37,422 research outputs found
Tachyon kinks on non BPS D-branes
We consider solitonic solutions of the DBI tachyon effective action for a
non-BPS brane. When wrapped on a circle, these solutions are regular and have a
finite energy. We show that in the decompactified limit, these solitons give
Sen's infinitely thin finite energy kink -- interpreted as a BPS brane --
provided that some conditions on the potential hold. In particular, if for
large the potential is exponential, , then Sen's solution is
only found for . For power-law potentials , one must have
. If these conditions are not satisfied, we show that the lowest energy
configuration is the unstable tachyon vacuum with no kinks. We examine the
stability of the solitons and the spectrum of small perturbations.Comment: 16 pages, 2 figure
Comparative study of spanning cluster distributions in different dimensions
The probability distributions of the masses of the clusters spanning from top
to bottom of a percolating lattice at the percolation threshold are obtained in
all dimensions from two to five. The first two cumulants and the exponents for
the universal scaling functions are shown to have simple power law variations
with the dimensionality. The cases where multiple spanning clusters occur are
discussed separately and compared.Comment: 8 pages, latex, 4 eps figures included, to appear in Int. Journal of
Modern Physics
Time and Tachyon
Recent analysis suggests that the classical dynamics of a tachyon on an
unstable D-brane is described by a scalar Born-Infeld type action with a
runaway potential. The classical configurations in this theory at late time are
in one to one correspondence with the configuration of a system of
non-interacting (incoherent), non-rotating dust. We discuss some aspects of
canonical quantization of this field theory coupled to gravity, and explore,
following earlier work on this subject, the possibility of using the scalar
field (tachyon) as the definition of time in quantum cosmology. At late `time'
we can identify a subsector in which the scalar field decouples from gravity
and we recover the usual Wheeler - de Witt equation of quantum gravity.Comment: LaTeX file, 24 page
CRAB Cavity in CERN SPS
Beam collisions with a crossing angle at the interaction point have been
applied in high intensity colliders to reduce the effects of parasitic
collisions which induce emittance growth and beam lifetime deterioration. The
crossing angle causes the geometrical reduction of the luminosity. Crab cavity
can be one of the most promising ways to compensate the crossing angle and to
realize effective head-on collisions. Moreover, the crab crossing mitigates the
synchro-betatron resonances due to the crossing angle. Crab cavity experiment
in SPS is proposed for deciding on a full crab-cavity implementation in LHC. In
this paper, we investigate the effects of crab crossing on beam dynamics and
its life time with the global scheme.Comment: 3 pp. 1st International Particle Accelerator Conference: IPAC'10,
23-28 May 2010: Kyoto, Japa
The Schrodinger Wave Functional and Closed String Rolling Tachyon
In this short note we apply Schrodinger picture description of the
minisuperspace approach to the closed string tachyon condensation. We will
calculate the rate of produced closed string and we will show that the density
of high massive closed string modes reaches the string density in time of order
one in string units.Comment: 12 page
Phase transitions in Ising model on a Euclidean network
A one dimensional network on which there are long range bonds at lattice
distances with the probability has been taken
under consideration. We investigate the critical behavior of the Ising model on
such a network where spins interact with these extra neighbours apart from
their nearest neighbours for . It is observed that there is
a finite temperature phase transition in the entire range. For , finite size scaling behaviour of various quantities are consistent with
mean field exponents while for , the exponents depend on
. The results are discussed in the context of earlier observations on
the topology of the underlying network.Comment: 7 pages, revtex4, 7 figures; to appear in Physical Review E, minor
changes mad
Energy Momentum Tensor and Marginal Deformations in Open String Field Theory
Marginal boundary deformations in a two dimensional conformal field theory
correspond to a family of classical solutions of the equations of motion of
open string field theory. In this paper we develop a systematic method for
relating the parameter labelling the marginal boundary deformation in the
conformal field theory to the parameter labelling the classical solution in
open string field theory. This is done by first constructing the
energy-momentum tensor associated with the classical solution in open string
field theory using Noether method, and then comparing this to the answer
obtained in the conformal field theory by analysing the boundary state. We also
use this method to demonstrate that in open string field theory the tachyon
lump solution on a circle of radius larger than one has vanishing pressure
along the circle direction, as is expected for a codimension one D-brane.Comment: LaTeX file, 25 pages; v2: minor addition
D-Brane Effective Actions and Particle Production near the Beginning of the Tachyon Condensation
In this paper we will study the quantum field theory of fluctuation modes
around the classical solution that describes tachyon condensation on unstable
D-brane.We will calculate the number of particle produced near the beginning of
the rolling tachyon process. We will perform this calculation for different
tachyon effective actions and we will find that the rate of the particle
production strongly depends on the form of the effective action used for the
description of the early stage of the tachyon condensation.Comment: 21 page
Delocalized, non-SUSY -branes, tachyon condensation and tachyon matter
We construct non-supersymmetric -brane solutions of type II supergravities
in arbitrary dimensions () delocalized in one of the spatial transverse
directions. By a Wick rotation we convert these solutions into Euclidean
-branes delocalized in the transverse time-like direction. The former
solutions in nicely interpolate between the -dimensional non-BPS
D-branes and the -dimensional BPS D-branes very similar to the picture of
tachyon condensation for the tachyonic kink solution on the non-BPS D-branes.
On the other hand the latter solutions interpolate between the
-dimensional non-BPS D-branes and the tachyon matter supergravity
configuration very similar to the picture of rolling tachyon on the non-BPS
D-branes.Comment: 15 pages, typos correcte
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