183 research outputs found
Black holes in asymptotically Lifshitz spacetimes with arbitrary critical exponent
Recently, a class of gravitational backgrounds in 3+1 dimensions have been
proposed as holographic duals to a Lifshitz theory describing critical
phenomena in 2+1 dimensions with critical exponent . We numerically
explore black holes in these backgrounds for a range of values of . We find
drastically different behavior for and
() the Lifshitz fixed point is repulsive (attractive) when going to larger
radial parameter . For the repulsive backgrounds, we find a continuous
family of black holes satisfying a finite energy condition. However, for
we find that the finite energy condition is more restrictive, and we expect
only a discrete set of black hole solutions, unless some unexpected
cancellations occur. For all black holes, we plot temperature as a function
of horizon radius . For we find that this curve
develops a negative slope for certain values of possibly indicating a
thermodynamic instability.Comment: 23 pages, 6 figures, references corrected, graphs made readable in
greyscal
Thermodynamics of black branes in asymptotically Lifshitz spacetimes
Recently, a class of gravitational backgrounds in 3+1 dimensions have been
proposed as holographic duals to a Lifshitz theory describing critical
phenomena in 2+1 dimensions with critical exponent . We continue our
earlier work \cite{Bertoldi:2009vn}, exploring the thermodynamic properties of
the "black brane" solutions with horizon topology . We find that
the black branes satisfy the relation where
is the energy density, is the temperature, and is the
entropy density. This matches the expected behavior for a 2+1 dimensional
theory with a scaling symmetry , .Comment: 8 pages, references added and regroupe
Coulomb Phase Gluon Scattering at Strong Coupling
We calculate corrections to gluon scattering amplitudes in a Coulomb phase
using gauge/string duality. The Coulomb phase considered is a maximal rank
breaking of . This problem
therefore has 3 scales involved: 1) the scale of the massive fields
arising from the spontaneous breaking of the gauge group; 2) The scale of the
scattering, characterized by the Mandelstam variables ; 3) The IR
regulator . We find corrections in the hard scattering limit , and also find below threshold corrections
with . We find that the corrections in the second case
are finite, and so are IR regulator independent.Comment: 17+17 pages, 3 figure
Lifshitz-like black brane thermodynamics in higher dimensions
Gravitational backgrounds in d+2 dimensions have been proposed as holographic
duals to Lifshitz-like theories describing critical phenomena in d+1 dimensions
with critical exponent z\geq 1. We numerically explore a
dilaton-Einstein-Maxwell model admitting such backgrounds as solutions. Such
backgrounds are characterized by a temperature T and chemical potential \mu,
and we find how to embed these solutions into AdS for a range of values of z
and d. We find no thermal instability going from the (T\ll\mu) to the (T\gg\mu)
regimes, regardless of the dimension, and find that the solutions smoothly
interpolate between the Lifshitz-like behaviour and the relativistic AdS-like
behaviour. We exploit some conserved quantities to find a relationship between
the energy density E, entropy density s, and number density n,
E=\frac{d}{d+1}(Ts+n\mu), as is required by the isometries of AdS_{d+2}.
Finally, in the (T\ll\mu) regime the entropy density is found to satisfy a
power law s \propto c T^{d/z} \mu^{(z-1)d/z}, and we numerically explore the
dependence of the constant c, a measure of the number of degrees of freedom, on
d and z.Comment: 22 pages, 5 images, references adde
Gauge Boson Mass Generation in AdS4
We investigate the role of boundary conditions in gauge theories in AdS4. The
presence of the boundary can break the gauge symmetry consistently with AdS4
isometries. We show that, as a consequence, the gauge bosons associated to the
broken symmetries become massive at one loop. In particular chiral gauge
theories such us the Standard Model are necessarily massive in AdS4. We briefly
discuss similarities with the Schwinger model and implications for CFTs in
three dimensions.Comment: 12 page
Localized Backreacted Flavor Branes in Holographic QCD
We investigate the perturbative (in ) backreaction of localized
D8 branes in D4-D8 systems including in particular the Sakai Sugimoto model. We
write down the explicit expressions of the backreacted metric, dilaton and RR
form. We find that the backreaction remains small up to a radial value of , and that the background functions are smooth except
at the D8 sources. In this perturbative window, the original embedding remains
a solution to the equations of motion. Furthermore, the fluctuations around the
original embedding, describing scalar mesons, do not become tachyonic due to
the backreaction in the perturbative regime. This is is due to a cancelation
between the DBI and CS parts of the D8 brane action in the perturbed
background.Comment: 1+48 pages (7 figures) + 15 pages, citations added & minor
correction
Canonical Coordinates and Meson Spectra for Scalar Deformed N=4 SYM from the AdS/CFT Correspondence
Five supersymmetric scalar deformations of the AdS_5xS^5 geometry are
investigated. By switching on condensates for the scalars in the N=4 multiplet
with a form which preserves a subgroup of the original R-symmetry, disk and
sphere configurations of D3-branes are formed in the dual supergravity
background. The analytic, canonical metric for each geometry is formulated and
the singularity structure is studied. Quarks are introduced into two of the
corresponding field theories using D7-brane probes and the pseudoscalar meson
spectrum is calculated. For one of the condensate configurations, a mass gap is
found and shown analytically to be present in the massless limit. It is also
found that there is a stepped spectrum with eigenstate degeneracy in the limit
of small quark masses. In the case of a second, similar deformation, it is
necessary to understand the full D3-D7 brane interaction to study the limit of
small quark masses. It is seen that simple solutions to the equations of motion
for the other three geometries are unlikely to exist.Comment: 16 pages, 7 figures, references added, typos correcte
Cascading Quivers from Decaying D-branes
We use an argument analogous to that of Kachru, Pearson and Verlinde to argue
that cascades in L^{a,b,c} quiver gauge theories always preserve the form of
the quiver, and that all gauge groups drop at each step by the number M of
fractional branes. In particular, we demonstrate that an NS5-brane that sweeps
out the S^3 of the base of L^{a,b,c} destroys M D3-branes.Comment: 11 pages, 1 figure; v2: references adde
Supersymmetric Branes on AdS_5 x Y^{p,q} and their Field Theory Duals
We systematically study supersymmetric embeddings of D-brane probes of
different dimensionality in the AdS_5xY^{p,q} background of type IIB string
theory. The main technique employed is the kappa symmetry of the probe's
worldvolume theory. In the case of D3-branes, we recover the known three-cycles
dual to the dibaryonic operators of the gauge theory and we also find a new
family of supersymmetric embeddings. The BPS fluctuations of dibaryons are
analyzed and shown to match the gauge theory results. Supersymmetric
configurations of D5-branes, representing domain walls, and of spacetime
filling D7-branes (which can be used to add flavor) are also found. We also
study the baryon vertex and some other embeddings which break supersymmetry but
are nevertheless stable.Comment: LaTeX, 2 figures, 54 pages; v2: discussions sharpened at several
points, new subsection and references adde
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