8,496 research outputs found
Aspects of Holographic Entanglement at Finite Temperature and Chemical Potential
We investigate the behavior of entanglement entropy at finite temperature and
chemical potential for strongly coupled large-N gauge theories in
-dimensions () that are dual to Anti-de Sitter-Reissner-Nordstrom
geometries in dimensions, in the context of gauge-gravity duality. We
develop systematic expansions based on the Ryu-Takayanagi prescription that
enable us to derive analytic expressions for entanglement entropy and mutual
information in different regimes of interest. Consequently, we identify the
specific regions of the bulk geometry that contribute most significantly to the
entanglement entropy of the boundary theory at different limits. We define a
scale, dubbed as the effective temperature, which determines the behavior of
entanglement in different regimes. At high effective temperature, entanglement
entropy is dominated by the thermodynamic entropy, however, mutual information
subtracts out this contribution and measures the actual quantum entanglement.
Finally, we study the entanglement/disentanglement transition of mutual
information in the presence of chemical potential which shows that the quantum
entanglement between two sub-regions decreases with the increase of chemical
potential.Comment: 38 pages, multiple figure
Strongly-coupled anisotropic gauge theories and holography
We initiate a non-perturbative study of anisotropic, non-conformal and
confining gauge theories that are holographically realized in gravity by
generic Einstein-Axion-Dilaton systems. In the vacuum our solutions describe RG
flows from a conformal field theory in the UV to generic scaling solutions in
the IR with generic hyperscaling violation and dynamical exponents and
. We formulate a generalization of the holographic c-theorem to the
anisotropic case. At finite temperature, we discover that the anisotropic
deformation reduces the confinement-deconfinement phase transition temperature
suggesting a possible alternative explanation of inverse magnetic catalysis
solely based on anisotropy. We also study transport and diffusion properties in
anisotropic theories and observe in particular that the butterfly velocity that
characterizes both diffusion and growth of chaos transverse to the anisotropic
direction, saturates a constant value in the IR which can exceed the bound
given by the conformal value.Comment: 6 pages, 4 figures; v2: minor improvements, references added, version
accepted for publication in PR
Entanglement and out-of-equilibrium dynamics in holographic models of de Sitter QFTs
In this paper we study various aspects of entanglement entropy in
strongly-coupled de Sitter quantum field theories in various dimensions. We
find gravity solutions that are dual to field theories in a fixed de Sitter
background, both in equilibrium and out-of-equilibrium configurations. The
latter corresponds to the Vaidya generalization of the AdS black hole solutions
with hyperbolic topology. We compute analytically the entanglement entropy of
spherical regions and show that there is a transition when the sphere is as big
as the horizon. We also explore thermalization in time-dependent situations in
which the system evolves from a non-equilibrium state to the Bunch-Davies
state. We find that the saturation time is equal to the light-crossing time of
the sphere. This behavior is faster than random walk and suggests the existence
of free light-like degrees of freedom.Comment: 39 pages, 11 figures; minor changes, conclusions unchange
Branes from Light: Embeddings and Energetics for Symmetric -Quarks in SYM
We construct the D3-brane dual to a -quark of
super-Yang-Mills theory in the totally symmetric representation of ,
undergoing arbitrary motion. Our method of construction generalizes previous
work by Mikhailov, and proceeds by shooting light rays inward from the anti-de
Sitter boundary, to trace out the brane embedding. We expect this method to
have wider relevance, and provide evidence for this by showing that it
correctly reproduces the known D5-brane embeddings dual to totally
antisymmetric -quarks. As an application of our solutions, we compute the
energy of the D3-brane and extract from it the -quark's intrinsic energy and
rate of radiation. The result matches expectations based on previous
calculations, and makes contact with the exact Bremsstrahlung function for the
fundamental representation.Comment: 1+28 pages, 3 figures. v2: references adde
Linear response of entanglement entropy from holography
For time-independent excited states in conformal field theories, the
entanglement entropy of small subsystems satisfies a `first law'-like relation,
in which the change in entanglement is proportional to the energy within the
entangling region. Such a law holds for time-dependent scenarios as long as the
state is perturbatively close to the vacuum, but is not expected otherwise. In
this paper we use holography to investigate the spread of entanglement entropy
for unitary evolutions of special physical interest, the so-called global
quenches. We model these using AdS-Vaidya geometries. We find that the first
law of entanglement is replaced by a linear response relation, in which the
energy density takes the role of the source and is integrated against a
time-dependent kernel with compact support. For adiabatic quenches the standard
first law is recovered, while for rapid quenches the linear response includes
an extra term that encodes the process of thermalization. This extra term has
properties that resemble a time-dependent `relative entropy'. We propose that
this quantity serves as a useful order parameter to characterize
far-from-equilibrium excited states. We illustrate our findings with concrete
examples, including generic power-law and periodically driven quenches.Comment: 31+3 pages, 8 figures; v2: typos fixed and references added; v3:
claims on universality sharpened (section 2.1), version to appear in JHE
Fast and Slow Coherent Cascades in Anti-de Sitter Spacetime
We study the phase and amplitude dynamics of small perturbations in 3+1
dimensional Anti-de Sitter spacetime using the truncated resonant
approximation, also known as the Two Time Framework (TTF). We analyse the phase
spectrum for different classes of initial data and find that higher frequency
modes turn on with coherently aligned phases. Combining numerical and
analytical results, we conjecture that there is a class of initial conditions
that collapse in infinite slow time and to which the well-studied case of the
two-mode, equal energy initial data belongs. We additionally study
perturbations that collapse in finite time, and find that the energy spectrum
approaches a power law, with the energy per mode scaling approximately as the
inverse first power of the frequency.Comment: 19 pages, multiple figures. v2: version published in CQ
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