2,134 research outputs found
Ginzburg-Landau theory of the cluster glass phase
On the basis of a recent field theory for site-disordered spin glasses a
Ginzburg-Landau free energy is proposed to describe the low temperatures glassy
phase(s) of site-disordered magnets. The prefactors of the cubic and dominant
quartic terms change gradually along the transition line in the
concentration-temperature phase diagram. Either of them may vanish at certain
points , where new transition lines originate. The new phases are
classifiedComment: 6 pages Revtex, 5 figures. To appear in J. Phys. A. Let
Quantum description of spherical spins
The spherical model for spins describes ferromagnetic phase transitions well,
but it fails at low temperatures. A quantum version of the spherical model is
proposed. It does not induce qualitative changes near the phase transition.
However, it produces a physical low temperature behavior. The entropy is
non-negative. Model parameters can be adapted to the description of real
quantum spins. Several applications are discussed. Zero-temperature quantum
phase transitions are analyzed for a ferromagnet and a spin glass in a
transversal field. Their crossover exponents are presented.Comment: 4 pages postscript. Revised version, to appear in Phys. Rev. Let
Thermodynamics of black holes: an analogy with glasses
The present equilibrium formulation of thermodynamics for black holes has
several drawbacks, such as assuming the same temperature for black hole and
heat bath. Recently the author formulated non-equilibrium thermodynamics for
glassy systems. This approach is applied to black holes, with the cosmic
background temperature being the bath temperature, and the Hawking temperature
the internal temperature. Both Hawking evaporation and absorption of background
radiation are taken into account.
It is argued that black holes did not form in the very early universe.Comment: 4 pages revtex; submitted to Phys. Rev. Let
A landscape of non-supersymmetric AdS vacua on coset manifolds
We construct new families of non-supersymmetric sourceless type IIA AdS4
vacua on those coset manifolds that also admit supersymmetric solutions. We
investigate the spectrum of left-invariant modes and find that most, but not
all, of the vacua are stable under these fluctuations. Generically, there are
also no massless moduli.Comment: 20 pages, 11 figures, v2: added some clarifications, references, v3:
corrections addressing comments refere
Nonrenormalizability of the Quantized Einstein-Maxwell System
The one-loop divergences of coupled general relativity and electrodynamics cannot be absorbed by renormalization
Hopping between Random Locations: Spectrum and Instanton
Euclidean random matrices appear in a broad class of physical problems
involving disorder. The problem of determining their spectra can be mapped,
using the replica method, into the study of a scalar field theory with an
interaction of the type e^(psi^2). We apply the instanton method to study their
spectral tails.Comment: 9 pages, Revtex, 2 postscript figure
The regularized BRST Jacobian of pure Yang-Mills theory
The Jacobian for infinitesimal BRST transformations of path integrals for
pure Yang-Mills theory, viewed as a matrix \unity +\Delta J in the space of
Yang-Mills fields and (anti)ghosts, contains off-diagonal terms. Naively, the
trace of vanishes, being proportional to the trace of the structure
constants. However, the consistent regulator \cR, constructed from a general
method, also contains off-diagonal terms. An explicit computation demonstrates
that the regularized Jacobian Tr\ \Delta J\exp -\cR /M^2 for is the variation of a local counterterm, which we give. This is a
direct proof at the level of path integrals that there is no BRST anomaly.Comment: 12 pages, latex, CERN-TH.6541/92, KUL-TF-92/2
On a Three-Dimensional Gravity Model with Higher Derivatives
The purpose of this work is to present a model for 3D massive gravity with
topological and higher-derivative terms. Causality and unitarity are discussed
at tree-level. Power-counting renormalizability is also contemplated.Comment: 9 pages, Latex, no figures; to be published in Gen. Rel. Gra
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