741 research outputs found
Finite Size Correction In A Disordered System - A New Divergence
We show that the amplitude of the finite size correction term for the th
moment of the partition function, for randomly interacting directed polymers,
diverges (on the high temperature side) as , as a critical
moment is approached. The exponent is independent of temperature but
does depend on the effective dimensionality. There is no such divergence on the
low temperature side (.Comment: 8 pages, Revtex, 5 figures. For figs, send mail to [email protected]
Spacetimes with Longitudinal and Angular Magnetic Fields in Third Order Lovelock Gravity
We obtain two new classes of magnetic brane solutions in third order Lovelock
gravity. The first class of solutions yields an -dimensional spacetime
with a longitudinal magnetic field generated by a static source. We generalize
this class of solutions to the case of spinning magnetic branes with one or
more rotation parameters. These solutions have no curvature singularity and no
horizons, but have a conic geometry. For the spinning brane, when one or more
rotation parameters are nonzero, the brane has a net electric charge which is
proportional to the magnitude of the rotation parameters, while the static
brane has no net electric charge. The second class of solutions yields a
pacetime with an angular magnetic field. These solutions have no curvature
singularity, no horizon, and no conical singularity. Although the second class
of solutions may be made electrically charged by a boost transformation, the
transformed solutions do not present new spacetimes. Finally, we use the
counterterm method in third order Lovelock gravity and compute the conserved
quantities of these spacetimes.Comment: 15 pages, no figur
From p-branes to Cosmology
We study the relationship between static p-brane solitons and cosmological
solutions of string theory or M-theory. We discuss two different ways in which
extremal p-branes can be generalised to non-extremal ones, and show how wide
classes of recently discussed cosmological models can be mapped into
non-extremal p-brane solutions of one of these two kinds. We also extend
previous discussions of cosmological solutions to include some that make use of
cosmological-type terms in the effective action that can arise from the
generalised dimensional reduction of string theory or M-theory.Comment: Latex, 24 pages, no figur
Loop-corrected entropy of near-extremal dilatonic p-branes
It has recently been shown that for certain classical p-branes, where the dilaton is regular on the horizon, the entropy and temperature satisfy the ideal-gas relation S\sim T^{p} in the near-extremal regime. We argue that by taking string and worldsheet loop corrections into account, the validity of this entropy/temperature relation may be extended to include those cases where the dilaton classically diverges on the horizon, thereby opening up the possibility of giving a microscopic interpretation of the entropy for all near-extremal p-branes
On the Bekenstein-Hawking Entropy, Non-Commutative Branes and Logarithmic Corrections
We extend earlier work on the origin of the Bekenstein-Hawking entropy to
higher-dimensional spacetimes. The mechanism of counting states is shown to
work for all spacetimes associated with a Euclidean doublet
of electric-magnetic dual brane pairs of type II
string-theory or M-theory wrapping the spacetime's event horizon plus the
complete internal compactification space. Non-Commutativity on the brane
worldvolume enters the derivation of the Bekenstein-Hawking entropy in a
natural way. Moreover, a logarithmic entropy correction with prefactor 1/2 is
derived.Comment: 17 pages, 2 figures; refs. adde
Magnetic Branes in -dimensional Einstein-Maxwell-dilaton gravity
We construct two new classes of spacetimes generated by spinning and
traveling magnetic sources in -dimensional Einstein-Maxwell-dilaton
gravity with Liouville-type potential. These solutions are neither
asymptotically flat nor (A)dS. The first class of solutions which yields a
-dimensional spacetime with a longitudinal magnetic field and
rotation parameters have no curvature singularity and no horizons, but have a
conic geometry. We show that when one or more of the rotation parameters are
nonzero, the spinning branes has a net electric charge that is proportional to
the magnitude of the rotation parameters. The second class of solutions yields
a static spacetime with an angular magnetic field, and have no curvature
singularity, no horizons, and no conical singularity. Although one may add
linear momentum to the second class of solutions by a boost transformation, one
does not obtain a new solution. We find that the net electric charge of these
traveling branes with one or more nonzero boost parameters is proportional to
the magnitude of the velocity of the branes. We also use the counterterm method
and calculate the conserved quantities of the solutions.Comment: 15 pages, the last version to appear in PR
Counterterm Method in Lovelock Theory and Horizonless Solutions in Dimensionally Continued Gravity
In this paper we, first, generalize the quasilocal definition of the stress
energy tensor of Einstein gravity to the case of Lovelock gravity, by
introducing the tensorial form of surface terms that make the action
well-defined. We also introduce the boundary counterterm that removes the
divergences of the action and the conserved quantities of the solutions of
Lovelock gravity with flat boundary at constant and . Second, we obtain
the metric of spacetimes generated by brane sources in dimensionally continued
gravity through the use of Hamiltonian formalism, and show that these solutions
have no curvature singularity and no horizons, but have conic singularity. We
show that these asymptotically AdS spacetimes which contain two fundamental
constants are complete. Finally we compute the conserved quantities of these
solutions through the use of the counterterm method introduced in the first
part of the paper.Comment: 15 pages, references added, typos correcte
Vicinal Surfaces, Fractional Statistics and Universality
We propose that the phases of all vicinal surfaces can be characterized by
four fixed lines, in the renormalization group sense, in a three-dimensional
space of coupling constants. The observed configurations of several Si surfaces
are consistent with this picture. One of these fixed lines also describes
one-dimensional quantum particles with fractional exclusion statistics. The
featureless steps of a vicinal surface can therefore be thought of as a
realization of fractional-statistics particles, possibly with additional
short-range interactions.Comment: 6 pages, revtex, 3 eps figures. To appear in Physical Review Letters.
Reference list properly arranged. Caption of Fig. 1 slightly reworded. Fig 3
(in color) is not part of the paper. It complements Fig.
Cosmological solutions, p-branes and the Wheeler-DeWitt equation
The low energy effective actions which arise from string theory or M-theory
are considered in the cosmological context, where the graviton, dilaton and
antisymmetric tensor field strengths depend only on time. We show that previous
results can be extended to include cosmological solutions that are related to
the E_N Toda equations. The solutions of the Wheeler-DeWitt equation in
minisuperspace are obtained for some of the simpler cosmological models by
introducing intertwining operators that generate canonical transformations
which map the theories into free theories. We study the cosmological properties
of these solutions, and also briefly discuss generalised Brans-Dicke models in
our framework. The cosmological models are closely related to p-brane solitons,
which we discuss in the context of the E_N Toda equations. We give the explicit
solutions for extremal multi-charge (D-3)-branes in the truncated system
described by the D_4 =O(4,4) Toda equations.Comment: 11 pages (2-column), Revte
Cosmological Solutions in String Theories
We obtain a large class of cosmological solutions in the
toroidally-compactified low energy limits of string theories in dimensions.
We consider solutions where a -dimensional subset of the spatial
coordinates, parameterising a flat space, a sphere, or an hyperboloid,
describes the spatial sections of the physically-observed universe. The
equations of motion reduce to Liouville or Toda equations, which
are exactly solvable. We study some of the cases in detail, and find that under
suitable conditions they can describe four-dimensional expanding universes. We
discuss also how the solutions in dimensions behave upon oxidation back to
the string theory or M-theory.Comment: Latex, 21 pages, a reference adjuste
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