Open String on Symmetric Product
NASA Astrophysics Data System (ADS)
Fuji, Hiroyuki; Matsuo, Yutaka
We discuss some basic properties of the open string on the symmetric product which is supposed to describe the open string field theory in discrete light-cone quantization (DLCQ). We first derive the consistent twisted boundary conditions for Annulus/Möbius/Klein Bottle diagrams and give the explicit form of the corresponding amplitude. They have the interpretation as the long open (or closed) string amplitude but the world sheet topology viewed from the short string and from the long string is in general different. Boundary (cross-cap) states of the short string are classified into three categories, the boundary (cross-cap) states of the long string and the "joint" state which connects two strings. The partition function has the typical structure of the string field theory in DLCQ. Tadpole condition is also analyzed and gives a reasonable gauge group SO(213).
Closed string cohomology in open string field theory
NASA Astrophysics Data System (ADS)
Moeller, Nicolas; Sachs, Ivo
2011-07-01
We show that closed string states in bosonic string field theory are encoded in the cyclic cohomology of cubic open string field theory (OSFT) which, in turn, classifies the deformations of OSFT. This cohomology is then shown to be independent of the open string background. Exact elements correspond to closed string gauge transformations, generic boundary deformations of Witten's 3-vertex and infinitesimal shifts of the open string background. Finally it is argued that the closed string cohomology and the cyclic cohomology of OSFT are isomorphic to each other.
AdS/QCD model from an effective action for open string tachyons
Iatrakis, Ioannis; Kiritsis, Elias; Paredes, Angel
2010-06-01
We construct a new, simple phenomenological model along the lines of AdS/QCD. The essential new ingredient is the brane-antibrane effective action including the open string tachyon proposed by Sen [Phys. Rev. D 68, 066008 (2003).]. Chiral symmetry breaking happens because of tachyon dynamics. We fit a large number of low-spin meson masses at the 10%-15% level. The only free parameters involved in the fits correspond to the overall QCD scale and the quark masses. Several aspects of previous models are qualitatively improved.
Summing Planar Bosonic Open Strings
Bardakci, Korkut
2006-02-16
In earlier work, planar graphs of massless {phi}{sup 3} theory were summed with the help of the light cone world sheet picture and the mean field approximation. In the present article, the same methods are applied to the problem of summing planar bosonic open strings. They find that in the ground state of the system, string boundaries form a condensate on the world sheet, and a new string emerges from this summation. Its slope is always greater than the initial slope, and it remains non-zero even when the initial slope is set equal to zero. If they assume the initial string tends to a field a theory in the zero slope limit, this result provides evidence for string formation in field theory.
Off-Shell Structure of the String Sigma Model
Alan Kostelecky, V.; Perry, Malcolm J.; Potting, Robertus
2000-05-15
The off-shell structure of the string sigma model is investigated. In the open bosonic string, nonperturbative effects appear to depend crucially on the regularization scheme. A scheme retaining the notion of string width reproduces the structure of Witten's string field theory. (c) 2000 The American Physical Society.
A monopole solution in open string theory
NASA Astrophysics Data System (ADS)
Behrndt, K.
1994-02-01
We investigate a solution of the Weyl invariance conditions in open string theory in four dimensions. In the closed string sector this solution is a combination of the SU(2) Wess-Zumino-Witten model and a Liouville theory. The investigation is carried out in the σ model approach where we have coupled all massless modes (especiallyan abelian gauge field via the boundary) and tachyon fields. Neglecting all higher derivatives in the field strength we get an exact result which can be interpreted as a monopole configuration living in non-trivia space-time. The masses of both tachyon fields are quantized by cWZW. But only for massless tachyons ( cWZW = 1) the corresponding vertex operators are well defined.
Fundamental string solutions in open string field theories
Michishita, Yoji
2006-02-15
In Witten's open cubic bosonic string field theory and Berkovits' superstring field theory we investigate solutions of the equations of motion with appropriate source terms, which correspond to Callan-Maldacena solution in Born-Infeld theory representing fundamental strings ending on the D-branes. The solutions are given in order by order manner, and we show some full order properties in the sense of {alpha}{sup '} expansion. In superstring case we show that the solution is 1/2 BPS in full order.
Open string in a nonrelativistic background
Kluson, J.
2010-05-15
This paper is devoted to the study of the open string description of Wilson loops and quarks in nonrelativistic quantum field theory that are expected to be dual of gravity in Schroedinger space-time.
String bit models for superstring
Bergman, O.; Thorn, C.B.
1995-12-31
The authors extend the model of string as a polymer of string bits to the case of superstring. They mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei invariant theory in (D {minus} 2) + 1 dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in D {minus} 2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in D dimensional space-time enjoying the full N = 2 Poincare supersymmetric dynamics of type II-B superstring.
String bit models for superstring
Bergman, O.; Thorn, C.B.
1995-11-15
We extend the model of string as a polymer of string bits to the case of superstring. We mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string we work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei-invariant theory in [({ital D}{minus}2)+1]-dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in {ital D}{minus}2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in {ital D}-dimensional space-time enjoying the full {ital N}=2 Poincare supersymmetric dynamics of type II-B superstring.
Open strings on D-branes and Hagedorn regime in string gas cosmology
Arslanargin, Ayse; Kaya, Ali
2009-03-15
We consider early time cosmic evolution in string gas cosmology dominated by open strings attached to D-branes. After reviewing statistical properties of open strings in D-brane backgrounds, we use dilaton-gravity equations to determine the string frame fields. Although, there are distinctions in the Hagedorn regime thermodynamics and dilaton coupling as compared to closed strings, it seems difficult to avoid Jeans instability and assume thermal equilibrium simultaneously, which is already a known problem for closed strings. We also examine characteristics of a possible subsequent large radius regime in this setup.
Open string Regge trajectory and its field theory limit
NASA Astrophysics Data System (ADS)
Rojas, Francisco; Thorn, Charles B.
2011-07-01
We study the properties of the leading Regge trajectory in open string theory including the open string planar one-loop corrections. With SU(N) Chan-Paton factors, the sum over planar open string multiloop diagrams describes the ’t Hooft limit N→∞ with Ngs2 fixed. Our motivation is to improve the understanding of open string theory at finite α' as a model of gauge field theories. SU(N) gauge theories in D space-time dimensions are described by requiring open strings to end on a stack of N Dp-branes of space-time dimension D=p+1. The large N leading trajectory α(t)=1+α't+Σ(t) can be extracted, through order g2, from the s→-∞ limit, at fixed t, of the four open string tree and planar loop diagrams. We analyze the t→0 behavior with the result that Σ(t)˜-Cg2(-α't)(D-4)/2/(D-4). This result precisely tracks the 1-loop Reggeized gluon of gauge theory in D>4 space-time dimensions. In particular, for D→4 it reproduces the known infrared divergences of gauge theory in 4 dimensions with a Regge trajectory behaving as -ln(-α't). We also study Σ(t) in the limit t→-∞ and show that, when D<8, it behaves as α't/(ln(-α't))γ, where γ>0 depends on D and the number of massless scalars. Thus, as long as 4
Solution of the dilaton problem in open bosonic string theories
Bern, Z. ); Dunbar, D.C. )
1991-01-01
One of the most remarkable features of string theories is that they seem to provide a framework for a consistent theory of quantum gravity which is unified with all other forces. String theories fall into the two basic, a priori equally interesting, categories of open and closed string theories. For the past five years virtually all attention has been focused on purely closed string theories even though the reincarnation of string theory began with the discovery of anomaly cancellation and finiteness in the Green-Schwarz open superstring. It is the authors' purpose in this essay to rekindle interest in open string theories as potential theories of nature, including gravity. All string theories naively contain a massless dilaton which couples with the strength of gravity in direct violation of experiment. They present a simple mechanism for giving the dilaton a mass in unoriented open bosonic string theories.
The decay of highly excited open strings
NASA Technical Reports Server (NTRS)
Mitchell, D.; Turok, N.; Wilkinson, R.; Jetzer, P.
1988-01-01
The decay rates of leading edge Regge trajectory states are calculated for very high level number in open bosonic string theories, ignoring tachyon final states. The optical theorem simplifies the analysis while enabling identification of the different mass level decay channels. The main result is that (in four dimensions) the greatest single channel is the emission of a single photon and a state of the next mass level down. A simple asymptotic formula for arbitrarily high level number is given for this process. Also calculated is the total decay rate exactly up to N=100. It shows little variation over this range but appears to decrease for larger N. The formalism is checked in examples and the decay rate of the first excited level calculated for open superstring theories. The calculation may also have implications for high spin meson resonances.
Metastable cosmic strings in realistic models
Holman, R.; Hsu, S.; Vachaspati, T.; Watkins, R. |
1992-11-01
The stability of the electroweak Z-string is investigated at high temperatures. The results show that, while finite temperature corrections can improve the stability of the Z-string, their effect is not strong enough to stabilize the Z-string in the standard electroweak model. Consequently, the Z-string will be unstable even under the conditions present during the electroweak phase transition. Phenomenologically viable models based on the gauge group SU(2){sub L} {times} SU(2) {sub R} {times} U(1){sub B-L} are then considered, and it is shown that metastable strings exist and are stable to small perturbations for a large region of the parameter space for these models. It is also shown that these strings are superconducting with bosonic charge carriers. The string superconductivity may be able to stabilize segments and loops against dynamical contraction. Possible implications of these strings for cosmology are discussed.
Metastable cosmic strings in realistic models
Holman, R. . Dept. of Physics); Hsu, S. . Lyman Lab. of Physics); Vachaspati, T. . Dept. of Physics and Astronomy); Watkins, R. Fermi National Accelerator Lab., Batavia, IL )
1992-01-01
The stability of the electroweak Z-string is investigated at high temperatures. The results show that, while finite temperature corrections can improve the stability of the Z-string, their effect is not strong enough to stabilize the Z-string in the standard electroweak model. Consequently, the Z-string will be unstable even under the conditions present during the electroweak phase transition. Phenomenologically viable models based on the gauge group SU(2)[sub L] [times] SU(2) [sub R] [times] U(1)[sub B-L] are then considered, and it is shown that metastable strings exist and are stable to small perturbations for a large region of the parameter space for these models. It is also shown that these strings are superconducting with bosonic charge carriers. The string superconductivity may be able to stabilize segments and loops against dynamical contraction. Possible implications of these strings for cosmology are discussed.
Relations between closed string amplitudes at higher-order tree level and open string amplitudes
NASA Astrophysics Data System (ADS)
Chen, Yi-Xin; Du, Yi-Jian; Ma, Qian
2010-01-01
KLT relations almost factorize closed string amplitudes on S by two open string tree amplitudes which correspond to the left- and the right-moving sectors. In this paper, we investigate string amplitudes on D and RP. We find that KLT factorization relations do not hold in these two cases. The relations between closed and open string amplitudes have new forms. On D and RP, the left- and the right-moving sectors are connected into a single sector. Then an amplitude with closed strings on D or RP can be given by one open string tree amplitude except for a phase factor. The relations depends on the topologies of the world-sheets. Under T-duality, the relations on D and RP give the amplitudes between closed strings scattering from D-brane and O-plane respectively by open string partial amplitudes. In the low energy limits of these two cases, the factorization relations for graviton amplitudes do not hold. The amplitudes for gravitons must be given by the new relations instead.
NASA Astrophysics Data System (ADS)
Dean, David Jarvis
1991-02-01
The purpose of this dissertation is to develop a dynamical 3 + 1-dimensional model of interacting hadrons in relativistic collisions. The model incorporates the valence quark structure functions of the hadrons into the dynamical Nambu-Goto string picture. The nucleon is viewed as an ensemble average of various initial string configurations such that the flavor averaged valence quark structure function is reproduced. A stochastic decay mechanism is also developed and applied to string fragmentation (hadronization). The interaction e^+e^-togamma ^{*}to q| q is studied at energies from sqrt{s} = 14 to 30 GeV, and decay parameters are chosen such that the correct experimental multiplicity of particles is obtained. Transverse momentum production is obtained by dynamically generating q| q pairs according to a phenomenological momentum distribution. The interaction mechanism between two colliding nucleons is based on a quark-quark scattering and exchange. The quark scattering cross section is parameterized to reproduce the experimental results. The interactions coupled with the hadronization mechanism successfully reproduce many of the observed inclusive distributions. These include, the charged particle, rapidity, scaled parallel momentum, and p_| distributions. At the present stage of numerical calculations p_ | < 1.1 GeV region has been studied. The model interaction is capable of investigating higher p_| values, which require better statistics and more computing time. Using this interaction, pp collisions at sqrt{s} = 19.4 and 53 GeV are studied and reasonable fits to data are obtained. A further application of the model involves the study of the nuclear attenuation effects observed in e^-A when compared to e ^-p collision experiments. These effects are also observed in the string-parton calculation. At energies of v < 10 GeV the nuclear medium influences the hadronization process. At higher energies the effect is negligible.
Raby, Stuart
2010-02-10
In this talk I review some recent progress in heterotic and F theory model building. I then consider work in progress attempting to find the F theory dual to a class of heterotic orbifold models which come quite close to the MSSM.
String Fragmentation Model in Space Radiation Problems
NASA Technical Reports Server (NTRS)
Tang, Alfred; Johnson, Eloise (Editor); Norbury, John W.; Tripathi, R. K.
2002-01-01
String fragmentation models such as the Lund Model fit experimental particle production cross sections very well in the high-energy limit. This paper gives an introduction of the massless relativistic string in the Lund Model and shows how it can be modified with a simple assumption to produce formulas for meson production cross sections for space radiation research. The results of the string model are compared with inclusive pion production data from proton-proton collision experiments.
28. Brick apartment buildings with arched window openings, string courses, ...
28. Brick apartment buildings with arched window openings, string courses, a brick cornice, and an interrupted brick frieze. - Butte Historic District, Bounded by Copper, Arizona, Mercury & Continental Streets, Butte, Silver Bow County, MT
Gauge invariant actions for string models
Banks, T.
1986-06-01
String models of unified interactions are elegant sets of Feynman rules for the scattering of gravitons, gauge bosons, and a host of massive excitations. The purpose of these lectures is to describe the progress towards a nonperturbative formulation of the theory. Such a formulation should make the geometrical meaning of string theory manifest and explain the many ''miracles'' exhibited by the string Feynman rules. There are some new results on gauge invariant observables, on the cosmological constant, and on the symmetries of interacting string field theory. 49 refs.
Entropy of bosonic open string and boundary conditions
NASA Astrophysics Data System (ADS)
Abdalla, M. C. B.; Graça, E. L.; Vancea, I. V.
2002-05-01
The entropy of the states associated to the solutions of the equations of motion of the bosonic open string with combinations of Neumann and Dirichlet boundary conditions is given. Also, the entropy of the string in the states Ai>=αi-10> and φa>=αa- 10> that describe the massless fields on the world-volume of the /Dp-brane is computed.
Gauge transformation of double field theory for open string
NASA Astrophysics Data System (ADS)
Ma, Chen-Te
2015-09-01
We combine symmetry structures of ordinary (parallel directions) and dual (transversal directions) coordinates to construct the Dirac-Born-Infeld theory. The ordinary coordinates are associated with the Neumann boundary conditions and the dual coordinates are associated with the Dirichlet boundary conditions. Gauge fields become scalar fields by exchanging the ordinary and dual coordinates. A gauge transformation of a generalized metric is governed by the generalized Lie derivative. The gauge transformation of the massless closed string theory gives the C -bracket, but the gauge transformation of the open string theory gives the F -bracket. The F -bracket with the strong constraints is different from the Courant bracket by an exact one-form. This exact one-form should come from the one-form gauge field. Based on a symmetry point of view, we deduce a suitable action with a nonzero H -flux at the low-energy level. From an equation of motion of the scalar dilaton, it defines a generalized scalar curvature. Finally, we construct a double sigma model with a boundary term and show that this model with constraints is classically equivalent to the ordinary sigma model.
Open/closed string duality and relativistic fluids
NASA Astrophysics Data System (ADS)
Niarchos, Vasilis
2016-07-01
We propose an open/closed string duality in general backgrounds extending previous ideas about open string completeness by Ashoke Sen. Our proposal sets up a general version of holography that works in gravity as a tomographic principle. We argue, in particular, that previous expectations of a supergravity/Dirac-Born-Infeld (DBI) correspondence are naturally embedded in this conjecture and can be tested in a well-defined manner. As an example, we consider the correspondence between open string field theories on extremal D-brane setups in flat space in the large-N , large 't Hooft limit, and asymptotically flat solutions in ten-dimensional type II supergravity. We focus on a convenient long-wavelength regime, where specific effects of higher-spin open string modes can be traced explicitly in the dual supergravity computation. For instance, in this regime we show how the full Abelian DBI action arises from supergravity as a straightforward reformulation of relativistic hydrodynamics. In the example of a (2 +1 )-dimensional open string theory this reformulation involves an Abelian Hodge duality. We also point out how different deformations of the DBI action, related to higher-derivative corrections and non-Abelian effects, can arise in this context as deformations in corresponding relativistic hydrodynamics.
No Strings Attached: Open Source Solutions
ERIC Educational Resources Information Center
Fredricks, Kathy
2009-01-01
Imagine downloading a new software application and not having to worry about licensing, finding dollars in the budget, or incurring additional maintenance costs. Imagine finding a Web design tool in the public domain--free for use. Imagine major universities that provide online courses with no strings attached. Imagine online textbooks without a…
On the large-scale structures formed by wakes of open cosmic strings
NASA Technical Reports Server (NTRS)
Hara, Tetsuya; Morioka, Shoji; Miyoshi, Shigeru
1990-01-01
Large-scale structures of the universe have been variously described as sheetlike, filamentary, cellular, bubbles or spongelike. Recently cosmic strings became one of viable candidates for a galaxy formation scenario, and some of the large-scale structures seem to be simply explained by the open cosmic strings. According to this scenario, sheets are wakes which are traces of moving open cosmic strings where dark matter and baryonic matter have accumulated. Filaments are intersections of such wakes and high density regions are places where three wakes intersect almost orthogonally. The wakes formed at t sub eq become the largest surface density among all wakes, where t sub eq is the epoch when matter density equals to radiation density. If we assume that there is one open cosmic string per each horizon, then it can be explained that the typical distances among wakes, filaments and clusters are also approx. 10(exp 2) Mpc. This model does not exclude a much more large scale structure. Open cosmic string may move even now and accumulate cold dark matter after its traces. However, the surface density is much smaller than the ones formed at t sub eq. From this model, it is expected that the typical high density region will have extended features such as six filaments and three sheets and be surrounded by eight empty regions (voids). Here, the authors are mainly concerned with such structures and have made numerical simulations for the formation of such large scale structures.
FAST TRACK COMMUNICATION: Open string pair creation from worldsheet instantons
NASA Astrophysics Data System (ADS)
Schubert, Christian; Torrielli, Alessandro
2010-10-01
Worldline instantons provide a particularly elegant way to derive Schwinger's well-known formula for the pair creation rate due to a constant electric field in quantum electrodynamics. In this communication, we show how to extend this method to the corresponding problem of open string pair creation.
The strings connection: MSSM-like models from strings
NASA Astrophysics Data System (ADS)
Nilles, Hans Peter
2014-05-01
String theory constructions towards the MSSM allow us to identify some general properties that could be relevant for tests at the LHC. They originate from the geometric structure of compactification and the location of fields in extra-dimensional space. Within the framework of the heterotic MiniLandscape we extract some generic lessons for supersymmetric model building. Among them is a specific pattern of SUSY breakdown based on mirage mediation and remnants of extended supersymmetry. This leads to a split spectrum with heavy scalars of the first two families of quarks and leptons and suppressed masses for gauginos, top partners and Higgs bosons. The models exhibit some specific form of hidden supersymmetry consistent with the high mass of the Higgs boson and all presently available experimental constraints. The most compelling picture is based on precision gauge coupling unification that might be in the kinematic reach of the LHC.
Unstable rotational states of string models and width of a hadron
Sharov, G. S.
2009-06-01
Rotational states (planar uniform rotations) of various string hadron models are tested for stability with respect to small disturbances. These models include an open or closed string carrying n massive points (quarks), and their rotational states result in a set of quasilinear Regge trajectories. It is shown that rotations of the linear string baryon model q-q-q and the similar states of the closed string are unstable, because spectra of small disturbances for these states contain complex frequencies, corresponding to exponentially growing modes of disturbances. Rotations of the linear model are unstable for any values of points' masses, but for the closed string we have the threshold effect. This instability is important for describing excited hadrons; in particular, it increases predictions for their width {gamma}. Predicted large values {gamma} for N, {delta} and strange baryons in comparison with experimental data result in unacceptability of the linear string model q-q-q for describing these baryon states.
Stochastic string models with continuous semimartingales
NASA Astrophysics Data System (ADS)
Bueno-Guerrero, Alberto; Moreno, Manuel; Navas, Javier F.
2015-09-01
This paper reformulates the stochastic string model of Santa-Clara and Sornette using stochastic calculus with continuous semimartingales. We present some new results, such as: (a) the dynamics of the short-term interest rate, (b) the PDE that must be satisfied by the bond price, and (c) an analytic expression for the price of a European bond call option. Additionally, we clarify some important features of the stochastic string model and show its relevance to price derivatives and the equivalence with an infinite dimensional HJM model to price European options.
Kahler stabilized, modular invariant heterotic string models
Gaillard, Mary K.; Gaillard, Mary K.; Nelson, Brent D.
2007-03-19
We review the theory and phenomenology of effective supergravity theories based on orbifold compactifications of the weakly-coupled heterotic string. In particular, we consider theories in which the four-dimensional theory displays target space modular invariance and where the dilatonic mode undergoes Kahler stabilization. A self-contained exposition of effective Lagrangian approaches to gaugino condensation and heterotic string theory is presented, leading to the development of the models of Binétruy, Gaillard and Wu. Various aspects of the phenomenology of this class of models are considered. These include issues of supersymmetry breaking and superpartner spectra, the role of anomalous U(1) factors, issues of flavor and R-parity conservation, collider signatures, axion physics, and early universe cosmology. For the vast majority of phenomenological considerations the theories reviewed here compare quite favorably to other string-derived models in the literature. Theoretical objections to the framework and directions for further research are identified and discussed.
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.
Computer Center: BASIC String Models of Genetic Information Transfer.
ERIC Educational Resources Information Center
Spain, James D., Ed.
1984-01-01
Discusses some of the major genetic information processes which may be modeled by computer program string manipulation, focusing on replication and transcription. Also discusses instructional applications of using string models. (JN)
On waveguide modeling of stiff piano strings
NASA Astrophysics Data System (ADS)
Ducasse, Éric
2005-09-01
Bensa et al. [J. Acoust. Soc. Am. 114, 1095-1107 (2003), Sec. IV] recently proposed a waveguide model for the transverse displacement of a stiff piano string. The study described here is an attempt to cast a complementary light on this topic, based on a common wave approach instead of a modal approach. A pair of weakly attenuated traveling waves and a pair of fast-decaying waves both satisfy the one-dimensional wave equation developed by Bensa et al. These solutions have to be carefully considered, however, for portions of string interacting with the hammer felt, the bridge, or the capo d'astro bar.
String coupling and interactions in type IIB matrix model
Kitazawa, Yoshihisa; Nagaoka, Satoshi
2009-05-15
We investigate the interactions of closed strings in a IIB matrix model. The basic interaction of the closed superstring is realized by the recombination of two intersecting strings. Such interaction is investigated in a IIB matrix model via two-dimensional noncommutative gauge theory in the IR limit. By estimating the probability of the recombination, we identify the string coupling g{sub s} in the IIB matrix model. We confirm that our identification is consistent with matrix string theory.
Thermofield dynamics extension of the open string field theory
NASA Astrophysics Data System (ADS)
Botta Cantcheff, M.; Scherer Santos, R. J.
2016-03-01
We study the application of the rules of thermofield dynamics (TFD) to the covariant formulation of open-string field theory. We extend the states space and fields according to the duplication rules of TFD and construct the corresponding classical action. The result is interpreted as a theory whose fields would encode the statistical information of open strings. The physical spectrum of the free theory is studied through the cohomology of the extended Becchi, Rouet, Stora and Tyutin (BRST) charge, and, as a result, we get new fields in the spectrum emerging by virtue of the quantum entanglement, and, noticeably, it presents degrees of freedom that could be identified as those of closed strings. We also show, however, that their appearing in the action is directly related to the choice of the inner product in the extended algebra, so that different sectors of fields could be eliminated from the theory by choosing that product conveniently. Finally, we study the extension of the three-vertex interaction and provide a simple prescription for it of which the results at tree level agree with those of the conventional theory.
Cosmic strings with curvature corrections
NASA Astrophysics Data System (ADS)
Boisseau, Bruno; Letelier, Patricio S.
1992-08-01
A generic model of string described by a Lagrangian density that depends on the extrinsic curvature of the string worldsheet is studied. Using a system of coordinates adapted to the string world sheet the equation of motion and the energy-momentum tensor are derived for strings evolving in curved spacetime. We find that the curvature corrections may change the relation between the string energy density and the tension. It can also introduce heat propagation along the string. We also find for the Polyakov as well as Nambu strings with a topological term that the open string end points can travel with a speed less than the velocity of light.
Subcritical string and large N QCD
Thorn, Charles B.
2008-10-15
We pursue the possibility of using subcritical string theory in 4 spacetime dimensions to establish a string dual for large N QCD. In particular we study the even G-parity sector of the 4 dimensional Neveu-Schwarz dual resonance model as the natural candidate for this string theory. Our point of view is that the open string dynamics given by this model will determine the appropriate subcritical closed string theory, a tree level background of which should describe the sum of planar multiloop open string diagrams. We examine the one-loop open string diagram, which contains information about the closed string spectrum at weak coupling. Higher loop open string diagrams will be needed to determine closed string interactions. We also analyze the field theory limit of the one-loop open string diagram and recover the correct running coupling behavior of the limiting gauge theory.
Modeling Regular Replacement for String Constraint Solving
NASA Technical Reports Server (NTRS)
Fu, Xiang; Li, Chung-Chih
2010-01-01
Bugs in user input sanitation of software systems often lead to vulnerabilities. Among them many are caused by improper use of regular replacement. This paper presents a precise modeling of various semantics of regular substitution, such as the declarative, finite, greedy, and reluctant, using finite state transducers (FST). By projecting an FST to its input/output tapes, we are able to solve atomic string constraints, which can be applied to both the forward and backward image computation in model checking and symbolic execution of text processing programs. We report several interesting discoveries, e.g., certain fragments of the general problem can be handled using less expressive deterministic FST. A compact representation of FST is implemented in SUSHI, a string constraint solver. It is applied to detecting vulnerabilities in web applications
Six open string disk amplitude in pure spinor superspace
NASA Astrophysics Data System (ADS)
Mafra, Carlos R.; Schlotterer, Oliver; Stieberger, Stephan; Tsimpis, Dimitrios
2011-05-01
The tree-level amplitude of six massless open strings is computed using the pure spinor formalism. The OPE poles among integrated and unintegrated vertices can be efficiently organized according to the cohomology of pure spinor superspace. The identification and use of these BRST structures and their interplay with the system of equations fulfilled by the generalized Euler integrals allow the full supersymmetric six-point amplitude to be written in compact form. Furthermore, the complete set of extended Bern-Carrasco-Johansson relations are derived from the monodromy properties of the disk world-sheet and explicitly verified for the supersymmetric numerator factors.
Knots and Gamma Classes in Open Topological String Theory
NASA Astrophysics Data System (ADS)
Mahowald, Matthew
This thesis explores some mathematical applications of string dualities in open topological string theory and presents some new techniques for studying and computing open Gromov-Witten invariants. First, we prove a mild generalization of the gamma class formula of [BCR13], and show that it applies in two novel examples: the quintic threefold Q with Lagrangian given by the real quintic QR Q, and for Lagrangians LK ? X = O P1 (--1, --1) obtained from the conormal bundles of (r, s) torus knots K ? S3 via the conifold transition. Disk enumeration on (Q, Q R ) was first considered in [PSW08], and disk enumeration for (X, LK) was studied in winding-1 in [DSV13]. The gamma class formula agrees with the results of [DSV13] and [PSW08], and we generalize the formula of [DSV13] to arbitrary winding. Next we study a relationship between mirror symmetry and knot contact homology described in [AENV14, AV12]. For knots K ? S 3 , large-N duality relates open Gromov-Witten theory on (X, L_K ) to SU (N) Chern-Simons theory on (S3, K). We use the conjecture of [AV12] to compute open Gromov-Witten invariants of (X, L K) through mirror symmetry in many examples, including several non-toric knots. We also find further evidence for this conjecture: for ( r, s) torus knots, we find a formula for the genus-0, 1-boundary-component, degree-d, winding-w open Gromov-Witten invariants of (X, LK ) using localization. This formula agrees with the results of the mirror symmetry calculation. Moreover, using this formula, we describe a method for obtaining the augmentation polynomial of a knot K from the open Gromov-Witten invariants of ( X, LK ). This method is shown to correctly recover the augmentation polynomial for the unknot and (3, 2) torus knot.
Supersymmetric Standard Model from the Heterotic String
Buchmueller, Wilfried; Hamaguchi, Koichi; Lebedev, Oleg; Ratz, Michael
2006-03-31
We present a Z{sub 6} orbifold compactification of the E{sub 8}xE{sub 8} heterotic string which leads to the (supersymmetric) standard model gauge group and matter content. The quarks and leptons appear as three 16-plets of SO(10), whereas the Higgs fields do not form complete SO(10) multiplets. The model has large vacuum degeneracy. For generic vacua, no exotic states appear at low energies and the model is consistent with gauge coupling unification. The top quark Yukawa coupling arises from gauge interactions and is of the order of the gauge couplings, whereas the other Yukawa couplings are suppressed.
Supersymmetric standard model from the heterotic string.
Buchmüller, Wilfried; Hamaguchi, Koichi; Lebedev, Oleg; Ratz, Michael
2006-03-31
We present a [FORMULA: SEE TEXT] orbifold compactification of the E8xE8 heterotic string which leads to the (supersymmetric) standard model gauge group and matter content. The quarks and leptons appear as three 16-plets of SO(10), whereas the Higgs fields do not form complete SO(10) multiplets. The model has large vacuum degeneracy. For generic vacua, no exotic states appear at low energies and the model is consistent with gauge coupling unification. The top quark Yukawa coupling arises from gauge interactions and is of the order of the gauge couplings, whereas the other Yukawa couplings are suppressed. PMID:16605895
String vertex operators and cosmic strings
NASA Astrophysics Data System (ADS)
Skliros, Dimitri; Hindmarsh, Mark
2011-12-01
We construct complete sets of (open and closed string) covariant coherent state and mass eigenstate vertex operators in bosonic string theory. This construction can be used to study the evolution of fundamental cosmic strings as predicted by string theory, and is expected to serve as a self-contained prototype toy model on which realistic cosmic superstring vertex operators can be based. It is also expected to be useful for other applications where massive string vertex operators are of interest. We pay particular attention to all the normalization constants, so that these vertices lead directly to unitary S-matrix elements.
Type 0 open string amplitudes and the tensionless limit
NASA Astrophysics Data System (ADS)
Rojas, Francisco
2014-12-01
The sum over planar multiloop diagrams in the NS + sector of type 0 open strings in flat spacetime has been proposed by Thorn as a candidate to resolve nonperturbative issues of gauge theories in the large N limit. With S U (N ) Chan-Paton factors, the sum over planar open string multiloop diagrams describes the 't Hooft limit N →∞ with N gs2 held fixed. By including only planar diagrams in the sum the usual mechanism for the cancellation of loop divergences (which occurs, for example, among the planar and Möbius strip diagrams by choosing a specific gauge group) is not available and a renormalization procedure is needed. In this article the renormalization is achieved by suspending total momentum conservation by an amount p ≡∑ i n ki≠0 at the level of the integrands in the integrals over the moduli and analytically continuing them to p =0 at the very end. This procedure has been successfully tested for the 2 and 3 gluon planar loop amplitudes by Thorn. Gauge invariance is respected and the correct running of the coupling in the limiting gauge field theory was also correctly obtained. In this article we extend those results in two directions. First, we generalize the renormalization method to an arbitrary n -gluon planar loop amplitude giving full details for the 4-point case. One of our main results is to provide a fully renormalized amplitude which is free of both UV and the usual spurious divergences leaving only the physical singularities in it. Second, using the complete renormalized amplitude, we extract the high-energy scattering regime at fixed angle (tensionless limit). Apart from obtaining the usual exponential falloff at high energies, we compute the full dependence on the scattering angle which shows the existence of a smooth connection between the Regge and hard scattering regimes.
With string model to time series forecasting
NASA Astrophysics Data System (ADS)
Pinčák, Richard; Bartoš, Erik
2015-10-01
Overwhelming majority of econometric models applied on a long term basis in the financial forex market do not work sufficiently well. The reason is that transaction costs and arbitrage opportunity are not included, as this does not simulate the real financial markets. Analyses are not conducted on the non equidistant date but rather on the aggregate date, which is also not a real financial case. In this paper, we would like to show a new way how to analyze and, moreover, forecast financial market. We utilize the projections of the real exchange rate dynamics onto the string-like topology in the OANDA market. The latter approach allows us to build the stable prediction models in trading in the financial forex market. The real application of the multi-string structures is provided to demonstrate our ideas for the solution of the problem of the robust portfolio selection. The comparison with the trend following strategies was performed, the stability of the algorithm on the transaction costs for long trade periods was confirmed.
Recurrence relations of higher spin BPST vertex operators for open strings
NASA Astrophysics Data System (ADS)
Fu, Chih-Hao; Lee, Jen-Chi; Tan, Chung-I.; Yang, Yi
2013-08-01
We calculate higher-spin Brower-Polchinski-Strassler-Tan (BPST) vertex operators for an open bosonic string and express these operators in terms of a Kummer function of the second kind. We derive an infinite number of recurrence relations among BPST vertex operators of different string states. These recurrence relations among BPST vertex operators lead to the recurrence relations among Regge string scattering amplitudes discovered recently.
Noncommutative-geometry model for closed bosonic strings
NASA Technical Reports Server (NTRS)
Sen, Siddhartha; Holman, R.
1987-01-01
It is shown how Witten's (1986) noncommutative geometry may be extended to describe the closed bosonic string. For closed strings, an explicit representation is provided of the integral operator needed to construct an action and of an associative product on string fields. The proper choice of the action of the integral operator and the associative product in order to give rise to a reasonable theory is explained, and the consequences of such a choice are discussed. It is shown that the ghost numbers of the operator and associative product can be chosen arbitrarily for both open and closed strings, and that this construct can be used as an action for interacting closed bosonic strings.
String model for the dynamics of glass-forming liquids.
Pazmiño Betancourt, Beatriz A; Douglas, Jack F; Starr, Francis W
2014-05-28
We test the applicability of a living polymerization theory to describe cooperative string-like particle rearrangement clusters (strings) observed in simulations of a coarse-grained polymer melt. The theory quantitatively describes the interrelation between the average string length L, configurational entropy Sconf, and the order parameter for string assembly Φ without free parameters. Combining this theory with the Adam-Gibbs model allows us to predict the relaxation time τ in a lower temperature T range than accessible by current simulations. In particular, the combined theories suggest a return to Arrhenius behavior near Tg and a low T residual entropy, thus avoiding a Kauzmann "entropy crisis." PMID:24880303
Big bang models in string theory
NASA Astrophysics Data System (ADS)
Craps, Ben
2006-11-01
These proceedings are based on lectures delivered at the 'RTN Winter School on Strings, Supergravity and Gauge Theories', CERN, 16 20 January 2006. The school was mainly aimed at PhD students and young postdocs. The lectures start with a brief introduction to spacetime singularities and the string theory resolution of certain static singularities. Then they discuss attempts to resolve cosmological singularities in string theory, mainly focusing on two specific examples: the Milne orbifold and the matrix big bang.
Nonorientable one-loop amplitudes for the bosonic open string: Electrostatics on a Moebius strip
Rodrigues, J.P.
1987-11-01
The partition function, N-point scalar, and four-point vector nonorientable one-loop amplitudes for the bosonic open string in the critical dimension are obtained using a first quantized path integral treatment of Polyakov's string that assumes scale independence.
Non-linear sigma-models and string theories
Sen, A.
1986-10-01
The connection between sigma-models and string theories is discussed, as well as how the sigma-models can be used as tools to prove various results in string theories. Closed bosonic string theory in the light cone gauge is very briefly introduced. Then, closed bosonic string theory in the presence of massless background fields is discussed. The light cone gauge is used, and it is shown that in order to obtain a Lorentz invariant theory, the string theory in the presence of background fields must be described by a two-dimensional conformally invariant theory. The resulting constraints on the background fields are found to be the equations of motion of the string theory. The analysis is extended to the case of the heterotic string theory and the superstring theory in the presence of the massless background fields. It is then shown how to use these results to obtain nontrivial solutions to the string field equations. Another application of these results is shown, namely to prove that the effective cosmological constant after compactification vanishes as a consequence of the classical equations of motion of the string theory. 34 refs. (LEW)
D-branes as coherent states in the open string channel
NASA Astrophysics Data System (ADS)
Botta Cantcheff, M.
2008-06-01
We show that bosonic D-branestates may be represented as coherent states in an open string representation. By using the thermo field dynamics (TFD) formalism, we may construct a condensed state of open string modes that encodes the information on the D-braneconfiguration. We also introduce a construction alternative to TFD, which does not require one to assume thermal equilibrium. It is shown that the dynamics of the system combined with the geometric properties of the duplication rules of TFD is sufficient to obtain the thermal states and their analytic continuations in a geometric fashion. We use this approach to show that a bosonic D-branestate in the open string sector may also be built as boundary states in a special sense. Some implications of this study for the interpretation of the open/closed duality and on the kinematic/algebraic structure of an open string field theory are also commented on.
Vortices and strings in a model ecosystem
NASA Astrophysics Data System (ADS)
Tainaka, Kei-Ichi
1994-11-01
We study the spatial pattern formation in a model ecosystem by the position-fixed reaction method. This ecosystem contains three biospecies whose competing powers are cyclic. It is well known that this system is self-organized into a quasistationary state, and that the mean-field approximation (MFA) never predicts such a pattern formation. Recently, several authors applied the pair approximation (PA), and obtained considerable improvements. However, applying PA to our ecosystem fails to yield such an improvement as revealed by computer simulations. The failures of MFA and PA may be attributed to the fact that both approximations neglect a long-range correlation. Thus we introduce the concept of topological defects, such as ``vortices'' or ``strings,'' and demonstrate that the dynamics of these defects can at least qualitatively account for the observed pattern formation dynamics.
Unconstrained variables of non-commutative open strings
NASA Astrophysics Data System (ADS)
De Andrade, Marco A.; Santos, Marcos A.; Vancea, Ion-Vasile
2001-06-01
The boundary conditions of the bosonic string theory in non-zero B-field background are equivalent to the second class constraints of a discretized version of the theory. By projecting the original canonical coordinates onto the constraint surface we derive a set of coordinates of string that are unconstrained. These coordinates represent a natural framework for the quantization of the theory.
Three Family Models from the Heterotic String
Raby, Stuart
2005-12-02
In this talk I outline work done in collaboration with R.J. Zhang and T. Kobayashi. We show how to construct the equivalent of three family orbifold GUTs in five dimensions from the heterotic string. I focus on one particular model with E(6) gauge symmetry in 5D, the third family and Higgs doublet coming from the 5D bulk and the first two families living on 4D SO(10) branes. Note the E(6) gauge symmetry is broken to Pati-Salam in 4D which subsequently breaks to the Standard Model gauge symmetry via the Higgs mechanism. The model has two flaws, one fatal and one perhaps only unaesthetic. The model has a small set of vector-like exotics with fractional electromagnetic charge. Unfortunately not all of these states obtain mass at the compactification scale. This flaw is fatal. The second problem is R parity violating interactions. These problems may be avoidable in alternate orbifold compactification schemes. It is these problems which we discuss in this talk.
Left-right symmetric heterotic-string derived models
Cleaver, Gerald B.; Faraggi, Alon E.; Savage, Christopher
2001-03-15
Recently it was demonstrated that free fermionic heterotic strings can produce models with solely the minimal supersymmetric standard model states in the low energy spectrum. This unprecedented result provides further strong evidence for the possibility that the true string vacuum shares some of the properties of the free fermionic models. Past free fermionic models have focused on several possible unbroken observable SO(10) subgroups at the string scale, which include the flipped SU(5) (FSU5), the Pati-Salam (PS) string models, and the string standard-like models (SLM). We extend this study to include the case in which the SO(10) symmetry is broken to the left-right symmetric (LRS) gauge group, SO(10){yields}SU(3){sub C}xU(1){sub B-L}xSU(2){sub L}xSU(2){sub R}. We present several models of this type and discuss their phenomenological features. The most striking new outcome of the LRS string models, in contrast with the case of the FSU5, the PS, and the SLM string models, is that they can produce effective field theories that are free of Abelian anomalies. We discuss the distinction between the two types of free fermionic models which result in the presence, or absence, of an anomalous U(1). As a counterexample we also present a LRS model that does contain an anomalous U(1). Additionally, we discuss how in string models the standard model spectrum may arise from the three 16 representations of SO(10), while the weak hypercharge does not have the canonical SO(10) embedding.
A note on probabilistic models over strings: the linear algebra approach.
Bouchard-Côté, Alexandre
2013-12-01
Probabilistic models over strings have played a key role in developing methods that take into consideration indels as phylogenetically informative events. There is an extensive literature on using automata and transducers on phylogenies to do inference on these probabilistic models, in which an important theoretical question is the complexity of computing the normalization of a class of string-valued graphical models. This question has been investigated using tools from combinatorics, dynamic programming, and graph theory, and has practical applications in Bayesian phylogenetics. In this work, we revisit this theoretical question from a different point of view, based on linear algebra. The main contribution is a set of results based on this linear algebra view that facilitate the analysis and design of inference algorithms on string-valued graphical models. As an illustration, we use this method to give a new elementary proof of a known result on the complexity of inference on the "TKF91" model, a well-known probabilistic model over strings. Compared to previous work, our proving method is easier to extend to other models, since it relies on a novel weak condition, triangular transducers, which is easy to establish in practice. The linear algebra view provides a concise way of describing transducer algorithms and their compositions, opens the possibility of transferring fast linear algebra libraries (for example, based on GPUs), as well as low rank matrix approximation methods, to string-valued inference problems. PMID:24135792
String networks in ZN Lotka-Volterra competition models
NASA Astrophysics Data System (ADS)
Avelino, P. P.; Bazeia, D.; Menezes, J.; de Oliveira, B. F.
2014-01-01
In this Letter we give specific examples of ZN Lotka-Volterra competition models leading to the formation of string networks. We show that, in order to promote coexistence, the species may arrange themselves around regions with a high number density of empty sites generated by predator-prey interactions between competing species. These configurations extend into the third dimension giving rise to string networks. We investigate the corresponding dynamics using both stochastic and mean field theory simulations, showing that the coarsening of these string networks follows a scaling law which is analogous to that found in other physical systems in condensed matter and cosmology.
On p-Adic Sector of Open Scalar Strings and Zeta Field Theory
Dragovich, Branko
2010-06-17
We consider construction of Lagrangians which may be suitable for description of p-adic sector of an open scalar string. Such Lagrangians have their origin in Lagrangian for a single p-adic string and they contain the Riemann zeta function with the d'Alembertian in its argument. However, investigation of the field theory with Riemann zeta function is interesting in itself as well. We present a brief review and some new results.
Modeling Harpsichord Plucking: The Plectrum and the String
NASA Astrophysics Data System (ADS)
Perng, Jack; Rossing, Thomas; Smith, Julius
2011-11-01
The harpsichord is a plucked string keyboard instrument that was popular during the Renaissance and Baroque music eras. Although it was later replaced by the more expressive piano, it has mounted a comeback due to the early music movement today. A physical model of the harpsichord's plucking mechanism is presented, detailing the plectrum-string interaction which illustrates many aspects of the harpsichord's characteristic sound.
Anomalous dimensions from rotating open strings in AdS/CFT
NASA Astrophysics Data System (ADS)
Braga, Nelson R. F.; Iancu, Edmond
2014-08-01
We propose a new entry within the dictionary of the AdS/CFT duality at strong coupling: in the limit of a large spin or a large R-charge, the anomalous dimension of the gauge theory operator dual to a semiclassical rotating string is proportional to the string proper length. This conjecture is motivated by a generalization to strings of the rule for computing anomalous dimensions of massive particles and supergravity fields in the anti-de Sitter space. We show that this proportionality holds for a rotating closed string in global AdS space, representing a high spin operator made of fields in the adjoint representation. It is also valid for closed strings rotating in S 5 (representing operators with large R-charge), for closed strings with multiple AdS spin, and for giant magnons. Based on this conjecture, we calculate the anomalous dimension δ of operators made of fields in the fundamental representation, associated with high spin mesons, and which are represented by rotating open strings attached to probe D7-branes. The result is a logarithmic dependence upon the spin, , similar to the closed string case. We show that the operator properties — anomalous dimension and spin — are obtained from measurements made by a local observer in the anti-de Sitter space. For the open string case, this ensures that these quantities are independent of the mass scale introduced by the D7-branes (the quark mass), as expected on physical grounds. In contrast, properties of the gauge theory states, like the energy, correspond to measurements by a gauge theory observer and depend upon the mass scale — once again, as expected.
An Integrated Model for Drill-String Dynamics
NASA Astrophysics Data System (ADS)
Tucker, W. R.; Wang, C.
1999-07-01
The vibrational states experienced by the active components of a drilling assembly such as that found in the oil or gas industry are discussed in the context of an integrated mathematical model. The work is motivated by the need to understand the complex vibrational states that such a system can exhibit in order to better control their constructive and destructive potential. The model is expressed in terms of six continuous independent degrees of freedom. Three locate the position of the centroid of the drill-string in space and three permit the dynamical state of the drill-string to be expressed in terms of flexural, torsional and shear strain, together with dilation and stretch. By supplementing the model with appropriate constitutive relations that relate these strains to bending and twisting couples together with shear and compression forces it can fully accommodate the modes of vibration that are traditionally associated with the motion of drill-strings in both straight and curved boreholes discussed in the engineering literature. These include axial motion along the length of the drill-string, torsional or rotational motion and transverse or lateral motion. Attention is given to the boundary conditions appropriate for an active drill-string and BHA stabiliser including an account of frictional simulations at the rock-interface, cutter simulations for different types of drill-bit and interactions between the bore cavity and the drill-string. The model is used to discuss the stability of axisymmetric drill-string configurations in vertical boreholes under both coupled torsional, axial and lateral perturbations as well as general non-perturbative coupled vibrational states under extreme conditions of lateral whirl.
Thickening the string. I. The string perfect dust
NASA Astrophysics Data System (ADS)
Stachel, John
1980-04-01
The classical theory of the geometrical string is developed as the theory of a simple, surface-forming timelike bivector field in an arbitrary background space-time. The stress-energy tensor for a perfect dust of such strings is written down, and the conservation laws for such a dust, as well as the equations of motion of the string, are derived from the vanishing of the divergence of the stress-energy tensor. (The boundary conditions for the open string are also derived from the junction conditions for the stress-energy tensor in Appendix A.) The generalization of this model to null strings, and to a perfect fluid of strings, are discussed, and will form the subject of the second and third papers in this series. The problem of a fully general-relativistic string theory, and an alternate approach to the string, based upon defining an acceleration tensor for two- (and higher) dimensional subspaces, are also discussed.
LRS Bianchi type-I string cosmological models in f (R, T) gravity
NASA Astrophysics Data System (ADS)
Kanakavalli, T.; Ananda Rao, G.
2016-07-01
Spatially homogeneous and anisotropic LRS Bianchi type-I space time is investigated in the presence of cosmic string source in a modified theory of gravitation formulated by Harko et al. (Phys. Rev. D 84:024020, 2011). We have solved the field equations using the equations of state for strings and presented cosmological models which describe geometric string, Takabayasi string and Reddy string in this particular theory. Some physical and kinematical parameters of the models are computed and discussed their physical significance.
sigma model approach to the heterotic string theory
Sen, A.
1985-09-01
Relation between the equations of motion for the massless fields in the heterotic string theory, and the conformal invariance of the sigma model describing the propagation of the heterotic string in arbitrary background massless fields is discussed. It is emphasized that this sigma model contains complete information about the string theory. Finally, we discuss the extension of the Hull-Witten proof of local gauge and Lorentz invariance of the sigma-model to higher order in ..cap alpha..', and the modification of the transformation laws of the antisymmetric tensor field under these symmetries. Presence of anomaly in the naive N = 1/2 supersymmetry transformation is also pointed out in this context. 12 refs.
Observations on open and closed string scattering amplitudes at high energies
NASA Astrophysics Data System (ADS)
Caputa, Pawel; Hirano, Shinji
2012-02-01
We study massless open and closed string scattering amplitudes in flat space at high energies. Similarly to the case of AdS space, we demonstrate that, under the T-duality map, the open string amplitudes are given by the exponential of minus minimal surface areas whose boundaries are cusped closed loops formed by lightlike momentum vectors. We show further that the closed string amplitudes are obtained by gluing two copies of minimal surfaces along their cusped lightlike boundaries. This can be thought of as a manifestation of the Kawai-Lewellen-Tye (KLT) relation at high energies. We also discuss the KLT relation in AdS/CFT and its possible connection to amplitudes in mathcal{N} = {8} supergravity as well as the correlator/amplitude duality.
Abelian cosmic string in the Starobinsky model of gravity
NASA Astrophysics Data System (ADS)
Morais Graça, J. P.
2016-03-01
In this paper, I analyze numerically the behaviour of the solutions corresponding to an Abelian string in the framework of the Starobinsky model. The role played by the quadratic term in the Lagrangian density f(R)=R+η {R}2 of this model is emphasized and the results are compared with the corresponding ones obtained in the framework of Einstein’s theory of gravity. I have found that the angular deficit generated by the string is lowered as the η parameter increases, allowing a well-behaved spacetime for a large range of values of the symmetry-breaking scale.
Renyi entropies for classical string-net models
NASA Astrophysics Data System (ADS)
Hermanns, M.; Trebst, S.
2014-05-01
In quantum mechanics, string-net condensed states—a family of prototypical states exhibiting nontrivial topological order—can be classified via their long-range entanglement properties, in particular, topological corrections to the prevalent area law of the entanglement entropy. Here we consider classical analogs of such string-net models whose partition function is given by an equal-weight superposition of classical string-net configurations. Our analysis of the Shannon and Renyi entropies for a bipartition of a given system reveals that the prevalent volume law for these classical entropies is augmented by subleading topological corrections that are intimately linked to the anyonic theories underlying the construction of the classical models. We determine the universal values of these topological corrections for a number of underlying anyonic theories including SU(2)k,SU(N)1, and SU(N)2 theories.
General analysis of dark radiation in sequestered string models
NASA Astrophysics Data System (ADS)
Cicoli, Michele; Muia, Francesco
2015-12-01
We perform a general analysis of axionic dark radiation produced from the decay of the lightest modulus in the sequestered LARGE Volume Scenario. We discuss several cases depending on the form of the Kähler metric for visible sector matter fields and the mechanism responsible for achieving a de Sitter vacuum. The leading decay channels which determine dark radiation predictions are to hidden sector axions, visible sector Higgses and SUSY scalars depending on their mass. We show that in most of the parameter space of split SUSY-like models squarks and sleptons are heavier than the lightest modulus. Hence dark radiation predictions previously obtained for MSSM-like cases hold more generally also for split SUSY-like cases since the decay channel to SUSY scalars is kinematically forbidden. However the inclusion of string loop corrections to the Kähler potential gives rise to a parameter space region where the decay channel to SUSY scalars opens up, leading to a significant reduction of dark radiation production. In this case, the simplest model with a shift-symmetric Higgs sector can suppress the excess of dark radiation Δ N eff to values as small as 0 .14, in perfect agreement with current experimental bounds. Depending on the exact mass of the SUSY scalars all values in the range 0 .14 ≲ Δ N eff ≲ 1 .6 are allowed. Interestingly dark radiation overproduction can be avoided also in the absence of a Giudice-Masiero coupling.
Searching for the standard model in the string landscape: SUSY GUTs
NASA Astrophysics Data System (ADS)
Raby, Stuart
2011-03-01
The standard model is the theory describing all observational data from the highest energies to the largest distances. (There is, however, one caveat: additional forms of energy, not part of the standard model, known as dark matter and dark energy must be included in order to describe the Universe at galactic scales and larger.) High energies refers to physics at the highest energy particle accelerators, including CERN's LEP II (which ceased operation in 2000 to begin construction of the Large Hadron Collider now in operation) and Fermilab's Tevatron, as well as to the energies obtained in particle jets created in so-called active galactic nuclei scattered throughout the visible Universe. Some of these extra-galactic particles bombard our own Earth in the form of cosmic rays, or super-energetic protons which scatter off nucei in the upper atmosphere. String theory is, on the other hand, an unfinished theoretical construct which attempts to describe all matter and their interactions in terms of the harmonic oscillations of open and/or closed strings. It is regarded as unfinished since at present it is a collection of ideas, tied together by powerful consistency conditions, called dualities, with the ultimate goal of finding the completed string theory. At the moment we only have descriptions which are valid in different mutually exclusive limits with names such as type I, IIA, IIB, heterotic, M and F theory. The string landscape has been described in the pages of many scholarly and popular works. It is perhaps best understood as the collection of possible solutions to the string equations; albeit these solutions look totally different in the different limiting descriptions. What do we know about the string landscape? We know that there are such a large number of possible solutions that the only way to represent this number is as 10500 or a 1 followed by 500 zeros. Note that this is not a precise value since the uncertainty is given by a number just as large
Proton stability and light Z' inspired by string derived models
Faraggi, Alon E.; Mehta, Viraf M.
2011-10-15
Proton stability is one of the most perplexing puzzles in particle physics. While the renormalizable standard model forbids proton decay mediating operators due to accidental global symmetries, many of its extensions introduce such dimension four, five and six operators. Furthermore, it is, in general, expected that quantum gravity only respects local gauge, or discreet, symmetries. String theory provides the arena to study particle physics in a consistent framework of perturbative quantum gravity. An appealing proposition, in this context, is that the dangerous operators are suppressed by an Abelian gauge symmetry, which is broken near the TeV scale. A viable U(1) symmetry should also be anomaly free, be family universal, and allow the generation of fermion masses via the Higgs mechanism. We discuss such U(1) symmetries that arise in quasirealistic free fermionic heterotic-string derived models. Ensuring that the U(1) symmetry is anomaly free at the low scale requires that the standard model spectrum is augmented by additional states that are compatible with the charge assignments in the string models. We construct such string-inspired models and discuss some of their phenomenological implications.
Nagao, G.
1987-12-01
We recalculate the bosonic 1-loop open string scattering amplitude using the results of the bosonic 1-loop closed string amplitude. The results show explicitly how the cancellation of divergences depends upon of a set of involution-dependent constants which relate the torus to the cylinder and Moebius strip. Such a set of involution-dependent constants exists at each loop level and thus provides a means with which to study the cancellation of divergences and the connection between the world-sheet and internal symmetries. 14 refs., 3 figs.
Cosmic D-strings as axionic D-term strings
Blanco-Pillado, Jose J.; Dvali, Gia; Redi, Michele
2005-11-15
In this work we derive nonsingular BPS string solutions from an action that captures the essential features of a D-brane-anti-D-brane system compactified to four dimensions. The model we consider is a supersymmetric Abelian Higgs model with a D-term potential coupled to an axion-dilaton multiplet. The strings in question are axionic D-term strings which we identify with the D-strings of type II string theory. In this picture the Higgs field represents the open string tachyon of the D-D pair and the axion is dual to a Ramond-Ramond form. The crucial term allowing the existence of nonsingular BPS strings is the Fayet-Iliopoulos term, which is related to the tensions of the D-string and of the parent branes. Despite the presence of the axion, the strings are BPS and carry finite energy, due to the fact that the space gets very slowly decompactified away from the core, screening the long range axion field (or equivalently the theory approaches an infinitely weak 4D coupling). Within our 4D effective action we also identify another class of BPS string solutions (s-strings) which have no ten-dimensional analog, and can only exist after compactification.
Pereira, José A
2014-08-01
Theoretical models designed to test the metabolism-first hypothesis for prebiotic evolution have yield strong indications about the hypothesis validity but could sometimes use a more extensive identification between model objects and real objects towards a more meaningful interpretation of results. In an attempt to go in that direction, the string-based model SSE ("steady state evolution") was developed, where abstract molecules (strings) and catalytic interaction rules are based on some of the most important features of carbon compounds in biological chemistry. The system is open with a random inflow and outflow of strings but also with a permanent string food source. Although specific catalysis is a key aspect of the model, used to define reaction rules, the focus is on energetics rather than kinetics. Standard energy change tables were constructed and used with standard formation reactions to track energy flows through the interpretation of equilibrium constant values. Detection of metabolic networks on the reaction system was done with elementary flux mode (EFM) analysis. The combination of these model design and analysis options enabled obtaining metabolic and catalytic networks showing several central features of biological metabolism, some more clearly than in previous models: metabolic networks with stepwise synthesis, energy coupling, catalysts regulation, SN2 coupling, redox coupling, intermediate cycling, coupled inverse pathways (metabolic cycling), autocatalytic cycles and catalytic cascades. The results strongly suggest that the main biological metabolism features, including the genotype-phenotype interpretation, are caused by the principles of catalytic systems and are prior to modern genetic systems principles. It also gives further theoretical support to the thesis that the basic features of biologic metabolism are a consequence of the time evolution of a random catalyst search working on an open system with a permanent food source. The importance
Instability of string models of baryons: Character and manifestations
Sharov, G. S.
2010-12-15
The character of the instability of a rotational state (rotation of the system at a constant speed) against small perturbations is studied in detail for the Y string model of the baryon. It is shown that the existing instability is due to the presence of repeated real-valued frequencies in the spectrum of small perturbations and that there are no complex-valued frequencies in this spectrum. This leads to a linear growth of small-perturbation amplitudes. A comparison of the Y configuration with the q-q-q linear string model of the baryon reveals a difference in the character of the instability of rotational states of these systems and in the manifestations of this instability. In particular, there are exponentially growing modes in the excitation spectrum of the linear model, which lead to an additional contribution to the baryon-state width.
On the nonlinear models of the vibrating string
NASA Astrophysics Data System (ADS)
Watzky, Alexandre
2005-09-01
Vibrations of strings (threads, wires, cables...) are of great interest because of their various domains of application. In musical acoustics, phenomena which could have been neglected elsewhere take a particular importance since perception, which is very sensitive to nonlinear effects, is involved. Some phenomena can also be emphasized when a string is coupled to a sound-radiating structure. Reliable physical models are thus necessary to account for these phenomena, and to understand the true behavior of a vibrating string. Despite the fact that the first nonlinear models were published more than one century ago, and that accurate equations of motion can be naturally achieved within a finite displacement continuum mechanics framework, general models never received the attention they deserved, most authors focusing on particular phenomena and often settling on approximate models. This can be explained by the awkward multiplicity of the involved phenomena. The aim of this presentation is to discuss the consequences of some common assumptions and the true nature of some observed couplings. Particular attention will be paid to the preponderance of the spatial shape of the modes, which are usually underestimated with respect to their temporal form.
Particle Identification in the Dynamical String-Parton Model of Relativistic Heavy-Ion Collisions
NASA Astrophysics Data System (ADS)
Malov, D. E.; Umar, A. S.; Ernst, D. J.; Dean, D. J.
The dynamical string-parton model for relativistic heavy-ion collisions is generalized to include particle identification of the final-state hadrons by phenomenologically quantizing the masses of the classical strings which result from string breaking. General features of the Nambu-Gotō strings are used to motivate a model that identifies a mass window near the physical mass of a meson, and does not allow the string to decay further if its mass falls within the window. Data from e+e- collisions in the region √ {s} =10 to 30 GeV are well reproduced by this model.
Dilaton stabilization in three-generation heterotic string model
NASA Astrophysics Data System (ADS)
Beye, Florian; Kobayashi, Tatsuo; Kuwakino, Shogo
2016-09-01
We study dilaton stabilization in heterotic string models. By utilizing the asymmetric orbifold construction, we construct an explicit three-generation model whose matter content in the visible sector is the supersymmetric standard model with additional vectorlike matter. This model does not contain any geometric moduli fields except the dilaton field. Model building at a symmetry enhancement point in moduli space enlarges the rank of the hidden gauge group. By analyzing multiple hidden gauge sectors, the dilaton field is stabilized by the racetrack mechanism. We also discuss a supersymmetry breaking scenario and F-term uplifting.
String theory effective action; String loop corrections
Tseytlin, A.A. )
1988-01-01
The authors discuss the general ideology of the computation of string loop corrections to the effective action for the massless modes of the string. Both the S-matrix and the sigma-model approaches are presented. It is emphasized that the effective action is more general and better defined object than the S-matrix. In particular, it is finite in spite of modular infinities that may be present in loop amplitudes computed near a wrong vacuum. The case of the disc topology in the open-closed string theory is treated in some detail. Some issues concerning the soft dilation vertex operators related to the infinities of the string amplitudes are discussed.
Numerical study of the simplest string bit model
NASA Astrophysics Data System (ADS)
Chen, Gaoli; Sun, Songge
2016-05-01
String bit models provide a possible method to formulate a string as a discrete chain of pointlike string bits. When the bit number M is large, a chain behaves as a continuous string. We study the simplest case that has only one bosonic bit and one fermionic bit. The creation and annihilation operators are adjoint representations of the U (N ) color group. We show that the supersymmetry reduces the parameter number of a Hamiltonian from 7 to 3 and, at N =∞ , ensures a continuous energy spectrum, which implies the emergence of one spatial dimension. The Hamiltonian H0 is constructed so that in the large N limit it produces a world sheet spectrum with one Grassmann world sheet field. We concentrate on the numerical study of the model in finite N . For the Hamiltonian H0, we find that the would-be ground energy states disappear at N =(M -1 ) /2 for odd M ≤11 . Such a simple pattern is spoiled if H has an additional term ξ Δ H which does not affect the result of N =∞ . The disappearance point moves to higher (lower) N when ξ increases (decreases). Particularly, the ±(H0-Δ H ) cases suggest a possibility that the ground state could survive at large M and M ≫N . Our study reveals that the model has stringy behavior: when N is fixed and large enough, the ground energy decreases linearly with respect to M , and the excitation energy is roughly of order M-1. We also verify that a stable system of Hamiltonian ±H0+ξ Δ H requires ξ ≥∓1 .
Introduction to string field theory
Lykken, J.; Raby, S.
1986-01-01
An action is proposed for an interacting closed bosonic string. Our formalism relies heavily on ideas discussed by Witten for the open bosonic string. The gauge fixed quantum action for the fully interacting open bosonic string is obtained.
Comparing double string theory actions
NASA Astrophysics Data System (ADS)
De Angelis, L.; Gionti S. J, G.; Marotta, R.; Pezzella, F.
2014-04-01
Aimed to a deeper comprehension of a manifestly T-dual invariant formulation of string theory, in this paper a detailed comparison between the non-covariant action proposed by Tseytlin and the covariant one proposed by Hull is done. These are obtained by making both the string coordinates and their duals explicitly appear, on the same footing, in the world-sheet action, so "doubling" the string coordinates along the compact dimensions. After a discussion on the nature of the constraints in both the models and the relative quantization, it results that the string coordinates and their duals behave like "non-commuting" phase space coordinates but their expressions in terms of Fourier modes generate the oscillator algebra of the standard bosonic string. A proof of the equivalence of the two formulations is given. Furthermore, open-string solutions are also discussed.
Conformal counterterms and boundary conditions for open strings
de Beer, W.
1988-03-15
It is explained how Neumann boundary conditions still lead to the mixed boundary conditions required to calculate the functional determinants in the Polyakov model. Neumann boundary conditions on the conformal factor are obtained, thereby negating the need for a finite counterterm in the quantum bare action.
An Evolutionary Model Based on Bit-String with Intelligence
NASA Astrophysics Data System (ADS)
He, Mingfeng; Pan, Qiuhui; Yu, Binglin
An evolutionary model based on bit-strings with intelligence is set up in this paper. In this model, gene is divided into two parts which relative to health and intelligence. The accumulated intelligence influences the survival process by the effect of food and space restrictions. We modify the Verhulst factor to study this effect. Both asexual and sexual model are discussed in this paper. The results show that after many time steps, stability is reached and the population self-organizes, just like the standard Penna model. The intelligence made the equilibrium to be reached larger both in asexual model and sexual model. Compared with asexual model the population size fluctuates more strongly in the sexual model.
Are cosmic strings gravitationally stable topological defects?
NASA Astrophysics Data System (ADS)
Gleiser, Reinaldo; Pullin, Jorge
1989-08-01
A possible mechanism for the dissapearance of an open cosmic string into gravitational radiation is described. This involves the splitting of an infinite straight cosmic string into two pieces whose ends are traveling outward at the speed of light with the associated emission of a gravitational shock wave. This model can also be used to describe the following situations: (1) the development of a growing region of different string tension within a cosmic string, and (2) the creation of a cosmic string in an otherwise flat background.
Universality and string theory
NASA Astrophysics Data System (ADS)
Bachlechner, Thomas Christian
The first run at the Large Hadron Collider has deeply challenged conventional notions of naturalness, and CMB polarization experiments are about to open a new window to early universe cosmology. As a compelling candidate for the ultraviolet completion of the standard model, string theory provides a prime opportunity to study both early universe cosmology and particle physics. However, relating low energy observations to ultraviolet physics requires knowledge of the metastable states of string theory through the study of vacua. While it is difficult to directly obtain infrared data from explicit string theory constructions, string theory imposes constraints on low energy physics. The study of ensembles of low energy theories consistent with ultra-violet constraints provides insight on generic features we might expect to occur in string compactifications. In this thesis we present a statistical treatment of vacuum stability and vacuum properties in the context of random supergravity theories motivated by string theory. Early universe cosmology provides another avenue to high energy physics. From the low energy perspective large field inflation is typically considered highly unnatural: the scale relevant for the diameter of flat regions in moduli space is sub-Planckian in regions of perturbative control. To approach this problem, we consider generic Calabi-Yau compactifications of string theory and find that super-Planckian diameters of axion fundamental domains in fact arise generically. We further demonstrate that such super-Planckian flat regions are plausibly consistent with theWeak Gravity Conjecture.
Velocity-dependent models for non-Abelian/entangled string networks
Avgoustidis, A.; Shellard, E. P. S.
2008-11-15
We develop velocity-dependent models describing the evolution of string networks that involve several types of interacting strings, each with a different tension. These incorporate the formation of Y-type junctions with links stretching between colliding strings, while always ensuring energy conservation. These models can be used to describe network evolution for non-Abelian strings as well as cosmic superstrings. The application to Z{sub N} strings in which interactions are topologically constrained, demonstrates that a scaling regime is generally reached which involves a hierarchy of string densities with the lightest most abundant. We also study hybrid networks of cosmic superstrings, where energetic considerations are more important in determining interaction outcomes. We again find that networks tend towards scaling, with the three lightest network components being dominant and having comparable number densities, while the heavier string states are suppressed. A more quantitative analysis depends on the precise calculation of the string interaction matrix using the underlying string or field theory. Nevertheless, these results provide further evidence that the presence of junctions in a string network does not obstruct scaling.
Supersymmetry and String Theory: Beyond the Standard Model
NASA Astrophysics Data System (ADS)
Dine, Michael
2007-01-01
The past decade has witnessed dramatic developments in the field of theoretical physics. This book is a comprehensive introduction to these recent developments. It contains a review of the Standard Model, covering non-perturbative topics, and a discussion of grand unified theories and magnetic monopoles. It introduces the basics of supersymmetry and its phenomenology, and includes dynamics, dynamical supersymmetry breaking, and electric-magnetic duality. The book then covers general relativity and the big bang theory, and the basic issues in inflationary cosmologies before discussing the spectra of known string theories and the features of their interactions. The book also includes brief introductions to technicolor, large extra dimensions, and the Randall-Sundrum theory of warped spaces. This will be of great interest to graduates and researchers in the fields of particle theory, string theory, astrophysics and cosmology. The book contains several problems, and password protected solutions will be available to lecturers at www.cambridge.org/9780521858410. Provides reader with tools to confront limitations of the Standard Model Includes several exercises and problems Solutions are available to lecturers at www.cambridge.org/9780521858410
A numerical study of the string function using a primitive equation ocean model
NASA Astrophysics Data System (ADS)
Tyler, R. H.; Käse, R.
We use results from a primitive-equation ocean numerical model (SCRUM) to test a theoretical 'string function' formulation put forward by Tyler and Käse in another article in this issue. The string function acts as a stream function for the large-scale potential energy flow under the combined beta and topographic effects. The model results verify that large-scale anomalies propagate along the string function contours with a speed correctly given by the cross-string gradient. For anomalies having a scale similar to the Rossby radius, material rates of change in the layer mass following the string velocity are balanced by material rates of change in relative vorticity following the flow velocity. It is shown that large-amplitude anomalies can be generated when wind stress is resonant with the string function configuration.
Three family GUT-like models from heterotic string
Takahashi, Kei-Jiro
2008-05-13
We construct three-family SU(5) and SO(10) GUT-like models, based on an orbifold in the E{sub 8}xE{sub 8} heterotic string theory [28]. We recently classified orbifolds on the E{sub 6} root lattice. Interestingly, we found that some of the twisted sectors from the Z{sub 3}xZ{sub 3} orbifold on the E{sub 6} root lattice have just three fixed tori respectively, and it leads to three degenerate massless states. These models also include strongly coupled sectors in the low energy and messenger states charged with both hidden and visible sectors. We present the massless spectra of the models, and consider their interactions.
Heat string model of bi-dimensional dc Glidarc
NASA Astrophysics Data System (ADS)
Pellerin, S.; Richard, F.; Chapelle, J.; Cormier, J.-M.; Musiol, K.
2000-10-01
The gliding arc discharge (`Glidarc') is the subject of renewed interest in application to a variety of chemical reactions. The gliding arc creates a weakly ionized gas `string' between two horn-shaped electrodes. In this paper, we present a simple model for a bi-dimensional dc Glidarc working in air, in which the conducting zone of the discharge that is heated by the Joule effect is considered as a hot wire cooled by an air flow. Inside this wire, the heat transfer results from thermal conduction. The exchange of heat between the hot wire and the air flow is assured by convection and depends on the wire radius and the relative velocity of the arc with respect to the gas flow. The model correctly describes experimental results and allows us to predict the working parameters of the Glidarc in different experimental situations.
Cosmic strings in hidden sectors: 1. Radiation of standard model particles
Long, Andrew J.; Hyde, Jeffrey M.; Vachaspati, Tanmay E-mail: jmhyde@asu.edu
2014-09-01
In hidden sector models with an extra U(1) gauge group, new fields can interact with the Standard Model only through gauge kinetic mixing and the Higgs portal. After the U(1) is spontaneously broken, these interactions couple the resultant cosmic strings to Standard Model particles. We calculate the spectrum of radiation emitted by these ''dark strings'' in the form of Higgs bosons, Z bosons, and Standard Model fermions assuming that string tension is above the TeV scale. We also calculate the scattering cross sections of Standard Model fermions on dark strings due to the Aharonov-Bohm interaction. These radiation and scattering calculations will be applied in a subsequent paper to study the cosmological evolution and observational signatures of dark strings.
Rokhsar-Kivelson model of quantum dimers as a gas of free fermionic strings
Orland, P. The City University of New York, Baruch College, 17 Lexington Ave., New York, New York 10010 )
1994-02-01
The (2+1)-dimensional quantum dimer model on a square lattice, proposed by Rokhsar and Kivelson as a theory of layered superconductivity, is shown to be equivalent to a many-body theory of free, transversely oscillating strings obeying Fermi statistics. A Jordan-Wigner construction for string field operators is presented. Topological defects are shown to be linearly confined in pairs by dynamical strings. Exact upper and lower bounds are placed on the ground-state energy and the string tension. It is argued that the system is in a spin-fluid phase and that there is no gap in the excitation spectrum.
SUSY breaking in local string/F-theory models
NASA Astrophysics Data System (ADS)
Blumenhagen, R.; Conlon, J. P.; Krippendorf, S.; Moster, S.; Quevedo, F.
2009-09-01
We investigate bulk moduli stabilisation and supersymmetry breaking in local string/F-theory models where the Standard Model is supported on a del Pezzo surface or singularity. Computing the gravity mediated soft terms on the Standard Model brane induced by bulk supersymmetry breaking in the LARGE volume scenario, we explicitly find suppressions by Ms/MP ~ Script V-1/2 compared to M3/2. This gives rise to several phenomenological scenarios, depending on the strength of perturbative corrections to the effective action and the source of de Sitter lifting, in which the soft terms are suppressed by at least MP/Script V3/2 and may be as small as MP/Script V2. Since the gravitino mass is of order M3/2 ~ MP/Script V, for TeV soft terms all these scenarios give a very heavy gravitino (M3/2 >= 108 GeV) and generically the lightest moduli field is also heavy enough (m >= 10 TeV) to avoid the cosmological moduli problem. For TeV soft terms, these scenarios predict a minimal value of the volume to be Script V ~ 106-7 in string units, which would give a unification scale of order MGUT ~ MsScript V1/6 ~ 1016 GeV. The strong suppression of gravity mediated soft terms could also possibly allow a scenario of dominant gauge mediation in the visible sector but with a very heavy gravitino M3/2 > 1 TeV.
Affleck-Dine baryogenesis in type IIB string models
NASA Astrophysics Data System (ADS)
Allahverdi, Rouzbeh; Cicoli, Michele; Muia, Francesco
2016-06-01
We propose a possible string embedding of Affleck-Dine baryogenesis in type IIB sequestered models where the late-time decay of the lightest modulus reheats the universe to relatively low temperatures. We show that if inflation is driven by a blow-up Kähler modulus, the Affleck-Dine field can become tachyonic during inflation if the Kähler metric for matter fields has an appropriate inflaton-dependent contribution. We find that the Affleck-Dine mechanism can generate the observed baryon asymmetry for natural values of the underlying parameters which lead also to successful inflation and low-energy gaugino masses in a split supersymmetry scenario. The reheating temperature from the lightest modulus decay is high enough to allow thermal Higgsino-like dark matter.
Topological phase transitions in the golden string-net model.
Schulz, Marc Daniel; Dusuel, Sébastien; Schmidt, Kai Phillip; Vidal, Julien
2013-04-01
We examine the zero-temperature phase diagram of the two-dimensional Levin-Wen string-net model with Fibonacci anyons in the presence of competing interactions. Combining high-order series expansions around three exactly solvable points and exact diagonalizations, we find that the non-Abelian doubled Fibonacci topological phase is separated from two nontopological phases by different second-order quantum critical points, the positions of which are computed accurately. These trivial phases are separated by a first-order transition occurring at a fourth exactly solvable point where the ground-state manifold is infinitely many degenerate. The evaluation of critical exponents suggests unusual universality classes. PMID:25167030
Effects of perturbative exchanges in a QCD-string model
J. Weda; J. Tjon
2004-03-01
The QCD-string model for baryons derived by Simonov and used for the calculation of baryon magnetic moments in a previous paper is extended to include also perturbative gluon and meson exchanges. The mass spectrum of the baryon multiplet is studied. For the meson interaction either the pseudoscalar or pseudovector coupling is used. Predictions are compared with the experimental data. Besides these exchanges the influence of excited quark orbitals on the baryon ground state are considered by performing a multichannel calculation. The nucleon-Delta splitting increases due to the mixing of higher quark states while the baryon magnetic momenta decrease. The multichannel calculation with perturbative exchanges is shown to yield reasonable magnetic moments while the mass spectrum is close to experiment.
Frequency-Zooming ARMA Modeling for Analysis of Noisy String Instrument Tones
NASA Astrophysics Data System (ADS)
Esquef, Paulo A. A.; Karjalainen, Matti; Välimäki, Vesa
2003-12-01
This paper addresses model-based analysis of string instrument sounds. In particular, it reviews the application of autoregressive (AR) modeling to sound analysis/synthesis purposes. Moreover, a frequency-zooming autoregressive moving average (FZ-ARMA) modeling scheme is described. The performance of the FZ-ARMA method on modeling the modal behavior of isolated groups of resonance frequencies is evaluated for both synthetic and real string instrument tones immersed in background noise. We demonstrate that the FZ-ARMA modeling is a robust tool to estimate the decay time and frequency of partials of noisy tones. Finally, we discuss the use of the method in synthesis of string instrument sounds.
Sequestering by global symmetries in Calabi-Yau string models
NASA Astrophysics Data System (ADS)
Andrey, Christopher; Scrucca, Claudio A.
2011-10-01
We study the possibility of realizing an effective sequestering between visible and hidden sectors in generic heterotic string models, generalizing previous work on orbifold constructions to smooth Calabi-Yau compactifications. In these theories, genuine sequestering is spoiled by interactions mixing chiral multiplets of the two sectors in the effective Kähler potential. These effective interactions however have a specific current-current-like structure and can be interpreted from an M-theory viewpoint as coming from the exchange of heavy vector multiplets. One may then attempt to inhibit the emergence of generic soft scalar masses in the visible sector by postulating a suitable global symmetry in the dynamics of the hidden sector. This mechanism is however not straightforward to implement, because the structure of the effective contact terms and the possible global symmetries is a priori model-dependent. To assess whether there is any robust and generic option, we study the full dependence of the Kähler potential on the moduli and the matter fields. This is well known for orbifold models, where it always leads to a symmetric scalar manifold, but much less understood for Calabi-Yau models, where it generically leads to a non-symmetric scalar manifold. We then examine the possibility of an effective sequestering by global symmetries, and argue that whereas for orbifold models this can be put at work rather naturally, for Calabi-Yau models it can only be implemented in rather peculiar circumstances.
Nagao, G.
1988-07-15
We recalculate the bosonic one-loop open-string scattering amplitude using the results of the bosonic one-loop closed-string amplitude. The results show explicitly how the cancellation of divergences depends upon a set of involution-dependent constants which relate the torus to the cylinder and Moebius strip. Such a set of involution-dependent constants exists at each loop level and thus provides a means with which to study the cancellation of divergences and the connection between the world sheet and internal symmetries.
Interaction of π and K mesons and nucleons in the model of composite superconformal strings
NASA Astrophysics Data System (ADS)
Kudryavtsev, V. A.; Semenova, A. N.
2013-07-01
We construct a model of composite superconformal strings to describe hadron interaction amplitudes and the hadron spectrum. It belongs to a new class of dual (string) models and falls outside the scope of the usual approaches. In the framework of this model, the ordinary hadron scale of the order of 1GeV-2 is regarded as a string scale α'. The supersymmetry requirements are satisfied only on the two-dimensional world surface. We calculate interaction amplitudes of π and K mesons in the framework of the theory. We find a method for removing the baryon parity degeneracy.
Vachaspati, Tanmay
2009-09-15
Recent astrophysical observations have motivated novel theoretical models of the dark matter sector. A class of such models predicts the existence of GeV scale cosmic strings that communicate with the standard model sector by Aharonov-Bohm interactions with electrically charged particles. We discuss the cosmology of these 'dark strings' and investigate possible observational signatures. More elaborate dark sector models are argued to contain hybrid topological defects that may also have observational signatures.
Searching for inflation in simple string theory models: An astrophysical perspective
NASA Astrophysics Data System (ADS)
Hertzberg, Mark P.; Tegmark, Max; Kachru, Shamit; Shelton, Jessie; Özcan, Onur
2007-11-01
Attempts to connect string theory with astrophysical observation are hampered by a jargon barrier, where an intimidating profusion of orientifolds, Kähler potentials, etc. dissuades cosmologists from attempting to work out the astrophysical observables of specific string theory solutions from the recent literature. We attempt to help bridge this gap by giving a pedagogical exposition with detailed examples, aimed at astrophysicists and high energy theorists alike, of how to compute predictions for familiar cosmological parameters when starting with a 10-dimensional string theory action. This is done by investigating inflation in string theory, since inflation is the dominant paradigm for how early universe physics determines cosmological parameters. We analyze three explicit string models from the recent literature, each containing an infinite number of vacuum solutions. Our numerical investigation of some natural candidate inflatons, the so-called “moduli fields,” fails to find inflation. We also find in the simplest models that, after suitable field redefinitions, vast numbers of these vacua differ only in an overall constant multiplying the effective inflaton potential, a difference which affects neither the potential’s shape nor its ability to support slow-roll inflation. This illustrates that even having an infinite number of vacua does not guarantee having inflating ones. This may be an artifact of the simplicity of the models that we study. Instead, more complicated string theory models appear to be required, suggesting that identifying the inflating subset of the string landscape will be challenging.
String Theoretic Toy Models of the Big Bang
NASA Astrophysics Data System (ADS)
Michelson, Jeremy
2006-03-01
Recently, examples of toy cosmologies have been found that are exact solutions of String Theory. These solutions have the feature that the theoretical framework permits reliable calculation arbitrarily close to the big bang singularity. Thus one can understand both the big bang, and late time physics. I will describe these toy cosmologies, and how they fit into String Theory's chains of equivalences between gravitational and nongravitational theories. These equivalences are the means by which one theoretically probes the big bang.
Scalar geometry and masses in Calabi-Yau string models
NASA Astrophysics Data System (ADS)
Farquet, Daniel; Scrucca, Claudio A.
2012-09-01
We study the geometry of the scalar manifolds emerging in the no-scale sector of Kähler moduli and matter fields in generic Calabi-Yau string compactifications, and describe its implications on scalar masses. We consider both heterotic and orientifold models and compare their characteristics. We start from a general formula for the Kähler potential as a function of the topological compactification data and study the structure of the curvature tensor. We then determine the conditions for the space to be symmetric and show that whenever this is the case the heterotic and the orientifold models give the same scalar manifold. We finally study the structure of scalar masses in this type of geometries, assuming that a generic superpotential triggers spontaneous supersymmetry breaking. We show in particular that their behavior crucially depends on the parameters controlling the departure of the geometry from the coset situation. We first investigate the average sGoldstino mass in the hidden sector and its sign, and study the implications on vacuum metastability and the mass of the lightest scalar. We next examine the soft scalar masses in the visible sector and their flavor structure, and study the possibility of realizing a mild form of sequestering relying on a global symmetry.
Bianchi type-VIh string cloud cosmological models with bulk viscosity
NASA Astrophysics Data System (ADS)
Tripathy, Sunil K.; Behera, Dipanjali
2010-11-01
String cloud cosmological models are studied using spatially homogeneous and anisotropic Bianchi type VIh metric in the frame work of general relativity. The field equations are solved for massive string cloud in presence of bulk viscosity. A general linear equation of state of the cosmic string tension density with the proper energy density of the universe is considered. The physical and kinematical properties of the models have been discussed in detail and the limits of the anisotropic parameter responsible for different phases of the universe are explored.
Evidence for string substructure
Bergman, O.
1996-06-01
The author argues that the behavior of string theory at high temperature and high longitudinal boosts, combined with the emergence of p-branes as necessary ingredients in various string dualities, point to a possible reformulation of strings, as well as p-branes, as composites of bits. He reviews the string-bit models, and suggests generalizations to incorporate p-branes.
Strings in AdS{sub 3} and the SL(2,R) WZW Model. Part 1: The spectrum
Maldacena, Juan; Ooguri, Hirosi
2000-05-19
In this paper we study the spectrum of bosonic string theory on AdS{sub 3}. We study classical solutions of the SL(2,R) WZW model, including solutions for long strings with non-zero winding number. We show that the model has a symmetry relating string configurations with different winding numbers. We then study the Hilbert space of the WZW model, including all states related by the above symmetry. This leads to a precise description of long strings. We prove a no-ghost theorem for all the representations that are involved and discuss the scattering of the long string.
NASA Astrophysics Data System (ADS)
Inácio, O.; Antunes, J.; Wright, M. C. M.
2008-02-01
Most theoretical studies of bowed-string instruments deal with isolated strings, pinned on fixed supports. In others, the instrument body dynamics have been accounted by using extremely simplified models of the string-body interaction through the instrument bridge. Such models have, nevertheless, been instrumental to the understanding of a very common and musically undesirable phenomenon known as the wolf note—a strong beating interplay between string and body vibrations. Cellos, bad and good, are particularly prone to this problem. In previous work, a computational method that allows efficient time-domain modelling of bowed strings based on a modal approach has been introduced. This has been extended to incorporate the complex dynamics of real-life instrument bodies, and their coupling to the string motions, using experimental dynamical body data. The string is modelled using its unconstrained modes, assuming pinned-pinned boundary conditions at the tailpiece and the nut. At the intermediary bridge location, the string-body coupling is enforced using the body impulse-response or modal data, as measured at the instrument bridge. In the present paper, this computational approach is applied to a specific cello, which provided experimental wolf-behaviour data under several bowing conditions, as well as laboratory measurements of the bridge impulse responses on which the numerical simulations were based. Interesting aspects of the string-body dynamical responses are highlighted by numerical simulations and the corresponding sounds and animations produced. Finally, a qualitative (and, when possible, quantitative) comparison of the experimental and numerical results is presented.
A simple model for the evolution of a non-Abelian cosmic string network
NASA Astrophysics Data System (ADS)
Cella, G.; Pieroni, M.
2016-06-01
In this paper we present the results of numerical simulations intended to study the behavior of non-Abelian cosmic strings networks. In particular we are interested in discussing the variations in the asymptotic behavior of the system as we variate the number of generators for the topological defects. A simple model which allows for cosmic strings is presented and its lattice discretization is discussed. The evolution of the generated cosmic string networks is then studied for different values for the number of generators for the topological defects. Scaling solution appears to be approached in most cases and we present an argument to justify the lack of scaling for the residual cases.
Urrestilla, Jon; Bevis, Neil; Hindmarsh, Mark; Kunz, Martin E-mail: n.bevis@imperial.ac.uk E-mail: martin.kunz@physics.unige.ch
2011-12-01
We present a significant update of the constraints on the Abelian Higgs cosmic string tension by cosmic microwave background (CMB) data, enabled both by the use of new high-resolution CMB data from suborbital experiments as well as the latest results of the WMAP satellite, and by improved predictions for the impact of Abelian Higgs cosmic strings on the CMB power spectra. The new cosmic string spectra [1] were improved especially for small angular scales, through the use of larger Abelian Higgs string simulations and careful extrapolation. If Abelian Higgs strings are present then we find improved bounds on their contribution to the CMB anisotropies, fd{sup AH} < 0.095, and on their tension, Gμ{sub AH} < 0.57 × 10{sup −6}, both at 95% confidence level using WMAP7 data; and fd{sup AH} < 0.048 and Gμ{sub AH} < 0.42 × 10{sup −6} using all the CMB data. We also find that using all the CMB data, a scale invariant initial perturbation spectrum, n{sub s} = 1, is now disfavoured at 2.4σ even if strings are present. A Bayesian model selection analysis no longer indicates a preference for strings.
NASA Technical Reports Server (NTRS)
Bennett, David P.
1988-01-01
Cosmic strings are linear topological defects which are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characterisitc microwave background anisotropy. It was recently discovered that details of cosmic string evolution are very differnt from the so-called standard model that was assumed in most of the string-induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain.
Bennett, D.P.
1988-07-01
Cosmic strings are linear topological defects that are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation that are based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characteristic microwave background anistropy. It has recently been discovered by F. Bouchet and myself that details of cosmic string evolution are very different from the so-called ''standard model'' that has been assumed in most of the string induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain. 29 refs., 9 figs.
p{sub t}-Multiplicity correlations in a multi-pomeron-exchange model with string collective effects
Armesto, N.; Derkach, D. A.; Feofilov, G. A.
2008-12-15
The
N{sub ch} - N{sub ch} correlations experimentally observed in the central rapidity region in pp and pp-bar collisions, in a wide energy range from the ISR to Tevatron, are described in the framework of a multi-Pomeron exchange model in which string collectivity has been included in an effective way. Three parameters are obtained from the fit to data: the string tension, the average number of particles per string, and a parameter which effectively introduces string collective effects. The model successfully reproduces the rise of
of charged particles, the flattening with growing rapidity density of charged particles and with the collision energy, and the negative p{sub t}-N{sub ch} correlation at low energies. The string tension and the average number of particles per string are energy independent, while the parameter that includes effectively string collective effects shows a smooth increasing behavior with energy.
Modeling of tension-modulated strings using finite difference and digital waveguide techniques
NASA Astrophysics Data System (ADS)
Pakarinen, Jyri
2005-09-01
Tension modulation is a nonlinear phenomenon where large-amplitude string vibrations cause the tension of the string to vary. This results in an initial pitch glide and energy coupling between modes, causing for example the generation of missing harmonics. The presentation discusses two methods for numerical simulation of the tension modulation nonlinearity from the sound synthesis point of view. The tension modulation is assumed to propagate instantaneously along the string. In the digital waveguide approach, spatially distributed fractional delay filters are used in modulating the string length during run time. Energy-preserving techniques can be used in implementing the fractional delays. In the finite difference approach, time-domain interpolation is used to artificially modulate the wave propagation velocity. The generation of missing harmonics is implemented in the finite difference model by creating an additional excitation point at the string termination. In the waveguide model, the same effect can be obtained by using suitable approximations in the string elongation calculation. Synthesis results for both techniques are presented. Also, a brief comparison of the models with a discussion on stability issues is provided. [This research has been funded by the Academy of Finland (Project No. 104934), S3TK graduate school, and Tekniikan edistamissaatio.
Stringly restrictions on the backgrounds in the heterotic sigma model
Sengupta, S. ); Majumdar, P. )
1992-03-21
This paper shows that for the heterotic string theory in the presence of arbitrary background gauge, gravitational and antisymmetric tensor fields, truncated by a general coordinate dependent compactification a la Scherk-Schwarz, the requirement of 2D conformal invariance is as restrictive as to inhibit supersymmetry breaking with vanishing cosmological constant.
Towards a nonsupersymmetric string phenomenology
NASA Astrophysics Data System (ADS)
Abel, Steven; Dienes, Keith R.; Mavroudi, Eirini
2015-06-01
Over the past three decades, considerable effort has been devoted to studying the rich and diverse phenomenologies of heterotic strings exhibiting spacetime supersymmetry. Unfortunately, during this same period, there has been relatively little work studying the phenomenologies associated with their nonsupersymmetric counterparts. The primary reason for this relative lack of attention is the fact that strings without spacetime supersymmetry are generally unstable, exhibiting large one-loop dilaton tadpoles. In this paper, we demonstrate that this hurdle can be overcome in a class of tachyon-free four-dimensional string models realized through coordinate-dependent compactifications. Moreover, as we shall see, it is possible to construct models in this class whose low-lying states resemble the Standard Model (or even potential unified extensions thereof)—all without any light superpartners, and indeed without supersymmetry at any energy scale. The existence of such models thus opens the door to general studies of nonsupersymmetric string phenomenology, and in this paper we proceed to discuss a variety of theoretical and phenomenological issues associated with such nonsupersymmetric strings. On the theoretical side, we discuss the finiteness properties of such strings, the general characteristics of their mass spectra, the magnitude and behavior of their one-loop cosmological constants, and their interpolation properties. By contrast, on the phenomenological side, the properties we discuss are more model-specific and include their construction techniques, their natural energy scales, their particle and charge assignments, and the magnitudes of their associated Yukawa couplings and scalar masses.
Effect of dark strings on semilocal strings
Brihaye, Yves; Hartmann, Betti
2009-12-15
Dark strings have recently been suggested to exist in new models of dark matter that explain the excessive electronic production in the Galaxy. We study the interaction of these dark strings with semilocal strings which are solutions of the bosonic sector of the standard model in the limitsin{sup 2}{theta}{sub w}=1, where {theta}{sub w} is the Weinberg angle. While embedded Abelian-Higgs strings exist for generic values of the coupling constants, we show that semilocal solutions with nonvanishing condensate inside the string core exist only above a critical value of the Higgs to gauge boson mass ratio when interacting with dark strings. Above this critical value, which is greater than unity, the energy per unit length of the semilocal-dark string solutions is always smaller than that of the embedded Abelian-Higgs-dark string solutions and we show that Abelian-Higgs-dark strings become unstable above this critical value. Different from the noninteracting case, we would thus expect semilocal strings to be stable for values of the Higgs to gauge boson mass ratio larger than unity. Moreover, the one-parameter family of solutions present in the noninteracting case ceases to exist when semilocal strings interact with dark strings.
Jackson, Mark G.
2007-04-15
The spectrum of (p,q) bound states of F- and D-strings has a distinctive square-root tension formula that is hoped to be a hallmark of fundamental cosmic strings. We point out that the Bogomol'nyi-Prasad-Sommerfield (BPS) bound for vortices in N=2 supersymmetric Abelian-Higgs models also takes the square-root form. In contrast to string theory, the most general supersymmetric field theoretic model allows for (p,q,r) strings, with three classes of strings rather than two. Unfortunately, we find that there do not exist BPS solutions except in the trivial case. The issue of whether there exist non-BPS solutions which may closely resemble the square-root form is left as an open question.
Two exercises in supersymmetry: a low-energy supergravity model and free string field theory
Preitschopf, C.R.
1986-09-01
The new features of a supersymmetric standard model in the presence of heavy families are studied. The minimal set of Higgs fields, the desert between the electroweak and the grand unification scale and perturbative values of the dimensionless parameters throughout this region are assumed. Using the numerical as well as the approximate analytic solution of the renormalization group equations, the evolution of all the parameters of the theory are studied in the case of large Yukawa couplings for the fourth family. The desired spontaneous symmetry breaking of the electroweak symmetry takes place only for a rather unnatural choice of the initial values of certain mass parameters at the grand unification scale. If it is gravitino mass smaller than 200 GeV the vacuum expectation values of the Higgs fields emerge necessarily in an interplay of the tree level Higgs potential and its quantum corrections and are approximately equal. The qurak masses of the fourth family are roughly 135 GeV, while the mass of the fourth charged lepton has an upper bound of 90 GeV. Further characteristic features of this scenario are one light neutral Higgs field of mass 50 GeV and gluino masses below 75 GeV. If the gravitino mass is higher than 200 GeV one obtains a scaled up version of the well-known three family, heavy top scenario with quark masses between 40 and 205 GeV and all superparticle masses heavier than 150 GeV except the photino, gluino, one chargino and one neutralino. The gauge-invariant theory of the free bosonic open string is generalized to treat closed strings and superstrings. All of these theories can be written as theories of string differential forms defined on suitable spaces. All of the bosonic theories have exactly the same structure; the Ramond theory takes an analogous first-order form. We show explicitly, how to gauge-fix each action to the light-cone gauge and to the Feynman-Siegel gauge.
String resonances at hadron colliders
NASA Astrophysics Data System (ADS)
Anchordoqui, Luis A.; Antoniadis, Ignatios; Dai, De-Chang; Feng, Wan-Zhe; Goldberg, Haim; Huang, Xing; Lüst, Dieter; Stojkovic, Dejan; Taylor, Tomasz R.
2014-09-01
We consider 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. Assuming that the fundamental string mass scale Ms is in the TeV range and that the theory is weakly coupled, we discuss possible signals of string physics at the upcoming HL-LHC run (integrated luminosity =3000 fb-1) with a center-of-mass energy of √s =14 TeV and at potential future pp colliders, HE-LHC and VLHC, operating at √s =33 and 100 TeV, respectively (with the same integrated luminosity). In such D-brane constructions, the dominant contributions to full-fledged string amplitudes for all the common QCD parton subprocesses leading to dijets and γ +jet are completely independent of the details of compactification and can be evaluated in a parameter-free manner. We make use of these amplitudes evaluated near the first (n=1) and second (n=2) resonant poles to determine the discovery potential for Regge excitations of the quark, the gluon, and the color singlet living on the QCD stack. We show that for string scales as large as 7.1 TeV (6.1 TeV) lowest massive Regge excitations are open to discovery at the ≥5σ in dijet (γ +jet) HL-LHC data. We also show that for n=1 the dijet discovery potential at HE-LHC and VLHC exceedingly improves: up to 15 TeV and 41 TeV, respectively. To compute the signal-to-noise ratio for n=2 resonances, we first carry out a complete calculation of all relevant decay widths of the second massive level string states (including decays into massless particles and a massive n=1 and a massless particle), where we rely on factorization and conformal field theory techniques. Helicity wave functions of arbitrary higher spin massive bosons are also constructed. We demonstrate that for string scales Ms≲10.5 TeV (Ms≲28 TeV) detection of n =2 Regge recurrences at HE-LHC (VLHC) would become the smoking gun for D
Modelling of helium-mediated quench propagation in the LHC prototype test string-1
NASA Astrophysics Data System (ADS)
Chorowski, M.; Grzegory, P.; Serio, L.; van Weelderen, R.
2000-08-01
The Large Hadron Collider (LHC) prototype test string-1, hereafter referred to as the string, is composed of three 10-m long prototype dipole magnets and one 6-m long prototype quadrupole magnet. The magnets are immersed in a pressurized static bath of superfluid helium that is maintained at a pressure of about 1 bar and at a temperature of about 1.9 K. This helium bath constitutes one single hydraulic unit, extending along 42.5 m of the string length. We have measured the triggering of quenches of the string magnets due to the quenching of a single dipole magnet located at the string's extremity, i.e., "quench propagation". Previously reported measurements enabled to establish that in this configuration the quench propagation is mediated by the helium and not by the inter-magnet bus bar connections [L. Coull, D. Hagedorn, G. Krainz, F. Rodriguez-Mateos, R. Schmidt, Quench propagation tests on the LHC superconducting magnet string, in: S. Myers, A. Pacheco, R. Pascual, C. Petit-Jean-Genaz, J. Poole (Eds.), Fifth European Particle Accelerator Conference - EPAC '96, Sitges, Barcelona, Spain, 10-14 June 1996, IOP, Bristol, 1996; F. Rodriguez-Mateos, R. Schmidt, L. Serio, Thermo-hydraulic quench propagation at the LHC superconducting magnet string, in: D. Dew-Hughes, R.G. Scurlock, J.H.P. Watson (Eds), 17th International Cryogenic Engineering Conference (ICEC-17), Bournemouth, UK, 14-17 July 1998, IOP, Bristol, 1998]. We present a model of helium-mediated quench propagation based on the qualitative conclusions of these two previous papers, and on additional information gained from a dedicated series of quench propagation measurements that were not previously reported. We will discuss the specific mechanisms and their main parameters involved at different timescales of the propagation process, and apply the model to make quantitative predictions.
Contact interactions in low scale string models with intersecting D6-branes
Chemtob, M.
2008-12-15
We evaluate the tree level four fermion string amplitudes in the TeV string mass scale models with intersecting D6-branes. The coefficient functions of contact interactions subsuming the contributions of string Regge resonance and winding mode excitations are obtained by subtracting out the contributions from the string massless and massive momentum modes. Numerical applications are developed for the standard-model-like solution of Cremades, Ibanez, and Marchesano for a toroidal orientifold with four intersecting D6-brane stacks. The chirality conserving contact interactions of the quarks and leptons are considered in applications to high-energy collider and flavor changing neutral current phenomenology. The two main free parameters consist of the string and compactification mass scales, m{sub s} and M{sub c}. Useful constraints on these parameters are derived from predictions for the Bhabha scattering differential cross section and for the observables associated to the mass shifts of the neutral meson systems K-K, B-B, D-D and the lepton number violating three-body leptonic decays of the charged leptons {mu} and {tau}.
Bit-strings and other modifications of Viviane model for language competition
NASA Astrophysics Data System (ADS)
de Oliveira, P. M. C.; Stauffer, D.; Lima, F. W. S.; Sousa, A. O.; Schulze, C.; Moss de Oliveira, S.
2007-03-01
The language competition model of Viviane de Oliveira et al. is modified by associating with each language a string of 32 bits. Whenever a language changes in this Viviane model, also one randomly selected bit is flipped. If then only languages with different bit-strings are counted as different, the resulting size distribution of languages agrees with the empirically observed slightly asymmetric log-normal distribution. Several other modifications were also tried but either had more free parameters or agreed less well with reality.
Torsional vibrations of helically buckled drill-strings: experiments and FE modelling
NASA Astrophysics Data System (ADS)
Kapitaniak, M.; Hamaneh, V. V.; Wiercigroch, M.
2016-05-01
This paper presents investigations of a complex drill-string vibrations on a novel experimental rig, developed by the Centre for Applied Dynamics Research at the University of Aberdeen. The rig is capable of exhibiting of all major types of drill-string vibrations, including torsional, axial and lateral modes. The importance of this work lies in the fact, that the experimental rig utilizes real industrial drill-bits and rock samples, which after careful identification of Torque On Bit (TOB) speed curves, allows to use an equivalent friction model to accommodate for both frictional and cutting components of the bit-rock interactions. Moreover, the proposed Finite Element model, after a careful calibration, is capable of replicating experimental results, for the prebuckled configuration of the drill-string. This allows us to observe the effect of winding and unwinding of the helical deformation during stick-slip motion.
Dynamics of Anisotropic Bianchi Type-III Bulk Viscous String Model with Magnetic Field
NASA Astrophysics Data System (ADS)
Singh, M. K.; Ram, Shri
2014-07-01
In this paper, we discuss the dynamics of spatially homogeneous and anisotropic Bianchi type-III string cosmological model in presence of bulk viscous fluid and electromagnetic field. Exact solutions of Einstein's field equations are obtained by assuming (i) a special form of the deceleration parameter and (ii) the component of the shear scalar tensor is proportional to mean Hubble parameter. The source of magnetic field is due to an electric current produced along z-axis. The role of bulk viscosity and magnetic field in establishing string phase of universe is presented. The physical and kinematical features of solutions are also discussed in detail.
The string prediction models as invariants of time series in the forex market
NASA Astrophysics Data System (ADS)
Pincak, R.
2013-12-01
In this paper we apply a new approach of string theory to the real financial market. The models are constructed with an idea of prediction models based on the string invariants (PMBSI). The performance of PMBSI is compared to support vector machines (SVM) and artificial neural networks (ANN) on an artificial and a financial time series. A brief overview of the results and analysis is given. The first model is based on the correlation function as invariant and the second one is an application based on the deviations from the closed string/pattern form (PMBCS). We found the difference between these two approaches. The first model cannot predict the behavior of the forex market with good efficiency in comparison with the second one which is, in addition, able to make relevant profit per year. The presented string models could be useful for portfolio creation and financial risk management in the banking sector as well as for a nonlinear statistical approach to data optimization.
Numerical analysis of the double scaling limit in the string type IIB matrix model.
Horata, S; Egawa, H S
2001-05-14
The bosonic IIB matrix model is studied using a numerical method. This model contains the bosonic part of the IIB matrix model conjectured to be a nonperturbative definition of the type IIB superstring theory. The large N scaling behavior of the model is shown performing a Monte Carlo simulation. The expectation value of the Wilson loop operator is measured and the string tension is estimated. The numerical results show the prescription of the double scaling limit. PMID:11384258
A Hybrid Resynthesis Model for Hammer-String Interaction of Piano Tones
NASA Astrophysics Data System (ADS)
Bensa, Julien; Jensen, Kristoffer; Kronland-Martinet, Richard
2004-12-01
This paper presents a source/resonator model of hammer-string interaction that produces realistic piano sound. The source is generated using a subtractive signal model. Digital waveguides are used to simulate the propagation of waves in the resonator. This hybrid model allows resynthesis of the vibration measured on an experimental setup. In particular, the nonlinear behavior of the hammer-string interaction is taken into account in the source model and is well reproduced. The behavior of the model parameters (the resonant part and the excitation part) is studied with respect to the velocities and the notes played. This model exhibits physically and perceptually related parameters, allowing easy control of the sound produced. This research is an essential step in the design of a complete piano model.
Bensa, Julien; Bilbao, Stefan; Kronland-Martinet, Richard; Smith, Julius O
2003-08-01
A model of transverse piano string vibration, second order in time, which models frequency-dependent loss and dispersion effects is presented here. This model has many desirable properties, in particular that it can be written as a well-posed initial-boundary value problem (permitting stable finite difference schemes) and that it may be directly related to a digital waveguide model, a digital filter-based algorithm which can be used for musical sound synthesis. Techniques for the extraction of model parameters from experimental data over the full range of the grand piano are discussed, as is the link between the model parameters and the filter responses in a digital waveguide. Simulations are performed. Finally, the waveguide model is extended to the case of several coupled strings. PMID:12942987
Homotopy Classification of Bosonic String Field Theory
NASA Astrophysics Data System (ADS)
Münster, Korbinian; Sachs, Ivo
2014-09-01
We prove the decomposition theorem for the loop homotopy Lie algebra of quantum closed string field theory and use it to show that closed string field theory is unique up to gauge transformations on a given string background and given S-matrix. For the theory of open and closed strings we use results in open-closed homotopy algebra to show that the space of inequivalent open string field theories is isomorphic to the space of classical closed string backgrounds. As a further application of the open-closed homotopy algebra, we show that string field theory is background independent and locally unique in a very precise sense. Finally, we discuss topological string theory in the framework of homotopy algebras and find a generalized correspondence between closed strings and open string field theories.
Modeling of wave propagation in drill strings using vibration transfer matrix methods.
Han, Je-Heon; Kim, Yong-Joe; Karkoub, Mansour
2013-09-01
In order to understand critical vibration of a drill bit such as stick-slip and bit-bounce and their wave propagation characteristics through a drill string system, it is critical to model the torsional, longitudinal, and flexural waves generated by the drill bit vibration. Here, a modeling method based on a vibration transfer matrix between two sets of structural wave variables at the ends of a constant cross-sectional, hollow, circular pipe is proposed. For a drill string system with multiple pipe sections, the total vibration transfer matrix is calculated by multiplying all individual matrices, each is obtained for an individual pipe section. Since drill string systems are typically extremely long, conventional numerical analysis methods such as a finite element method (FEM) require a large number of meshes, which makes it computationally inefficient to analyze these drill string systems numerically. The proposed "analytical" vibration transfer matrix method requires significantly low computational resources. For the validation of the proposed method, experimental and numerical data are obtained from laboratory experiments and FEM analyses conducted by using a commercial FEM package, ANSYS. It is shown that the modeling results obtained by using the proposed method are well matched with the experimental and numerical results. PMID:23967925
The Area Law in Matrix Models for Large N QCD Strings
NASA Astrophysics Data System (ADS)
Anagnostopoulos, K. N.; Bietenholz, W.; Nishimura, J.
We study the question whether matrix models obtained in the zero volume limit of 4d Yang-Mills theories can describe large N QCD strings. The matrix model we use is a variant of the Eguchi-Kawai model in terms of Hermitian matrices, but without any twists or quenching. This model was originally proposed as a toy model of the IIB matrix model. In contrast to common expectations, we do observe the area law for Wilson loops in a significant range of scale of the loop area. Numerical simulations show that this range is stable as N increases up to 768, which strongly suggests that it persists in the large N limit. Hence the equivalence to QCD strings may hold for length scales inside a finite regime.
[The string of Einthoven's string galvanometer].
Wyers, P J
1996-01-01
The Dutch physiologist Willem Einthoven (1860-1927) published in 1901 his construction of a string galvanometer. With this apparatus he opened the era for electrocardiography. As the quality of his instrument largely depended on the string of the string galvanometer it is surprising to note that in his publications Einthoven never mentioned the exact way of producing the string. However, Einthoven's hand written laboratory notes are preserved at the Museum Boerhaave in Leiden. From these notes it comes clear what problems Einthoven had with the string. To get a very thin thread of quarts he first used the method of shooting the thread as was described by Boys (1887), later the blowing method of Nichols (1894). The silvering of the thread was done first chemically, later by cathode spray. In all cases premature breaking of the thread was a nuisance. Because of these failures Einthoven might have decided not to publish any details. PMID:11624925
NASA Astrophysics Data System (ADS)
Andronov, E.; Vechernin, V.
2016-01-01
The long-range rapidity correlations between the multiplicities (n-n) and the transverse momentum and the multiplicity (pT-n) of charge particles are analyzed in the framework of the simple string inspired model with two types of sources. The sources of the first type correspond to the initial strings formed in a hadronic collision. The sources of the second type imitate the appearance of the emitters of a new kind resulting from interaction (fusion) of the initial strings. The model enabled to describe effectively the influence of the string fusion effects on the strength both the n-n and the pT-n correlations. It was found that in the region, where the process of string fusion comes into play, the calculation results predict the non-monotonic behaviour of the n-n and pT-n correlation coefficients with the growth of the mean number of initial strings, i.e. with the increase of the collision centrality. It was shown also that the increase of the event-by-event fluctuation in the number of primary strings leads to the change of the pT-n correlation sign from negative to positive. One can try to search these signatures of string collective phenomena in interactions of various nuclei at different energies varying the class of collision centrality and its width.
Complexity of chromatin folding is captured by the strings and binders switch model.
Barbieri, Mariano; Chotalia, Mita; Fraser, James; Lavitas, Liron-Mark; Dostie, Josée; Pombo, Ana; Nicodemi, Mario
2012-10-01
Chromatin has a complex spatial organization in the cell nucleus that serves vital functional purposes. A variety of chromatin folding conformations has been detected by single-cell imaging and chromosome conformation capture-based approaches. However, a unified quantitative framework describing spatial chromatin organization is still lacking. Here, we explore the "strings and binders switch" model to explain the origin and variety of chromatin behaviors that coexist and dynamically change within living cells. This simple polymer model recapitulates the scaling properties of chromatin folding reported experimentally in different cellular systems, the fractal state of chromatin, the processes of domain formation, and looping out. Additionally, the strings and binders switch model reproduces the recently proposed "fractal-globule" model, but only as one of many possible transient conformations. PMID:22988072
Propagation of cosmic rays through the atmosphere in the quark-gluon strings model
NASA Technical Reports Server (NTRS)
Erlykin, A. D.; Krutikova, N. P.; Shabelski, Y. M.
1985-01-01
The quark-gluon strings model succeeds in the description of multiple hadron production in the central rapidity region of nucleon-nucleon interctions. This model was developed for hadron-nucleus interactions and used for calculation of the cosmic ray propagation through the atmosphere. It is shown that at energies 10 to the 11th power to the 12th power eV, this model gives a satisfactory description of experimental data. But with the increase of the energy up to approximately 10 to the 14th power eV, results of calculations and of experiments begin to differ and this difference rises with the energy. It may indicate that the scaling violation in the fragmentation region of inclusive spectra for hadron-nucleus interactions is stronger than in the quark-gluon strings model.
Martins, R. A.
2007-08-15
The recent extension of the standard model to include massive neutrinos in the framework of noncommutative geometry and the spectral action principle involves new scalar fields and their interactions with the usual complex scalar doublet. After ensuring that they bring no unphysical consequences, we address the question of how these fields affect the physics predicted in the Weinberg-Salam theory, particularly in the context of the electroweak phase transition. Applying the Dolan-Jackiw procedure, we calculate the finite temperature corrections, and find that the phase transition is first order. The new scalar interactions significantly improve the stability of the electroweak Z string, through the 'bag' phenomenon described by Vachaspati and Watkins ['Bound states can stabilize electroweak strings', Phys. Lett. B 318, 163-168 (1993)]. (Recently, cosmic strings have climbed back into interest due to a new evidence.) Sourced by static embedded strings, an internal space analogy of Cartan's torsion is drawn, and a possible Higgs-force-like 'gravitational' effect of this nonpropagating torsion on the fermion masses is described. We also check that the field generating the Majorana mass for the {nu}{sub R} is nonzero in the physical vacuum.
Energy Science and Technology Software Center (ESTSC)
2014-09-19
This software record documents the OpenStudio fault model development portion of the Fault Detection and Diagnostics LDRD project.The software provides a suite of OpenStudio measures (scripts) for modeling typical HVAC system faults in commercial buildings and also included supporting materials: example projects and OpenStudio measures for reporting fault costs and energy impacts.
Mirage Models Confront the LHC: The Phenomenology of String-Motivated Effective Field Theories
NASA Astrophysics Data System (ADS)
Kaufman, Bryan
In this dissertation, I study a class of string-motivated effective supergravity theories in light of data from the LHC. I will consider three models that exhibit so-called 'mirage mediation'. I first consider the Binetruy-Gaillard-Wu (BGW) model, a model arising from heterotic string theory in which the dilaton is stabilized via non-perturbative corrections to the Kahler metric. I then consider the Kachru-Kallosh-Linde-Trivedi (KKLT) model, a model of Type-IIB string theory compactified on a Calabi-Yau orientifold, and an extension known as deflected mirage mediation (DMM) where contributions from gauge mediation are added to those arising from gravity mediation and anomaly mediation. The sequence of these three models allows an exploration in which the three dominant methods of communicating SUSY breaking appear in differing ratios. For each model, I outline the extent to which the phenomenologically-motived parameter space can be ruled out by existing experimental data before discussing how the remaining parameter space may be probed by continuing studies at the LHC and dark matter direct detection experiments.
Kantowski-Sachs bulk viscous string cosmological model in f(R,T) gravity
NASA Astrophysics Data System (ADS)
Reddy, D. R. K.; Anitha, S.; Umadevi, S.
2014-05-01
A spatially homogenous and anisotropic Kantowski-Sachs space-time is considered in the presence of bulk viscous fluid containing one-dimensional cosmic strings in the framework of the f ( R, T) gravity proposed by Harko et al. (Phys. Rev. D 84, 024020, (2011)). Some physically plausible conditions have been used to obtain a determinate solution of the field equations. A cosmological model, in this theory, is presented and some physical and kinematical properties of the model are also studied.
Light-light and heavy-light mesons in the model of QCD string with quarks at the ends
NASA Astrophysics Data System (ADS)
Nefediev, A. V.
2002-06-01
The variational einbein field method is applied to the model of the QCD string with quarks at the ends for the case of light-light and heavy-light mesons. Special attention is payed to the proper string dynamics. The correct string slope of the Regge trajectories is reproduced for light-light states which comes out from the picture of rotating string. Masses of several low-lying orbitally and radially excited states in the D, Ds, B, and Bs meson spectra are calculated and a good agreement with the experimental data as well as with recent lattice calculations is found. The role of the string correction to the interquark interaction is discussed at the example of the identification of D*' (2637) state recently claimed by DELPHI Collaboration. For the heavy-light mesons the standard constants used in Heavy Quark Effective Theory are extracted and compared to the results of other approaches.
Gauge coupling unification in heterotic string models with gauge mediated supersymmetry breaking
Anandakrishnan, Archana; Raby, Stuart
2011-04-01
We calculate the weak scale minimal supersymmetric standard model spectrum starting from a heterotic string theory compactified on an anisotropic orbifold. Supersymmetry breaking is mediated by vectorlike exotics that arise naturally in heterotic string theories. The messengers that mediate supersymmetry breaking come in incomplete grand unified theory (GUT) multiplets and give rise to nonuniversal gaugino masses at the GUT scale. Models with nonuniversal gaugino masses at the GUT scale have the attractive feature of allowing for precision gauge coupling unification at the GUT scale with negligible contributions from threshold corrections near the unification scale. The unique features of this minimally supersymmetric standard model spectrum are light gluinos and also large mass differences between the lightest and the next-to-lightest neutralinos and charginos which could lead to interesting signatures at the colliders.
Semilocal cosmic string networks
Achucarro, Ana; Salmi, Petja; Urrestilla, Jon
2007-06-15
We report on a large-scale numerical study of networks of semilocal cosmic strings in flat space in the parameter regime in which they are perturbatively stable. We find a population of segments with an exponential length distribution and indications of a scaling network without significant loop formation. Very deep in the stability regime strings of superhorizon size grow rapidly and ''percolate'' through the box. We believe these should lead at late times to a population of infinite strings similar to topologically stable strings. However, the strings are very light; scalar gradients dominate the energy density, and the network has thus a global texturelike signature. As a result, the observational constraints, at least from the temperature power spectrum of the cosmic microwave background, on models predicting semilocal strings should be closer to those on global textures or monopoles, rather than on topologically stable gauged cosmic strings.
AdS5×S(5) mirror model as a string sigma model.
Arutyunov, Gleb; van Tongeren, Stijn J
2014-12-31
Doing a double Wick rotation in the world sheet theory of the light cone AdS5×S(5) superstring results in an inequivalent, so-called mirror theory that plays a central role in the field of integrability in the AdS-CFT correspondence. We show that this mirror theory can be interpreted as the light cone theory of a free string on a different background. This background is related to dS5×H(5) by a double T-duality, and has hidden supersymmetry. The geometry can also be extracted from an integrable deformation of the AdS5×S(5) sigma model, and we prove the observed mirror duality of these deformed models at the bosonic level as a byproduct. While we focus on AdS5×S(5), our results apply more generally. PMID:25615306
Mirage Models Confront the LHC: Kähler-Stabilized Heterotic String Theory
NASA Astrophysics Data System (ADS)
Kaufman, Bryan; Nelson, Brent
2013-04-01
We begin the study of a class of string-motivated effective supergravity theories in light of current data from the CERN Large Hadron Collider (LHC). In particular, the case of heterotic string theory in which the dilaton is stabilized via non-perturbative corrections to the Kähler metric will be discussed. This model is highly constrained and therefore predictive. We find that most of the reasonable parameter space afforded to the model - representing the strong dynamics of a presumed gaugino condensation in the hidden sector - is now observationally disfavored by the LHC results. What limited parameter space that remains will be definitively explored within the first year of operation at √{ s} = 13 TeV , and much will be explored even before data-taking ends in 2013. Expected signatures for a number of benchmark points are discussed. This represents the first example of an explicit string-based model with the potential to be falsified by observational data. We find that the surviving space of the model makes a precise prediction as to the relation of many superpartner masses, as well as the manner in which the correct dark matter relic density is obtained. Implications for current and future dark matter search experiments are discussed.
Mirage Models Confront the LHC: Kähler-Stabilized Heterotic String Theory
NASA Astrophysics Data System (ADS)
Kaufman, Bryan; Nelson, Brent
2013-04-01
We begin the study of a class of string-motivated effective supergravity theories in light of current data from the CERN Large Hadron Collider (LHC). In particular, the case of heterotic string theory in which the dilaton is stabilized via non-perturbative corrections to the Kähler metric will be discussed. This model is highly constrained and therefore predictive. We find that most of the reasonable parameter space afforded to the model -- representing the strong dynamics of a presumed gaugino condensation in the hidden sector -- is now observationally disfavored by the LHC results. What limited parameter space that remains will be definitively explored within the first year of operation at √s = 13,, and much will be explored even before data-taking ends in 2013. Expected signatures for a number of benchmark points are discussed. This represents the first example of an explicit string-based model with the potential to be falsified by observational data. We find that the surviving space of the model makes a precise prediction as to the relation of many superpartner masses, as well as the manner in which the correct dark matter relic density is obtained. Implications for current and future dark matter search experiments are discussed.
String states, loops and effective actions in noncommutative field theory and matrix models
NASA Astrophysics Data System (ADS)
Steinacker, Harold C.
2016-09-01
Refining previous work by Iso, Kawai and Kitazawa, we discuss bi-local string states as a tool for loop computations in noncommutative field theory and matrix models. Defined in terms of coherent states, they exhibit the stringy features of noncommutative field theory. This leads to a closed form for the 1-loop effective action in position space, capturing the long-range non-local UV/IR mixing for scalar fields. The formalism applies to generic fuzzy spaces. The non-locality is tamed in the maximally supersymmetric IKKT or IIB model, where it gives rise to supergravity. The linearized supergravity interactions are obtained directly in position space at one loop using string states on generic noncommutative branes.
NASA Astrophysics Data System (ADS)
March, N. H.; Moreno, A. J.
2016-06-01
The critical exponent ν for randomly branched polymers with dimensionality d equal to 3, is known exactly as 1/2. Here, we invoke an already available string theory model to predict the remaining static critical exponents. Utilizing results of Hsu et al. (Comput Phys Commun. 2005;169:114-116), results are added for d = 8. Experiment plus simulation would now be important to confirm, or if necessary to refine, the proposed values.
Bevis, Neil; Hindmarsh, Mark; Kunz, Martin; Urrestilla, Jon
2007-03-15
We present the first field-theoretic calculations of the contribution made by cosmic strings to the temperature power spectrum of the cosmic microwave background (CMB). Unlike previous work, in which strings were modeled as idealized one-dimensional objects, we evolve the simplest example of an underlying field theory containing local U(1) strings, the Abelian Higgs model. Limitations imposed by finite computational volumes are overcome using the scaling property of string networks and a further extrapolation related to the lessening of the string width in comoving coordinates. The strings and their decay products, which are automatically included in the field theory approach, source metric perturbations via their energy-momentum tensor, the unequal-time correlation functions of which are used as input into the CMB calculation phase. These calculations involve the use of a modified version of CMBEASY, with results provided over the full range of relevant scales. We find that the string tension {mu} required to normalize to the WMAP 3-year data at multipole l=10 is G{mu}=[2.04{+-}0.06(stat.){+-}0.12(sys.)]x10{sup -6}, where we have quoted statistical and systematic errors separately, and G is Newton's constant. This is a factor 2-3 higher than values in current circulation.
Infrared dynamics of a large N QCD model, the massless string sector and mesonic spectra
NASA Astrophysics Data System (ADS)
Dasgupta, Keshav; Gale, Charles; Mia, Mohammed; Richard, Michael; Trottier, Olivier
2015-07-01
A consistency check for any UV complete model for large N QCD should be, among other things, the existence of a well-defined vector and scalar mesonic spectra. In this paper, we use our UV complete model in type IIB string theory to study the IR dynamics and use this to predict the mesonic spectra in the dual type IIA side. The advantage of this approach is two-fold: not only will this justify the consistency of the supergravity approach, but it will also give us a way to compare the IR spectra and the model with the ones proposed earlier by Sakai and Sugimoto. Interestingly, the spectra coming from the massless stringy sector are independent of the UV physics, although the massive string sector may pose certain subtleties regarding the UV contributions as well as the mappings to actual QCD. Additionally, we find that a component of the string landscape enters the picture: there are points in the landscape where the spectra can be improved somewhat over the existing results in the literature. These points in the landscape in-turn also determine certain background supergravity components and fix various pathologies that eventually lead to a consistent low energy description of the theory.
Exact string theory model of closed timelike curves and cosmological singularities
Johnson, Clifford V.; Svendsen, Harald G.
2004-12-15
We study an exact model of string theory propagating in a space-time containing regions with closed timelike curves (CTCs) separated from a finite cosmological region bounded by a big bang and a big crunch. The model is an nontrivial embedding of the Taub-NUT geometry into heterotic string theory with a full conformal field theory (CFT) definition, discovered over a decade ago as a heterotic coset model. Having a CFT definition makes this an excellent laboratory for the study of the stringy fate of CTCs, the Taub cosmology, and the Milne/Misner-type chronology horizon which separates them. In an effort to uncover the role of stringy corrections to such geometries, we calculate the complete set of {alpha}{sup '} corrections to the geometry. We observe that the key features of Taub-NUT persist in the exact theory, together with the emergence of a region of space with Euclidean signature bounded by timelike curvature singularities. Although such remarks are premature, their persistence in the exact geometry is suggestive that string theory is able to make physical sense of the Milne/Misner singularities and the CTCs, despite their pathological character in general relativity. This may also support the possibility that CTCs may be viable in some physical situations, and may be a natural ingredient in pre-big bang cosmological scenarios.
NASA Astrophysics Data System (ADS)
Cappelli, Andrea; Castellani, Elena; Colomo, Filippo; Di Vecchia, Paolo
2012-04-01
Part I. Overview: 1. Introduction and synopsis; 2. Rise and fall of the hadronic string G. Veneziano; 3. Gravity, unification, and the superstring J. H. Schwarz; 4. Early string theory as a challenging case study for philosophers E. Castellani; Part II. The Prehistory: The Analytic S-Matrix: 5. Introduction to Part II; 6. Particle theory in the sixties: from current algebra to the Veneziano amplitude M. Ademollo; 7. The path to the Veneziano model H. R. Rubinstein; 8. Two-component duality and strings P. G. O. Freund; 9. Note on the prehistory of string theory M. Gell-Mann; Part III. The Dual Resonance Model: 10. Introduction to Part III; 11. From the S-matrix to string theory P. Di Vecchia; 12. Reminiscence on the birth of string theory J. A. Shapiro; 13. Personal recollections D. Amati; 14. Early string theory at Fermilab and Rutgers L. Clavelli; 15. Dual amplitudes in higher dimensions: a personal view C. Lovelace; 16. Personal recollections on dual models R. Musto; 17. Remembering the 'supergroup' collaboration F. Nicodemi; 18. The '3-Reggeon vertex' S. Sciuto; Part IV. The String: 19. Introduction to Part IV; 20. From dual models to relativistic strings P. Goddard; 21. The first string theory: personal recollections L. Susskind; 22. The string picture of the Veneziano model H. B. Nielsen; 23. From the S-matrix to string theory Y. Nambu; 24. The analogue model for string amplitudes D. B. Fairlie; 25. Factorization in dual models and functional integration in string theory S. Mandelstam; 26. The hadronic origins of string theory R. C. Brower; Part V. Beyond the Bosonic String: 27. Introduction to Part V; 28. From dual fermion to superstring D. I. Olive; 29. Dual models with fermions: memoirs of an early string theorist P. Ramond; 30. Personal recollections A. Neveu; 31. Aspects of fermionic dual models E. Corrigan; 32. The dual quark models K. Bardakci and M. B. Halpern; 33. Remembering the dawn of relativistic strings J.-L. Gervais; 34. Early string theory in
NASA Astrophysics Data System (ADS)
Kraniotis, G. V.
In this work, we review recent work on string cosmology. The need for an inflationary era is well known. Problems of Standard Cosmology such as horizon, flatness, monopole and entropy find an elegant solution in the inflationary scenario. On the other hand no adequate inflationary model has been constructed so far. In this review we discuss the attempts that have been made in the field of string theory for obtaining an adequate Cosmological Inflationary Epoch. In particular, orbifold compactifications of string theory which are constrained by target-space duality symmetry offer as natural candidates for the role of inflatons the orbifold moduli. Orbifold moduli dynamics is very constrained by duality symmetry and offers a concrete framework for discussing Cosmological Inflation. We discuss the resulting cosmology assuming that nonperturbative dynamics generates a moduli potential which respects target-space modular invariance. Various modular forms for the nonperturbative superpotential and Kähler potential which include the absolute modular invariant j(T) besides the Dedekind eta function η(T) are discussed. We also review scale-factor duality and pre-Big-Bang scenarios in which inflation is driven by the kinetic terms of the dilaton modulus. In this context we discuss the problem of graceful exit and review recent attempts for solving the problem of exiting from inflation. The possibility of obtaining inflation through the D-terms in string models with anomalous UA(1) and other Abelian factors is reviewed. In this context we discuss how the slow-roll problem in supergravity models with F-term inflation can be solved by D-term inflation. We also briefly review the consequences of duality for a generalized Heisenberg uncertainty principle and the structure of space-time at short scales. The problem of the Cosmological Constant is also briefly discussed.
Unitary-matrix models as exactly solvable string theories
NASA Technical Reports Server (NTRS)
Periwal, Vipul; Shevitz, Danny
1990-01-01
Exact differential equations are presently found for the scaling functions of models of unitary matrices which are solved in a double-scaling limit, using orthogonal polynomials on a circle. For the case of the simplest, k = 1 model, the Painleve II equation with constant 0 is obtained; possible nonperturbative phase transitions exist for these models. Equations are presented for k = 2 and 3, and discussed with a view to asymptotic behavior.
Tensionless strings from worldsheet symmetries
NASA Astrophysics Data System (ADS)
Bagchi, Arjun; Chakrabortty, Shankhadeep; Parekh, Pulastya
2016-01-01
We revisit the construction of the tensionless limit of closed bosonic string theory in the covariant formulation in the light of Galilean conformal symmetry that rises as the residual gauge symmetry on the tensionless worldsheet. We relate the analysis of the fundamentally tensionless theory to the tensionless limit that is viewed as a contraction of worldsheet coordinates. Analysis of the quantum regime uncovers interesting physics. The degrees of freedom that appear in the tensionless string are fundamentally different from the usual string states. Through a Bogoliubov transformation on the worldsheet, we link the tensionless vacuum to the usual tensile vacuum. As an application, we show that our analysis can be used to understand physics of strings at very high temperatures and propose that these new degrees of freedom are naturally connected with the long-string picture of the Hagedorn phase of free string theory. We also show that tensionless closed strings behave like open strings.
Which String Breaks? Revisited
NASA Astrophysics Data System (ADS)
Frye, Christopher
2011-03-01
Many have seen the common introductory physics demonstration in which a heavy ball hangs from a string, with another identical string hanging freely from the ball. When the instructor pulls the bottom string slowly, the top string breaks. However, when the instructor pulls the bottom string very rapidly, the bottom string breaks. This simple experiment is used to demonstrate inertia and Newton's laws. In The Physics Teacher of November 1996, there is an article in which the authors create a model of this problem in an attempt to explain the outcomes quantitatively. However, their analysis gave strange results. Using an improved model, I will show that the results of this demonstration can be obtained using only simple calculations. This work was funded by a RAMP grant from the University of Central Florida.
Minimal Pati-Salam model from string theory unification
Dent, James B.; Kephart, Thomas W.
2008-06-01
We provide what we believe is the minimal three family N=1 SUSY and conformal Pati-Salam model from type IIB superstring theory. This Z{sub 3} orbifolded AdS x S{sup 5} model has long lived protons and has potential phenomenological consequences for LHC (Large Hadron Collider)
NASA Astrophysics Data System (ADS)
Clancy, Dominic; Feinstein, Alexander; Lidsey, James E.; Tavakol, Reza
1999-04-01
Global symmetries of the string effective action are employed to generate tilted, homogeneous Bianchi type VIh string cosmologies from a previously known stiff perfect fluid solution to Einstein gravity. The dilaton field is not constant on the surfaces of homogeneity. The future asymptotic state of the models is interpreted as a plane wave and is itself an exact solution to the string equations of motion to all orders in the inverse string tension. An inhomogeneous generalization of the Bianchi type III model is also found.
Open Rotor Aeroacoustic Modelling
NASA Technical Reports Server (NTRS)
Envia, Edmane
2012-01-01
Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.
Open Rotor Aeroacoustic Modeling
NASA Technical Reports Server (NTRS)
Envia, Edmane
2012-01-01
Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.
A Note on Cosmic (p,q,r) Strings
Jackson, Mark G.; /Fermilab
2006-10-01
The spectrum of (p, q) bound states of F- and D-strings has a distinctive square-root tension formula that is hoped to be a hallmark of fundamental cosmic strings. We point out that the BPS bound for vortices in N = 2 supersymmetric Abelian-Higgs models also takes the square-root form. In contrast to string theory, the most general supersymmetric field theoretic model allows for (p, q, r) strings, with three classes of strings rather than two. Unfortunately, we find that there do not exist BPS solutions except in the trivial case. The issue of whether there exist non-BPS solutions which may closely resemble the square-root form is left as an open question.
Modeling coiled-tubing velocity strings for gas wells
Martinez, J.; Martinez, A.
1998-02-01
Because of its ability to prolong well life, its relatively low expense, and the relative ease with which it is installed, coiled tubing has become a preferred remedial method of tubular completion for gas wells. Of course, the difficulty in procuring wireline-test data is a drawback to verifying the accuracy of the assumptions and predictions used for coiled-tubing selection. This increases the importance of the prediction-making process, and, as a result, places great emphasis on the modeling methods that are used. This paper focuses on the processes and methods for achieving sound multiphase-flow predictions by looking at the steps necessary to arrive at coiled-tubing selection. Furthermore, this paper examines the variables that serve as indicators of the viability of each tubing size, especially liquid holdup. This means that in addition to methodology, emphasis is placed on the use of a good wellbore model. The computer model discussed is in use industry wide.
String-charge duality in integrable lattice models
NASA Astrophysics Data System (ADS)
Ilievski, Enej; Quinn, Eoin; De Nardis, Jacopo; Brockmann, Michael
2016-06-01
We derive an explicit mapping between the spectra of conserved local operators of integrable quantum lattice models and the density distributions of their thermodynamic particle content. This is presented explicitly for the Heisenberg XXZ spin chain. As an application we discuss a quantum quench scenario, in both the gapped and critical regimes. We outline an exact technique which allows for an efficient implementation on periodic matrix product states. In addition, for certain simple product states we obtain analytic closed-form expressions in terms of solutions to Hirota functional relations. Remarkably, no reference to a maximal entropy principle is invoked.
Topological Landau-Ginzburg model of two-dimensional string theory
NASA Astrophysics Data System (ADS)
Ghoshal, Debashis; Mukhi, Sunil
1994-08-01
We study a topological Landau-Ginzburg model with superpotential W( X) = X-1. This is argued to be equivalent to c = 1 string theory compactified at the self-dual radius. We compute the tree-level correlation function of N tachyons in this theory and show their agreement with matrix-model results. We also discuss the nature of contract terms, the perturbed superpotential and the flow of operators in the small phase space. The role of gravitational descendants in this theory is examined, and the tachyon two-point function in genus 1 is obtained using a conjectured modification of the gravitational recursion relations.
The 750 GeV di-photon LHC excess and extra Z^' s in heterotic-string derived models
NASA Astrophysics Data System (ADS)
Faraggi, Alon E.; Rizos, John
2016-03-01
The ATLAS and CMS collaborations recently recorded possible di-photon excess at 750 GeV and a less significant di-boson excess around 1.9 TeV. Such excesses may be produced in heterotic string derived Z^' models, where the di-photon excess may be connected with the Standard Model singlet scalar responsible for the Z^' symmetry breaking, whereas the di-boson excess arises from production of the extra vector boson. Additional vector-like states in the string Z^' model are instrumental to explain the relatively large width of the di-photon events and mandated by anomaly cancellation to be in the vicinity of the Z^' breaking scale. Wilson line breaking of the non-Abelian gauge symmetries in the string models naturally gives rise to dark matter candidates. Future collider experiments will discriminate between the high-scale heterotic-string models, which preserve the perturbative unification paradigm indicated by the Standard Model data, versus the low scale string models. We also discuss the possibility for the production of the diphoton events with high scale U(1)_{Z^' } breaking.
NASA Astrophysics Data System (ADS)
Susskind, Leonard
2013-01-01
After reviewing the original motivation for the formulation of string theory and what we learned from it, I discuss some of the implications of the holographic principle and of string dualities for the question of the building blocks of nature.
Weigel, H.; Quandt, M.; Graham, N.
2011-03-11
We study the quantum stabilization of a cosmic string by a heavy fermion doublet in a reduced version of the standard model. We show that charged strings, obtained by populating fermionic bound state levels, become stable if the electroweak bosons are coupled to a fermion that is less than twice as heavy as the top quark. This result suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model. Numerically we find the most favorable string profile to be a simple trough in the Higgs vacuum expectation value of radius {approx_equal}10{sup -18} m. The vacuum remains stable in our model, because neutral strings are not energetically favored.
Stable charged cosmic strings.
Weigel, H; Quandt, M; Graham, N
2011-03-11
We study the quantum stabilization of a cosmic string by a heavy fermion doublet in a reduced version of the standard model. We show that charged strings, obtained by populating fermionic bound state levels, become stable if the electroweak bosons are coupled to a fermion that is less than twice as heavy as the top quark. This result suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model. Numerically we find the most favorable string profile to be a simple trough in the Higgs vacuum expectation value of radius ≈10(-18) m. The vacuum remains stable in our model, because neutral strings are not energetically favored. PMID:21469786
Vorticity and hydrodynamic helicity in heavy-ion collisions in the hadron-string dynamics model
NASA Astrophysics Data System (ADS)
Teryaev, Oleg; Usubov, Rahim
2015-07-01
The hydrodynamic helicity separation effect in noncentral heavy-ion collisions is investigated using the hadron-string dynamics (HSD) model. Computer simulations are done to calculate velocity and hydrodynamic helicity on a mesh in a small volume around the center of the reaction. The time dependence of hydrodynamic helicity is observed for various impact parameters and different calculation methods. Comparison with a similar earlier work is carried out. A new quantity related to jet handedness is used to probe for p -odd effects in the final state.
String Comparator Metrics and Enhanced Decision Rules in the Fellegi-Sunter Model of Record Linkage.
ERIC Educational Resources Information Center
Winkler, William E.
To locate matches across pairs of lists without unique identifiers it is sometimes necessary to compare strings of letters. String comparators are used in production computer matching software during the Post Enumeration Survey for the 1990 U.S. census. A string comparator metric is described that partially accounts for: (1) typographical…
ERIC Educational Resources Information Center
Mesa Public Schools, AZ.
Designed for music educators instructing grades 4 through 8 in string instruments, this Mesa (Arizona) public schools guide presents information on the string curriculum, orchestras, and practicing. The goals and objectives for string instruments delineate grade levels and how student skills will be verified. Following 17 curriculum goal tests,…
NASA Astrophysics Data System (ADS)
Rossing, Thomas D.
In the next three chapters we consider the science of hammered string instruments. In this chapter, we present a brief discussion of vibrating strings excited by a hard or soft hammer. Chapter 20 discusses the most important hammered string instrument, the piano - probably the most versatile and popular of all musical instruments. Chapter 21 discusses hammered dulcimers, especially the American folk dulcimer.
Cosmic strings and galaxy formation
NASA Technical Reports Server (NTRS)
Bertschinger, Edmund
1989-01-01
The cosmogonical model proposed by Zel'dovich and Vilenkin (1981), in which superconducting cosmic strings act as seeds for the origin of structure in the universe, is discussed, summarizing the results of recent theoretical investigations. Consideration is given to the formation of cosmic strings, the microscopic structure of strings, gravitational effects, cosmic string evolution, and the formation of galaxies and large-scale structure. Simulation results are presented in graphs, and several outstanding issues are listed and briefly characterized.
Structure formation in a string-inspired modification of the cold dark matter model
Gubser, Steven S.; Peebles, P.J.E.
2004-12-15
Motivated in part by string theory, we consider the idea that the standard {lambda}CDM cosmological model might be modified by the effect of a long-range scalar dark matter interaction. The variant of this widely-discussed notion considered here is suggested by the Brandenberger-Vafa [R. H. Brandenberger and C. Vafa, Nucl. Phys. B316, 391 (1989).] picture for why we perceive three spatial dimensions. In this picture there may be at least two species of dark matter particles, with scalar charges such that the scalar interaction attracts particles with like sign and repels unlike signs. The net charge vanishes. Under this condition the evolution of the mass distribution in linear perturbation theory is the same as in the {lambda}CDM cosmology, and both models therefore can equally well pass the available cosmological tests. The physics can be very different on small scales, however: if the scalar interaction has the strength suggested by simple versions of the string scenario, nonlinear mass concentrations are unstable against separation into charged halos with properties unlike the standard model prediction and possibly of observational interest.
Structure formation in a string-inspired modification of the cold dark matter model
NASA Astrophysics Data System (ADS)
Gubser, Steven S.; Peebles, P. J. E.
2004-12-01
Motivated in part by string theory, we consider the idea that the standard ΛCDM cosmological model might be modified by the effect of a long-range scalar dark matter interaction. The variant of this widely-discussed notion considered here is suggested by the Brandenberger-Vafa [R. H. BrandenbergerC. Vafa, Nucl. Phys.B3161989391] picture for why we perceive three spatial dimensions. In this picture there may be at least two species of dark matter particles, with scalar charges such that the scalar interaction attracts particles with like sign and repels unlike signs. The net charge vanishes. Under this condition the evolution of the mass distribution in linear perturbation theory is the same as in the ΛCDM cosmology, and both models therefore can equally well pass the available cosmological tests. The physics can be very different on small scales, however: if the scalar interaction has the strength suggested by simple versions of the string scenario, nonlinear mass concentrations are unstable against separation into charged halos with properties unlike the standard model prediction and possibly of observational interest.
Evolution of cosmic string networks
NASA Technical Reports Server (NTRS)
Albrecht, Andreas; Turok, Neil
1989-01-01
A discussion of the evolution and observable consequences of a network of cosmic strings is given. A simple model for the evolution of the string network is presented, and related to the statistical mechanics of string networks. The model predicts the long string density throughout the history of the universe from a single parameter, which researchers calculate in radiation era simulations. The statistical mechanics arguments indicate a particular thermal form for the spectrum of loops chopped off the network. Detailed numerical simulations of string networks in expanding backgrounds are performed to test the model. Consequences for large scale structure, the microwave and gravity wave backgrounds, nucleosynthesis and gravitational lensing are calculated.
Mirage models confront the LHC: Kähler-stabilized heterotic string theory
NASA Astrophysics Data System (ADS)
Kaufman, Bryan L.; Nelson, Brent D.; Gaillard, Mary K.
2013-07-01
We begin the study of a class of string-motivated effective supergravity theories in light of current data from the CERN Large Hadron Collider (LHC). The case of heterotic string theory, in which the dilaton is stabilized via nonperturbative corrections to the Kähler metric, will be considered first. The model, which represents the strong dynamics of a presumed gaugino condensation in the hidden sector, is highly constrained and therefore predictive. We find that much of the parameter space associated with confined hidden sector gauge groups up to rank five is now observationally disfavored by the LHC results. Most of the theoretically motivated parameter space that remains can be probed with data that has already been collected, and most of the remainder will be definitively explored within the first year of operation at s=13TeV. Expected signatures for a number of benchmark points are discussed. We find that the surviving space of the model makes a precise prediction as to the relation of many superpartner masses, as well as the manner in which the correct dark matter relic density is obtained. Implications for current and future dark matter search experiments are discussed.
Analytical derivation of thermodynamic characteristics of lipid bilayer from a flexible string model
NASA Astrophysics Data System (ADS)
Mukhin, Sergei I.; Baoukina, Svetlana
2005-06-01
We introduce a flexible string model of the hydrocarbon chain and derive an analytical expression for the lateral pressure profile across the hydrophobic core of the membrane. The pressure profile influences the functioning of the embedded proteins and is difficult to measure experimentally. In our model the hydrocarbon chain is represented as a flexible string of finite thickness with a given bending rigidity. In the mean-field approximation we substitute the entropic repulsion between neighboring chains in a lipid membrane by an effective potential. The effective potential is determined self-consistently. The arbitrary chain conformation is expanded over eigenfunctions of the self-adjoint operator of the chain energy density. The lateral pressure distribution across the bilayer is calculated using the path integral technique. We found that the pressure profile is mainly formed by the sum of the partial contributions of a few discrete lowest-energy “eigenconformations.” The dependences on temperature and area per lipid of the lateral pressure produced by the hydrocarbon chains are found. We also calculated the chain contribution to the area compressibility modulus and the temperature coefficient of area expansion.
Extra Z^' }s and W^' }s in heterotic-string derived models
NASA Astrophysics Data System (ADS)
Faraggi, Alon E.; Guzzi, Marco
2015-11-01
The ATLAS and CMS collaborations recently recorded possible excess in the di-boson production at the di-boson invariant mass at around 2 TeV. Such an excess may be produced if there exist additional Z^' } and/or W^' } at that scale. We survey the extra Z^' }s and W^' }s that may arise from semi-realistic heterotic-string vacua in the free fermionic formulation in the seven distinct cases: U(1)_{Z^' }}in SO(10); family universal U(1)_{Z^' }}notin SO(10); non-universal U(1)_{Z^' }}; hidden sector U(1) symmetries and kinetic mixing; left-right symmetric models; Pati-Salam models; leptophobic and custodial symmetries. Each case has a distinct signature associated with the extra symmetry breaking scale. In one of the cases we explore the discovery potential at the LHC using resonant leptoproduction. The existence of an extra vector boson with the reported properties will significantly constrain the space of allowed string vacua.
Searching for features of a string-inspired inflationary model with cosmological observations
NASA Astrophysics Data System (ADS)
Cai, Yi-Fu; Ferreira, Elisa G. M.; Hu, Bin; Quintin, Jerome
2015-12-01
The latest Planck results show a power deficit in the temperature anisotropies near ℓ≈20 in the cosmic microwave background (CMB). This observation can hardly be explained within the standard inflationary Λ -cold-dark-matter (Λ CDM ) scenario. In this paper we consider a string theory inspired inflationary model (axion monodromy inflation) with a step-like modulation in the potential which gives rise to observable signatures in the primordial perturbations. One interesting phenomenon is that the primordial scalar modes experience a sudden suppression at a critical scale when the modulation occurs. By fitting to the CMB data, we find that the model can nicely explain the ℓ≈20 power deficit anomaly as well as predict specific patterns in the temperature-polarization correlation and polarization autocorrelation spectra. Though the significance of the result is not sufficient to claim a detection, our analysis reveals that fundamental physics at extremely high energy scales, namely, some effects inspired by string theory, may be observationally testable in forthcoming cosmological experiments.
Supersymmetry and String Theory
NASA Astrophysics Data System (ADS)
Dine, Michael
2016-01-01
Preface to the first edition; Preface to the second edition; A note on choice of metric; Text website; Part I. Effective Field Theory: The Standard Model, Supersymmetry, Unification: 1. Before the Standard Model; 2. The Standard Model; 3. Phenomenology of the Standard Model; 4. The Standard Model as an effective field theory; 5. Anomalies, instantons and the strong CP problem; 6. Grand unification; 7. Magnetic monopoles and solitons; 8. Technicolor: a first attempt to explain hierarchies; Part II. Supersymmetry: 9. Supersymmetry; 10. A first look at supersymmetry breaking; 11. The Minimal Supersymmetric Standard Model; 12. Supersymmetric grand unification; 13. Supersymmetric dynamics; 14. Dynamical supersymmetry breaking; 15. Theories with more than four conserved supercharges; 16. More supersymmetric dynamics; 17. An introduction to general relativity; 18. Cosmology; 19. Astroparticle physics and inflation; Part III. String Theory: 20. Introduction; 21. The bosonic string; 22. The superstring; 23. The heterotic string; 24. Effective actions in ten dimensions; 25. Compactification of string theory I. Tori and orbifolds; 26. Compactification of string theory II. Calabi–Yau compactifications; 27. Dynamics of string theory at weak coupling; 28. Beyond weak coupling: non-perturbative string theory; 29. Large and warped extra dimensions; 30. The landscape: a challenge to the naturalness principle; 31. Coda: where are we headed?; Part IV. The Appendices: Appendix A. Two-component spinors; Appendix B. Goldstone's theorem and the pi mesons; Appendix C. Some practice with the path integral in field theory; Appendix D. The beta function in supersymmetric Yang–Mills theory; References; Index.
Supermassive cosmic string compactifications
Blanco-Pillado, Jose J.; Reina, Borja; Sousa, Kepa; Urrestilla, Jon E-mail: borja.reina@ehu.es E-mail: jon.urrestilla@ehu.es
2014-06-01
The space-time dimensions transverse to a static straight cosmic string with a sufficiently large tension (supermassive cosmic strings) are compact and typically have a singularity at a finite distance form the core. In this paper, we discuss how the presence of multiple supermassive cosmic strings in the 4d Abelian-Higgs model can induce the spontaneous compactification of the transverse space and explicitly construct solutions where the gravitational background becomes regular everywhere. We discuss the embedding of this model in N = 1 supergravity and show that some of these solutions are half-BPS, in the sense that they leave unbroken half of the supersymmetries of the model.
Behavior of Tachyon in String Cosmology Based on Gauged WZW Model
NASA Astrophysics Data System (ADS)
Lee, Sunggeun; Nam, Soonkeon
We investigate a string theoretic cosmological model in the context of the gauged Wess-Zumino-Witten model. Our model is based on a product of non-compact coset space and a spectator flat space; [SL(2, R)/U(1)]k × ℝ2. We extend the formerly studied semiclassical consideration with infinite Kac-Moody level k to a finite one. In this case, the tachyon field appears in the effective action, and we solve the Einstein equation to determine the behavior of tachyon as a function of time. We find that tachyon field dominates over dilaton field in early times. In particular, we consider the energy conditions of the matter fields consisting of the dilaton and the tachyon which affect the initial singularity. We find that not only the strong energy but also the null energy condition is violated.
Model of the N-quark potential in SU(N) gauge theory using gauge-string duality
NASA Astrophysics Data System (ADS)
Andreev, Oleg
2016-05-01
We use gauge-string duality to model the N-quark potential in pure Yang-Mills theories. For SU (3), the result agrees remarkably well with lattice simulations. The model smoothly interpolates between almost the Δ-law at short distances and the Y-law at long distances.
Monte Carlo simulations of two-dimensional Hubbard models with string bond tensor-network states
NASA Astrophysics Data System (ADS)
Song, Jeong-Pil; Wee, Daehyun; Clay, R. T.
2015-03-01
We study charge- and spin-ordered states in the two-dimensional extended Hubbard model on a triangular lattice at 1/3 filling. While the nearest-neighbor Coulomb repulsion V induces charge-ordered states, the competition between on-site U and nearest-neighbor V interactions lead to quantum phase transitions to an antiferromagnetic spin-ordered phase with honeycomb charge order. In order to avoid the fermion sign problem and handle frustrations here we use quantum Monte Carlo methods with the string-bond tensor network ansatz for fermionic systems in two dimensions. We determine the phase boundaries of the several spin- and charge-ordered states and show a phase diagram in the on-site U and the nearest-neighbor V plane. The numerical accuracy of the method is compared with exact diagonalization results in terms of the size of matrices D. We also test the use of lattice symmetries to improve the string-bond ansatz. Work at Mississippi State University was supported by the US Department of Energy grant DE-FG02-06ER46315.
Mirage models confront the LHC. II. Flux-stabilized type IIB string theory
NASA Astrophysics Data System (ADS)
Kaufman, Bryan L.; Nelson, Brent D.
2014-04-01
We continue the study of a class of string-motivated effective supergravity theories in light of current data from the CERN Large Hadron Collider (LHC). In this installment we consider type IIB string theory compactified on a Calabi-Yau orientifold in the presence of fluxes, in the manner originally formulated by Kachru et al. We allow for a variety of potential uplift mechanisms and embeddings of the Standard Model field content into D3-and D7-brane configurations. We find that an uplift sector independent of the Kähler moduli, as is the case with anti-D3-branes, is inconsistent with data unless the matter and Higgs sectors are localized on D7 branes exclusively, or are confined to twisted sectors between D3-and D7-branes. We identify regions of parameter space for all possible D-brane configurations that remain consistent with Planck observations on the dark matter relic density and measurements of the CP-even Higgs mass at the LHC. Constraints arising from LHC searches at √s =8 TeV and the LUX dark matter detection experiment are discussed. The discovery prospects for the remaining parameter space at dark matter direct-detection experiments are described, and signatures for detection of superpartners at the LHC with √s =14 TeV are analyzed.
Non-linear sigma model in 1 + 1 dimensions, supergravity and the spinning string
NASA Astrophysics Data System (ADS)
Abdalla, E.; Jasinschi, R. S.
1984-02-01
The non-linear σ supersymmetric model in 1 + 1 dimensions is coupled to supergravity. When we quantize the theory, the matter fields acquire mass dynamically, which leads to the breaking of the Weyl invariance. This fact implies that the two-point functions of the gravitino and the graviton, obtained from the effective action, become non-trivial. Particularly, the two-point function of the gravitino presents a pole in the infrared region. We conjecture that this pole is related to the confinement of all supersymmetric degrees of freedom of the theory. If we restrain the integration domain of x1 to a finite length L (breaking all invariances of the theory), there appears a mass term in the two-point function of the gravitino, which decreases exponentially with L. In this context we relate this model with that of the supersymmetric string and define a stability criterion for the latter.
NASA Astrophysics Data System (ADS)
Rossing, Thomas D.; Hanson, Roger J.
In the next eight chapters, we consider some aspects of the science of bowed string instruments, old and new. In this chapter, we present a brief discussion of bowed strings, a subject that will be developed much more thoroughly in Chap. 16. Chapters 13-15 discuss the violin, the cello, and the double bass. Chapter 17 discusses viols and other historic string instruments, and Chap. 18 discusses the Hutchins-Schelleng violin octet.
p-Adic Strings and Their Applications
Freund, Peter G. O.
2006-03-29
The theory of p-adic strings is reviewed along with some of their applications, foremost among them to the tachyon condensation problem in string theory. Some open problems are discussed, in particular that of the superstring in 10 dimensions as the end-stage of the 26-dimensional closed bosonic string's tachyon condensation.
NASA Astrophysics Data System (ADS)
Frampton, Paul H.
2016-04-01
In this note, I recollect a two-week period in September 1968 when I factorized the Veneziano model using string variables in Chicago. Professor Yoichiro Nambu went on to calculate the N-particle dual resonance model and then to factorize it on an exponential degeneracy of states. That was in 1968 and the following year 1969 he discovered the string action. I also include some other reminiscences of Nambu who passed away on July 5, 2015.
Battye, R.A.; Shellard, E.P. |
1995-12-01
We discuss radiative backreaction for global strings described by the Kalb-Ramond action with an analogous derivation to that for the point electron in classical electrodynamics. We show how local corrections to the equations of motion allow one to separate the self-field of the string from that of the radiation field. Modifications to this {open_quote}{open_quote}local backreaction approximation{close_quote}{close_quote} circumvent the runaway solutions, allowing these corrections to be used to evolve string trajectories numerically. Comparisons are made with analytic and numerical radiation calculations from previous work and the merits and limitations of this approach are discussed. {copyright} {ital 1995 The American Physical Society.}
Anisotropic string cosmological models in Heckmann-Schucking space-time
NASA Astrophysics Data System (ADS)
Goswami, G. K.; Dewangan, R. N.; Yadav, A. K.; Pradhan, A.
2016-02-01
In the present work we have searched the existence of the late time acceleration of the universe with string fluid as source of matter in anisotropic Heckmann-Schucking space-time by using 287 high red shift (0.3 ≤ z≤1.4) SN Ia data of observed absolute magnitude along with their possible error from Union 2.1 compilation. It is found that the best fit values for (\\varOmegam)0, (\\varOmega_{\\varLambda})0, (\\varOmega_{σ })0 and (q)0 are 0.2820, 0.7177, 0.0002 & -0.5793 respectively. Several physical aspects and geometrical properties of the model are discussed in detail.
Circumventing the eta problem in building an inflationary model in string theory
Easson, Damien A.; Gregory, Ruth
2009-10-15
The eta problem is one of the most significant obstacles to building a successful inflationary model in string theory. Planck mass suppressed corrections to the inflaton potential generally lead to inflaton masses of order the Hubble scale and generate contributions of order unity to the {eta} slow-roll parameter rendering prolonged slow-roll inflation impossible. We demonstrate the severity of this problem in the context of brane antibrane inflation in a warped throat of a Calabi-Yau flux compactification with all phenomenologically dangerous moduli stabilized. Using numerical solutions we show that the eta problem can be avoided in scenarios where the inflaton is nonminimally coupled to gravity and has Dirac-Born-Infeld kinetic term. We show that the resulting cosmic microwave background observables such as measures of non-Gaussianites can, in principle, serve as a probe of scalar-gravity couplings.
Cosmic string catalysis of skyrmion decay
NASA Technical Reports Server (NTRS)
Gregory, Ruth; Davis, Anne-Christine; Brandenberger, Robert
1988-01-01
The Callan-Witten picture is developed for monopole catalyzed skyrmion decay in order to analyze the corresponding cosmic string scenario. It is discovered that cosmic strings (both ordinary and superconducting) can catalyze proton decay, but that this catalysis only occurs on the scale of the core of the string. In order to do this we have to develop a vortex model for the superconducting string. An argument is also given for the difference in the enhancement factors for monopoles and strings.
Low dimensional models for stick-slip vibration of drill-strings
NASA Astrophysics Data System (ADS)
Silveira, M.; Wiercigroch, M.
2009-08-01
Effective reduction of drill-string vibration is still a major problem in drilling industry and therefore robust predictive tools need to be developed. In this paper we study two low dimensional nonlinear models. The first is a 1-DOF torsional model of the botom-hole assembly (BHA). The second model is a 3-DOF torsional system having in addition to the BHA a rotary table, which allows simulation of interactions for which there is experimental evidence. Three different friction models with increasing levels of complexity are applied to determine their influence in the dynamical responses. Comparison between the dynamic responses for three friction models shows that the dangerous stick-slip limit-cycles do not change qualitatively. Simulations show that, if appropriately controlled, large amplitude stick-slip limit-cycles can change to small amplitude limit-cycles in Model 2. In Model 1, with constant velocity of the rotary table, it goes from a large amplitude stick-slip limit-cycle to a fixed point. Bifurcation diagrams confirm the existence of a set of parameters in which the system operates without stick-slip vibration.
String completion of an SU(3)c ⊗ SU(3)L ⊗ U(1)X electroweak model
NASA Astrophysics Data System (ADS)
Addazi, Andrea; Valle, J. W. F.; Vaquera-Araujo, C. A.
2016-08-01
The extended electroweak SU(3)c ⊗ SU(3)L ⊗ U(1)X symmetry framework "explaining" the number of fermion families is revisited. While 331-based schemes can not easily be unified within the conventional field theory sense, we show how to do it within an approach based on D-branes and (un)oriented open strings, on Calabi-Yau singularities. We show how the theory can be UV-completed in a quiver setup, free of gauge and string anomalies. Lepton and baryon numbers are perturbatively conserved, so neutrinos are Dirac-type, and their lightness results from a novel TeV scale seesaw mechanism. Dynamical violation of baryon number by exotic instantons could induce neutron-antineutron oscillations, with proton decay and other dangerous R-parity violating processes strictly forbidden.
Classical probes of string/gauge theory duality
NASA Astrophysics Data System (ADS)
Ishizeki, Riei
The AdS/CFT correspondence has played an important role in the recent development of string theory. The reason is that it proposes a description of certain gauge theories in terms of string theory. It is such that simple string theory computations give information about the strong coupling regime of the gauge theory. Vice versa, gauge theory computations give information about string theory and quantum gravity. Although much is known about AdS/CFT, the precise map between the two sides of the correspondence is not completely understood. In the unraveling of such map classical string solutions play a vital role. In this thesis, several classical string solutions are proposed to help understand the AdS/CFT duality. First, rigidly rotating strings on a two-sphere are studied. Taking special limits of such solutions leads to two cases: the already known giant magnon solution, and a new solution which we call the single spike solution. Next, we compute the scattering phase shift of the single spike solutions and compare the result with the giant magnon solutions. Intriguingly, the results are the same up to non-logarithmic terms, indicating that the single spike solution should have the same rich spin chain structure as the giant magnon solution. Afterward, we consider open string solutions ending on the boundary of AdS5. The lines traced by the ends of such open strings can be viewed as Wilson loops in N = 4 SYM theory. After applying an inversion transformation, the open Wilson loops become closed Wilson loops whose expectation value is consistent with previously conjectured results. Next, several Wilson loops for N = 4 SYM in an AdS5 pp-wave background are considered and translated to the pure AdS 5 background and their interpretation as forward quark-gluon scattering is suggested. In the last part of this thesis, a class of classical solutions for closed strings moving in AdS3 x S 1 ⊂ AdS5 x S5 with energy E and spin S in AdS3 and angular momentum J and winding m
Quantum Strings and Superstrings
NASA Astrophysics Data System (ADS)
Grigore, D. R.
In the first sections of this paper we give an elementary but rigorous approach to the construction of the quantum Bosonic and supersymmetric string system continuing the analysis of Dimock. This includes the construction of the DDF operators without using the vertex algebras. Next we give a rigorous proof of the equivalence between the light-cone and the covariant quantization methods. Finally, we provide a new and simple proof of the BRST quantization for these string models.
Open source layered sensing model
NASA Astrophysics Data System (ADS)
Rovito, Todd V.; Abayowa, Bernard O.; Talbert, Michael L.
2011-06-01
This paper will look at using open source tools (Blender [17], LuxRender [18], and Python [19]) to build an image processing model for exploring combinations of sensors/platforms for any given image resolution. The model produces camera position, camera attitude, and synthetic camera data that can be used for exploitation purposes. We focus on electro-optical (EO) visible sensors to simplify the rendering but this work could be extended to use other rendering tools that support different modalities. Due to the computational complexity of ray tracing we employ the Amazon Elastic Cloud Computer to help speed up the generation of large ray traced scenes. The key idea of the paper is to provide an architecture for layered sensing simulation which is modular in design and constructed on open-source off-the-shelf software. This architecture shows how leveraging existing open-source software allows for practical layered sensing modeling to be rapidly assimilated and utilized in real-world applications. In this paper we demonstrate our model output is automatically exploitable by using generated data with an innovative video frame mosaic algorithm.
750 GeV diphotons from closed string states
NASA Astrophysics Data System (ADS)
Anchordoqui, Luis A.; Antoniadis, Ignatios; Goldberg, Haim; Huang, Xing; Lüst, Dieter; Taylor, Tomasz R.
2016-04-01
We show that low-mass-scale string compactifications, with a generic D-brane configuration that realizes the standard model by open strings, can explain the relatively broad peak in the diphoton invariant mass spectrum at 750 GeV recently reported by the ATLAS and CMS Collaborations. Under reasonable assumptions, we demonstrate that the excess could originate from a closed string (possibly axionic) excitation φ that has a coupling with gauge kinetic terms. We estimate the φ production rate from photon-photon fusion in elastic pp scattering, using the effective photon and narrow width approximations. For string scales above today's lower limit Ms ≈ 7 TeV, we can accommodate the diphoton rate observed at Run II while maintaining consistency with Run I data.
Constructing de Sitter vacua in no-scale string models without uplifting
NASA Astrophysics Data System (ADS)
Covi, Laura; Gomez-Reino, Marta; Gross, Christian; Palma, Gonzalo A.; Scrucca, Claudio A.
2009-03-01
We develop a method for constructing metastable de Sitter vacua in Script N = 1 supergravity models describing the no-scale volume moduli sector of Calabi-Yau string compactifications. We consider both heterotic and orientifold models. Our main guideline is the necessary condition for the existence of metastable vacua coming from the Goldstino multiplet, which constrains the allowed scalar geometries and supersymmetry-breaking directions. In the simplest non-trivial case where the volume is controlled by two moduli, this condition simplifies and turns out to be fully characterised by the intersection numbers of the Calabi-Yau manifold. We analyse this case in detail and show that once the metastability condition is satisfied it is possible to reconstruct in a systematic way the local form of the superpotential that is needed to stabilise all the fields. We apply then this procedure to construct some examples of models where the superpotential takes a realistic form allowed by flux backgrounds and gaugino condensation effects, for which a viable vacuum arises without the need of invoking corrections to the Kähler potential breaking the no-scale property or uplifting terms. We finally discuss the prospects of constructing potentially realistic models along these lines.
The social structure of experimental'' strings at Fermilab; a physics and detector driven model
Bodnarczuk, M.
1990-12-12
Physicists in HEP have been forced to organize large scientific projects without a well defined organizational or sociological model to guide them. In the absence of such models, what structures do experimentalists use to develop social structures in HEP In this paper, I claim that physicists organize around what they know best, the physics problems they study and the detectors and devices they study them with. After describing the advent of management'' in HEP, I use a case study of 4 Fermilab experiments as the base upon which to propose a physics and detector driven model of social structure for experiments. In addition, I show how this model can be extended to describe strings'' of experiments, where continuities of physics interests, spectrometer design, and a core group of physicists become a definable sociological unit that can exist for over 15 years. A dominate theme that emerges from my analysis is the conscious attempt on the part of experimenters to remove the uncertainties that are part of the practice of HEP.
Botelho, L.C.L.
1987-02-15
In this paper, we investigate the role of the chiral anomaly in determining the spectrum at the saddle-point approximation D..-->..-infinity of the recently considered Polyakov formulation of bosonic strings moving in R/sup D/ x G with K = 2, where G is the group manifold SO(N). The main result is, opposite to the critical dimension, that the spectrum is not sensitive to the model chiral anomaly in the D..-->..-infinity limit.
NASA Astrophysics Data System (ADS)
Wang, Hai Tao; Cho, Sam Young
2015-01-01
In order to investigate the quantum phase transition in the one-dimensional quantum compass model, we numerically calculate non-local string correlations, entanglement entropy and fidelity per lattice site by using the infinite matrix product state representation with the infinite time evolving block decimation method. In the whole range of the interaction parameters, we find that four distinct string orders characterize the four different Haldane phases and the topological quantum phase transition occurs between the Haldane phases. The critical exponents of the string order parameters β = 1/8 and the cental charges c = 1/2 at the critical points show that the topological phase transitions between the phases belong to an Ising type of universality classes. In addition to the string order parameters, the singularities of the second derivative of the ground state energies per site, the continuous and singular behaviors of the Von Neumann entropy and the pinch points of the fidelity per lattice site manifest that the phase transitions between the phases are of the second-order, in contrast to the first-order transition suggested in previous studies.
Wang, Hai Tao; Cho, Sam Young
2015-01-14
In order to investigate the quantum phase transition in the one-dimensional quantum compass model, we numerically calculate non-local string correlations, entanglement entropy and fidelity per lattice site by using the infinite matrix product state representation with the infinite time evolving block decimation method. In the whole range of the interaction parameters, we find that four distinct string orders characterize the four different Haldane phases and the topological quantum phase transition occurs between the Haldane phases. The critical exponents of the string order parameters β = 1/8 and the cental charges c = 1/2 at the critical points show that the topological phase transitions between the phases belong to an Ising type of universality classes. In addition to the string order parameters, the singularities of the second derivative of the ground state energies per site, the continuous and singular behaviors of the Von Neumann entropy and the pinch points of the fidelity per lattice site manifest that the phase transitions between the phases are of the second-order, in contrast to the first-order transition suggested in previous studies. PMID:25478955
Jamieson, Randall K; Mewhort, D J K
2010-05-01
Jamieson and Mewhort (2009a) demonstrated that performance in the artificial-grammar task could be understood using an exemplar model of memory. We reinforce the position by testing the model against data for individual test items both in a standard artificial-grammar experiment and in a string-completion variant of the standard procedure. We argue that retrieval is sensitive to structure in memory. The work ties performance in the artificial-grammar task to principles of explicit memory. PMID:19851941
Cosmic sparks from superconducting strings.
Vachaspati, Tanmay
2008-10-01
We investigate cosmic sparks from cusps on superconducting cosmic strings in light of the recently discovered millisecond radio burst by Lorimer et al.. We find that the observed duration, fluence, spectrum, and event rate can be reasonably explained by grand unification scale superconducting cosmic strings that carry currents approximately 10{5} GeV. The superconducting string model predicts an event rate that falls off only as S{-1/2}, where S is the energy flux, and hence predicts a population of very bright bursts. Other surveys, with different observational parameters, are shown to impose tight constraints on the superconducting string model. PMID:18851517
Cosmic Sparks from Superconducting Strings
Vachaspati, Tanmay
2008-10-03
We investigate cosmic sparks from cusps on superconducting cosmic strings in light of the recently discovered millisecond radio burst by Lorimer et al.. We find that the observed duration, fluence, spectrum, and event rate can be reasonably explained by grand unification scale superconducting cosmic strings that carry currents {approx}10{sup 5} GeV. The superconducting string model predicts an event rate that falls off only as S{sup -1/2}, where S is the energy flux, and hence predicts a population of very bright bursts. Other surveys, with different observational parameters, are shown to impose tight constraints on the superconducting string model.
Transverse structure of the QCD string
Meyer, Harvey B.
2010-11-15
The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is a particularly natural probe at next-to-leading order. Second, we derive the constraints imposed by open-closed string duality on the transverse structure of the string. We show that a total of three independent ''gravitational'' form factors characterize the transverse profile of the closed string, and obtain the interpretation of recent effective string theory calculations: the square radius of a closed string of length {beta} defined from the slope of its gravitational form factor, is given by (d-1/2{pi}{sigma})log({beta}/4r{sub 0}) in d space dimensions. This is to be compared with the well-known result that the width of the open string at midpoint grows as (d-1/2{pi}{sigma})log(r/r{sub 0}). We also obtain predictions for transition form factors among closed-string states.
Open-closed homotopy algebra in mathematical physics
Kajiura, Hiroshige; Stasheff, Jim
2006-02-15
In this paper we discuss various aspects of open-closed homotopy algebras (OCHAs) presented in our previous paper, inspired by Zwiebach's open-closed string field theory, but that first paper concentrated on the mathematical aspects. Here we show how an OCHA is obtained by extracting the tree part of Zwiebach's quantum open-closed string field theory. We clarify the explicit relation of an OCHA with Kontsevich's deformation quantization and with the B-models of homological mirror symmetry. An explicit form of the minimal model for an OCHA is given as well as its relation to the perturbative expansion of open-closed string field theory. We show that our open-closed homotopy algebra gives us a general scheme for deformation of open string structures (A{sub {infinity}} algebras) by closed strings (L{sub {infinity}} algebras)
Casalbuoni, Roberto; Gomis, Joaquim; Longhi, Giorgio
2007-12-15
We construct a classical nonrelativistic string model in 3+1 dimensions. The model contains a spurion tensor field that is responsible for the noncommutative structure of the model. Under double-dimensional reduction the model reduces to the exotic nonrelativistic particle in 2+1 dimensions.
Analytical model for CMB temperature angular power spectrum from cosmic (super-)strings
Yamauchi, Daisuke; Yoo, Chul-Moon; Sasaki, Misao; Takahashi, Keitaro; Sendouda, Yuuiti
2010-09-15
We present a new analytical method to calculate the small angle cosmic microwave background (CMB) temperature angular power spectrum due to cosmic (super-)string segments. In particular, using our method, we clarify the dependence on the intercommuting probability P. We find that the power spectrum is dominated by Poisson-distributed string segments. The power spectrum for a general value of P has a plateau on large angular scales and shows a power-law decrease on small angular scales. The resulting spectrum in the case of conventional cosmic strings is in very good agreement with the numerical result obtained by Fraisse et al.. Then we estimate the upper bound on the dimensionless tension of the string for various values of P by assuming that the fraction of the CMB power spectrum due to cosmic (super-)strings is less than ten percent at various angular scales up to l=2000. We find that the amplitude of the spectrum increases as the intercommuting probability. As a consequence, strings with smaller intercommuting probabilities are found to be more tightly constrained.
Cell-balancing currents in parallel strings of a battery system
NASA Astrophysics Data System (ADS)
Dubarry, Matthieu; Devie, Arnaud; Liaw, Bor Yann
2016-07-01
Lithium-ion batteries are attractive for vehicle electrification or grid modernization applications. In these applications, battery packs are required to have multiple-cell configurations and battery management system to operate properly and safely. Here, a useful equivalent circuit model was developed to simulate the spontaneous transient balancing currents among parallel strings in a battery system. The simulation results were validated with experimental data to illustrate the accuracy and validity of the model predictions. Understanding the transient behavior of such cell and string balancing in a parallel circuit configuration is very important to assess the impacts of current fluctuation and cell variability on a battery system's performance, regarding durability, reliability, safety, abuse tolerance and failure prevention, including possible short circuit or open circuit conditions. Additional features and advantages, including the ability to assessing impacts on the performance of the string assemblies from string swapping or cell/module replacement in the strings, could be realized to aid battery management, maintenance and repair.
The minimal SUSY B - L model: simultaneous Wilson lines and string thresholds
NASA Astrophysics Data System (ADS)
Deen, Rehan; Ovrut, Burt A.; Purves, Austin
2016-07-01
In previous work, we presented a statistical scan over the soft supersymmetry breaking parameters of the minimal SUSY B - L model. For specificity of calculation, unification of the gauge parameters was enforced by allowing the two Z_3× Z_3 Wilson lines to have mass scales separated by approximately an order of magnitude. This introduced an additional "left-right" sector below the unification scale. In this paper, for three important reasons, we modify our previous analysis by demanding that the mass scales of the two Wilson lines be simultaneous and equal to an "average unification" mass < M U >. The present analysis is 1) more "natural" than the previous calculations, which were only valid in a very specific region of the Calabi-Yau moduli space, 2) the theory is conceptually simpler in that the left-right sector has been removed and 3) in the present analysis the lack of gauge unification is due to threshold effects — particularly heavy string thresholds, which we calculate statistically in detail. As in our previous work, the theory is renormalization group evolved from < M U > to the electroweak scale — being subjected, sequentially, to the requirement of radiative B - L and electroweak symmetry breaking, the present experimental lower bounds on the B - L vector boson and sparticle masses, as well as the lightest neutral Higgs mass of ˜125 GeV. The subspace of soft supersymmetry breaking masses that satisfies all such constraints is presented and shown to be substantial.
A string-inspired model for the low-ℓ CMB
NASA Astrophysics Data System (ADS)
Kitazawa, N.; Sagnotti, A.
2015-07-01
We present a semi-analytic exploration of some low-ℓ angular power spectra inspired by “brane supersymmetry breaking (BSB)”. This mechanism splits Bose and Fermi excitations in string theory, leaving behind an exponential potential that is just too steep for the inflaton to emerge from the initial singularity while descending it. As a result, the scalar generically bounces against the exponential wall, which typically introduces an infrared depression and a pre-inflationary peak in the power spectrum of scalar perturbations. We elaborate on a possible link between this phenomenon and the low-ℓ CMB. For the first 32 multipoles, combining the hard exponential with a milder one leading to ns ≃ 0.96 and with a small Gaussian bump, we have attained a reduction of χ2 to about 46% of the standard ΛCDM setting, with both WMAP9 and PLANCK 2013 data. This result corresponds to a χ2/DOF of about 0.45, to be compared with a ΛCDM value of about 0.85. The preferred choices combine naturally quadrupole depression, a first peak around ℓ = 5 and a wide minimum around ℓ = 20. We have also gathered some evidence that similar spectra emerge if the hard exponential is combined with more realistic models of inflation. A problem of the preferred examples is their slow convergence to an almost scale-invariant profile.
Average formation lengths of baryons and antibaryons in a string model
Grigoryan, L.
2011-01-15
In this work the investigation of the space-time scales of the hadronization process in the framework of a string model is continued. The average formation lengths of several widely used species of baryons (antibaryons) such as p(p-bar), n(n-bar), {Delta}({Delta}-bar), {Lambda}({Lambda}-bar), and {Sigma}({Sigma}-bar) are studied. It is shown that they depend on electrical charges or, more precisely, on the quark contents of the hadrons. In particular, the average formation lengths of positively charged hadrons, for example, protons, are considerably larger than those of their negatively charged antiparticles, antiprotons. This statement for all nuclear targets and any values of the Bjorken scaling variable x{sub Bj} is fulfilled. The main mechanism is direct production. Additional production mechanism as a result of the decay of resonances gives small contribution. It is shown that the average formation lengths of protons (antiprotons) are slowly increasing (decreasing) functions of x{sub Bj}, whereas the ones of neutrons and antineutrons are slowly decreasing functions of x{sub Bj}. The shape and behavior of average formation lengths for baryons qualitatively coincide with the ones for pseudoscalar mesons obtained earlier.
Evolution of cosmic string networks
NASA Technical Reports Server (NTRS)
Albrecht, Andreas; Turok, Neil
1989-01-01
Results on cosmic strings are summarized including: (1) the application of non-equilibrium statistical mechanics to cosmic string evolution; (2) a simple one scale model for the long strings which has a great deal of predictive power; (3) results from large scale numerical simulations; and (4) a discussion of the observational consequences of our results. An upper bound on G mu of approximately 10(-7) emerges from the millisecond pulsar gravity wave bound. How numerical uncertainties affect this are discussed. Any changes which weaken the bound would probably also give the long strings the dominant role in producing observational consequences.
The Open Learning Object Model to Promote Open Educational Resources
ERIC Educational Resources Information Center
Fulantelli, Giovanni; Gentile, Manuel; Taibi, Davide; Allegra, Mario
2008-01-01
In this paper we present the results of research work, that forms part of the activities of the EU-funded project SLOOP: Sharing Learning Objects in an Open Perspective, aimed at encouraging the definition, development and management of Open Educational Resources based on the Learning Object paradigm (Wiley, 2000). We present a model of Open…
Strings and their compactification from the particle viewpoint
Slansky, R.
1986-01-01
A series of four lectures is given which deals with the particle formulation of string theory. An introductory lecture is given on where the idea of strings comes from and what strings are. An introduction is given to simple Lie algebras and their representations. Compactified strings and the heterotic theories are discussed, showing how infinite-dimensional Kac-Moody affine algebras can be spectrum generating algebras in (open) string theories. The spectrum of excited states of the heterotic string is examined, and comments are made on representations of affine algebras. Some aspects are shown of the algebraic structure of compactified closed bosonic strings. (LEW)
NASA Astrophysics Data System (ADS)
Ueresin, C.; Decker, L.; Treite, P.
In 2011, Linde Cryogenics, a division of Linde Process Plants, Tulsa, Oklahoma, was awarded the contract to deliver a 500 W at 2 K superfluid cryogenic plant to Fermi National Accelerator Laboratory (FNAL) in Batavia, Illinois, USA. This system includes a cold compressor string with three centrifugal compressors and a vacuum pump skid with five volumetric pumps in parallel used to pump down helium to its saturation pressure corresponding to 2 K. Linde Kryotechnik AG, Pfungen Switzerland engineered and supplied the cold compressor system and commissioned it with its control logic to cover the complete range of system operation. The paper outlines issues regarding compressor design, compressor string modeling, control algorithms, controller performance, and surge protection.
Cosmic strings and superconducting cosmic strings
NASA Technical Reports Server (NTRS)
Copeland, Edmund
1988-01-01
The possible consequences of forming cosmic strings and superconducting cosmic strings in the early universe are discussed. Lecture 1 describes the group theoretic reasons for and the field theoretic reasons why cosmic strings can form in spontaneously broken gauge theories. Lecture 2 discusses the accretion of matter onto string loops, emphasizing the scenario with a cold dark matter dominated universe. In lecture 3 superconducting cosmic strings are discussed, as is a mechanism which leads to the formation of structure from such strings.
Amore, Paolo; Fernández, Francisco M.; Garcia, Javier; Gutierrez, German
2014-04-15
We study both analytically and numerically the spectrum of inhomogeneous strings with PT-symmetric density. We discuss an exactly solvable model of PT-symmetric string which is isospectral to the uniform string; for more general strings, we calculate exactly the sum rules Z(p)≡∑{sub n=1}{sup ∞}1/E{sub n}{sup p}, with p=1,2,… and find explicit expressions which can be used to obtain bounds on the lowest eigenvalue. A detailed numerical calculation is carried out for two non-solvable models depending on a parameter, obtaining precise estimates of the critical values where pair of real eigenvalues become complex. -- Highlights: •PT-symmetric Hamiltonians exhibit real eigenvalues when PT symmetry is unbroken. •We study PT-symmetric strings with complex density. •They exhibit regions of unbroken PT symmetry. •We calculate the critical parameters at the boundaries of those regions. •There are exact real sum rules for some particular complex densities.
NASA Astrophysics Data System (ADS)
Haghighat, Babak; Iqbal, Amer; Kozçaz, Can; Lockhart, Guglielmo; Vafa, Cumrun
2015-03-01
M2 branes suspended between adjacent parallel M5 branes lead to light strings, the `M-strings'. In this paper we compute the elliptic genus of M-strings, twisted by maximally allowed symmetries that preserve 2 d (2, 0) supersymmetry. In a codimension one subspace of parameters this reduces to the elliptic genus of the (4, 4) supersymmetric A n-1 quiver theory in 2 d. We contrast the elliptic genus of N M-strings with the (4, 4) sigma model on the N-fold symmetric product of . For N = 1 they are the same, but for N > 1 they are close, but not identical. Instead the elliptic genus of (4, 4) N M-strings is the same as the elliptic genus of (4, 0) sigma models on the N-fold symmetric product of , but where the right-moving fermions couple to a modification of the tangent bundle. This construction arises from a dual A n-1 quiver 6 d gauge theory with U(1) gauge groups. Moreover, we compute the elliptic genus of domain walls which separate different numbers of M2 branes on the two sides of the wall.
Giant gravitons - with strings attached (III)
NASA Astrophysics Data System (ADS)
Bekker, David; de Mello Koch, Robert; Stephanou, Michael
2008-02-01
We develop techniques to compute the one-loop anomalous dimensions of operators in the Script N = 4 super Yang-Mills theory that are dual to open strings ending on boundstates of sphere giant gravitons. Our results, which are applicable to excitations involving an arbitrary number of open strings, generalize the single string results of hep-th/0701067. The open strings we consider carry angular momentum on an S3 embedded in the S5 of the AdS5 × S5 background. The problem of computing the one loop anomalous dimensions is replaced with the problem of diagonalizing an interacting Cuntz oscillator Hamiltonian. Our Cuntz oscillator dynamics illustrates how the Chan-Paton factors for open strings propagating on multiple branes can arise dynamically.
Light-like big bang singularities in string and matrix theories
NASA Astrophysics Data System (ADS)
Craps, Ben; Evnin, Oleg
2011-10-01
Important open questions in cosmology require a better understanding of the big bang singularity. In string and matrix theories, light-like analogues of cosmological singularities (singular plane wave backgrounds) turn out to be particularly tractable. We give a status report on the current understanding of such light-like big bang models, presenting both solved and open problems.
Cosmic strings from supersymmetric flat directions
Cui Yanou; Morrissey, David E.; Martin, Stephen P.; Wells, James D.
2008-02-15
Flat directions are a generic feature of the scalar potential in supersymmetric gauge field theories. They can arise, for example, from D-terms associated with an extra Abelian gauge symmetry. Even when supersymmetry is broken softly, there often remain directions in the scalar field space along which the potential is almost flat. Upon breaking a gauge symmetry along one of these almost-flat directions, cosmic strings may form. Relative to the standard cosmic string picture based on the Abelian Higgs model, these flat-direction cosmic strings have the extreme type-I properties of a thin gauge core surrounded by a much wider scalar field profile. We perform a comprehensive study of the microscopic, macroscopic, and observational characteristics of this class of strings. We find many differences from the standard string scenario, including stable higher winding-mode strings, the dynamical formation of higher mode strings from lower ones, and a resultant multitension scaling string network in the early universe. These strings are only moderately constrained by current observations, and their gravitational wave signatures may be detectable at future gravity wave detectors. Furthermore, there is the interesting but speculative prospect that the decays of cosmic string loops in the early universe could be a source of ultrahigh-energy cosmic rays or nonthermal dark matter. We also compare the observational signatures of flat-direction cosmic strings with those of ordinary cosmic strings as well as (p,q) cosmic strings motivated by superstring theory.
Extending the isolated horizon phase space to string-inspired gravity models
NASA Astrophysics Data System (ADS)
Liko, Tomas
An isolated horizon (IH) is a null hypersurface at which the geometry is held fixed. This generalizes the notion of an event horizon so that the black hole is an object that is in local equilibrium with its (possibly) dynamic environment. The first law of IH mechanics that arises from the framework relates quantities that are all defined at the horizon. IHs have been extensively studied in Einstein gravity with various matter couplings and rotation, and in asymptotically flat and asymptotically anti-de Sitter (ADS) spacetimes in all dimensions D ≥ 3. Motivated by the nonuniqueness of black holes in higher dimensions and by the black-hole/string correspondence principle, we devote this thesis to the extension of the framework to include IHs in string-inspired gravity models, specifically to Einstein-Maxwell-Chern-Simons (EM-CS) theory and to Einstein-Gauss-Bonnet (EGB) theory in higher dimensions. The focus is on determining the generic features of black holes that are solutions to the field equations of the theories under consideration. To this end, we construct a covariant phase space for both theories; this allows us to prove that the corresponding weakly IHs (WIHs) satisfy the zeroth and first laws of black-hole mechanics. For EM-CS theory, we find that in the Emit when the surface gravity of the horizon goes to zero there is a topological constraint. Specifically, the integral of the scalar curvature of the cross sections of the horizon has to be positive when the dominant energy condition is satisfied and the cosmological constant A is zero or positive. There is no constraint on the topology of the horizon cross sections when Λ < 0. These results on topology of IHs are independent of the material content of the stress-energy tensor, and therefore the conclusions for EM-CS theory carry over to theories with arbitrary matter fields (minimally) coupled to Einstein gravity. In addition, we consider rotating IHs in asymptotically ADS and flat spacetimes, and
NASA Astrophysics Data System (ADS)
Alvarez, Enrique; Meessen, Patrick
1999-02-01
This is the written version of a set of introductory lectures to string theory. The lectures were given at the Universidad Autónoma de Madrid in the semester 1997/98 and at the VI Escuela de Otoño de Física Teórica, held in Santiago de Compostela (10-23 september 1998).
ERIC Educational Resources Information Center
New York State Education Dept., Albany. Bureau of Secondary Curriculum Development.
Intended primarily for use by instrumental music teachers who do not have a major concentration in strings, this guide provides pertinent basic resources, materials, teaching--learning expectation, and a general overall guide to achievement levels at various stages of development. Discussions are presented of Choosing the Proper Method Book,…
Hoeflinger, J P; de Supinski, B R
2005-06-01
The memory model of OpenMP has been widely misunderstood since the first OpenMP specification was published in 1997 (Fortran 1.0). The proposed OpenMP specification (version 2.5) includes a memory model section to address this issue. This section unifies and clarifies the text about the use of memory in all previous specifications, and relates the model to well-known memory consistency semantics. In this paper, we discuss the memory model and show its implications for future distributed shared memory implementations of OpenMP.
False beats in coupled piano string unisons
NASA Astrophysics Data System (ADS)
Capleton, Brian
2004-02-01
The behavior of a unison pair of piano strings coupled by the soundboard bridge, when one string has localized anisotropy in the reactive part of the bridge admittance for a given partial frequency, can be investigated using a theoretical matrix description. The anisotropy can cause what in piano tuning terminology is referred to as ``false beating'' in a partial of the single string. A mathematical model can be used to illustrate how ``mistunings'' between the strings of the unison (measured when the strings are sounding in isolation from each other) may theoretically arise as a consequence of the normal practice in piano tuning, of eliminating or reducing audible beating in the unison when both strings are sounding. ``False beats'' in a single string partial can be ``inherited'' by a partial of the coupled unison's spectrum, and mistunings between the strings can eliminate or reduce the appearance of this inheritance.
False beats in coupled piano string unisons.
Capleton, Brian
2004-02-01
The behavior of a unison pair of piano strings coupled by the soundboard bridge, when one string has localized anisotropy in the reactive part of the bridge admittance for a given partial frequency, can be investigated using a theoretical matrix description. The anisotropy can cause what in piano tuning terminology is referred to as "false beating" in a partial of the single string. A mathematical model can be used to illustrate how "mistunings" between the strings of the unison (measured when the strings are sounding in isolation from each other) may theoretically arise as a consequence of the normal practice in piano tuning, of eliminating or reducing audible beating in the unison when both strings are sounding. "False beats" in a single string partial can be "inherited" by a partial of the coupled unison's spectrum, and mistunings between the strings can eliminate or reduce the appearance of this inheritance. PMID:15000199
Relation between strings and ribbon knots
Ahmed, E. Mansoura Univ. ); El-Rifai, E.A. ); Abdellatif, R.A. )
1991-02-01
A ribbon knot can be representation as the propagation of an open string in (Euclidean) space-time. By imposing physical conditions plus an ansatz on the string scattering amplitude. The authors get invariant polynomials of ribbon knots which correspond to Jones and Wadati et al. polynomials for ordinary knots. Motivated by the string scattering vertices, they derive an algebra which is a generalization of Hecke and Murakami-Birman-Wenzel (BMW) algebras of knots.
Relation between strings and ribbon knots
NASA Astrophysics Data System (ADS)
Ahmed, E.; El-Rifai, E. A.; Abdellatif, R. A.
1991-02-01
A ribbon knot can be represented as the propagation of an open string in (Euclidean) space-time. By imposing physical conditions plus an ansatz on the string scattering amplitude, we get invariant polynomials of ribbon knots which correspond to Jones and Wadati et al. polynomials for ordinary knots. Motivated by the string scattering vertices, we derive an algebra which is a generalization of Hecke and Murakami-Birman-Wenzel (BMW) algebras of knots.
Fermionic Subspaces of the Bosonic String
NASA Astrophysics Data System (ADS)
Chattaraputi, A.; Englert, F.; Houart, L.; Taormina, A.
A universal symmetric truncation of the bosonic string Hilbert space yields all known closed fermionic string theories in ten dimensions, their D-branes and their open descendants. We highlight the crucial role played by group theory and two-dimensional conformal field theory in the construction and emphasize the predictive power of the truncation. Such circumstantial evidence points towards the existence of a mechanism which generates space-time fermions out of bosons dynamically within the framework of bosonic string theory.
Fermionic subspaces of the bosonic string
NASA Astrophysics Data System (ADS)
Chattaraputi, Auttakit; Englert, François; Houart, Laurent; Taormina, Anne
2003-06-01
A universal symmetric truncation of the bosonic string Hilbert space yields all known closed fermionic string theories in ten dimensions, their D-branes and their open descendants. We highlight the crucial role played by group theory and two-dimensional conformal field theory in the construction and emphasize the predictive power of the truncation. Such circumstantial evidence points towards the existence of a mechanism which generates spacetime fermions out of bosons dynamically within the framework of bosonic string theory.
Bachas, C.P.
1988-01-01
We review the construction and properties of four dimensional string models, using free fermions on the world-sheet. We prove that as opposed to gauge symmetries, broken space-time supersymmetry can only be restored continuously by decompactification. 40 refs.
NASA Astrophysics Data System (ADS)
Bautista, I.; Téllez, A. Fernandez; Ghosh, Premomoy
2015-10-01
We analyze high-multiplicity proton-proton (p p ) collision data in the framework of the string percolation model that has been successful in describing several phenomena of multiparticle production, including the signatures of recent discovery of strongly interacting partonic matter, the quark-gluon plasma, in relativistic heavy-ion collisions. Our study in terms of the ratio of shear viscosity and entropy density (η /s ) and the [Lattice Quantum Chromodinamics (LQCD)] predicted signature of QCD change of phase, in terms of the effective number of degrees of freedom (ɛ /T4), reiterates the possibility of a strongly interacting collective medium in these events.
Spin-dependent effects in the roughened string model for heavy quarkonia
Kaur, R. ); Bambah, B.A. )
1993-06-01
Using the recently proposed roughened string potential for heavy quarkonium, we calculate the spin splitting in the [ital J]/[psi] and [Upsilon] systems. We show how the departure from linearity of this potential affects the hyperfine splitting in the [ital P] levels of these systems, in a way consistent with experimental data. This lends support to the recent observations that the confining part of the interquark potential is weaker than linear.
Ahn, C.
1989-08-01
We study two aspects of one loop structures in quantum field theories which describe two different areas of particle physics: the one loop unitarity behavior of the Standard Model of electroweak interactions and modular invariance of string model theory. Loop expansion has its importance in that it contains quantum fluctuations due to all physical states in the theory. Therefore, by studying the various models to one loop, we can understand how the contents of the theory can contribute to physically measurable quantities and how the consistency at quantum level restricts the physical states of the theory, as well. In the first half of the thesis, we study one loop corrections to the process {ital e}{sup +}{ital e}{sup {minus}} {yields} {ital W}{sup +}{ital W}{sup {minus}}. In this process, there is a delicate unitarity-saving cancellation between s-channel and t-channel tree level Feynman diagrams. If the one loop contribution due to heavy particles corrects the channels asymmetrically, the cancellation, hence unitarity, will be delayed up to the mass scale of these heavy particles. We refer to this phenomena as the unitarity delay effect. Due to this effect, cross section below these mass scales can have significant radiative corrections which may provide an appropriate window through which we can see the high energy structure of the Standard Model from relatively low energy experiments. In the second half, we will show how quantum consistency can restrict the physical states in string theory. 53 refs., 13 figs.
ERIC Educational Resources Information Center
Hoover, Todd F.
2010-01-01
The "Magic" String is a discrepant event that includes a canister with what appears to be the end of two strings protruding from opposite sides of it. Due to the way the strings are attached inside the canister, it appears as if the strings can magically switch the way they are connected. When one string end is pulled, the observer's expectation…
String mediated phase transitions
NASA Technical Reports Server (NTRS)
Copeland, ED; Haws, D.; Rivers, R.; Holbraad, S.
1988-01-01
It is demonstrated from first principles how the existence of string-like structures can cause a system to undergo a phase transition. In particular, the role of topologically stable cosmic string in the restoration of spontaneously broken symmetries is emphasized. How the thermodynamic properties of strings alter when stiffness and nearest neighbor string-string interactions are included is discussed.
NASA Astrophysics Data System (ADS)
Sumitomo, Yoske; Tye, S.-H. Henry; Wong, Sam S. C.
2013-07-01
We study a racetrack model in the presence of the leading α'-correction in flux compactification in Type IIB string theory, for the purpose of getting conceivable de-Sitter vacua in the large compactified volume approximation. Unlike the Kähler Uplift model studied previously, the α'-correction is more controllable for the meta-stable de-Sitter vacua in the racetrack case since the constraint on the compactified volume size is very much relaxed. We find that the vacuum energy density Λ for de-Sitter vacua approaches zero exponentially as the volume grows. We also analyze properties of the probability distribution of Λ in this class of models. As in other cases studied earlier, the probability distribution again peaks sharply at Λ = 0. We also study the Racetrack Kähler Uplift model in the Swiss-Cheese type model.
Open intersection numbers, Kontsevich-Penner model and cut-and-join operators
NASA Astrophysics Data System (ADS)
Alexandrov, Alexander
2015-08-01
We continue our investigation of the Kontsevich-Penner model, which describes intersection theory on moduli spaces both for open and closed curves. In particular, we show how Buryak's residue formula, which connects two generating functions of intersection numbers, appears in the general context of matrix models and tau-functions. This allows us to prove that the Kontsevich-Penner matrix integral indeed describes open intersection numbers. For arbitrary N we show that the string and dilaton equations completely specifythe solution of the KP hierarchy. We derive a complete family of the Virasoro and W-constraints, and using these constraints, we construct the cut-and-join operators. The case N = 1, corresponding to open intersection numbers, is particularly interesting: for this case we obtain two different families of the Virasoro constraints, so that the difference between them describes the dependence of the tau-function on even times.
Svrcek, Peter; Witten, Edward; /Princeton, Inst. Advanced Study
2006-06-09
In the context of string theory, axions appear to provide the most plausible solution of the strong CP problem. However, as has been known for a long time, in many string-based models, the axion coupling parameter Fa is several orders of magnitude higher than the standard cosmological bounds. We re-examine this problem in a variety of models, showing that Fa is close to the GUT scale or above in many models that have GUT-like phenomenology, as well as some that do not. On the other hand, in some models with Standard Model gauge fields supported on vanishing cycles, it is possible for Fa to be well below the GUT scale.
Recurrence relations of Kummer functions and Regge string scattering amplitudes
NASA Astrophysics Data System (ADS)
Lee, Jen-Chi; Mitsuka, Yoshihiro
2013-04-01
We discover an infinite number of recurrence relations among Regge string scattering amplitudes [11, 30] of different string states at arbitrary mass levels in the open bosonic string theory. As a result, all Regge string scattering amplitudes can be algebraically solved up to multiplicative factors. Instead of decoupling zero-norm states in the fixed angle regime, the calculation is based on recurrence relations and addition theorem of Kummer functions of the second kind. These recurrence relations among Regge string scattering amplitudes are dual to linear relations or symmetries among high-energy fixed angle string scattering amplitudes discovered previously.
The Commercial Open Source Business Model
NASA Astrophysics Data System (ADS)
Riehle, Dirk
Commercial open source software projects are open source software projects that are owned by a single firm that derives a direct and significant revenue stream from the software. Commercial open source at first glance represents an economic paradox: How can a firm earn money if it is making its product available for free as open source? This paper presents the core properties of com mercial open source business models and discusses how they work. Using a commercial open source approach, firms can get to market faster with a superior product at lower cost than possible for traditional competitors. The paper shows how these benefits accrue from an engaged and self-supporting user community. Lacking any prior comprehensive reference, this paper is based on an analysis of public statements by practitioners of commercial open source. It forges the various anecdotes into a coherent description of revenue generation strategies and relevant business functions.