256 research outputs found
Jet quenching in shock waves
We study the propagation of an ultrarelativistic light quark jet inside a
shock wave using the holographic principle. The maximum stopping distance and
its dependency on the energy of the jet is obtained
Defect formation beyond kibble-zurek mechanism and holography
We study the dynamic after a smooth quench across a continuous transition
from the disordered phase to the ordered phase. Based on scaling ideas, linear
response and the spectrum of unstable modes, we develop a theoretical
framework, valid for any second order phase transition, for the early-time
evolution of the condensate in the broken phase. Our analysis unveils a novel
period of non-adiabatic evolution after the system passes through the phase
transition, where a parametrically large amount of coarsening occurs before a
well-defined condensate forms. Our formalism predicts a rate of defect
formation parametrically smaller than the Kibble-Zurek prediction and yields a
criterion for the break-down of Kibble-Zurek scaling for sufficiently fast
quenches. We numerically test our formalism for a thermal quench in a 2 + 1
dimensional holographic superfluid. These findings, of direct relevance in a
broad range of fields including cold atom, condensed matter, statistical
mechanism and cosmology, are an important step towards a more quantitative
understanding of dynamical phase transitions.We thank Laurence Yaffe for useful discussions. The work of P. M. C. is supported by the Fundamental Laws Initiative of the Center for the Fundamental Laws of Nature at Harvard University. The work of H. L. is partially supported by the U.S. Department of Energy (DOE) under Cooperative Research Agreement No. DE-FG0205ER41360. A. M. G.-G. was supported by Engineering and Physical Sciences Research Council, Grant No. EP/I004637/1; Fundação para a Ciência e a Tecnologia, Grant No. PTDC/FIS/111348/2009; and a Marie Curie International Reintegration Grant No. PIRG07-GA-2010-268172.This is the final version of the article. It first appeared from APS via http://dx.doi.org/10.1103/PhysRevX.5.02101
Thermalization from gauge/gravity duality: Evolution of singularities in unequal time correlators
We consider a gauge/gravity dual model of thermalization which consists of a
collapsing thin matter shell in asymptotically Anti-de Sitter space. A central
aspect of our model is to consider a shell moving at finite velocity as
determined by its equation of motion, rather than a quasi-static approximation
as considered previously in the literature. By applying a divergence matching
method, we obtain the evolution of singularities in the retarded unequal time
correlator , which probes different stages of the thermalization. We
find that the number of singularities decreases from a finite number to zero as
the gauge theory thermalizes. This may be interpreted as a sign of decoherence.
Moreover, in a second part of the paper, we show explicitly that the thermal
correlator is characterized by the existence of singularities in the complex
time plane. By studying a quasi-static state, we show the singularities at real
times originate from contributions of normal modes. We also investigate the
possibility of obtaining complex singularities from contributions of
quasi-normal modes.Comment: 35 pages, 4 figure
Heavy quarks in a magnetic field
The motion of a heavy charged quark in a magnetic field is analyzed in the
vacuum of strongly coupled CFT. The motion of the quark is dissipative. It
moves in spiral until it eventually comes to rest. The world-sheet geometry is
locally AdS_2 but has a time dependent horizon. The string profile in the
static gauge extends from the boundary till a point where an embedding
singularity exists. Connections with other circular string motions are
established.Comment: (v3) Misprints corrected, discussion on moving horizons improved and
enhance
Jet quenching in hot strongly coupled gauge theories simplified
Theoretical studies of jet stopping in strongly-coupled QCD-like plasmas have
used gauge-gravity duality to find that the maximum stopping distance scales
like E^{1/3} for large jet energies E. In recent work studying jets that are
created by finite-size sources in the gauge theory, we found an additional
scale: the typical (as opposed to maximum) jet stopping distance scales like
(EL)^{1/4}, where L is the size of the space-time region where the jet is
created. In this paper, we show that the results of our previous, somewhat
involved computation in the gravity dual, and the (EL)^{1/4} scale in
particular, can be very easily reproduced and understood in terms of the
distance that high-energy particles travel in AdS_5-Schwarzschild space before
falling into the black brane. We also investigate how stopping distances depend
on the conformal dimension of the source operator used to create the jet.Comment: 30 pages, 10 figure
Meson Thermalization in Various Dimensions
In gauge/gravity duality framework the thermalization of mesons in strongly
coupled (p+1)-dimensional gauge theories is studied for a general Dp-Dq system,
q>=p, using the flavour Dq-brane as a probe. Thermalization corresponds to the
horizon formation on the flavour Dq-brane. We calculate the thermalization
time-scale due to a time-dependent change in the baryon number chemical
potential, baryon injection in the field theory. We observe that for such a
general system it has a universal behaviour depending only on the t'Hooft
coupling constant and the two parameters which describe how we inject baryons
into the system. We show that this universal behaviour is independent of the
details of the theory whether it is conformal and/or supersymmetric.Comment: 26 pages, 2 figure
Time singularities of correlators from Dirichlet conditions in AdS/CFT
Within AdS/CFT, we establish a general procedure for obtaining the leading
singularity of two-point correlators involving operator insertions at different
times. The procedure obtained is applied to operators dual to a scalar field
which satisfies Dirichlet boundary conditions on an arbitrary time-like surface
in the bulk. We determine how the Dirichlet boundary conditions influence the
singularity structure of the field theory correlation functions. New
singularities appear at boundary points connected by null geodesics bouncing
between the Dirichlet surface and the boundary. We propose that their
appearance can be interpreted as due to a non-local double trace deformation of
the dual field theory, in which the two insertions of the operator are
separated in time. The procedure developed in this paper provides a technical
tool which may prove useful in view of describing holographic thermalization
using gravitational collapse in AdS space.Comment: 30 pages, 3 figures. Version as in JHE
The Gluonic Field of a Heavy Quark in Conformal Field Theories at Strong Coupling
We determine the gluonic field configuration sourced by a heavy quark
undergoing arbitrary motion in N=4 super-Yang-Mills at strong coupling and
large number of colors. More specifically, we compute the expectation value of
the operator tr[F^2+...] in the presence of such a quark, by means of the
AdS/CFT correspondence. Our results for this observable show that signals
propagate without temporal broadening, just as was found for the expectation
value of the energy density in recent work by Hatta et al. We attempt to shed
some additional light on the origin of this feature, and propose a different
interpretation for its physical significance. As an application of our general
results, we examine when the quark undergoes oscillatory motion,
uniform circular motion, and uniform acceleration. Via the AdS/CFT
correspondence, all of our results are pertinent to any conformal field theory
in 3+1 dimensions with a dual gravity formulation.Comment: 1+38 pages, 16 eps figures; v2: completed affiliation; v3: corrected
typo, version to appear in JHE
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