147 research outputs found
Semiclassical decay of near extremal fivebranes
We argue that a near-extremal charge- type II NS fivebrane can be reliably
described in semiclassical string perturbation theory as long as both and
are large, where is the energy density in string units. For
a small value of the asymptotic string coupling , the dynamics in the throat
surrounding the fivebrane reduces to the CGHS model with massive fields. We
find that the energy density leaks off the brane in the form of Hawking
radiation at a rate of order in string units independently of
to leading order. In the limit the radiation persists but never
reaches asymptotic infinity because the throat becomes infinitely long.Comment: 3 pages, harvma
Large N Limit of Non-Commutative Gauge Theories
Using the correspondence between gauge theories and string theory in curved
backgrounds, we investigate aspects of the large limit of non-commutative
gauge theories by considering gravity solutions with fields. We argue that
the total number of physical degrees of freedom at any given scale coincides
with the commutative case. We then compute a two-point correlation function
involving momentum components in the directions of the -field. In the UV
regime, we find that the two-point function decays exponentially with the
momentum. A calculation of Wilson lines suggests that strings cannot be
localized near the boundary. We also find string configurations that are
localized in a finite region of the radial direction. These are worldsheet
instantons.Comment: 21 pages, harvmac. Some errors in correlators corrected, minor
corrections to the Lorentzian solution
Statistical Entropy of Near Extremal Five-branes
The Hawking Beckenstein entropy of near extremal fivebranes is calculated in
terms of a gas of strings living on the fivebrane. These fivebranes can also be
viewed as near extremal black holes in five dimensions.Comment: 8 pages, uses harvma
Dual composition of odd-dimensional models
A general way of interpreting odd dimensional models as a doublet of chiral
models is discussed. Based on the equations of motion this dual composition is
illustrated. Examples from quantum mechanics, field theory and gravity are
considered. Specially the recently advocated topologically massive gravity is
analysed in some details.Comment: minor modification
N=2 Extremal Black Holes and Intersecting Branes
Using a simple hypothesis about the degrees of freedom of intersecting branes
we find a microscopic counting argument that reproduces the entropy of a class
of BPS black holes of type IIA string theory on general Calabi Yau three folds.Comment: 4 pages, no figures. Typos correcte
Supersymmetric Field Theory in 2T-physics
We construct N=1 supersymmetry in 4+2 dimensions compatible with the
theoretical framework of 2T physics field theory and its gauge symmetries. The
fields are arranged into 4+2 dimensional chiral and vector supermultiplets, and
their interactions are uniquely fixed by SUSY and 2T-physics gauge symmetries.
Many 3+1 spacetimes emerge from 4+2 by gauge fixing. Gauge degrees of freedom
are eliminated as one comes down from 4+2 to 3+1 dimensions without any
remnants of Kaluza-Klein modes. In a special gauge, the remaining physical
degrees of freedom, and their interactions, coincide with ordinary N=1
supersymmetric field theory in 3+1 dimensions. In this gauge, SUSY in 4+2 is
interpreted as superconformal symmetry SU(2,2|1) in 3+1 dimensions.
Furthermore, the underlying 4+2 structure imposes some interesting restrictions
on the emergent 3+1 SUSY field theory, which could be considered as part of the
predictions of 2T-physics. One of these is the absence of the troublesome
renormalizable CP violating F*F terms. This is good for curing the strong CP
violation problem of QCD. An additional feature is that the superpotential is
required to have no dimensionful parameters. To induce phase transitions, such
as SUSY or electro-weak symmetry breaking, a coupling to the dilaton is needed.
This suggests a common origin of phase transitions that is driven by the vacuum
value of the dilaton, and need to be understood in a cosmological scenario as
part of a unified theory that includes the coupling of supergravity to matter.
Another interesting aspect is the possibility to utilize the inherent 2T gauge
symmetry to explore dual versions of the N=1 theory in 3+1 dimensions. This is
expected to reveal non-perturbative aspects of ordinary 1T field theory.Comment: 54 pages, late
Statistical Entropy of Nonextremal Four-Dimensional Black Holes and U-Duality
We identify the states in string theory which are responsible for the entropy
of near-extremal rotating four-dimensional black holes in supergravity.
For black holes far from extremality (with no rotation), the Bekenstein-Hawking
entropy is exactly matched by a mysterious duality invariant extension of the
formulas derived for near-extremal black holes states.Comment: 9 pages, harvma
Wilson Loops as Precursors
There is substantial evidence that string theory on AdS_5 x S_5 is a
holographic theory in which the number of degrees of freedom scales as the area
of the boundary in Planck units. Precisely how the theory can describe bulk
physics using only surface degrees of freedom is not well understood. A
particularly paradoxical situation involves an event deep in the interior of
the bulk space. The event must be recorded in the (Schroedinger Picture) state
vector of the boundary theory long before a signal, such as a gravitational
wave, can propagate from the event to the boundary. In a previous paper with
Polchinski, we argued that the "precursor" operators which carry information
stored in the wave during the time when it vanishes in a neighborhood of the
boundary are necessarily non-local. In this paper we argue that the precursors
cannot be products of local gauge invariant operators such as the energy
momentum tensor. In fact gauge theories have a class of intrinsically non-local
operators which cannot be built from local gauge invariant objects. These are
the Wilson loops. We show that the precursors can be identified with Wilson
loops whose spatial size is dictated by the UV-IR connection.Comment: 23 pages, no figure
Nonextremal Black Hole Microstates and U-duality
A six-parameter family of five-dimensional black hole solutions is
constructed which are labeled by their mass, two asymptotic scalar fields and
three charges. It is shown that the Bekenstein-Hawking entropy is exactly
matched, arbitrarily far from extremality, by a simple but mysterious
duality-invariant extension of previously derived formulae for the number of
D-brane states in string theory.Comment: 19 page
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