetry, we construct and classify traversable static TSWs in spherical, planar (or cylindrical) and hyperbolic symmetries. In spherical geometry, we find the higher dimensional counterpart of Barceló and Visser’s wormholes, which are stable against spherically symmetric perturbations. We also find the classes of TSWs in planar and hyperbolic symmetries with a negative cosmological constant, which are stable against perturbations preserving symmetries. In most cases, stable wormholes are found with the combination of an electric charge and a negative cosmological constant. However, as special cases, we find stable wormholes even with vanishing cosmological constant in spherical symmetry and with vanishing electric charge in hyperbolic symmetry.
Giant leaps and minimal branes in multidimensional flux landscapes
NASA Astrophysics Data System (ADS)
Brown, Adam R.; Dahlen, Alex
2011-07-01
There is a standard story about decay in multidimensional flux landscapes: that from any state, the fastest decay is to take a small step, discharging one flux unit at a time; that fluxes with the same coupling constant are interchangeable; and that states with N units of a given flux have the same decay rate as those with -N. We show that this standard story is false. The fastest decay is a giant leap that discharges many different fluxes in unison; this decay is mediated by a “minimal” brane that wraps the internal manifold and exhibits behavior not visible in the effective theory. We discuss the implications for the cosmological constant problem.
Holography, brane intersections and six-dimensional SCFTs
NASA Astrophysics Data System (ADS)
Bobev, Nikolay; Dibitetto, Giuseppe; Gautason, Friðrik Freyr; Truijen, Brecht
2017-02-01
We study supersymmetric intersections of NS5-, D6- and D8-branes in type IIA string theory. We focus on the supergravity description of this system and identify a "near horizon" limit in which we recover the recently classified supersymmetric seven-dimensional AdS solutions of massive type IIA supergravity. Using a consistent truncation to seven-dimensional gauged supergravity we construct a universal supersymmetric deformation of these AdS vacua. In the holographic dual six-dimensional (1,0) superconformal field theory this deformation describes a universal RG flow on the tensor branch of the vacuum moduli space triggered by a vacuum expectation value for a protected scalar operator of dimension four.
TOPICAL REVIEW: Quasinormal modes of black holes and black branes
NASA Astrophysics Data System (ADS)
Berti, Emanuele; Cardoso, Vitor; Starinets, Andrei O.
2009-08-01
Quasinormal modes are eigenmodes of dissipative systems. Perturbations of classical gravitational backgrounds involving black holes or branes naturally lead to quasinormal modes. The analysis and classification of the quasinormal spectra require solving non-Hermitian eigenvalue problems for the associated linear differential equations. Within the recently developed gauge-gravity duality, these modes serve as an important tool for determining the near-equilibrium properties of strongly coupled quantum field theories, in particular their transport coefficients, such as viscosity, conductivity and diffusion constants. In astrophysics, the detection of quasinormal modes in gravitational wave experiments would allow precise measurements of the mass and spin of black holes as well as new tests of general relativity. This review is meant as an introduction to the subject, with a focus on the recent developments in the field.
ERIC Educational Resources Information Center
Brisco, Nicole
2011-01-01
Build, create, make, blog, develop, organize, structure, perform. These are just a few verbs that illustrate the visual world. These words create images that allow students to respond to their environment. Visual culture studies recognize the predominance of visual forms of media, communication, and information in the postmodern world. This…
NASA Astrophysics Data System (ADS)
Rador, Tonguç
2005-06-01
We show that, in the context of dilaton gravity, a recently proposed democratic principle for intersection possibilities of branes winding around extra dimensions yield stabilization, even with the inclusion of momentum modes of the wrapped branes on top of the winding modes. The constraints for stabilization massaged by string theory inputs forces the number of observed dimensions to be three. We also discuss consequences of adding ordinary matter living in the observed dimensions.
Decay of type 0 Neveu-Schwarz 5-branes to nothing
NASA Astrophysics Data System (ADS)
Imamura, Yosuke
2004-01-01
The perturbative vacuum of type 0 string theory is unstable due to the existence of the closed string tachyon. This instability can be removed by S1 compactification with the twisted boundary condition for the tachyon field. We show that even in this situation unwrapped NS5-branes are unstable and decay to bubbles of nothing smoothly without tunneling any potential barrier. We discuss a relation between the closed string tachyon condensation and the instability of NS5-branes.
D-brane propagation in two-dimensional black hole geometries
NASA Astrophysics Data System (ADS)
Nakayama, Yu; Rey, Soo-Jong; Sugawara, Yuji
2005-09-01
We study propagation of D0-brane in two-dimensional lorentzian black hole backgrounds by the method of boundary conformal field theory of SL(2,Bbb R)/U(1) supercoset at level k. Typically, such backgrounds arise as near-horizon geometries of k coincident non-extremal NS5-branes, where 1/k measures curvature of the backgrounds in string unit and hence size of string worldsheet effects. At classical level, string worldsheet effects are suppressed and D0-brane propagation in the lorentzian black hole geometry is simply given by the Wick rotation of D1-brane contour in the euclidean black hole geometry. Taking account of string worldsheet effects, boundary state of the lorentzian D0-brane is formally constructible via Wick rotation from that of the euclidean D1-brane. However, the construction is subject to ambiguities in boundary conditions. We propose exact boundary states describing the D0-brane, and clarify physical interpretations of various boundary states constructed from different boundary conditions. As it falls into the black hole, the D0-brane radiates off to the horizon and to the infinity. From the boundary states constructed, we compute physical observables of such radiative process. We find that part of the radiation to infinity is in effective thermal distribution at the Hawking temperature. We also find that part of the radiation to horizon is in the Hagedorn distribution, dominated by massive, highly non-relativistic closed string states, much like the tachyon matter. Remarkably, such distribution emerges only after string worldsheet effects are taken exactly into account. From these results, we observe that nature of the radiation distribution changes dramatically across the conifold geometry k = 1 (k = 3 for the bosonic case), exposing the `string - black hole transition' therein.
Yang-Mills instantons sitting on a Ricci-flat worldspace of double D4-branes
Kim, Hongsu; Yoon, Yongsung
2001-06-15
Thus far, there seem to be no complete criteria that can settle the issue as to what the correct generalization of the Dirac-Born-Infeld (DBI) action, describing the low-energy dynamics of the D-branes, to the non-Abelian case would be. According to recent suggestions, one might pass the issue of worldvolume solitons from an Abelian to non-Abelian setting by considering the stack of multiple, coincident D-branes and use it as a guideline to construct or censor the relevant non-Abelian version of the DBI action. In this spirit, here we are interested in the explicit construction of SU(2) Yang-Mills (YM) instanton solutions in the background geometry of two coincident probe D4-brane worldspaces, particularly when the metric of the target spacetime in which the probe branes are embedded is given by the Ricci-flat, magnetic extremal 4-brane solution in type IIA supergravity theory with its worldspace metric being given by that of Taub{endash}Newman-Unti-Tamburino (NUT) and Eguchi-Hanson solutions, the two best-known gravitational instantons. Then we demonstrate that, with this YM instanton-gravitational instanton configuration on the probe D4-brane worldvolume, the energy of the probe branes attains its minimum value and hence enjoys a stable state provided one employs Tseytlin's non-Abelian DBI action for the description of multiple probe D-branes. In this way, we support the arguments in the literature in favor of Tseytlin's proposal for the non-Abelian DBI action.
NASA Astrophysics Data System (ADS)
Ivashchuk, V. D.; Melnikov, V. N.
2000-09-01
Multidimensional model describing the cosmological evolution of n Einstein spaces in the theory with l scalar fields and forms is considered. When electromagnetic composite p-brane ansatz is adopted, and certain restrictions on the parameters of the model are imposed, the dynamics of the model near the singularity is reduced to a billiard on the (N-1)-dimensional Lobachevsky space HN-1, N=n+l. The geometrical criterion for the finiteness of the billiard volume and its compactness is used. This criterion reduces the problem to the problem of illumination of (N-2)-dimensional sphere SN-2 by pointlike sources. Some examples with billiards of finite volume and hence oscillating behavior near the singularity are considered. Among them examples with square and triangle two-dimensional billiards (e.g., that of the Bianchi-IX model) and a four-dimensional billiard in ``truncated'' D=11 supergravity model (without the Chern-Simons term) are considered. It is shown that the inclusion of the Chern-Simons term destroys the confining of a billiard.
Real-world emissions from model year 1993, 2000, and 2010 passenger cars
Ross, M.; Goodwin, R.; Watkins, R.
1995-11-01
Air pollution by cars and light trucks is a major problem in metropolitan areas in the United States and around the world. Much of the discussion of this issue is based on the emissions per vehicle mile as determined under somewhat artificial testing conditions. The pollutants actually emitted vary considerably with the particular vehicle and the way it is driven, but the average emissions per mile are much higher than the test values. This report concerns the sources and levels of excess emissions, and the potential for reducing them. The history of automotive emissions regulation reveals remarkable success in reducing the emissions of carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NO{sub x}) from new automobiles - as measured in certification tests. The grams-per-mile (g/mile) standards for these tests are stringent, with 96% reductions mandated in comparison to the estimated pre-control (mid-1960s) levels for CO and HC; and 75% reductions mandated for NO{sub x}. Powerful new technologies have been developed and incorporated into every new vehicle in order to accomplish these reductions. Most noteworthy are the catalytic converter and closed-loop engine controls; the latter includes sensors before and after the engine proper, and computer analysis of the information leading to real-time control of fuel injection, with the principal objective of maintaining just the right chemical balance of fuel and air. The average lifetime real-world g/mile emissions associated with conventional gasoline fueled cars for model years 1993, 2000, and 2010 have been projected. Results are discussed.
Improved method for roadside barrier length of need modeling using real-world trajectories.
Johnson, Nicholas S; Thomson, Robert; Gabler, Hampton C
2015-07-01
The 2011 AASHTO Roadside Design Guide (RDG) contains perhaps the most widely used procedure for choosing an appropriate length of need (LON) for roadside barriers. However, this procedure has several limitations. The procedure uses a highly simplified model of vehicle departure, and the procedure does not allow designers to specify an explicit level of protection. A new procedure for choosing LON that addresses these limitations is presented in this paper. This new procedure is based on recent, real-world road departure trajectories and uses this departure data in a more realistic way. The new procedure also allows LON to be specified for a precisely known level of protection - a level which can be based on number of crashes, injury outcomes or even estimated crash cost - while still remaining straightforward and quick to use like the 2011 RDG procedure. In this analysis, the improved procedure was used to explore the effects of the RDG procedure's assumptions. LON recommendations given by the 2011 RDG procedure were compared with recommendations given by this improved procedure. For 55 mph roads, the 2011 RDG procedure appears to lead to a LON sufficient to intercept between 80% and 90% of right-side departures that would otherwise strike a hazard located 10 m from the roadway. For hazards closer than 10 m, the 2011 RDG procedure intercepts progressively higher percentages of real-world departures. This suggests the protection level provided by the 2011 RDG procedure varies with the hazard offset, becoming more conservative as the hazard moves closer to the roadway. The improved procedure, by comparison, gives a consistent protection level regardless of hazard location.
3-D world modeling based on combinatorial geometry for autonomous robot navigation
Goldstein, M.; Pin, F.G.; de Saussure, G.; Weisbin, C.R.
1987-01-01
In applications of robotics to surveillance and mapping at nuclear facilities, the scene to be described is fundamentally three-dimensional. Usually, only partial information concerning the 3-D environment is known a-priori. Using an autonomous robot, this information may be updated using range data to provide an accurate model of the environment. Range data quantify the distances from the sensor focal plane to the object surface. In other words, the 3-D coordinates of discrete points on the object surface are known. The approach proposed herein for 3-D world modeling is based on the Combinatorial Geometry (C.G.) Method which is widely used in Monte Carlo particle transport calculations. First, each measured point on the object surface is surrounded by a small solid sphere with a radius determined by the range to that point. Then, the 3-D shapes of the visible surfaces are obtained by taking the (Boolean) union of all the spheres. The result is a concise and unambiguous representation of the object's boundary surfaces. The distances from discrete points on the robot's boundary surface to various objects are calculated effectively using the C.G. type of representation. This feature is particularly useful for navigation purposes. The efficiency of the proposed approach is illustrated by a simulation of a spherical robot navigating in a 3-D room with several static obstacles.
Reconstruction of a Real World Social Network using the Potts Model and Loopy Belief Propagation
Bisconti, Cristian; Corallo, Angelo; Fortunato, Laura; Gentile, Antonio A.; Massafra, Andrea; Pellè, Piergiuseppe
2015-01-01
The scope of this paper is to test the adoption of a statistical model derived from Condensed Matter Physics, for the reconstruction of the structure of a social network. The inverse Potts model, traditionally applied to recursive observations of quantum states in an ensemble of particles, is here addressed to observations of the members' states in an organization and their (anti)correlations, thus inferring interactions as links among the members. Adopting proper (Bethe) approximations, such an inverse problem is showed to be tractable. Within an operational framework, this network-reconstruction method is tested for a small real-world social network, the Italian parliament. In this study case, it is easy to track statuses of the parliament members, using (co)sponsorships of law proposals as the initial dataset. In previous studies of similar activity-based networks, the graph structure was inferred directly from activity co-occurrences: here we compare our statistical reconstruction with such standard methods, outlining discrepancies and advantages. PMID:26617539
Quantum dynamics of spinless particles on a brane coupled to a bulk gauge field
NASA Astrophysics Data System (ADS)
Brandt, F. T.; Sánchez-Monroy, J. A.
2017-04-01
We investigate the effective dynamics for spinless charged particles, in the presence of Abelian gauge field, constrained to an m-dimensional curved pseudo-Riemannian submanifold (brane) of an n-dimensional pseudo-Riemannian manifold (bulk). We employ the confining potential approach and a perturbative expansion for the Klein–Gordon and Schrödinger equations is derived. This allows us to obtain the effective Klein–Gordon and Schrödinger equations on a brane, in terms of the extrinsic curvatures, the intrinsic curvature and the extrinsic torsion. We show that the presence of a bulk gauge field induces a Zeeman coupling whenever the codimension is greater than one, even if the brane and the bulk are flat. The effect of a non-minimal coupling with the Ricci scalar curvature of the bulk is also considered. The results presented here can be applied in at least two physical scenarios: brane gravity, when the brane is four-dimensional, and condensed matter, when the bulk is a four-dimensional flat manifold and the brane is three- or two-dimensional.
Localization and mass spectra of fermions on symmetric and asymmetric thick branes
Liu Yuxiao; Fu, C.-E; Zhao Li; Duan Yishi
2009-09-15
A three-parameter (positive odd integer s, thickness factor {lambda}, and asymmetry factor a) family of asymmetric thick brane solutions in five dimensions were constructed from a two-parameter (s and {lambda}) family of symmetric ones in by R. Guerrero, R. O. Rodriguez, and R. Torrealba in [Phys. Rev. D 72, 124012 (2005).]. The values s=1 and s{>=}3 correspond to single branes and double branes, respectively. These branes have very rich inner structure. In this paper, by presenting the mass-independent potentials of Kaluza-Klein (KK) modes in the corresponding Schroedinger equations, we investigate the localization and mass spectra of fermions on the symmetric and asymmetric thick branes in an anti-de Sitter background. In order to analyze the effect of gravity-fermion interaction (i.e., the effect of the inner structure of the branes) and scalar-fermion interaction to the spectrum of fermion KK modes, we consider three kinds of typical kink-fermion couplings. The spectra of left chiral fermions for these couplings consist of a bound zero mode and a series of gapless continuous massive KK modes, some discrete bound KK modes including zero mode (exist mass gaps), and a series of continuous massive KK modes, infinite discrete bound KK modes, respectively. The structures of the spectra are investigated in detail.
Brane realization of q-theory and the cosmological constant problem
NASA Astrophysics Data System (ADS)
Klinkhamer, F. R.; Volovik, G. E.
2016-05-01
We discuss the cosmological constant problem using the properties of a freely suspended two-dimensional condensed-matter film, i.e., an explicit realization of a 2D brane. The large contributions of vacuum fluctuations to the surface tension of this film are cancelled in equilibrium by the thermodynamic potential arising from the conservation law for particle number. In short, the surface tension of the film vanishes in equilibrium due to a thermodynamic identity. This 2D brane can be generalized to a 4D brane with gravity. For the 4D brane, the analogue of the 2D surface tension is the 4D cosmological constant, which is also nullified in full equilibrium. The 4D brane theory provides an alternative description of the phenomenological q-theory of the quantum vacuum. As for other realizations of the vacuum variable q, such as the 4-form field-strength realization, the main ingredient is the conservation law for the variable q, which makes the vacuum a self-sustained system. For a vacuum within this class, the nullification of the cosmological constant takes place automatically in equilibrium. Out of equilibrium, the cosmological constant can be as large as suggested by naive estimates based on the summation of zero-point energies. In this brane description, q-theory also corresponds to a generalization of unimodular gravity.
U(1) gauge field localization on a Bloch brane with Chumbes-Holf da Silva-Hott mechanism
NASA Astrophysics Data System (ADS)
Zhao, Zhen-Hua; Liu, Yu-Xiao; Zhong, Yuan
2014-08-01
We follow the Chumbes-Holf da Silva-Hott mechanism to study the (quasi)localization of the U(1) gauge field on the Bloch brane. The localization and resonances of the U(1) gauge field are discussed for four kinds of Bloch brane solutions: the original and generalized Bloch brane solutions, as well as the degenerate Bloch brane solutions I and II. With the Chumbes-Holf da Silva-Hott mechanism, we find that the mass spectrum of the gauge field Kaluza-Klein modes is continuous and there is no tachyonic mode. The zero mode is localized on all the branes and there are resonant Kaluza-Klein modes on the degenerate Bloch branes.
New instantons in AdS4/CFT3 from D4-branes wrapping some of CP3
NASA Astrophysics Data System (ADS)
Naghdi, M.
2013-07-01
With use of a 6-form field strength of ten-dimensional type IIA supergravity over AdS4×CP3, when S7/Zk is considered as a S1 Hopf fibration on CP3, we earn a fully localized solution in the bulk of Euclideanized AdS4. Indeed, this object appears in the external space because of wrapping a D4(M5)-brane over some parts of the respective internal spaces. Interestingly, this supersymmetry breaking SU(4)×U(1)-singlet mode exists in already known spectra when one uses the 8c gravitino representation of SO(8). To adjust the boundary theory, we should swap the original 8s and 8c representations for supercharges and fermions in the Aharony-Bergman-Jafferis-Maldacena model. The procedure could later be interpreted as adding an anti-D4(M5)-brane to the prime N=6 membrane theory, resulting in a N=0 antimembrane theory while other symmetries are preserved. Then, according to the well-known state-operator correspondence rules, we find a proper dual operator with the conformal dimension of Δ+=3 that matches to the bulk massless pseudoscalar state. After that, by making use of some fitting Ansätze for the used matter fields, we arrive at an exact boundary solution and comment on the other related issues as well.
Performance changes in world-class kayakers following two different training periodization models.
García-Pallarés, Jesús; García-Fernández, Miguel; Sánchez-Medina, Luis; Izquierdo, Mikel
2010-09-01
This study was undertaken to compare training-induced changes in selected physiological, body composition and performance variables following two training periodization models: traditional (TP) versus block periodization (BP). Ten world-class kayakers were assessed four times during a training cycle over two consecutive seasons. On each occasion, subjects completed an incremental test to exhaustion on the kayak ergometer to determine peak oxygen uptake (VO(2peak)), VO(2) at second ventilatory threshold (VO(2) VT2), peak blood lactate, paddling speed at VO(2peak) (PS(peak)) and VT2 (PS( VT2)), power output at VO(2peak) (Pw(peak)) and VT2 (Pw( VT2)), stroke rate at VO(2peak) (SR(peak)) and VT2 (SR( VT2)) as well as heart rate at VO(2peak) and VT2. Volume and exercise intensity were quantified for each endurance training session. Both TP and BP cycles resulted in similar gains in VO(2peak) (11 and 8.1%) and VO(2) VT2 (9.8 and 9.4%), even though the TP cycle was 10 weeks and 120 training hours longer than the BP cycle. Following BP paddlers experienced larger gains in PS(peak), Pw(peak) and SR(peak) than those observed with TP. These findings suggest that BP may be more effective than TP for improving the performance of highly trained top-level kayakers. Although both models allowed significant improvements of selected physiological and kayaking performance variables, the BP program achieved similar results with half the endurance training volume used in the TP model. A BP design could be a more useful strategy than TP to maintain the residual training effects as well as to achieve greater improvements in certain variables related to kayaking performance.
Learning to Teach in the Figured World of Reform Mathematics: Negotiating New Models of Identity
ERIC Educational Resources Information Center
Ma, Jasmine Y.; Singer-Gabella, Marcy
2011-01-01
Starting from the assertion that traditional and reform mathematics pedagogy constitute two distinct figured worlds of teaching and learning, the authors explore the initiation of prospective teachers into the figured world of reform mathematics pedagogy. To become successful teachers in reform-oriented classrooms, prospective teachers must learn…
Modified World Café Discussion Model for Conference and Course Settings
ERIC Educational Resources Information Center
Cassidy, Alice; Fox, Joanne
2013-01-01
A group facilitation technique called World Café usually involves dividing a large number of people into smaller groups at tables, exploring a variety of topics around a key focus, and collecting ideas from the discussions to debrief later as a large group. We used a modified version of World Café during the new Cracker Barrel session format at…