2,852 research outputs found
Brownian Motion in Robertson-Walker Space-Times from electromagnetic Vacuum Fluctuations
We consider classical particles coupled to the quantized electromagnetic
field in the background of a spatially flat Robertson-Walker universe. We find
that these particles typically undergo Brownian motion and acquire a non-zero
mean squared velocity which depends upon the scale factor of the universe. This
Brownian motion can be interpreted as due to non-cancellation of
anti-correlated vacuum fluctuations in the time dependent background
space-time. We consider several types of coupling to the electromagnetic field,
including particles with net electric charge, a magnetic dipole moment, and
electric polarizability. We also investigate several different model scale
factors.Comment: 29 pages, 7 figure
Scalar and Spinor Particles in the Spacetime of a Domain Wall in String Theory
We consider scalar and spinor particles in the spacetime of a domain wall in
the context of low energy effective string theories, such as the generalized
scalar-tensor gravity theories. This class of theories allows for an arbitrary
coupling of the wall and the (gravitational) scalar field. First, we derive the
metric of a wall in the weak-field approximation and we show that it depends on
the wall's surface energy density and on two post-Newtonian parameters. Then,
we solve the Klein-Gordon and the Dirac equations in this spacetime. We obtain
the spectrum of energy eigenvalues and the current density in the scalar and
spinor cases, respectively. We show that these quantities, except in the case
of the energy spectrum for a massless spinor particle, depend on the parameters
that characterize the scalar-tensor domain wall.Comment: LATEX file, 21 pages, revised version to appear in Phys. Rev.
On Matrix Superpotential and Three-Component Normal Modes
We consider the supersymmetric quantum mechanics (SUSY QM) with three-
component normal modes for the Bogomol'nyi-Prasad-Sommerfield (BPS) states. An
explicit form of the SUSY QM matrix superpotential is presented and the
corresponding three-component bosonic zero-mode eigenfunction is investigated.Comment: 17 pages, no figure. Paper accepted for publication in Journal of
Physics A: Mathematical and Theoretica
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
Teor de fósforo em feijão caupi (Vigna unguiculata L.), cultivado em diferentes sistemas de manejos.
O presente trabalho teve como objetivo avaliar a influÍncia do sistema de manejo de solo nos teores de fÛsforo em plantas da cultivar R-17 gurguÈia, de ciclo curto (45 dias
Nonrelativistic Scattering Analysis of Charged Particle by a Magnetic Monopole in the Global Monopole Background
We analyze the nonrelativistic quantum scattering problem of a charged
particle by an Abelian magnetic monopole in the background of a global
monopole. In addition to the magnetic and geometric effects, we consider the
influence of the electrostatic self-interaction on the charged particle.
Moreover, for the specific case where the electrostatic self-interaction
becomes attractive, charged particle-monopole bound system can be formed and
the respective energy spectrum is hydrogen-like one.Comment: 10 pages. Contribution to the Proceedings of "2nd International
Londrina Winter School Mathematical Methods in Physics". August 26-30, 2002,
Londrina, PR, Brazi
Características fisico-químicas de frutos de taperebá (Spondia mombin L.) coletados em área de ocorrência de mosca-das-frutas
Este trabalho teve por objetivo avaliar as características físico-químicas de frutos de taperebá a partir de amostras coletadas em dois pontos distintos no município de Mazagão (AP), local reconhecidamente de ocorrência de moscas-das-frutas
Some boundary effects in quantum field theory
We have constructed a quantum field theory in a finite box, with periodic
boundary conditions, using the hypothesis that particles living in a finite box
are created and/or annihilated by the creation and/or annihilation operators,
respectively, of a quantum harmonic oscillator on a circle. An expression for
the effective coupling constant is obtained showing explicitly its dependence
on the dimension of the box.Comment: 12 pages, Late
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