658 research outputs found
On axially symmetrical solitons in Abelian-Higgs models
A numerical search for bosonic superconducting static vortex rings in a
model is presented. The fate of these rings without
current, is to shrink due to their tension until extinction. The
superconductivity of the loop does not seem to prevent shrinking. Current
quenching takes place before stabilization.Comment: 15 pages, 8 figures, Accepted for publication in Physica
Assessing eating disordered behaviour in overweight children and adolescents: bridging the gap between a self-report questionnaire and a gold standard interview
Polarized Dirac fermions in de Sitter spacetime
The tetrad gauge invariant theory of the free Dirac field in two special
moving charts of the de Sitter spacetime is investigated pointing out the
operators that commute with the Dirac one. These are the generators of the
symmetry transformations corresponding to isometries that give rise to
conserved quantities according to the Noether theorem. With their help the
plane wave spinor solutions of the Dirac equation with given momentum and
helicity are derived and the final form of the quantum Dirac field is
established. It is shown that the canonical quantization leads to a correct
physical interpretation of the massive or massless fermion quantum fields.Comment: 19 pages, LaTeX w AMS sym
Abelian Higgs Hair for Electrically Charged Dilaton Black Holes
It is argued that an electronically charged dilaton black hole can support a
long range field of a Nielsen-Olesen string. Combining both numerical and
perturbative techniques we examine the properties of an Abelian-Higgs vortex in
the presence of the black hole under consideration. Allowing the black hole to
approach extremality we found that all fields of the vortex are expelled from
the extreme black hole. In the thin string limit we obtained the metric of a
conical electrically charged dilaton black hole. The effect of the vortex can
be measured from infinity justifying its characterization as black hole hair.Comment: 13 pages, 14 figures, Revtex, to appear in Phys.Rev.D1
Gauge fixing and the Hamiltonian for cylindrical spacetimes
We introduce a complete gauge fixing for cylindrical spacetimes in vacuo
that, in principle, do not contain the axis of symmetry. By cylindrically
symmetric we understand spacetimes that possess two commuting spacelike Killing
vectors, one of them rotational and the other one translational. The result of
our gauge fixing is a constraint-free model whose phase space has four
field-like degrees of freedom and that depends on three constant parameters.
Two of these constants determine the global angular momentum and the linear
momentum in the axis direction, while the third parameter is related with the
behavior of the metric around the axis. We derive the explicit expression of
the metric in terms of the physical degrees of freedom, calculate the reduced
equations of motion and obtain the Hamiltonian that generates the reduced
dynamics. We also find upper and lower bounds for this reduced Hamiltonian that
provides the energy per unit length contained in the system. In addition, we
show that the reduced formalism constructed is well defined and consistent at
least when the linear momentum in the axis direction vanishes. Furthermore, in
that case we prove that there exists an infinite number of solutions in which
all physical fields are constant both in the surroundings of the axis and at
sufficiently large distances from it. If the global angular momentum is
different from zero, the isometry group of these solutions is generally not
orthogonally transitive. Such solutions generalize the metric of a spinning
cosmic string in the region where no closed timelike curves are present.Comment: 12 pages, accepted for publication in Physical Review
- …