86 research outputs found
Phase Structure of Non-Compact QED3 and the Abelian Higgs Model
We review the phase structure of a three-dimensional, non-compact Abelian
gauge theory (QED3) as a function of the number of 4-component massless
fermions. There is a critical up to which there is dynamical fermion
mass generation and an associated global symmetry breaking. We discuss various
approaches to the determination of , which lead to estimates ranging from
to . This theory with N=2 has been employed as an effective
continuum theory for the 2D quantum antiferromagnet where the observed Neel
ordering corresponds to dynamical fermion mass generation. Thus the value of
is of some physical interest. We also consider the phase structure of the
model with a finite gauge boson mass (the Abelian Higgs model).Comment: 14 pages, corrected the normalization of the fermion condensate in
section V, corrected a typo in the reference
Spectrum and Statistical Entropy of AdS Black Holes
Popular approaches to quantum gravity describe black hole microstates
differently and apply different statistics to count them. Since the
relationship between the approaches is not clear, this obscures the role of
statistics in calculating the black hole entropy. We address this issue by
discussing the entropy of eternal AdS black holes in dimension four and above
within the context of a midisuperspace model. We determine the black hole
eigenstates and find that they describe the quantization in half integer units
of a certain function of the Arnowitt-Deser-Misner (ADM) mass and the
cosmological constant. In the limit of a vanishing cosmological constant (the
Schwarzschild limit) the quantized function becomes the horizon area and in the
limit of a large cosmological constant it approaches the ADM mass of the black
holes. We show that in the Schwarzschild limit the area quatization leads to
the Bekenstein-Hawking entropy if Boltzmann statistics are employed. In the
limit of a large cosmological constant the Bekenstein-Hawking entropy can be
recovered only via Bose statistics. The two limits are separated by a first
order phase transition, which seems to suggest a shift from "particle-like"
degrees of freedom at large cosmological constant to geometric degrees of
freedom as the cosmological constant approaches zero.Comment: 14 pages. No figures. Some references added. Version to appear in
Phys. Rev.
Stability of D-brane embeddings in nontrivial backgrounds
We propose a new analytical method for determining whether nonsupersymmetric
probe branes embedded in nontrivial backgrounds are perturbatively stable or
not. The method is based on a relationship between zero mass solutions of the
relevant DBI equations of motion and tachyonic solutions. Furthermore, due to
the above relation, the question, of whether a classical solution is stable or
not, can be answered simply by studying the derivatives of that solution with
respect to its integration constants. Finally, we illustrate the efficiency of
this method by applying it to several interesting examples.Comment: 18 pages; introductory material added in Section 2, journal versio
An evaluation of the analytic continuation by duality technique
In Nucl. Phys. B391 (1993) 127, the value of the oblique correction parameter
S for walking technicolor theories was estimated using a technique called
Analytic Continuation by Duality (ACD). We apply the ACD technique to the
perturbative vacuum polarization function and find that it fails to reproduce
the well known result S=1/6\pi. This brings into question the reliability of
the ACD technique and the ACD estimate of S.Comment: 8 pages, LaTeX, 1 postscript figure. Uses cite.sty, sprocl.sty, and
epsfig.sty. Talk presented at the 1996 International Workshop on Perspectives
of Strong Coupling Gauge Theories (SCGT'96), 13-16 Nov. 1996, Nagoy
Analytic approximation to 5 dimensional Black Holes with one compact dimension
We study black hole solutions in space, using an expansion to
fourth order in the ratio of the radius of the horizon, , and the
circumference of the compact dimension, . A study of geometric and
thermodynamic properties indicates that the black hole fills the space in the
compact dimension at . At the same value of
the entropies of the uniform black string and of the black hole are
approximately equal.Comment: 21 pages, 4 figures. Replaces previous version, with added references
and slightly altered discussio
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