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V. B. Bezerra

Publications and source records attributed to V. B. Bezerra.

143 records · Page 8Linked to original sources
arXiv2001

Gravitational field around a screwed superconducting cosmic string in scalar-tensor theories

We obtain the solution that corresponds to a screwed superconducting cosmic string (SSCS) in the framework of a general scalar-tensor theory including torsion. We investigate the metric of the SSCS in Brans-Dicke theory with torsion and analyze the case without torsion. We show that in the case with torsion the space-time background presents other properties different from that in which torsion is absent. When the spin vanish, this torsion is a $ϕ$-gradient and then it propagates outside of the string. We investigate the effect of torsion on the gravitational force and on the geodesics of a test-particle moving around the SSCS. The accretion of matter by wakes formation when a SSCS moves with speed $v $ is investigated. We compare our results with those obtained for cosmic strings in the framework of scalar-tensor theory.

hep-th↗
arXiv2001

Surface impedance and the Casimir force

The impedance boundary condition is used to calculate the Casimir force in configurations of two parallel plates and a shpere (spherical lens) above a plate at both zero and nonzero temperature. The impedance approach allows one to find the Casimir force between the realistic test bodies regardless of the electromagnetic fluctuations inside the media. Although this approach is an approximate one, it has wider areas of application than the Lifshitz theory of the Casimir force. The general formulas of the impedance approach to the theory of the Casimir force are given and the formal substitution is found for connecting it with the Lifshitz formula. The range of micrometer separations between the test bodies which is interesting from the experimental point of view is investigated in detail. It is shown that at zero temperature the results obtained on the basis of the surface impedance method are in agreement with those obtained in framework of the Lifshitz theory within a fraction of a percent. The temperature correction to the Casimir force from the impedance method coincides with that from the Lifshitz theory up to four significant figures. The case of millimeter separations which corresponds to the normal skin effect is also considered. At zero temperature the obtained results have good agreement with the Lifshitz theory. At nonzero temperature the impedance approach is not subject to the interpretation problems peculiar to the zero-frequency term of the Lifshitz formula in dissipative media.

quant-ph↗
arXiv2001

Self-energy and Self-force in the Space-time of a Thick Cosmic String

We calculate the self-energy and self-force for an electrically charged particle at rest in the background of Gott-Hiscock cosmic string space-time. We found the general expression for the self-energy which is expressed in terms of the $S$ matrix of the scattering problem. The self-energy continuously falls down outward from the string's center with maximum at the origin of the string. The self-force is repulsive for an arbitrary position of the particle. It tends to zero in the string's center and also far from the string and it has a maximum value at the string's surface. The plots of the numerical calculations of the self-energy and self-force are shown.

hep-th↗
arXiv2000

Ground State Energy of Massive Scalar Field Inside a Spherical Region in the Global Monopole Background

Using the zeta function regularization method we calculate the ground state energy of scalar massive field inside a spherical region in the space-time of a point-like global monopole. Two cases are investigated: (i) We calculate the Casimir energy inside a sphere of radius $R$ and make an analytical analysis about it. We observe that this energy may be positive or negative depending on metric coefficient $α$ and non-conformal coupling $ξ$. In the limit $R\to\infty$ we found a zero result. (ii) In the second model we surround the monopole by additional sphere of radius $r_0<R$ and consider scalar field confined in the region between these two spheres. In the latter, the ground state energy presents an additional contribution due to boundary at $r_0$ which is divergent for small radius. Additional comments about renormalization are considered.

hep-th↗
arXiv2000

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.

gr-qc↗
arXiv2000

Landau Levels in the Presence of Topological Defects

We study the Landau levels associated with electrons moving in a magnetic field in the presence of a continuous distribution of disclinations, a magnetic screw dislocation and a dispiration. We focus on the influence of these topological defects on the spectrum of the electron(or hole) in a magnetic field in the framework of the geometric theory of defects in solids of Katanaev and Volovich. The presence of the defects breaks the degeneracy of the Landau levels in different ways depending on the defect. Exact expressions for energies and eigenfuctions are found for all cases.

quant-ph↗
arXiv2000

Vacuum Polarization in the Spacetime of a Scalar-Tensor Cosmic String

We study the vacuum polarization effect in the spacetime generated by a magnetic flux cosmic string in the framework of a scalar-tensor gravity. The vacuum expectation values of the energy-momentum tensor of a conformally coupled scalar field are calculated. The dilaton's contribution to the vacuum polarization effect is shown explicitly.

gr-qc↗
arXiv2000

Dilaton Gravity with a Non-minmally Coupled Scalar Field

We discuss the two-dimensional dilaton gravity with a scalar field as the source matter. The coupling between the gravity and the scalar, massless, field is presented in an unusual form. We work out two examples of these couplings and solutions with black-hole behaviour are discussed and compared with those found in the literature.

gr-qc↗
arXiv2000

Black hole formation in bidimensional dilaton gravity coupled to scalar matter systems

This work deals with the formation of black hole in bidimensional dilaton gravity coupled to scalar matter fields. We investigate two scalar matter systems, one described by a sixth power potential and the other defined with two scalar fields containing up to the fourth power in the fields. The topological solutions that appear in these cases allow the formation of black holes in the corresponding dilaton gravity models.

hep-th↗
arXiv1999

Higher order conductivity corrections to the Casimir force

The finite conductivity corrections to the Casimir force in two configurations are calculated in the third and fourth orders in relative penetration depth of electromagnetic zero oscillations into the metal. The obtained analytical perturbation results are compared with recent computations. Applications to the modern experiments are discussed.

quant-ph↗
arXiv1999

Vacuum Polarization of Massless Spinor Field in Global Monopole Spacetime

We calculate the renormalized vacuum average of the energy-momentum tensor of massless left-handed spinor field in the pointlike global monopole spacetime using point-separation approach. The general structure of the vacuum average of the energy-momentum tensor is obtained and expressed in terms of $ ^{ren}$ component, explicit form of which is analyzed in great details for arbitrary solid angle deficit.

gr-qc↗
arXiv1999

Ground State Energy of Massive Scalar Field in the Global Monopole Background

We consider the ground state energy of scalar massive field in the spacetime of a pointlike global monopole. Using zeta function regularization method we obtain the heat kernel coefficients for this system. We show that the coefficient $B_1$ contains additional contribution due to the non-trivial topological structure of the spacetime. Taking into account the heat kernel coefficients we obtain that the ground state energy of the scalar field is zero. We also discuss our result using dimensional considerations.

gr-qc↗
arXiv1998

Self-forces in the Spacetime of Multiple Cosmic Strings

We calculate the electromagnetic self-force on a stationary linear distribution of four-current in the spacetime of multiple cosmic strings. It is shown that if the current is infinitely thin and stretched along a line which is parallel to the strings the problem admits an explicit solution.

gr-qc↗
arXiv1995

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.

gr-qc↗