800 research outputs found
Bundles of Interacting Strings in Two Dimensions
Bundles of strings which interact via short-ranged pair potentials are
studied in two dimensions. The corresponding transfer matrix problem is solved
analytically for arbitrary string number N by Bethe ansatz methods. Bundles
consisting of N identical strings exhibit a unique unbinding transition. If the
string bundle interacts with a hard wall, the bundle may unbind from the wall
via a unique transition or a sequence of N successive transitions. In all
cases, the critical exponents are independent of N and the density profile of
the strings exhibits a scaling form that approaches a mean-field profile in the
limit of large N.Comment: 8 pages (latex) with two figure
New nonuniform black string solutions
We present nonuniform vacuum black strings in five and six spacetime
dimensions. The conserved charges and the action of these solutions are
computed by employing a quasilocal formalism. We find qualitative agreement of
the physical properties of nonuniform black strings in five and six dimensions.
Our results offer further evidence that the black hole and the black string
branches merge at a topology changing transition. We generate black string
solutions of the Einstein-Maxwell-dilaton theory by using a Harrison
transformation. We argue that the basic features of these solutions can be
derived from those of the vacuum black string configurations.Comment: 30 pages, 12 figures; v2: more details on numerical method,
references added; v3: references added, minor revisions, version accepted by
journa
Universal spectral statistics of Andreev billiards: semiclassical approach
The classification of universality classes of random-matrix theory has
recently been extended beyond the Wigner-Dyson ensembles. Several of the novel
ensembles can be discussed naturally in the context of superconducting-normal
hybrid systems. In this paper, we give a semiclassical interpretation of their
spectral form factors for both quantum graphs and Andreev billiards.Comment: final improved version (to be published in Physical Review E), 6
pages, revtex
Multi-patch methods in general relativistic astrophysics - I. Hydrodynamical flows on fixed backgrounds
Many systems of interest in general relativistic astrophysics, including
neutron stars, accreting compact objects in X-ray binaries and active galactic
nuclei, core collapse, and collapsars, are assumed to be approximately
spherically symmetric or axisymmetric. In Newtonian or fixed-background
relativistic approximations it is common practice to use spherical polar
coordinates for computational grids; however, these coordinates have
singularities and are difficult to use in fully relativistic models. We
present, in this series of papers, a numerical technique which is able to use
effectively spherical grids by employing multiple patches. We provide detailed
instructions on how to implement such a scheme, and present a number of code
tests for the fixed background case, including an accretion torus around a
black hole.Comment: 26 pages, 20 figures. A high-resolution version is available at
http://www.cct.lsu.edu/~bzink/papers/multipatch_1.pd
Multisphalerons in the Weinberg-Salam Theory
We construct multisphaleron solutions in the Weinberg-Salam theory. The
multisphaleron solutions carry Chern-Simons charge , where is an
integer, counting the winding of the fields in the azimuthal angle. The
well-known sphaleron has . The multisphalerons possess axial symmetry and
parity reflection symmetry. We vary the Higgs mass and the mixing angle. For
small the energies of the multisphalerons are on the order of times the
energy of the sphaleron and their magnetic dipole moments are on the order of
times the magnetic dipole moment of the sphaleron.Comment: 18 pages, latex, 17 figures in uuencoded postscript files. THU-94/1
Variational Density Matrix Method for Warm Condensed Matter and Application to Dense Hydrogen
A new variational principle for optimizing thermal density matrices is
introduced. As a first application, the variational many body density matrix is
written as a determinant of one body density matrices, which are approximated
by Gaussians with the mean, width and amplitude as variational parameters. The
method is illustrated for the particle in an external field problem, the
hydrogen molecule and dense hydrogen where the molecular, the dissociated and
the plasma regime are described. Structural and thermodynamic properties
(energy, equation of state and shock Hugoniot) are presented.Comment: 26 pages, 13 figures. submitted to Phys. Rev. E, October 199
New generalized nonspherical black hole solutions
We present numerical evidence for the existence of several types of static
black hole solutions with a nonspherical event horizon topology in
spacetime dimensions. These asymptotically flat configurations are found for a
specific metric ansatz and can be viewed as higher dimensional counterparts of
the static black rings, dirings and black Saturn. Similar to that case,
they are supported against collapse by conical singularities. The issue of
rotating generalizations of these solutions is also considered.Comment: 47 pages, 11 figures, some comments adde
A Monopole-Antimonopole Solution of the SU(2) Yang-Mills-Higgs Model
As shown by Taubes, in the Bogomol'nyi-Prasad-Sommerfield limit the SU(2)
Yang-Mills-Higgs model possesses smooth finite energy solutions, which do not
satisfy the first order Bogomol'nyi equations. We construct numerically such a
non-Bogomol'nyi solution, corresponding to a monopole-antimonopole pair, and
extend the construction to finite Higgs potential.Comment: 11 pages, including 4 eps figures, LaTex format using RevTe
High-statistics finite size scaling analysis of U(1) lattice gauge theory with Wilson action
We describe the results of a systematic high-statistics Monte-Carlo study of
finite-size effects at the phase transition of compact U(1) lattice gauge
theory with Wilson action on a hypercubic lattice with periodic boundary
conditions. We find unambiguously that the critical exponent nu is lattice-size
dependent for volumes ranging from 4^4 to 12^4. Asymptotic scaling formulas
yield values decreasing from nu(L >= 4) = 0.33 to nu(L >= 9) = 0.29. Our
statistics are sufficient to allow the study of different phenomenological
scenarios for the corrections to asymptotic scaling. We find evidence that
corrections to a first-order transition with nu=0.25 provide the most accurate
description of the data. However the corrections do not follow always the
expected first-order pattern of a series expansion in the inverse lattice
volume V^{-1}. Reaching the asymptotic regime will require lattice sizes
greater than L=12. Our conclusions are supported by the study of many cumulants
which all yield consistent results after proper interpretation.Comment: revtex, 12 pages, 9 figure
A thermodynamically self-consistent theory for the Blume-Capel model
We use a self-consistent Ornstein-Zernike approximation to study the
Blume-Capel ferromagnet on three-dimensional lattices. The correlation
functions and the thermodynamics are obtained from the solution of two coupled
partial differential equations. The theory provides a comprehensive and
accurate description of the phase diagram in all regions, including the wing
boundaries in non-zero magnetic field. In particular, the coordinates of the
tricritical point are in very good agreement with the best estimates from
simulation or series expansion. Numerical and analytical analysis strongly
suggest that the theory predicts a universal Ising-like critical behavior along
the -line and the wing critical lines, and a tricritical behavior
governed by mean-field exponents.Comment: 11 figures. to appear in Physical Review
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