44 research outputs found
Complex marginal deformations of D3-brane geometries, their Penrose limits and giant gravitons
We apply the Lunin--Maldacena construction of gravity duals to beta-deformed
gauge theories to a class of Type IIB backgrounds with U(1)^3 global symmetry,
which include the multicenter D3-brane backgrounds dual to the Coulomb branch
of N=4 super Yang-Mills and the rotating D3-brane backgrounds dual to the
theory at finite temperature and chemical potential. After a general
discussion, we present the full form of the deformed metrics for three special
cases, which can be used for the study of various aspects of the
marginally-deformed gauge theories. We also construct the Penrose limits of the
solutions dual to the Coulomb branch along a certain set of geodesics and, for
the resulting PP--wave metrics, we examine the effect of beta-deformations on
the giant graviton states. We find that giant gravitons exist only up to a
critical value of the sigma-deformation parameter, are not degenerate in energy
with the point graviton, and remain perturbatively stable. Finally, we probe
the sigma-deformed multicenter solutions by examining the static heavy-quark
potential by means of Wilson loops. We find situations that give rise to
complete screening as well as linear confinement, with the latter arising is an
intriguing way reminiscent of phase transitions in statistical systems.Comment: 53 pages, 5 figures; v3: version to appear in Nucl. Phys.
On three-point correlation functions in the gauge/gravity duality
We study the effect of marginal and irrelevant deformations on the
renormalization of operators near a CFT fixed point. New divergences in a given
operator are determined by its OPE with the operator D that generates the
deformation. This provides a scheme to compute the couplings a_DAB between the
operator D and two arbitrary operators O_A and O_B. We exemplify for the case
of N=4 SYM, considering the simplest case of the exact Lagrangian deformation.
In this case the deformed anomalous dimension matrix is determined by the
derivative of the anomalous dimension matrix with respect to the coupling. We
use integrability techniques to compute the one-loop couplings a_LAB between
the Lagrangian and two distinct large operators built with Magnons, in the
SU(2) sector of the theory. Then we consider a_DAA at strong coupling, and show
how to compute it using the gauge/gravity duality, when D is a chiral operator
dual to any supergravity field and O_A is dual to a heavy string state. We
exemplify for the Lagrangian and operators O_A dual to heavy string states,
showing agreement with the prediction derived from the renormalization group
arguments
On the velocity and chemical-potential dependence of the heavy-quark interaction in N=4 SYM plasmas
We consider the interaction of a heavy quark-antiquark pair moving in N=4 SYM
plasma in the presence of non-vanishing chemical potentials. Of particular
importance is the maximal length beyond which the interaction is practically
turned off. We propose a simple phenomenological law that takes into account
the velocity dependence of this screening length beyond the leading order and
in addition its dependence on the R-charge. Our proposal is based on studies
using rotating D3-branes.Comment: 24 pages, 10 figures; v2: energy regularization discussed in detail,
references added, version to appear in Phys. Rev.
Three-point correlation functions from semiclassical circular strings
The strong-coupling limit of three-point correlation functions of local
operators can be analyzed beyond the supergravity regime using vertex operators
representing spinning string states. When two of the vertex operators
correspond to heavy string states having large quantum numbers, while the third
operator corresponds to a light state with fixed charges, the correlator can be
computed in the large string tension limit by means of a semiclassical
approximation. We study the case when the heavy string states are circular
string solutions with one AdS_5 spin and three different angular momenta along
S^5, for several choices of the light string state.Comment: 13 pages. Latex. v2: Misprints corrected and references adde
Holographic duals of SQCD models in low dimensions
We obtain gravity duals to supersymmetric gauge theories in two and three
spacetime dimensions with unquenched flavor. The supergravity solutions are
generated by a set of color branes wrapping a compact cycle in a Calabi-Yau
threefold, together with another set of flavor branes extended along the
directions orthogonal to the cycle wrapped by the color branes. We construct
supergravity backgrounds which include the backreaction induced by a smeared
set of flavor branes, which act as delocalized dynamical sources of the
different supergravity fields.Comment: 42 pages, 5 figures;v2: typos correcte
D3/D7 Quark-Gluon Plasma with Magnetically Induced Anisotropy
We study the effects of the temperature and of a magnetic field in the setup
of an intersection of D3/D7 branes, where a large number of D7 branes is
smeared in the transverse directions to allow for a perturbative solution in a
backreaction parameter. The magnetic field sources an anisotropy in the plasma,
and we investigate its physical consequences for the thermodynamics and energy
loss of particles probing the system. In particular we comment on the
stress-energy tensor of the plasma, the propagation of sound in the directions
parallel and orthogonal to the magnetic field, the drag force of a quark moving
through the medium and jet quenching.Comment: 29 pages + appendices, 5 figures. v2 Version to appear in JHEP, with
minor revisions, references added and typos correcte
Gravity duals for the Coulomb branch of marginally deformed N=4 Yang-Mills
Supergravity backgrounds dual to a class of exactly marginal deformations of
N supersymmetric Yang-Mills can be constructed through an SL(2,R) sequence of
T-dualities and coordinate shifts. We apply this transformation to multicenter
solutions and derive supergravity backgrounds describing the Coulomb branch of
N=1 theories at strong 't Hooft coupling as marginal deformations of N=4
Yang-Mills. For concreteness we concentrate to cases with an SO(4)xSO(2)
symmetry preserved by continuous distributions of D3-branes on a disc and on a
three-dimensional spherical shell. We compute the expectation value of the
Wilson loop operator and confirm the Coulombic behaviour of the heavy
quark-antiquark potential in the conformal case. When the vev is turned on we
find situations where a complete screening of the potential arises, as well as
a confining regime where a linear or a logarithmic potential prevails depending
on the ratio of the quark-antiquark separation to the typical vev scale. The
spectra of massless excitations on these backgrounds are analyzed by turning
the associated differential equations into Schrodinger problems. We find
explicit solutions taking into account the entire tower of states related to
the reduction of type-IIB supergravity to five dimensions, and hence we go
beyond the s-wave approximation that has been considered before for the
undeformed case. Arbitrary values of the deformation parameter give rise to the
Heun differential equation and the related Inozemtsev integrable system, via a
non-standard trigonometric limit as we explicitly demonstrate.Comment: 43 pages, Latex, 2 figures. v2: References added. v3: small typos
corrected, published versio
Holographic Hadrons in a Confining Finite Density Medium
We study a sector of the hadron spectrum in the presence of finite baryon
density. We use a non-supersymmetric gravity dual to a confining guage theory
which exhibits a running dilaton. The interaction of mesons with the finite
density medium is encoded in the dual theory by a force balancing between
flavor D7-branes and a baryon vertex provided by a wrapped D5-brane. When the
current quark mass m_q is sufficiently large, the meson mass reduces,
exhibiting an interesting spectral flow as we increase the baryon density while
it has a more complicated behaviour for very small m_q.Comment: 34 pages, 20 figures, errors for some figures are fixe
Holographic flavor in N=4 gauge theories in 3d from wrapped branes
We study the addition of flavor to the gravity dual of N=4 three-dimensional
gauge theories obtained by wrapping D4-branes on a two-cycle of a
non-compact Calabi-Yau two-fold. In this setup the flavor is introduced by
adding another set of D4-branes that are extended along the non-compact
directions of the Calabi-Yau which are normal to the cycle which the color
branes wrap. The analysis is performed both in the quenched and unquenched
approximations. In this latter case we compute the backreacted metric and we
show that it reproduces the running of the gauge coupling. The meson spectrum
and the behavior of Wilson loops are also discussed and the holographic
realization of the Higgs branch is analyzed. Other aspects of this system
studied are the entanglement entropy and the non-relativistic version of our
backgrounds.Comment: 44 pages, 6 figure