2071005
Spacetime Virasoro algebra from strings on zero radius AdS3
We study bosonic string theory in the light-cone gauge on AdS3 spacetime with zero radius of curvature (in string units) R/(?')1/2 = 0. We find that the worldsheet theory admits an infinite number of conserved quantities which are naturally interpreted as spacetime charges and which form a representation of (two commuting copies of) a Virasoro algebra. Near the boundary of AdS3 these charges are found to be isomorphic to the infinite set of asymptotic Killing vectors of AdS3 found originally by Brown and Henneaux. In addition to the spacetime Virasoro algebra, there is a worldsheet Virasoro algebra that generates diffeomorphisms of the spatial coordinate of the string worldsheet. We find that if the worldsheet Virasoro algebra has a central extension then the spacetime Virasoro algebra acquires a central extension via a mechanism similar to that encountered in the context of the SL(2,) WZW model. Our observations are consistent with a recently proposed duality between bosonic strings on zero radius AdSd+1 and free field theory in d dimensions.
10546536
Instabilities of the small black hole: a view from N = 4 SYM
We compute a one-loop effective action for the constant modes of the scalars and the Polyakov loop matrix of = 4 SYM on S3 at finite temperature and weak 't Hooft coupling. Above a critical temperature, the effective potential develops new unstable directions accompanied by new saddle points which only preserve an SO(5) subgroup of the SO(6) global R-symmetry. We identify this phenomenon as the weak coupling version of the well known Gregory-Laflamme localization instability in the gravity dual of the strongly coupled field theory: The small AdS5 black hole when viewed as a ten dimensional, asymptotically AdS5 × S5 solution smeared on the S5 is unstable to localization on S5. Our effective potential, in a specific Lorentzian continuation, can provide a qualitative holographic description of the decay of the ``topological black hole'' into the AdS bubble of nothing.
17544914
Precision test of AdS/CFT in Lunin-Maldacena background
We obtain the solutions and explicitly calculate the energy for a class of two-spin semiclassical string states in the Lunin-Maldacena background. These configurations are the β-deformed versions of the folded string solutions in AdS5 × S5 background. They correspond to certain single trace operators in the = 1 superconformal β deformation of = 4 Yang-Mills. We calculate the one loop anomalous dimension for the dual single trace operators from the associated twisted spin chain with a general two-cut distribution of Bethe roots. Our results show a striking match between the two calculations. We demonstrate the natural identification of parameters on the two sides of the analysis, and explain the significance of the Virasoro constraint associated with the winding motion of semiclassical strings from the perspective of the spin chain solution.
117647469
Non-Equilibrium Dynamics in a New Inflation Model and Cosmological Perturbations
14488849
Inflaton decay in de Sitter spacetime
We study the decay of scalar fields, in particular the inflaton, into lighter scalars in a de Sitter spacetime background. After providing a practical definition of the rate, we focus on the case of an inflaton interacting with a massless scalar field either minimally or conformally coupled to the curvature. The evolution equation for the expectation value of the inflaton is obtained to one loop order in perturbation theory and the decay rate is recognized from the solution. We find the remarkable result that this decay rate displays an equilibrium Bose-enhancement factor with an effective temperature given by the Hawking temperature H/2{pi}, where H is the Hubble constant. This contribution is interpreted as the {open_quotes}stimulated emission{close_quotes} of bosons in a thermal bath at the Hawking temperature. In the context of new inflation scenarios, we show that inflaton decay into conformally coupled massless fields slows down the rolling of the expectation value. Decay into Goldstone bosons is also studied. Contact with stochastic inflation is established by deriving the Langevin equation for the coarse-grained expectation value of the inflaton field to one-loop order in this model. We find that the noise is Gaussian and correlated (colored) and its correlations are related tomore » the dissipative ({open_quotes}decay{close_quotes}) kernel via a generalized fluctuation-dissipation relation. {copyright} {ital 1997} {ital The American Physical Society}« less
15505916
Exact Superpotentials from Matrix Models
Dijkgraaf and Vafa (DV) have conjectured that the exact superpotential for a large class of = 1 SUSY gauge theories can be extracted from the planar limit of a certain holomorphic matrix integral. We test their proposal against existing knowledge for a family of deformations of = 4 SUSY Yang-Mills theory involving an arbitrary polynomial superpotential for one of the three adjoint chiral superfields. Specifically, we compare the DV prediction for these models with earlier results based on the connection between SUSY gauge theories and integrable systems. We find complete agreement between the two approaches. In particular we show how the DV proposal allows the extraction of the exact eigenvalues of the adjoint scalar in the confining vacuum and hence computes all related condensates of the finite-N gauge theory. We extend these results to include Leigh-Strassler deformations of the = 4 theory.
118298053
Role of Isospin Degree of freedom on the impact parameter dependence of balance energy
For this study we have simulated the 28Ni58+28Ni58 and 26Fe58+26Fe58 systems at incident energies ranging from 45 MeV/nucleon to 105 MeV/nucleon by using soft equation of state. The geometry of reactions chosen are = b/bmax = 0.2, 0.4, 0.5, 0.6, and 0.7.The Px/A is becoming more positive for neutron - rich system 26Fi58 as compared to neutron-poor system 28Ni58. This point towards the higher value of balance energy for 26Fi58 system. Further study in this direction is ongoing.
16460683
MODEL INDEPENDENT CONSTRAINTS ON NON-ELECTRONIC FLAVORS IN THE SOLAR BORON NEUTRINO FLUX
We perform the most general model-independent analysis of the latest 391-Day Salt Phase SNO Data Set incorporating the super-Kamiokande ES flux measurement and obtain bounds on the antineutrino and sterile neutrino flux in the solar 8B neutrino flux reaching the detectors on the earth. The muon/tauon antineutrino flux is found to be disallowed at 1.4σ C.L. The sterile flux is found to be nonzero at about 1.26 standard deviations.
119296892
STRING COSMOLOGY IN ANISOTROPIC BIANCHI-II SPACETIME
The present study deals with a spatially homogeneous and anisotropic Bianchi-II cosmological model representing massive strings. The energy–momentum tensor, as formulated by Letelier,10 has been used to construct a massive string cosmological model for which the expansion scalar is proportional to one of the components of shear tensor. The Einstein's field equations have been solved by applying a variation law for generalized Hubble's parameter that yields a constant value of deceleration parameter in Bianchi-II spacetime. A comparative study of accelerating and decelerating modes of the evolution of universe has been carried out in the presence of string scenario. The study reveals that massive strings dominate the early Universe. The strings eventually disappear from the Universe for sufficiently large times, which is in agreement with the current astronomical observations.
120654378
Bianchi-I Space-time with Variable Gravitational and Cosmological “Constants”
We consider Einstein’s field equations with variable gravitational and cosmological “constants” for a spatially homogeneous and anisotropic Bianchi-I space-time. A law of variation for the Hubble parameter, which is related to the average scale factor and yields a constant value of the deceleration parameter, is assumed to solve the field equations. The gravitational constant is allowed to follow a power-law form. We find that a time-increasing gravitational constant is suitable for describing the present evolution of universe. The solutions reveal the dynamics of a universe, which expands forever. The physical interpretation of the solutions is discussed in detail.
118517206
Boson stars in a theory of complex scalar fields coupled to the U(1) gauge field and gravity
We study boson shells and boson stars in a theory of a complex scalar field coupled to the gauge field and Einstein gravity with the potential . This could be considered either as a theory of a massive complex scalar field coupled to an electromagnetic field and gravity in a conical potential, or as a theory in the presence of a potential that is an overlap of a parabolic and conical potential. Our theory has a positive cosmological constant . Boson stars are found to come in two types, having either ball-like or shell-like charge density. We studied the properties of these solutions and also determined their domains of existence for some specific values of the parameters of the theory. Similar solutions have also been obtained by Kleihaus, Kunz, Laemmerzahl and List, in a V-shaped scalar potential.