Papers by Alexandre Carvalho
The European Physical Journal C, 2014
In this contribution, some solutions of the Klein-Gordon equation in Gödel-type metrics with an e... more In this contribution, some solutions of the Klein-Gordon equation in Gödel-type metrics with an embedded cosmic string are considered. The quantum dynamics of a scalar particle in three spaces whose metrics are described by different classes of Gödel solutions, with a cosmic string passing through the spaces, is found. The energy levels and eigenfunctions of the Klein-Gordon operator are obtained. We show that these eigenvalues and eigenfunctions depend on the parameter characterizing the presence of a cosmic string in the space-time. We note that the presence of topological defects breaks the degeneracy of energy levels.
Physics Letters, Section A: General, Atomic and Solid State Physics, 2008
In this article we use a geometric approach to study geometric phases in graphitic cones. The spi... more In this article we use a geometric approach to study geometric phases in graphitic cones. The spinor that describes the low energy states near the Fermi energy acquires a phase when transported around the apex of the cone, as found by a holonomy transformation. This topological result can be viewed as an analogue of the Aharonov-Bohm effect. The topological analysis is extended to a system with n cones, whose resulting configuration is described by an effective defect.
Progress of Theoretical Physics, 2010
In this contribution we present a study of the quantum scattering of a neutral particle with an i... more In this contribution we present a study of the quantum scattering of a neutral particle with an induced electric dipole moment in the presence of a charged topological defect exposed to an uniform magnetic field. We consider a geometric modification in the Hamiltonian provoked by charged screw dislocation and a repulsive potential originated from deformation potential theory. We analyze the quantum scattering for this electric dipole by this topological defect. We determine the condition for which it is possible to find a geometric phase acquired by the wave function of the electric dipole.
International Journal of Modern Physics A, 2004
In this work, we study a charged particle in the presence of both a continuous distribution of di... more In this work, we study a charged particle in the presence of both a continuous distribution of disclinations and a continuous distribution of edge dislocations in the framework of the geometrical theory of defects. We obtain the self-energy for a single charge both in the internal and external regions of either distribution. For both distributions, the result in the outside region is the self-energy that a single charge experiments in the presence of a single defect.
General Relativity and Gravitation, 2007
In this work we investigate loop variables in Friedman-Robertson-Walker spacetime. We analyze the... more In this work we investigate loop variables in Friedman-Robertson-Walker spacetime. We analyze the parallel transport of vectors and spinors in several paths in this spacetime in order to classify its global properties. The band holonomy invariance is analysed in this background.
Europhysics Letters (EPL), 2007
Using a geometric approach for the propagation of light in anisotropic media, we investigate what... more Using a geometric approach for the propagation of light in anisotropic media, we investigate what effect the director field of disclinations may have on the polarization state of light. Parallel transport around the defect, of the spinor describing the polarization, indicates the acquisition of a topological phase, in analogy with the Aharonov-Bohm effect.
Europhysics Letters (EPL), 2004
We consider a Volovik's analog model for description of a topological defects in a superfluid and... more We consider a Volovik's analog model for description of a topological defects in a superfluid and we investigate the scattering of quasiparticles in this background. The analog of the gravitational Aharonov-Bohm in this system is found. An analysis of this problem employing loop variables is considered and corroborates for the existence of the Aharonov-Bohm effect in this system. The results presented here may be used to study the Aharonov-Bohm effect in superconductors.
Classical and Quantum Gravity, 2003
In this paper we analyze in the Wilson loop context the parallel transport of vectors and spinors... more In this paper we analyze in the Wilson loop context the parallel transport of vectors and spinors around a closed loop in the background space-time of a rotating black string in order to classify its global properties. We also examine particular closed orbits in this space-time and verify the Mandelstam relations.
Modern Physics Letters A, 2006
In this work we investigate quasiparticles in the background of defects in solids using the geome... more In this work we investigate quasiparticles in the background of defects in solids using the geometric theory of defects. We use the parallel transport matrix to study the Aharonov–Bohm effect in this background. For quasiparticles moving in this effective medium we demonstrate an effect similar to the gravitational Aharonov–Bohm effect. We analyze this effect in an elastic medium with one and N defects.
In this article we discuss the analogy between superfluids and a spinning thick cosmic string. We... more In this article we discuss the analogy between superfluids and a spinning thick cosmic string. We use the geometrical approach to obtain the geometrical phases for a phonon in the presence of a vortex. We use loop variables for a geometric description of Aharonov-Bohm effect in these systems. We use holonomy transformations to characterize globally the "space-time" of a vortex
Physical Review D, 2004
In this work we study scalar fields in a Friedmann-Robertson-Walker space-time. We use the invari... more In this work we study scalar fields in a Friedmann-Robertson-Walker space-time. We use the invariant operator formulation of Lewis and Riesenfeld in order to study the behavior of scalar fields placed in the Friedmann-Robertson-Walker space-time. In addition, we construct the coherent states in this background and establish the existence of squeezed states.
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Papers by Alexandre Carvalho