299 research outputs found
Jet Quenching in Non-Conformal Holography
We use our non-conformal holographic bottom-up model for QCD described in
1012.0116 to further study the effect of the QCD trace anomaly on the energy
loss of both light and heavy quarks in a strongly coupled plasma. We compute
the nuclear modification factor for bottom and charm quarks in an
expanding plasma with Glauber initial conditions. We find that the maximum
stopping distance of light quarks in a non-conformal plasma scales with the
energy with a temperature (and energy) dependent effective power.Comment: 4 pages, 1 figure. Proceedings for Quark Matter 201
Flavor brane on the baryonic branch of moduli space
We study an extra flavor in the cascading SU((k+1)M)xSU(k M) gauge theory by
adding probe D7-brane to the geometry. By finding a solution to the
kappa-symmetry equation we establish that the D7-brane is mutually
supersymmetric with the background everywhere on the baryonic branch of moduli
space. We also discuss possible applications of this result.Comment: 15 pages; v2 typo corrected, references adde
Debye screening in strongly coupled N=4 supersymmetric Yang-Mills plasma
Using the AdS/CFT correspondence, we examine the behavior of correlators of
Polyakov loops and other operators in N=4 supersymmetric Yang-Mills theory at
non-zero temperature. The implications for Debye screening in this strongly
coupled non-Abelian plasma, and comparisons with available results for thermal
QCD, are discussed.Comment: 21 pages, 5 figures, significantly expanded discussion of Polyakov
loop correlator and static quark-antiquark potentia
Chiral Symmetry Breaking and External Fields in the Kuperstein-Sonnenschein Model
A novel holographic model of chiral symmetry breaking has been proposed by
Kuperstein and Sonnenschein by embedding non-supersymmetric probe D7 and
anti-D7 branes in the Klebanov-Witten background. We study the dynamics of the
probe flavours in this model in the presence of finite temperature and a
constant electromagnetic field. In keeping with the weakly coupled field theory
intuition, we find the magnetic field promotes spontaneous breaking of chiral
symmetry whereas the electric field restores it. The former effect is
universally known as the "magnetic catalysis" in chiral symmetry breaking. In
the presence of an electric field such a condensation is inhibited and a
current flows. Thus we are faced with a steady-state situation rather than a
system in equilibrium. We conjecture a definition of thermodynamic free energy
for this steady-state phase and using this proposal we study the detailed phase
structure when both electric and magnetic fields are present in two
representative configurations: mutually perpendicular and parallel.Comment: 50 pages, multiple figures, minor typo fixed, references adde
Quantum Back Reaction to asymptotically AdS Black Holes
We analyze the effects of the back reaction due to a conformal field theory
(CFT) on a black hole spacetime with negative cosmological constant. We study
the geometry numerically obtained by taking into account the energy momentum
tensor of CFT approximated by a radiation fluid. We find a sequence of
configurations without a horizon in thermal equilibrium (CFT stars), followed
by a sequence of configurations with a horizon. We discuss the thermodynamic
properties of the system and how back reaction effects alter the space-time
structure. We also provide an interpretation of the above sequence of solutions
in terms of the AdS/CFT correspondence. The dual five-dimensional description
is given by the Karch-Randall model, in which a sequence of five-dimensional
floating black holes followed by a sequence of brane localized black holes
correspond to the above solutions.Comment: 13 pages, 10 figure
Zero Sound in Effective Holographic Theories
We investigate zero sound in -dimensional effective holographic theories,
whose action is given by Einstein-Maxwell-Dilaton terms. The bulk spacetimes
include both zero temperature backgrounds with anisotropic scaling symmetry and
their near-extremal counterparts obtained in 1006.2124 [hep-th], while the
massless charge carriers are described by probe D-branes. We discuss
thermodynamics of the probe D-branes analytically. In particular, we clarify
the conditions under which the specific heat is linear in the temperature,
which is a characteristic feature of Fermi liquids. We also compute the
retarded Green's functions in the limit of low frequency and low momentum and
find quasi-particle excitations in certain regime of the parameters. The
retarded Green's functions are plotted at specific values of parameters in
, where the specific heat is linear in the temperature and the
quasi-particle excitation exists. We also calculate the AC conductivity in
-dimensions as a by-product.Comment: 29 pages, 1 figur
Dynamics of Fundamental Matter in N=2* Yang-Mills Theory
We study the dynamics of quenched fundamental matter in
supersymmetric large SU(N) Yang-Mills theory at zero temperature. Our tools
for this study are probe D7-branes in the holographically dual
Pilch-Warner gravitational background. Previous work using
D3-brane probes of this geometry has shown that it captures the physics of a
special slice of the Coulomb branch moduli space of the gauge theory, where the
constituent D3-branes form a dense one dimensional locus known as the
enhancon, located deep in the infrared. Our present work shows how this physics
is supplemented by the physics of dynamical flavours, revealed by the D7-branes
embeddings we find. The Pilch-Warner background introduces new divergences into
the D7-branes free energy, which we are able to remove with a single
counterterm. We find a family of D7-brane embeddings in the geometry and
discuss their properties. We study the physics of the quark condensate,
constituent quark mass, and part of the meson spectrum. Notably, there is a
special zero mass embedding that ends on the enhancon, which shows that while
the geometry acts repulsively on the D7-branes, it does not do so in a way that
produces spontaneous chiral symmetry breaking.Comment: 24 pages, 8 figures. Corrected typos, added comment about
counterterm. To appear in JHE
Non-conformal examples of AdS/CFT
Asymptotically anti-de Sitter spacetimes with Poincare invariance along the
boundary can describe, via the AdS/CFT correspondence, either relevant
deformations of a conformal field theory or non-conformal vacuum states. I
consider examples of both types constructed in the framework of
five-dimensional gauged supergravity. I explain the proof and motivation of a
gravitational ``c-theorem'' which is independent of dimension. I show how one
class of examples can be elevated to ten-dimensional geometries involving
distributions of parallel D3-branes. For these cases some peculiar properties
of two-point functions emerge, and I close with speculations on their physical
origin.Comment: 16 pages, two figures, latex. Strings '99 tal
Mass and Gauge Invariance IV (Holography for the Karch-Randall Model)
We argue that the Karch-Randall compactification is holographically dual to a
4-d conformal field theory coupled to gravity on Anti de Sitter space. Using
this interpretation we recover the mass spectrum of the model. In particular,
we find no massless spin-2 states. By giving a purely 4-d interpretation to the
compactification we make clear that it represents the first example of a local
4-d field theory in which general covariance does not imply the existence of a
massless graviton. We also discuss some variations of the Karch-Randall model
discussed in the literature, and we examine whether its properties are generic
to all conformal field theory.Comment: 26 pages, uses package latexsym. Note added in proo
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