112 research outputs found
Classical Dynamics of Point Particles in 2+1 Gravity
The relation between Einstein gravity and the Chern-Simons gauge theory of
the Poincare' group is discussed at the classical level.Comment: 16 pages, 4 figures not included, (replaced version with correct
macros) Talk presented at the Workshop on Random Surfaces and 2-D Quantum
Gravity, June 1991, Barcelona, to appear in Nucl. Phys. B (Proc. Suppl.),
J.Ambjorn et al. ed
Schroedinger Self-adjoint Extension and Quantum Field Theory
We argue that the results obtained using the quantum mechanical method of
self-adjoint extension of the Schr\"odinger Hamiltonian can also be derived
using Feynman perturbation theory in the investigation of the corresponding
non-relativistic field theories. We show that this is indeed what happens in
the study of an anyon system, and, in doing so, we establish a field
theoretical description for ``colliding anyons", {\it i.e.} anyons whose
quantum mechanical wave functions satisfy the non-conventional boundary
conditions obtained with the method of self-adjoint extension. We also show
that analogous results hold for a system of non-abelian Chern-Simons particles.Comment: 9 pages, Plain LaTex, MIT-CTP-232
The bound state Aharonov-Bohm effect around a cosmic string revisited
In this article we observe that the self-adjoint extension of the Hamiltonian
of a particle moving around a shielded cosmic string gives rise to a
gravitational analogue of the bound state Aharonov-Bohm effect.Comment: 2 pages, no figure
Model Dependence of Baryon Decay Enhancement by Cosmic Strings
Cosmic strings arising from GUTs can catalyse baryon decay processes with
strong interaction cross sections. We examine the mechanism by which the cross
section is enhanced and find that it depends strongly on the details of the
distribution of gauge fields within the string core. We propose a calculational
scheme for estimating wavefunction amplification factors and also a physical
understanding of the nature of the enhancement process.Comment: 20 pages, LaTeX, DAMTP-R92/2
On the scattering amplitude in the Aharonov-Bohm gauge field
A general expression for the scattering amplitude of nonrelativistic spinless
particles in the Aharonov-Bohm gauge potential is obtained within the time
independent formalism. The result is valid also in the backward and forward
directions as well as for any choice of the boundary conditions on the wave
function at the flux tube position.Comment: 18 pages, plain TE
Euclidean thermal spinor Green's function in the spacetime of a straight cosmic string
Within the framework of the quantum field theory at finite temperature on a
conical space, we determine the Euclidean thermal spinor Green's function for a
massless spinor field. We then calculate the thermal average of the
energy-momentum tensor of a thermal bath of massless fermions. In the
high-temperature limit, we find that the straight cosmic string does not
perturb the thermal bathComment: 11 pages, latex, no figure
Pauli-Lubanski scalar in the Polygon Approach to 2+1-Dimensional Gravity
In this paper we derive an expression for the conserved Pauli-Lubanski scalar
in 't Hooft's polygon approach to 2+1-dimensional gravity coupled to point
particles. We find that it is represented by an extra spatial shift in
addition to the usual identification rule (being a rotation over the cut). For
two particles this invariant is expressed in terms of 't Hooft's phase-space
variables and we check its classical limit.Comment: Some errors are corrected and a new introduction and discussion are
added. 6 pages Latex, 4 eps-figure
Time-dependent quantum scattering in 2+1 dimensional gravity
The propagation of a localized wave packet in the conical space-time created
by a pointlike massive source in 2+1 dimensional gravity is analyzed. The
scattering amplitude is determined and shown to be finite along the classical
scattering directions due to interference between the scattered and the
transmitted wave functions. The analogy with diffraction theory is emphasized.Comment: 15 pages in LaTeX with 3 PostScript figure
Geodesics around line defects in elastic solids
Topological defects in solids, usually described by complicated boundary
conditions in elastic theory, may be described more simply as sources of a
gravity- like deformation field in the geometric approach of Katanaev and
Volovich. This way, the deformation field is described by non-Euclidean metric
that incorporates the boundary imposed by the defects. A possible way of
gaining some insight into the motion of particles in a medium with topological
defects (e.g., electrons in a dislocated metal) is to look at the geodesics of
the medium around the defect. In this work, we find the exact solution for the
geodesic equation for elastic medium with a generic line defect, the
dispiration, that can either be a screw dislocation or a wedge disclination for
particular choices of its parameters.Comment: 10 pages, Latex, 4 figures, accepted for publication in Phys. Lett.
Dirac fields in the background of a magnetic flux string and spectral boundary conditions
We study the problem of a Dirac field in the background of an Aharonov-Bohm
flux string. We exclude the origin by imposing spectral boundary conditions at
a finite radius then shrinked to zero. Thus, we obtain a behaviour of
eigenfunctions which is compatible with the self-adjointness of the radial
Hamiltonian and the invariance under integer translations of the reduced flux.
After confining the theory to a finite region, we check the consistency with
the index theorem, and evaluate its vacuum fermionic number and Casimir energy.Comment: 9 pages, 1 figure Two references added To be published in
International Journal of Modern Physics
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