958 research outputs found
Metabolism and activity of zoxazolamine in white rats during forced immobilization with and without hyperthermia
The influence of restraint of rats held either at normal body temperature or at lowered body temperature as related to the effects of the muscle relaxant zoxazolamine was studied. The techniques used and experimental results obtained are presented
On jet quenching parameters in strongly coupled non-conformal gauge theories
Recently Liu, Rajagopal and Wiedemann (LRW) [hep-ph/0605178] proposed a first
principle, nonperturbative quantum field theoretic definition of ``jet
quenching parameter'' \hat{q} used in models of medium-induced radiative parton
energy loss in nucleus-nucleus collisions at RHIC. Relating \hat{q} to a
short-distance behavior of a certain light-like Wilson loop, they used gauge
theory-string theory correspondence to evaluate \hat{q} for the strongly
coupled N=4 SU(N_c) gauge theory plasma. We generalize analysis of LRW to
strongly coupled non-conformal gauge theory plasma. We find that a jet
quenching parameter is gauge theory specific (not universal). Furthermore, it
appears it's value increases as the number of effective adjoint degrees of
freedom of a gauge theory plasma increases.Comment: 14 pages, latex; v2: PRD versio
Viscosity Bound and Causality in Superfluid Plasma
It was argued by Brigante et.al that the lower bound on the ratio of the
shear viscosity to the entropy density in strongly coupled plasma is translated
into microcausality violation in the dual gravitational description. Since
transport properties of the system characterize its infrared dynamics, while
the causality of the theory is determined by its ultraviolet behavior, the
viscosity bound/microcausality link should not be applicable to theories that
undergo low temperature phase transitions. We present an explicit model of
AdS/CFT correspondence that confirms this fact.Comment: 27 pages, 5 figures. References added, typos fixe
Transport coefficients, membrane couplings and universality at extremality
We present an efficient method for computing the zero frequency limit of
transport coefficients in strongly coupled field theories described
holographically by higher derivative gravity theories. Hydrodynamic parameters
such as shear viscosity and conductivity can be obtained by computing residues
of poles of the off-shell lagrangian density. We clarify in which sense these
coefficients can be thought of as effective couplings at the horizon, and
present analytic, Wald-like formulae for the shear viscosity and conductivity
in a large class of general higher derivative lagrangians. We show how to apply
our methods to systems at zero temperature but finite chemical potential. Our
results imply that such theories satisfy universally in the
Einstein-Maxwell sector. Likewise, the zero frequency limit of the real part of
the conductivity for such systems is shown to be universally zero, and we
conjecture that higher derivative corrections in this sector do not modify this
result to all orders in perturbation theory.Comment: 29 pages, v2: Small text changes for clarity, typos correcte
Gauge/gravity correspondence in accelerating universe
We discuss time-dependent backgrounds of type IIB supergravity realizing
gravitation duals of gauge theories formulated in de Sitter space-time as a
tool of embedding de Sitter in a supergravity. We show that only the
gravitational duals to non-conformal gauge theories are sensitive to a specific
value of a Hubble parameter. We consider two nontrivial solutions of this type:
a gravity dual to six-dimensional (1,1) little string theory, and to a
four-dimensional cascading SU(N+M)xSU(N) supersymmetric gauge theory (related
to fractional D3-branes on a singular conifold according to Klebanov et al), in
accelerating universe. In both cases we argue that the IR singularity of the
geometry is regulated by the expansion of the gauge theory background
space-time.Comment: 13 pages, harvmac, v2: reference added, v3: D3,NS5 discussion
improved, PRD versio
Gauge/string correspondence in curved space
We discuss Gubser-Klebanov-Polyakov proposal for the gauge/string theory
correspondence for gauge theories in curved space. Specifically, we consider
Klebanov-Tseytlin cascading gauge theory compactified on S^3. We explain regime
when this gauge theory is a small deformation of the superconformal N=1 gauge
theory on the world volume of regular D3-branes at the tip of the conifold. We
study closed string states on the leading Regge trajectory in this background,
and attempt to identify the dual gauge theory twist two operators.Comment: 26 pages, v2: refs adde
Higher Derivative Corrections to R-charged Black Holes: Boundary Counterterms and the Mass-Charge Relation
We carry out the holographic renormalization of Einstein-Maxwell theory with
curvature-squared corrections. In particular, we demonstrate how to construct
the generalized Gibbons-Hawking surface term needed to ensure a perturbatively
well-defined variational principle. This treatment ensures the absence of ghost
degrees of freedom at the linearized perturbative order in the
higher-derivative corrections. We use the holographically renormalized action
to study the thermodynamics of R-charged black holes with higher derivatives
and to investigate their mass to charge ratio in the extremal limit. In five
dimensions, there seems to be a connection between the sign of the higher
derivative couplings required to satisfy the weak gravity conjecture and that
violating the shear viscosity to entropy bound. This is in turn related to
possible constraints on the central charges of the dual CFT, in particular to
the sign of c-a.Comment: 30 pages. v2: references added, some equations simplifie
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