366 research outputs found
Hydrodynamics of fundamental matter
First and second order transport coefficients are calculated for the strongly
coupled N=4 SYM plasma coupled to massless fundamental matter in the Veneziano
limit. The results, including among others the value of the bulk viscosity and
some relaxation times, are presented at next-to-leading order in the flavor
contribution. The bulk viscosity is found to saturate Buchel's bound. This
result is also captured by an effective single-scalar five-dimensional
holographic dual in the Chamblin-Reall class and it is suggested to hold, in
the limit of small deformations, for generic plasmas with gravity duals,
whenever the leading conformality breaking effects are driven by marginally
(ir)relevant operators. This proposal is then extended to other relations for
hydrodynamic coefficients, which are conjectured to be universal for every
non-conformal plasma with a dual Chamblin-Reall-like description. Our analysis
extends to any strongly coupled gauge theory describing the low energy dynamics
of Nc>>1 D3-branes at the tip of a generic Calabi-Yau cone. The fundamental
fields are added by means of 1<<Nf<<Nc homogeneously smeared D7-branes.Comment: 24 pages. V2: Important improvements in the discussion of the results
in section 1. References adde
The fundamental non critical string
We obtain the (super) gravity solution in arbitrary space-time dimension less
than ten, that gives a low energy description of a fundamental string embedded
in a non critical vacuum, product of -dimensional Minkowski space-time and a
cigar-like geometry with scale . This solution, one of the few known
examples of objects doubly localized, both at the origin of the transverse
space as well as at the tip of the cigar, is determined by its charge under
the Kalb-Ramond gauge field , and presumably preserves, for even ,
supercharges. Moreover, we show that the solution is reliable
at least in a region far away from both origins, as it is the case with the
well known branes of critical string theory.Comment: 10 pages, latex file, one figure, to be published in Physics Letters
Towards multi-scale dynamics on the baryonic branch of Klebanov-Strassler
We construct explicitly a new class of backgrounds in type-IIB supergravity
which generalize the baryonic branch of Klebanov-Strassler. We apply a
solution-generating technique that, starting from a large class of solutions of
the wrapped-D5 system, yields the new solutions, and then proceed to study in
detail their properties, both in the IR and in the UV. We propose a simple
intuitive field theory interpretation of the rotation procedure and of the
meaning of our new solutions within the Papadopoulos-Tseytlin ansatz, in
particular in relation to the duality cascade in the Klebanov-Strassler
solution. The presence in the field theory of different VEVs for operators of
dimensions 2, 3 and 6 suggests that this is an important step towards the
construction of the string dual of a genuinely multi-scale (strongly coupled)
dynamical model.Comment: 37 pages, 7 figures. References added, version to appear in JHE
Heavy quark density in N=4 SYM: from hedgehog to Lifshitz spacetimes
We study the effect of an order N^2 density of heavy quarks in strongly
coupled N=4 SUSY Yang-Mills theory in the large N limit. This is achieved in
the type IIB supergravity dual by introducing a uniformly smeared density of
macroscopic string sources stretching to the boundary of AdS_5 x S^5. The
backreacted system exhibits a flow from an AdS_5 "hedgehog" geometry to a
scaling Lifshitz-like solution Lif_5 x S^5 with dynamical critical exponent
z=7, wherein the scaling symmetry is broken by a logarithmic running dilaton.
We find an exact black brane solution within the scaling regime which describes
the low temperature thermodynamics of the system.Comment: 20 pages, 2 figures, references adde
Exploring improved holographic theories for QCD: Part II
This paper is a continuation of ArXiv:0707.1324 where improved holographic
theories for QCD were set up and explored. Here, the IR confining geometries
are classified and analyzed. They all end in a "good" (repulsive) singularity
in the IR. The glueball spectra are gaped and discrete, and they favorably
compare to the lattice data. Quite generally, confinement and discrete spectra
imply each other. Asymptotically linear glueball masses can also be achieved.
Asymptotic mass ratios of various glueballs with different spin also turn out
to be universal. Mesons dynamics is implemented via space filling D4-anti-D4
brane pairs. The associated tachyon dynamics is analyzed and chiral symmetry
breaking is shown. The dynamics of the RR axion is analyzed, and the
non-perturbative running of the QCD theta-angle is obtained. It is shown to
always vanish in the IR.Comment: 65+18 pages, 20 figures (v3) Some modifications in Appendix E
explaining in more detail the issue of initial conditions; typos corrected.
Published versio
New checks and subtleties for AdS/CFT and a-maximization
We provide a cross-check of AdS/CFT and a-charge maximization for a four
dimensional =1 SCFT with irrational R-charges. The gauge theory is the low
energy effective theory of N D3-branes at the tip of the complex cone over the
first del Pezzo surface. By carefully taking into account the subtle issue of
flavor symmetry breaking at the fixed point, we show, using a-maximization,
that this theory has in fact irrational central charge and R-charges. Our
results perfectly match with those inherited from the recently discovered
supergravity dual background. Along analogous lines, we make novel predictions
for the still unknown AdS dual of the quiver theory for the second del Pezzo
surface. This should flow to a SCFT with irrational charges, too. All of our
results differ from previous findings in the literature and outline interesting
subtleties in a-maximization and AdS/CFT techniques overlooked in the past.Comment: Latex, 16 pagex, 2 figures; v2, comments and a reference added; v3,
typos correcte
Space-time filling branes in non critical (super) string theories
We consider solutions of (super) gravities associated to non-critical (super)
string theories in arbitrary space-time dimension D=p+3, that describe
generically non extremal black p-branes charged under NSNS or RR gauge fields,
embedded in some non critical vacuum. In the case of vacuum (uncharged)
backgrounds, we solve completely the problem obtaining all the possible
solutions, that consist of the (p+1)-dimensional Minkowski space times a linear
dilaton times a S^1, and a three parameter family of solutions that include
(p+1)-dimensional Minkowski space times the cigar, and its T-dual
(p+1)-dimensional Minkowski space times the trumpet. For NSNS charged
solutions, we also solve in closed form the problem, obtaining several families
of solutions, that include in particular the fundamental non-critical string
solution embedded in the cigar vacuum, recently found in hep-th/0604202, a
solution that we interpret as a fundamental non-critical string embedded in the
linear dilaton vacuum, and a two-parameter family of regular curvature
solutions asymptotic to AdS_{1,2}\times S^1. In the case of RR charged
Dp-branes solutions, an ansatz allows us to find a non conformal, constant
curvature, asymptotically AdS_{1,p+1} space, T-dual to AdS_{1,p+2}, together
with a two-parameter family of solutions that includes the non conformal, AdS
black hole like solution associated with the earlier space. The solutions
obtained by T-duality are Einstein spaces consisting of a two-parameter family
of conformal, constant dilaton solutions, that include, in particular, the AdS
black hole of hep-th/0403254. We speculate about the possible applications of
some of them in the framework of the gauge-gravity correspondence.Comment: 34 pages, 10 figures, to be published by Nuclear Physics
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