6,243 research outputs found
The Dual Formulation of Cosmic Strings and Vortices
We study four dimensional systems of global, axionic and local strings. By
using the path integral formalism, we derive the dual formulation of these
systems, where Goldstone bosons, axions and missive vector bosons are described
by antisymmetric tensor fields, and strings appear as a source for these tensor
fields. We show also how magnetic monopoles attached to local strings are
described in the dual formulation. We conclude with some remarks.Comment: 18 pages, CU-TP-588 and CERN-TH.6780/9
A relativistic study of Bessel beams
We present a fully relativistic analysis of Bessel beams revealing some
noteworthy features that are not explicit in the standard description. It is
shown that there is a reference frame in which the field takes a particularly
simple form, the wave appearing to rotate in circles. The concepts of
polarization and angular momentum for Bessel beams is also reanalyzed.Comment: 11 pages, 2 fig
Creation of vortices in a Bose-Einstein condensate by a Raman technique
We propose a method for taking a Bose-Einstein condensate in the ground trap
state simultaneously to a different atomic hyperfine state and to a vortex trap
state. This can be accomplished through a Raman scheme in which one of the two
copropagating laser beams has a higher-order Laguerre-Gaussian mode profile.
Coefficients relating the beam waist, pulse area, and trap potentials for a
complete transfer to the m = 1 vortex are calculated for a condensate in the
non-interacting and strongly interacting regimes.Comment: RevTex, 4 pages, 2 PostScript figure
Vortex Dynamics in Self-Dual Chern-Simons Higgs Systems
We consider vortex dynamics in self-dual Chern-Simons Higgs systems. We show
that the naive Aharanov-Bohm phase is the inverse of the statistical phase
expected from the vortex spin, and that the self-dual configurations of
vortices are degenerate in energy but not in angular momentum. We also use the
path integral formalism to derive the dual formulation of Chern-Simons Higgs
systems in which vortices appear as charged particles. We argue that besides
the electromagnetic interaction, there is an additional interaction between
vortices, the so-called Magnus force, and that these forces can be put together
into a single `dual electromagnetic' interaction. This dual electromagnetic
interaction leads to the right Aharanov-Bohm phase. We also derive and study
the effective action for slowly moving vortices, which contains terms both
linear and quadratic in the vortex velocity.Comment: 36 pages and three figures (available under request), Columbia and
CERN preprin
On the gravitational, dilatonic and axionic radiative damping of cosmic strings
We study the radiation reaction on cosmic strings due to the emission of
dilatonic, gravitational and axionic waves. After verifying the (on average)
conservative nature of the time-symmetric self-interactions, we concentrate on
the finite radiation damping force associated with the half-retarded minus
half-advanced ``reactive'' fields. We revisit a recent proposal of using a
``local back reaction approximation'' for the reactive fields. Using
dimensional continuation as convenient technical tool, we find, contrary to
previous claims, that this proposal leads to antidamping in the case of the
axionic field, and to zero (integrated) damping in the case of the
gravitational field. One gets normal positive damping only in the case of the
dilatonic field. We propose to use a suitably modified version of the local
dilatonic radiation reaction as a substitute for the exact (non-local)
gravitational radiation reaction. The incorporation of such a local
approximation to gravitational radiation reaction should allow one to complete,
in a computationally non-intensive way, string network simulations and to give
better estimates of the amount and spectrum of gravitational radiation emitted
by a cosmologically evolving network of massive strings.Comment: 48 pages, RevTex, epsfig, 1 figure; clarification of the domain of
validity of the perturbative derivation of the string equations of motion,
and of their renormalizabilit
Can the Gravitational Wave Background from Inflation be Detected Locally?
The Cosmic Background Explorer (COBE) detection of microwave background
anisotropies may contain a component due to gravitational waves generated by
inflation. It is shown that the gravitational waves from inflation might be
seen using `beam-in-space' detectors, but not the Laser Interferometer Gravity
Wave Observatory (LIGO). The central conclusion, dependent only on weak
assumptions regarding the physics of inflation, is a surprising one. The larger
the component of the COBE signal due to gravitational waves, the {\em smaller}
the expected local gravitational wave signal.Comment: 8 pages, standard LaTeX (no figures), SUSSEX-AST 93/7-
The Dynamical State and Mass-Concentration Relation of Galaxy Clusters
We use the Millennium Simulation series to study how the dynamical state of
dark matter halos affects the relation between mass and concentration. We find
that a large fraction of massive systems are identified when they are
substantially out of equilibrium and in a particular phase of their dynamical
evolution: the more massive the halo, the more likely it is found at a
transient stage of high concentration. This state reflects the recent assembly
of massive halos and corresponds to the first pericentric passage of
recently-accreted material when, before virialization, the kinetic and
potential energies reach maximum and minimum values, respectively. This result
explains the puzzling upturn in the mass-concentration relation reported in
recent work for massive halos; indeed, the upturn disappears when only
dynamically-relaxed systems are considered in the analysis. Our results warn
against applying simple equilibrium models to describe the structure of rare,
massive galaxy clusters and urges caution when extrapolating scaling laws
calibrated on lower-mass systems, where such deviations from equilibrium are
less common. The evolving dynamical state of galaxy clusters ought to be
carefully taken into account if cluster studies are to provide precise
cosmological constraints.Comment: 8 Pages. Minor changes to match published versio
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