Eugênio R. Bezerra de Mello

Effects of anomalous magnetic moment in the quantum motion of neutral particle in magnetic and electric fields produced by a linear source in a conical spacetime

In this paper we analyse the effect of the anomalous magnetic moment on the non-relativistic quantum motion of a neutral particle in magnetic and electric fields produced by linear sources of constant current and charge density, respectively.

Abelian–Higgs strings in Rastall gravity

In this paper we analyze Abelian–Higgs strings in a phenomenological model that takes quantum effects in curved space–time into account. This model, first introduced by Rastall, cannot be derived from an action principle. We formulate phenomenological equations of motion under the guiding principle of minimal possible deformation of the standard equations. We construct string solutions that asymptote to a flat space–time with a deficit angle by solving the set of coupled nonlinear ordinary differential equations numerically. Decreasing the Rastall parameter from its Einstein gravity value, we find that the deficit angle of the space–time increases and becomes equal to at some critical value of this parameter that depends on the remaining couplings in the model. For smaller values, the resulting solutions are supermassive string solutions possessing a singularity at a finite distance from the string core. Assuming the Higgs boson mass to be on the order of the gauge boson mass, we also find that in Rastall gravity this happens only when the symmetry breaking scale is on the order of the Planck mass. We observe that for specific values of the parameters in the model, the energy per unit length becomes proportional to the winding number, i.e. the degree of the map . Unlike in the Bogomolnyi–Prasad–Sommerfield (BPS) limit in Einstein gravity, this is, however, not connected to an underlying mathematical structure, but rather constitutes a would-be-BPS bound.

Induced fermionic current densities by magnetic flux in higher dimensional cosmic string spacetime

In this paper, we analyze the vacuum fluctuations of quantum fermionic current densities, jA(x), induced by a magnetic flux running along the core of the conical space produced by the presence of cosmic string, in a (1 + d)-dimensional bulk, for 2 ≤ d ≤ 5. In order to develop this investigation, we construct an expression for the fermionic propagator, which can be applied for those different dimensions of the spacetime. Two specific analyses for the induced current densities are presented: (i) for massless fields in three and four dimensions and (ii) for massive fields in all dimensions considered. In the latter, specific values for the parameters which codify the presence of the cosmic string and the fractional part of the ratio of the magnetic flux to the quantum one are considered. Although being a very special situation and somewhat unnatural, the corresponding analysis of induced fermionic current densities under this circumstance may shed light on the qualitative behavior of these quantities in a more general situation.

Vacuum polarization by a global monopole with finite core

We investigate the effects of a (D+1)-dimensional global monopole core on the behavior of a quantum massive scalar field with general curvature coupling parameter. In the general case of the spherically symmetric static core, formulae are derived for the Wightman function, for the vacuum expectation values of the field square and the energy-momentum tensor in the exterior region. These expectation values are presented as the sum of point-like global monopole part and the core induced one. The asymptotic behavior of the core induced vacuum densities is investigated at large distances from the core, near the core and for small values of the solid angle corresponding to strong gravitational fields. In particular, in the latter case we show that the behavior of the vacuum densities is drastically different for minimally and non-minimally coupled fields. As an application of general results the flower-pot model for the monopoles core is considered and the expectation values inside the core are evaluated.

Gravitating non-Abelian cosmic strings

In this paper we study regular cosmic string solutions of the non-Abelian Higgs model coupled with the Einstein gravity. In order to do that, we constructed a set of coupled differential ordinary equation. Because there is no closed solution for this set of equations, we solve it numerically. The solutions that we are interested in asymptote to a flat space-time with a planar angle deficit. This model under consideration present two bosonic sectors, besides the non-Abelian gauge one, coupled minimally with the gravitational fields. The two bosonic sectors may present a direct coupling, which plays an important role on the behavior of the matter and gauge fields and also on the behavior on the geometry of the spacetime. We explicitly analyze the behaviors of the energy density and planar angle deficit as function of the energy scale where the gauge symmetry is spontaneously broken and the coupling interaction between the bosonic sectors.

Non-Abelian cosmic strings in de Sitter and anti–de Sitter space

In this paper we investigate the non-Abelian cosmic string in de Sitter and anti-de Sitter spacetimes. In order to do that we construct the complete set of equations of motion considering the presence of a cosmological constant. By using numerical analysis we provide the behavior of the Higgs and gauge fields and also for the metric tensor for specific values of the physical parameters of the theory. For de Sitter case, we find the appearance of horizons that although being consequence of the presence of the cosmological constant it strongly depends on the value of the gravitational coupling. In the anti-de Sitter case, we find that the system does not present horizons. In fact the new feature of this system is related with the behavior of the (00) and (zz) components of the metric tensor. They present a strongly increasing for large distance from the string.

Azimuthal Fermionic Current in the Cosmic String Spacetime Induced by a Magnetic Tube

In this paper, we analyze the vacuum azimuthal fermionic current induced by a magnetic field confined in a cylindrical tube of finite radius

Non-Abelian cosmic string in the Starobinsky model of gravity

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Induced fermionic current by a magnetic flux in a cosmic string spacetime at finite temperature

, in the cosmic string spacetime. Three distinct configurations for the magnetic field are taken into account: (i) a cylindrical shell of radius

WIGHTMAN FUNCTIONS IN DE SITTER AND ANTI-DE SITTER SPACETIMES IN THE PRESENCE OF COSMIC STRINGS

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