2,533 research outputs found
Electrostatic in Reissner-Nordstrom space-time with a conical defect
We calculate the electrostatic potential generated by a point charge in the
space-time of Reissner-Nordstrom with a conical defect. An expression for the
self-energy is also presented.Comment: 7 pages, LATEX fil
Casimir-Polder interaction between an atom and a conducting wall in cosmic string spacetime
The Casimir-Polder interaction potential is evaluated for a polarizable
microparticle and a conducting wall in the geometry of a cosmic string
perpendicular to the wall. The general case of the anisotropic polarizability
tensor for the microparticle is considered. The corresponding force is a
function of the wall-microparticle and cosmic string-microparticle distances.
Depending on the orientation of the polarizability tensor principal axes the
force can be either attractive or repulsive. The asymptotic behavior of the
Casimir-Polder potential is investigated at large and small separations
compared to the wavelength of the dominant atomic transitions. We show that the
conical defect may be used to control the strength and the sign of the
Casimir-Polder force.Comment: 17 pages, 3 figure
Fermionic current densities induced by magnetic flux in a conical space with a circular boundary
We investigate the vacuum expectation value of the fermionic current induced
by a magnetic flux in a (2+1)-dimensional conical spacetime in the presence of
a circular boundary. On the boundary the fermionic field obeys MIT bag boundary
condition. For irregular modes, a special case of boundary conditions at the
cone apex is considered, when the MIT bag boundary condition is imposed at a
finite radius, which is then taken to zero. We observe that the vacuum
expectation values for both charge density and azimuthal current are periodic
functions of the magnetic flux with the period equal to the flux quantum
whereas the expectation value of the radial component vanishes. For both
exterior and interior regions, the expectation values of the current are
decomposed into boundary-free and boundary-induced parts. For a massless field
the boundary-free part in the vacuum expectation value of the charge density
vanishes, whereas the presence of the boundary induces nonzero charge density.
Two integral representations are given for the boundary-free part in the case
of a massive fermionic field for arbitrary values of the opening angle of the
cone and magnetic flux. The behavior of the induced fermionic current is
investigated in various asymptotic regions of the parameters. At distances from
the boundary larger than the Compton wavelength of the fermion particle, the
vacuum expectation values decay exponentially with the decay rate depending on
the opening angle of the cone. We make a comparison with the results already
known from the literature for some particular cases.Comment: 34 pages, 6 figure
Vacuum polarization induced by a cylindrical boundary in the cosmic string spacetime
In this paper we investigate the Wightman function, the renormalized vacuum
expectation values of the field square, and the energy-momentum tensor for a
massive scalar field with general curvature coupling inside and outside of a
cylindrical shell in the generalized spacetime of straight cosmic string. For
the general case of Robin boundary condition, by using the generalized
Abel-Plana formula, the vacuum expectation values are presented in the form of
the sum of boundary-free and boundary-induced parts. The asymptotic behavior of
the vacuum expectation values of the field square, energy density and stresses
are investigated in various limiting cases. The generalization of the results
to the exterior region is given for a general cylindrically symmetric static
model of the string core with finite support.Comment: 21 pages, 5 figure
Relativistic Quantum Scattering on a Cone
We study the relativistic quantum mechanical scattering of a bosonic particle
by an infinite straight cosmic string, considering the non-minimal coupling
between the bosonic field and the scalar curvature. In this case, an effective
two-dimensional delta-function interaction takes place besides the usual
topological scattering and a renormalization procedure is necessary in order to
treat the problem that appears in connection with the delta-function.Comment: 22 pages, LATEX fil
Self-Forces on Electric and Magnetic Linear Sources in the Space-Time of a Cosmic String
In this paper we calculate the magnetic and electric self-forces, induced by
the conical structure of a cosmic string space-time, on a long straight wire
which presents either a constant current or a linear charge density. We also
show how these self-forces are related by a Lorentz tranformation and, in this
way, explain what two different inertial observers detect in their respective
frames.Comment: 10 pages, LaTeX, to be published in Phys. Rev. D
On a generalized gravitational Aharonov-Bohm effect
A massless spinor particle is considered in the background gravitational
field due to a rotating body. In the weak field approximation it is shown that
the solution of the Weyl equations depend on the angular momentum of the
rotating body, which does not affect the curvature in this approximation. This
result may be looked upon as a generalization of the gravitational
Aharonov-Bohm effect.Comment: 10 pages, LATEX fil
Self-similar magnetoresistance of Fibonacci ultrathin magnetic films
We study numerically the magnetic properties (magnetization and
magnetoresistance) of ultra-thin magnetic films (Fe/Cr) grown following the
Fibonacci sequence. We use a phenomenological model which includes Zeeman,
cubic anisotropy, bilinear and biquadratic exchange energies. Our physical
parameters are based on experimental data recently reported, which contain
biquadratic exchange coupling with magnitude comparable to the bilinear
exchange coupling. When biquadratic exchange coupling is sufficiently large a
striking self-similar pattern emerges.Comment: 5 pages, 5 EPS figures, REVTeX, accepted for publication in Phys.
Rev.
Nonrelativistic Quantum Analysis of the Charged Particle-Dyon System on a Conical Spacetime
In this paper we develop the nonrelativistic quantum analysis of the charged
particle-dyon system in the spacetime produced by an idealized cosmic string.
In order to do that, we assume that the dyon is superposed to the cosmic
string. Considering this peculiar configuration {\it conical} monopole
harmonics are constructed, which are a generalizations of previous monopole
harmonics obtained by Wu and Yang(1976 {\it Nucl. Phys. B} {\bf 107} 365)
defined on a conical three-geometry. Bound and scattering wave functions are
explicitly derived. As to bound states, we present the energy spectrum of the
system, and analyze how the presence of the topological defect modifies
obtained result. We also analyze this system admitting the presence of an extra
isotropic harmonic potential acting on the particle. We show that the presence
of this potential produces significant changes in the energy spectrum of the
system.Comment: Paper accepted for publication in Classical and Quantum Gravit
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