823 research outputs found
On effective action of string theory flux compactifications
We discuss four dimensional effective actions of string theory flux
compactifications. These effective actions describe four dimensional gravity
coupled to overall Kahler modulus of the compactification manifold. We
demonstrate the agreement between ten dimensional equations of motion of
supergravity with localized branes, and equations of motion derived from the
effective action. The agreement is lost however if one evaluates the full
effective action on the equations of motion for a subset of the supergravity
modes, provided these modes depend on-shell on the Kahler modulus.Comment: 25 pages; v2: refs adde
The black hole in the throat - thermodynamics of strongly coupled cascading gauge theories
We numerically construct black hole solutions corresponding to the
deconfined, chirally symmetric phase of strongly coupled cascading gauge
theories at various temperatures. We compute the free energy as a function of
the temperature, and we show that it becomes positive below some critical
temperature, indicating the possibility of a first order phase transition at
which the theory deconfines and restores the chiral symmetry.Comment: 45 pages, 13 figures, latex. v2: typo 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
Holographic dual of the Eguchi-Kawai mechanism
archiveprefix: arXiv primaryclass: hep-th reportnumber: NORDITA-2014-40, UUITP-03-14, QMUL-PH-14-08 slaccitation: %%CITATION = ARXIV:1404.0225;%%archiveprefix: arXiv primaryclass: hep-th reportnumber: NORDITA-2014-40, UUITP-03-14, QMUL-PH-14-08 slaccitation: %%CITATION = ARXIV:1404.0225;%%archiveprefix: arXiv primaryclass: hep-th reportnumber: NORDITA-2014-40, UUITP-03-14, QMUL-PH-14-08 slaccitation: %%CITATION = ARXIV:1404.0225;%%The work of K.Z. was supported by
the ERC advanced grant No 341222, by the Marie Curie network GATIS of the European
Union’s FP7 Programme under REA Grant Agreement No 317089, and by the Swedish
Research Council (VR) grant 2013-4329. DY acknowledges NORDITA where this work
was begun, during his time as a NORDITA fellow
The Fate of the Sound and Diffusion in Holographic Magnetic Field
It was shown in arXiv:0810.4094 [hep-th] that in the presence of the magnetic
field the sound waves in (2+1) dimensional plasma disappear and are replaces by
a diffusive mode. Similarly, the shear and charge diffusion fluctuations form a
subdiffusive mode. However, since the limit of small magnetic field does not
commute with the hydrodynamic limit it is not obvious whether or not these
modes are stable under higher order corrections. Using AdS/CFT correspondence
we show that in the case of M2-brane plasma these modes do exist as we find the
corresponding supergravity solutions. This allowed us to compute the
conductivity and the shear viscosity to all orders in magnetic field. We find
that the viscosity to entropy ratio saturates the Kovtun-Son-Starinets bound.
This extends the universality property of the shear viscosity to the case of
the strongly coupled plasma in external magnetic field.Comment: 23 pages; minor corrections, references adde
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
Transport properties of N=4 supersymmetric Yang-Mills theory at finite coupling
Gauge theory-string theory duality describes strongly coupled N=4
supersymmetric SU(n) Yang-Mills theory at finite temperature in terms of near
extremal black 3-brane geometry in type IIB string theory. We use this
correspondence to compute the leading correction in inverse 't Hooft coupling
to the shear diffusion constant, bulk viscosity and the speed of sound in the
large-n N=4 supersymmetric Yang-Mills theory plasma. The transport coefficients
are extracted from the dispersion relation for the shear and the sound wave
lowest quasinormal modes in the leading order alpha'-corrected black D3 brane
geometry. We find the shear viscosity extracted from the shear diffusion
constant to agree with result of [hep-th/0406264]; also, the leading correction
to bulk viscosity and the speed of sound vanishes. Our computation provides a
highly nontrivial consistency check on the hydrodynamic description of the
alpha'-corrected nonextremal black branes in string theory.Comment: 19 pages, LaTe
Holographic renormalization of cascading gauge theories
We perform a holographic renormalization of cascading gauge theories.
Specifically, we find the counter-terms that need to be added to the
gravitational action of the backgrounds dual to the cascading theory of
Klebanov and Tseytlin, compactified on an arbitrary four-manifold, in order to
obtain finite correlation functions (with a limited set of sources). We show
that it is possible to truncate the action for deformations of this background
to a five dimensional system coupling together the metric and four scalar
fields. Somewhat surprisingly, despite the fact that these theories involve an
infinite number of high-energy degrees of freedom, we find finite answers for
all one-point functions (including the conformal anomaly). We compute
explicitly the renormalized stress tensor for the cascading gauge theories at
high temperature and show how our finite answers are consistent with the
infinite number of degrees of freedom. Finally, we discuss ambiguities
appearing in the holographic renormalization we propose for the cascading gauge
theories; our finite results for the one-point functions have some ambiguities
in curved space (including the conformal anomaly) but not in flat space.Comment: 65 pages (46 pages + appendix), latex. v2: added references. v3:
added a reference and a footnot
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
- …