22 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.
A New Anomaly-Free Gauged Supergravity in Six Dimensions
We present a new anomaly-free gauged N=1 supergravity model in six
dimensions. The gauge group is E_7xG_2xU(1)_R, with all hyperinos transforming
in the product representation {56,14). The theory admits monopole
compactifications to R^4xS^2, leading to D=4 effective theories with broken
supersymmetry and massless fermions.Comment: 9 pages, RevTeX
Gauged D=7 Supergravity on the S**1/Z_2 Orbifold
We construct the most general couplings of a bulk seven-dimensional
Yang-Mills-Einstein N=2 supergravity with a boundary six-dimensional chiral
N=(0,1) theory of vectors and charged hypermultiplets. The boundary consists of
two brane worlds sitting at the fixed points of an S^1/Z_2 compactification of
the seven-dimensional bulk supergravity. The resulting 6D massless spectrum
surviving the orbifold projection is anomalous. By introducing boundary fields
at the orbifold fixed points, we show that all anomalies are cancelled by a
Green-Schwarz mechanism. In addition, all couplings of the boundary fields to
the bulk are completely specified by supersymmetry. We emphasize that there is
no bulk Chern-Simons term to cancel the anomalies. The latter is traded for a
Green-Schwarz term which emerges in the boundary theory after a duality
transformation implemented to construct the bulk supergravity.Comment: LaTeX, 42 pages; typos corrected, reference added, version to appear
in Phys. Rev.
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.
Stability of strings dual to flux tubes between static quarks in N=4 SYM
Computing heavy quark-antiquark potentials within the AdS/CFT correspondence
often leads to behaviors that differ from what one expects on general physical
grounds and field-theory considerations. To isolate the configurations of
physical interest, it is of utmost importance to examine the stability of the
string solutions dual to the flux tubes between the quark and antiquark. Here,
we formulate and prove several general statements concerning the perturbative
stability of such string solutions, relevant for static quark-antiquark pairs
in a general class of backgrounds, and we apply the results to N=4 SYM at
finite temperature and at generic points of the Coulomb branch. In all cases,
the problematic regions are found to be unstable and hence physically
irrelevant.Comment: 43 pages, 18 figures; v3: typos correcte
Stability of string configurations dual to quarkonium states in AdS/CFT
We extend our earlier work, regarding the perturbative stability of string
configurations used for computing the interaction potential of heavy quarks
within the gauge/gravity correspondence, to cover a more general class of
gravity duals. We provide results, mostly based on analytic methods and
corroborated by numerical calculations, which apply to strings in a general
class of backgrounds that encompass boosted, spinning and marginally-deformed
D3-brane backgrounds. For the case of spinning branes we demonstrate in a few
examples that perturbative stability of strings requires strong conditions
complementing those following by thermodynamic stability of the dual field
theories. For marginally-deformed backgrounds, we find that even in the
conformal case stability may require an upper value for the imaginary part of
the deformation parameter, whereas in regions of the Coulomb branch where there
exists linear confinement we find that there exist stable string configurations
for certain ranges of values of this parameter. We finally discuss the case of
open strings with fixed endpoints propagating in Rindler space, which turns out
to have an exact classical-mechanical analog.Comment: 41 pages, 16 figures; v2: minor typos corrected, version to appear in
Nucl. Phys.
Three-dimensional AdS gravity and extremal CFTs at c=8m
We note that Witten's proposed duality between extremal c=24k CFTs and
three-dimensional anti-de Sitter gravity may possibly be extended to central
charges that are multiples of 8, for which extremal self-dual CFTs are known to
exist up to c=40. All CFTs of this type with central charge 24 or higher,
provided that they exist, have the required mass gap and may serve as candidate
duals to three-dimensional gravity at the corresponding values of the
cosmological constant. Here, we compute the genus one partition function of
these theories up to c=88, we give exact and approximate formulas for the
degeneracies of states, and we determine the genus two partition functions of
the theories up to c=40.Comment: 17 pages, harvmac; v2: references added, version accepted in JHE
Supergravity and the jet quenching parameter in the presence of R-charge densities
Following a recent proposal, we employ the AdS/CFT correspondence to compute
the jet quenching parameter for N=4 Yang-Mills theory at nonzero R-charge
densities. Using as dual supergravity backgrounds non-extremal rotating branes,
we find that the presence of the R-charges generically enhances the jet
quenching phenomenon. However, at fixed temperature, this enhancement might or
might not be a monotonically increasing function of the R-charge density and
depends on the number of independent angular momenta describing the solution.
We perform our analysis for the canonical as well as for the grand canonical
ensemble which give qualitatively similar results.Comment: 18 pages, 2 figures; v3: clarifying comments added, references added,
version to appear in JHE
Conformal chiral boson models on twisted doubled tori and non-geometric string vacua
We derive and analyze the conditions for quantum conformal and Lorentz
invariance of the duality symmetric interacting chiral boson sigma-models,
which are conjectured to describe non-geometric string theory backgrounds. The
one-loop Weyl and Lorentz anomalies are computed for the general case using the
background field method. Subsequently, our results are applied to a class of
(on-shell) Lorentz invariant chiral boson models which are based on twisted
doubled tori. Our findings are in agreement with those expected from the
effective supergravity approach, thereby firmly establishing that the chiral
boson models under consideration provide the string worldsheet description of
N=4 gauged supergravities with electric gaugings. Furthermore, they demonstrate
that twisted doubled tori are indeed the doubled internal geometries underlying
a large class of non-geometric string compactifications. For compact gaugings
the associated chiral boson models are automatically conformal, a fact that is
explained by showing that they are actually chiral WZW models in disguise.Comment: 37 pages; v2: minor improvements, version to appear in Nucl. Phys.