14,890 research outputs found
2D Black Hole and Holographic Renormalization Group
In hep-th/0311177, the Large renormalization group (RG) flows of a
modified matrix quantum mechanics on a circle, capable of capturing effects of
nonsingets, were shown to have fixed points with negative specific heat. The
corresponding rescaling equation of the compactified matter field with respect
to the RG scale, identified with the Liouville direction, is used to extract
the two dimensional Euclidean black hole metric at the new type of fixed
points. Interpreting the large RG flows as flow velocities in holographic
RG in two dimensions, the flow equation of the matter field around the black
hole fixed point is shown to be of the same form as the radial evolution
equation of the appropriate bulk scalar coupled to 2D black hole.Comment: 21 page
The Qt distribution of the Breit current hemisphere in DIS as a probe of small-x broadening effects
We study the distribution 1/sigma dsigma/dQt, where Qt is the modulus of the
transverse momentum vector, obtained by summing over all hadrons, in the
current hemisphere of the DIS Breit frame. We resum the large logarithms in the
small Qt region, to next-to--leading logarithmic accuracy, including the
non-global logarithms involved. We point out that this observable is simply
related to the Drell-Yan vector boson and predicted Higgs Qt spectra at hadron
colliders. Comparing our predictions to existing HERA data thus ought to be a
valuable source of information on the role or absence of small-x (BFKL)
effects, neglected in conventional resummations of such quantities.Comment: 16 pages, 3 figures, uses JHEP3.cl
Two-step melting of the vortex solid in layered superconductors with random columnar pins
We consider the melting of the vortex solid in highly anisotropic layered
superconductors with a small concentration of random columnar pinning centers.
Using large-scale numerical minimization of a free-energy functional, we find
that melting of the low-temperature, nearly crystalline vortex solid (Bragg
glass) into a vortex liquid occurs in two steps as the temperature increases:
the Bragg glass and liquid phases are separated by an intermediate Bose glass
phase. A suitably defined local melting temperature exhibits spatial variation
similar to that observed in experiments.Comment: To appear in Phys. Rev. Let
Melting and structure of the vortex solid in strongly anisotropic layered superconductors with random columnar pins
We study the melting transition of the low-temperature vortex solid in
strongly anisotropic layered superconductors with a concentration of random
columnar pinning centers small enough so that the areal density of the pins is
much less than that of the vortex lines. Both the external magnetic field and
the columnar pins are assumed to be oriented perpendicular to the layers Our
method, involving numerical minimization of a model free energy functional,
yields not only the free energy values at the local minima of the functional
but also the detailed density distribution of the system at each minimum: this
allows us to study in detail the structure of the different phases. We find
that at these pin concentrations and low temperatures, the thermodynamically
stable state is a topologically ordered Bragg glass. This nearly crystalline
state melts into an interstitial liquid (a liquid in which a small fraction of
vortex lines remain localized at the pinning centers) in two steps, so that the
Bragg glass and the liquid are separated by a narrow phase that we identify
from analysis of its density structure as a polycrystalline Bose glass. Both
the Bragg glass to Bose glass and the Bose glass to interstitial liquid
transitions are first-order. We also find that a local melting temperature
defined using a criterion based on the degree of localization of the vortex
lines exhibits spatial variations similar to those observed in recent
experiments.Comment: 17 page
Spatial persistence and survival probabilities for fluctuating interfaces
We report the results of numerical investigations of the steady-state (SS)
and finite-initial-conditions (FIC) spatial persistence and survival
probabilities for (1+1)--dimensional interfaces with dynamics governed by the
nonlinear Kardar--Parisi--Zhang (KPZ) equation and the linear
Edwards--Wilkinson (EW) equation with both white (uncorrelated) and colored
(spatially correlated) noise. We study the effects of a finite sampling
distance on the measured spatial persistence probability and show that both SS
and FIC persistence probabilities exhibit simple scaling behavior as a function
of the system size and the sampling distance. Analytical expressions for the
exponents associated with the power-law decay of SS and FIC spatial persistence
probabilities of the EW equation with power-law correlated noise are
established and numerically verified.Comment: 11 pages, 5 figure
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