26 research outputs found
Vacuum Polarization of a Charged Massless Scalar Field on Cosmic String Spacetime in the Presence of a Magnetic Field
In this paper we consider a charged massless scalar quantum field operator in
the spacetime of an idealized cosmic string, i.e., an infinitely long, straight
and static cosmic string, which presents a magnetic field confined in a
cylindrical tube of finite radius. Three distinct situations are taking into
account in this analysis: {\it{i)}} a homogeneous field inside the tube,
{\it{ii)}} a magnetic field proportional to and {\it{iii)}} a cylindrical
shell with -function. In these three cases the axis of the infinitely
long tube of radius coincides with the cosmic string. In order to study the
vacuum polarization effects outside the tube, we explicitly calculate the
Euclidean Green function associated with this system for the three above
situations, considering points in the region outside the tube.Comment: 26 pages, LaTex format, 3 figure
A pragmatic approach to the problem of the self-adjoint extension of Hamilton operators with the Aharonov-Bohm potential
We consider the problem of self-adjoint extension of Hamilton operators for
charged quantum particles in the pure Aharonov-Bohm potential (infinitely thin
solenoid). We present a pragmatic approach to the problem based on the
orthogonalization of the radial solutions for different quantum numbers. Then
we discuss a model of a scalar particle with a magnetic moment which allows to
explain why the self-adjoint extension contains arbitrary parameters and give a
physical interpretation.Comment: 8 pages, LaTeX, to appear in J. Phys.
Perturbative Study of Bremsstrahlung and Pair-Production by Spin-1/2 Particles in the Aharonov-Bohm Potential
In the presence of an external Aharonov-Bohm potential, we investigate the
two QED processes of the emission of a bremsstrahlung photon by an electron,
and the production of an electron-positron pair by a single photon.
Calculations are carried out using the Born approximation within the framework
of covariant perturbation theory to lowest non-vanishing order in \alpha. The
matrix element for each process is derived, and the corresponding differential
cross-section is calculated. In the non-relativistic limit, the resulting
angular and spectral distributions and some polarization properties are
considered, and compared to results of previous works.Comment: 15 pages, RevTex 4, 2 figures, submitted for publicatio
Fluctuations in the current and energy densities around a magnetic flux carrying cosmic string
We calculate the fluctuations in the current and energy densities for the
case of a quantized, minimally coupled, massless, complex scalar field around a
straight and infinitesimally thin cosmic string carrying magnetic flux. At zero
temperature, we evaluate the fluctuations in the current and energy densities
for arbitrary flux and deficit angle. At a finite temperature, we evaluate the
fluctuations in the energy density for the special case wherein the flux is
absent and the deficit angle equals . We find that, quite generically, the
dimensionless ratio of the variance to the mean-squared values of the current
and energy densities are of order unity which suggests that the fluctuations
around cosmic strings can be considered to be large.Comment: RevTeX, 13 Pages, 3 Figure
Radiative Corrections to the Aharonov-Bohm Scattering
We consider the scattering of relativistic electrons from a thin magnetic
flux tube and perturbatively calculate the order , radiative
correction, to the first order Born approximation. We show also that the second
order Born amplitude vanishes, and obtain a finite inclusive cross section for
the one-body scattering which incorporates soft photon bremsstrahlung effects.
Moreover, we determine the radiatively corrected Aharonov-Bohm potential and,
in particular, verify that an induced magnetic field is generated outside of
the flux tube.Comment: 14 pages, revtex, 3 figure
Polyhedral Cosmic Strings
Quantum field theory is discussed in M\"obius corner kaleidoscopes using the
method of images. The vacuum average of the stress-energy tensor of a free
field is derived and is shown to be a simple sum of straight cosmic string
expressions, the strings running along the edges of the corners. It does not
seem possible to set up a spin-half theory easily.Comment: 15 pages, 4 text figures not include
Scalar Pair Production in the Aharonov-Bohm Potential
In the framework of QED, scalar pair production by a single linearly
polarized high-energy photon in the presence of an external Aharonov-Bohm
potential is investigated. The exact scattering solutions of the Klein-Gordon
equation in cylindrically symmetric field are constructed and used to write the
first order transition amplitude. The matrix elements and the corresponding
differential scattering cross-section are calculated. The pair production at
both the nonrelativistic and the ultrarelativistic limits is discussed.Comment: 13 pages, 1 figur