13 research outputs found
Gravity Dual Corrections to the Heavy Quark Potential at Finite-Temperature
We apply gauge/gravity duality to compute corrections to the heavy
quark potentials of a quark--anti-quark pair () and of a quark--quark
pair () immersed into the strongly coupled N = 4 SYM plasma. On the gravity
side these corrections come from the exchanges of supergravity modes between
two string worldsheets stretching from the UV boundary of AdS space to the
black hole horizon in the bulk and smeared over . We find that the
contributions to the potential coming from the exchanges of all of
the relevant modes (such as dilaton, massive scalar, 2-form field, and
graviton) are all attractive, leading to an attractive net potential.
We show that at large separations and/or high-temperature the potential
is of Yukawa-type, dominated by the graviton exchange, in agreement with
earlier findings. On the other hand, at small- the potential
scales as . In the case of potential the 2-form
contribution changes sign and becomes repulsive: however, the net
potential remains attractive. At large- it is dominated by the graviton
exchange, while at small- the potential becomes Coulomb-like.Comment: 45 pages, 14 figures; v2: refs added, typos correcte
PQChPT with Staggered Sea and Valence Ginsparg-Wilson Quarks: Vector Meson Masses
We consider partially quenched, mixed chiral perturbation theory with
staggered sea and Ginsparg-Wilson valence quarks in order to extract a
chiral-continuum extrapolation expression for the vector meson mass up to order
O(a^2), at one-loop level. Based on general principles, we accomplish the task
without explicitly constructing a sophisticated, heavy vector meson chiral
Lagrangian.Comment: 12 pages, 1 figure, REVTe
Dimension Six Corrections to the Vector Sector of AdS/QCD Model
We study the effects of dimension six terms on the predictions of the
holographic model for the vector meson form factors and determine the
corrections to the electric radius, the magnetic and the quadrupole moments of
the rho-meson. We show that the only dimension six terms which contribute
nontrivially to the vector meson form factors are X^2F^2 and F^3. It appears
that the effect from the former term is equivalent to the metric deformation
and can change only masses, decay constants and charge radii of vector mesons,
leaving the magnetic and the quadrupole moments intact. The latter term gives
different contributions to the three form factors of the vector meson and
changes the values of the magnetic and the quadrupole moments. The results
suggest that the addition of the higher dimension terms improves the
holographic model.Comment: 6 pages, RevTex, revised version, accepted for publication in Physics
Letters
Towards the Gravity Dual of Quarkonium in the Strongly Coupled QCD Plasma
We build a "bottom-up" holographic model of charmonium by matching the
essential spectral data. We argue that this data must include not only the
masses but also the decay constants of the J/psi and psi' mesons. Relative to
the "soft-wall" models for light mesons, such a matching requires two new
features in the holographic potential: an overall upward shift as well as a
narrow "dip" near the holographic boundary. We calculate the spectral function
as well as the position of the complex singularities (quasinormal frequencies)
of the retarded correlator of the charm current at finite temperatures. We
further extend this analysis by showing that the residues associated with these
singularities are given by the boundary derivative of the appropriately
normalized quasinormal mode. We find that the "melting" of the J/psi spectral
peak occurs at a temperature of about 540 MeV, or 2.8 T_c, in good agreement
with lattice results.Comment: 13 pages, 9 figure
Analyticity, Unitarity and One-loop Graviton Corrections to Compton Scattering
We compute spin-flip cross section for graviton photoproduction on a spin-1/2
target of finite mass. Using this tree-level result, we find one-loop graviton
correction to the spin-flip low-energy forward Compton scattering amplitude by
using Gerasimov-Drell-Hearn sum rule. We show that this result agrees with the
corresponding perturbative computations, implying the validity of the sum rule
at one-loop level, contrary to the previous claims. We discuss possible effects
from the black hole production and string Regge trajectory exchange at very
high energies. These effects seem to soften the UV divergence present at
one-loop graviton level. Finally, we discuss the relation of these observations
with the models that involve extra dimensions.Comment: 15 pages, 3 figure
New Sum Rules from Low Energy Compton Scattering on Arbitrary Spin Target
We derive two sum rules by studying the low energy Compton scattering on a
target of arbitrary (nonzero) spin j. In the first sum rule, we consider the
possibility that the intermediate state in the scattering can have spin |j \pm
1| and the same mass as the target. The second sum rule applies if the theory
at hand possesses intermediate narrow resonances with masses different from the
mass of the scatterer. These sum rules are generalizations of the
Gerasimov-Drell-Hearn-Weinberg sum rule. Along with the requirement of tree
level unitarity, they relate different low energy couplings in the theory.
Using these sum rules, we show that in certain cases the gyromagnetic ratio can
differ from the "natural" value g=2, even at tree level, without spoiling
perturbative unitarity. These sum rules can be used as constraints applicable
to all supergravity and higher-spin theories that contain particles charged
under some U(1) gauge field. In particular, applied to four dimensional N=8
supergravity in a spontaneously broken phase, these sum rules suggest that for
the theory to have a good ultraviolet behavior, additional massive states need
to be present, such as those coming from the embedding of the N=8 supergravity
in type II superstring theory. We also discuss the possible implications of the
sum rules for QCD in the large-N_c limit.Comment: 18 pages, v2: discussion on black hole contribution is included,
references added; v3: extended discussion in introduction, version to appear
in JHE
Form Factors and Wave Functions of Vector Mesons in Holographic QCD
Within the framework of a holographic dual model of QCD, we develop a
formalism for calculating form factors of vector mesons. We show that the
holographic bound states can be described not only in terms of eigenfunctions
of the equation of motion, but also in terms of conjugate wave functions that
are close analogues of quantum-mechanical bound state wave functions. We derive
a generalized VMD representation for form factors, and find a very specific VMD
pattern, in which form factors are essentially given by contributions due to
the first two bound states in the Q^2-channel. We calculate electric radius of
the rho-meson, finding the value _C = 0.53 fm^2.Comment: 7 pages, RevTex. References were added, some modifications in the
text were mad
Long-Range Rapidity Correlations in Heavy Ion Collisions at Strong Coupling from AdS/CFT
We use AdS/CFT correspondence to study two-particle correlations in heavy ion
collisions at strong coupling. Modeling the colliding heavy ions by shock waves
on the gravity side, we observe that at early times after the collision there
are long-range rapidity correlations present in the two-point functions for the
glueball and the energy-momentum tensor operators. We estimate rapidity
correlations at later times by assuming that the evolution of the system is
governed by ideal Bjorken hydrodynamics, and find that glueball correlations in
this state are suppressed at large rapidity intervals, suggesting that
late-time medium dynamics can not "wash out" the long-range rapidity
correlations that were formed at early times. These results may provide an
insight on the nature of the "ridge" correlations observed in heavy ion
collision experiments at RHIC and LHC, and in proton-proton collisions at LHC.Comment: 32 pages, 2 figures; v2: typos corrected, references adde