48,982 research outputs found
Monopoles and Knots in Skyrme Theory
We show that the Skyrme theory actually is a theory of monopoles which allows
a new type of solitons, the topological knots made of monopole-anti-monopole
pair,which is different from the well-known skyrmions. Furthermore, we derive a
generalized Skyrme action from the Yang-Mills action of QCD, which we propose
to be an effective action of QCD in the infra-red limit. We discuss the
physical implications of our results.Comment: 4 pages. Phys. Rev. Lett. in pres
The Entropy Function for the Black Holes of Nariai Class
Based on the fact that the near horizon geometry of the extremal
Schwarzschild-de Sitter black holes is Nariai geometry, we define the black
holes of Nariai class as the configuration whose near-horizon geometry is
factorized as two dimensional de Sitter space-time and some compact topology,
that is Nariai geometry. We extend the entropy function formalism to the case
of the black holes of Nariai class. The conventional entropy function (for the
extremal black holes) is defined as Legendre transformation of Lagrangian
density, thus the `Routhian density', over two dimensional anti-de Sitter. As
for the black holes of Nariai class, it is defined as {\em minus} `Routhian
density' over two dimensional de Sitter space-time. We found an exact agreement
of the result with Bekenstein-Hawking entropy. The higher order corrections are
nontrivial only when the space-time dimension is over four, that is, .
There is a subtlety as regards the temperature of the black holes of Nariai
class. We show that in order to be consistent with the near horizon geometry,
the temperature should be non-vanishing despite the extremality of the black
holes.Comment: references added, compatible with the published versio
Schwinger Effect in Non-parallel D1-branes: A Path Integral Approach
We study the Schwinger effect in a system of non-parallel D1-branes for the
bosonic strings using the path integral formalism. We drive the string pair
creation rate by calculating the one loop vacuum amplitude of the setup in
presence of the background electric filed defined along one of the D1-branes.
We find an angle dependent minimum value for the background field and show that
the decaying of vacuum into string pairs takes place for the field above this
value. It is shown that in limit the vacuum
becomes stable and thus no pair creation occurs
Inflating magnetically charged braneworlds
Numerical solutions of Einstein, scalar, and gauge field equations are found
for static and inflating defects in a higher-dimensional spacetime. The defects
have -dimensional core and magnetic monopole configuration in
extra dimensions. For symmetry-breaking scale below the critical value
, the defects are characterized by a flat worldsheet geometry and
asymptotically flat extra dimensions. The critical scale is comparable
to the higher-dimensional Planck scale and has some dependence on the gauge and
scalar couplings. For , the extra dimensions degenerate into a
`cigar', and for all static solutions are singular. The
singularity can be removed if the requirement of staticity is relaxed and
defect cores are allowed to inflate. The inflating solutions have de Sitter
worldsheets and cigar geometry in the extra dimensions. Exact analytic
solutions describing the asymptotic behavior of these inflating monopoles are
found and the parameter space of these solutions is analyzed.Comment: 35 pages, revtex, 18 eps figure
Gravitational field of vacuumless defects
It has been recently shown that topological defects can arise in symmetry
breaking models where the scalar field potential has no minima and is
a monotonically decreasing function of . Here we study the
gravitational fields produced by such vacuumless defects in the cases of both
global and gauge symmetry breaking. We find that a global monopole has a
strongly repulsive gravitational field, and its spacetime has an event horizon
similar to that in de Sitter space. A gauge monopole spacetime is essentially
that of a magnetically charged black hole. The gravitational field of a global
string is repulsive and that of a gauge string is attractive at small distances
and repulsive at large distances. Both gauge and global string spacetimes have
singularities at a finite distance from the string core.Comment: 19 pages, REVTeX, 6 Postscript figure
Purification through Zeno-like Measurements
A series of frequent measurements on a quantum system (Zeno-like
measurements) is shown to result in the ``purification'' of another quantum
system in interaction with the former. Even though the measurements are
performed on the former system, their effect drives the latter into a pure
state, irrespectively of its initial (mixed) state, provided certain conditions
are satisfied.Comment: REVTeX4, 4 pages, 1 figure; to be published in Phys. Rev. Lett.
(2003
Polarization of Prompt J/psi at the Tevatron
The polarization of prompt J/psi at the Fermilab Tevatron is calculated
within the nonrelativistic QCD factorization framework. The contribution from
radiative decays of P-wave charmonium states decreases, but does not eliminate,
the transverse polarization at large transverse momentum. The angular
distribution parameter alpha for leptonic decays of the J/\psi is predicted to
increase from near 0 at p_T = 5 GeV to about 0.5 at p_T = 20 GeV. The
prediction is consistent with measurements by the CDF Collaboration at
intermediate values of p_T, but disagrees by about 3 standard deviations at the
largest values of p_T measured.Comment: 4 pages, 2 figures, one reference added, accepted for publication in
Phys. Rev.
- …