Quantum corrections to screening at strong coupling
We compute a certain class of corrections to (specific) screening lengths in strongly coupled non-abelian plasmas using the AdS/CFT correspondence. In this holographic framework, these corrections arise from various higher curvature interactions modifying the leading Einstein gravity action. The changes in the screening lengths are perturbative in inverse powers of the `t Hooft coupling or of the number of colors, as can be made precise in the context where the dual gauge theory is superconformal. We also compare the results of these holographic calculations to lattice results for the analogous screening lengths in QCD. In particular, we apply these results within the program of making quantitative comparisons between the strongly coupled quark-gluon plasma and holographic descriptions of conformal field theory.

title: Accelerating Bianchi Type-V Cosmology with Perfect Fluid and Heat Flow in Sáez-Ballester Theory
abstract: In this paper we discuss the law of variation of scale factor $a = (t^{k}e^{t})^{\frac{1}{n}}$ which yields a time-dependent deceleration parameter (DP) representing a new class of models that generate a transition of universe from the early decelerated phase to the recent accelerating phase. Exact solutions of Einstein’s modified field equations in Bianchi type-V space-time with perfect fluid and heat conduction are obtained within the framework of Sáez-Ballester scalar-tensor theory of gravitation and the model is found to be in good agreement with recent observations. We find, for n=3,k=1, the present value of DP in derived model as q0=−0.67 which is very near to the observed value of DP at present epoch. We find that the time-dependent DP is sensible for the present day Universe and give an earmark description of evolution of universe. Some physical and geometric properties of the models are also discussed.

title: Entanglement entropy for singular surfaces
abstract: A bstractWe study entanglement entropy for regions with a singular boundary in higher dimensions using the AdS/CFT correspondence and find that various singularities make new universal contributions. When the boundary CFT has an even spacetime dimension, we find that the entanglement entropy of a conical surface contains a term quadratic in the logarithm of the UV cut-off. In four dimensions, the coefficient of this contribution is proportional to the central charge c. A conical singularity in an odd number of spacetime dimensions contributes a term proportional to the logarithm of the UV cut-off. We also study the entanglement entropy for various boundary surfaces with extended singularities. In these cases, similar universal terms may appear depending on the dimension and curvature of the singular locus.

title: Multipoint correlators of conformal field theories: implications for quantum critical transport
abstract: We compute three-point correlators between the stress-energy tensor and con- served currents of conformal field theories (CFTs) in 2+1 dimensions. We first compute the correlators in the large-flavor-number expansion of conformal gauge theories and then do the computation using holography. In the holographic approach, the correlators are computed from an e↵ective action on 3+1 dimensional anti-de Sitter space (AdS4), and depend upon the co-ecient, , of a four-derivative term in the action. We find a precise match between the CFT and the holographic results, thus fixing the values of . The CFTs of free fermions and bosons take the values =1 /12,1/12 respectively, and so saturate the bound | | 1/12 obtained earlier from the holographic theory; the correlator of the conserved gauge flux of U(1) gauge theories takes intermediate values of . The value of also controls the fre- quency dependence of the conductivity, and other properties of quantum-critical transport at non-zero temperatures. Our results for the values of lead to an appealing physical inter- pretation of particle-like or vortex-like transport near quantum phase transitions of interest in condensed matter physics. This paper includes appendices reviewing key features of the AdS/CFT correspondence for condensed matter physicists.

title: Quantum Statistical Metastability Revisited
abstract: Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213AbstractWe calculate the decay rate for a state prepared in a thermal density ma-trix centered on a metastable ground state. We ﬁnd a rate that is intrinsicallytime dependent, as opposed to the constant rates of previous works. The ratevanishes at early times, rises to a maximum and eventually falls-oﬀ to zeroas a consequence of unitary time evolution. Finally, we discuss extensions ofthis calculation to ﬁeld theories and possible implications for both sphaleronmediated transitions and ﬁrst order inﬂationary theories.

title: Reheating the postinflationary universe
abstract: We consider the non-equilibrium evolution of the inflaton field coupled to both lighter scalars and fermions. The dissipational dynamics of this field is studied and found to be quite different than that believed in inflationary models. In particular, the damping time scale for the expectation value of the zero momentum mode of the inflaton can be much shorter than that given by the single particle decay rate when the inflaton amplitudes are large, as in chaotic inflation scenarios. We find that the reheating temperature may depart considerably from the usual estimates.

title: Preheating in FRW Universes
abstract: The nonlinear time evolution of the quantum fields is studied in the O(N) model for large N in a radiation dominated FRW universe, with a view towards the phenomenon of explosive particle production due to either spinodal instabilities or parametric amplification, i.e. preheating. Quantum backreaction effects due to the produced particles are included consistently within the large N approximation. We find that preheating persists when the expansion is included, although the amount of particle production is reduced compared to the values found in Minkowski space. We also see that the behavior of the evolving zero mode is very different from that in Minkowski space, though the late time behavior in all cases is determined by a sum rule that implies the existence of Goldstone bosons in the final state.