187 research outputs found
Constraints on Conformal Windows from Holographic Duals
We analyze a beta function with the analytic form of
Novikov-Shifman-Vainshtein-Zakharov result in the five dimensional
gravity-dilaton environment. We show how dilaton inherits poles and fixed
points of such beta function through the zeros and points of extremum in its
potential. Super Yang-Mills and supersymmetric QCD are studied in detail and
Seiberg's electric-magnetic duality in the dilaton potential is explicitly
demonstrated. Non-supersymmetric proposals of similar functional form are
tested and new insights into the conformal window as well as determinations of
scheme-independent value of the anomalous dimension at the fixed point are
presented.Comment: Fig. 5b is corrected to match the discussion in the tex
Holography and Thermodynamics of 5D Dilaton-gravity
The asymptotically-logarithmically-AdS black-hole solutions of 5D dilaton
gravity with a monotonic dilaton potential are analyzed in detail. Such
theories are holographically very close to pure Yang-Mills theory in four
dimensions. The existence and uniqueness of black-hole solutions is shown. It
is also shown that a Hawking-Page transition exists at finite temperature if
and only if the potential corresponds to a confining theory. The physics of the
transition matches in detail with that of deconfinement of the Yang-Mills
theory. The high-temperature phase asymptotes to a free gluon gas at high
temperature matching the expected behavior from asymptotic freedom. The thermal
gluon condensate is calculated and shown to be crucial for the existence of a
non-trivial deconfining transition. The condensate of the topological charge is
shown to vanish in the deconfined phase.Comment: LaTeX, 61 pages (main body) + 58 pages (appendix), 25 eps figures.
Revised version, published in JHEP. Two equations added in Section 7.4; typos
corrected; references adde
A Holographic Model of Strange Metals
We give a review on our recent work arXiv:1006.0779 [hep-th] and
arXiv:1006.1719 [hep-th], in which properties of holographic strange metals
were investigated. The background is chosen to be anisotropic scaling solution
in Einstein-Maxwell-Dilaton theory with a Liouville potential. The effects of
bulk Maxwell field, an extra U(1) gauge field and probe D-branes on the DC
conductivity, the DC Hall conductivity and the AC conductivity are extensively
analyzed. We classify behaviors of the conductivities according to the
parameter ranges in the bulk theory and characterize conditions when the
holographic results can reproduce experimental data.Comment: 34 pages, 15 figures, minor correction
On the YM and QCD spectra from five dimensional strings
We consider a non-critical five dimensional string setup which could provide
a dual description of QCD in the limit of large number of colors and flavors.
The model corresponds to N_c color D3-branes and N_f D4/anti D4-brane pairs
supporting flavor degrees of freedom. The matching of the string model spectrum
with the dual field theory one is considered. We discuss the consequences of
the possible matching of the gravity modes with the light glueballs and the
interpretation of the brane spectrum in Yang-Mills and QCD.Comment: 21 pages; V2: added corrections and references to match the published
versio
Spectral Functions in Holographic Renormalization Group Flows
The spectrum of two-point functions in a holographic renormalization group
flow from an ultraviolet (UV) to an infrared (IR) conformal fixed point is
necessarily continuous. For a toy model, the spectral function does not only
show the expected UV and IR behaviours, but other interesting features such as
sharp peaks and oscillations in the UV. The spectral functions for the
SU(3)xU(1) flow in AdS_4/CFT_3 and the SU(2)xU(1) flow in AdS_5/CFT_4 are
calculated numerically. They exhibit a simple cross-over behaviour and
reproduce the conformal dimensions of the dual operators in the UV and IR
conformal phases.Comment: 20 pages, 6 figures v2: added referene
The Penrose limit of AdS*S space and holography
In the Penrose limit, AdS*S space turns into a Cahen-Wallach (CW) space whose
Killing vectors satisfy a Heisenberg algebra. This algebra is mapped onto the
holographic screen on the boundary of AdS. I show that the Heisenberg algebra
on the boundary of AdS may be obtained directly from the CW space by
appropriately constraining the states defined on it. The transformations
generated by the constraint are similar to gauge transformations. The
``holographic screen'' on the CW space is thus obtained as a ``gauge-fixing''
condition.Comment: 12 pages, improved discussion, to appear in Mod. Phys. Lett.
Improved Holographic QCD
We provide a review to holographic models based on Einstein-dilaton gravity
with a potential in 5 dimensions. Such theories, for a judicious choice of
potential are very close to the physics of large-N YM theory both at zero and
finite temperature. The zero temperature glueball spectra as well as their
finite temperature thermodynamic functions compare well with lattice data. The
model can be used to calculate transport coefficients, like bulk viscosity, the
drag force and jet quenching parameters, relevant for the physics of the
Quark-Gluon Plasma.Comment: LatEX, 65 pages, 28 figures, 9 Tables. Based on lectures given at
several Schools. To appear in the proceedinds of the 5th Aegean School
(Milos, Greece
In search of the QCD-Gravity correspondence
Quantum Chromodynamics (QCD) is the fundamental theory of strong
interactions. It describes the behavior of quarks and gluons which are the
smallest known constituents of nuclear matter. The difficulties in solving the
theory at low energies in the strongly interacting, non-perturbative regime
have left unanswered many important questions in QCD, such as the nature of
confinement or the mechanism of hadronization. In these lectures oriented
towards the students we introduce two classes of dualities that attempt to
reproduce many of the features of QCD, while making the treatment at strong
coupling more tractable: (1) the AdS/CFT correspondence between a specific
class of string theories and a conformal field theory and (2) an effective
low-energy theory of QCD dual to classical QCD on a curved conformal
gravitational background. The hope is that by applying these dualities to the
evaluation of various properties of the strongly-interacting matter produced in
heavy ion collisions one can understand how QCD behaves at strong coupling. We
give an outline of the applications, with emphasis on two transport
coefficients of QCD matter -- shear and bulk viscosities.Comment: 31 pages, 7 figures; Lectures delivered by D. Kharzeev at the
International QGP Winter School, Jaipur, India, February 1-3, 200
Orbiting Membranes in M-theory on AdS_7 x S^4 Background
We study classical solutions describing rotating and boosted membranes on
AdS_7 x S^4 background in M-theory. We find the dependence of the energy on the
spin and R-charge of these solutions. In the flat space limit we get E ~
S^{2/3}, while for AdS at leading order E-S grows as S^{1/3}. The membranes on
AdS_4 x S^7 background have briefly been studied as well.Comment: 13 pages, latex, v2: a note and refs. added, some typos correcte
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
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