J. Spinelly

Spinor Green function in higher-dimensional cosmic string space-time in the presence of magnetic flux

In this paper we investigate the vacuum polarization effects associated with quantum fermionic charged fields in a generalized (d+1)−dimensional cosmic string space-times considering the presence of a magnetic flux along the string. In order to develop this analysis we calculate a general expression for the respective Green function, valid for several different values of d, which is expressed in terms of a bispinor associated with the square of the Dirac operator. Adopting this result, we explicitly calculate the renormalized vacuum expectation values of the energy-momentum tensors, TABRen., associated with massless fields. Moreover, for specific values of the parameters which codify the cosmic string and the fractional part of the ratio of the magnetic flux by the quantum one, we were able to present in closed forms the bispinor and the respective Green function for massive fields.

Vacuum polarization of a charged massless scalar field on cosmic string spacetime in the presence of a magnetic field

In this paper, we consider a charged massless scalar quantum field operator in the spacetime of an idealized cosmic string, i.e., an infinitely long, straight and static cosmic string, which presents a magnetic field confined in a cylindrical tube of finite radius. Three distinct situations are taken into account in this analysis: (i) a homogeneous field inside the tube, (ii) a magnetic field proportional to 1/r and (iii) a cylindrical shell with δ-function. In these three cases, the axis of the infinitely long tube of radius R coincides with the cosmic string. In order to study the vacuum polarization effects outside the tube, we explicitly calculate the Euclidean Green function associated with this system for the three above situations, considering points in the region outside the tube. Having these Green functions we calculate the renormalized vacuum expectation values, *(x)(x)Ren and νμ(x)Ren, associated with the charged field. In the evaluation of these vacuum polarization effects, two contributions appear for the three models. The first are the standard ones due to the conical geometry of the spacetime and the magnetic flux. The second contributions appear as extra terms. They are corrections due to the finite thickness of the radius of the tube. These extra terms provide relevant contributions, even for points very far away from the system, like a long-range effect.

VACUUM POLARIZATION OF A CHARGED MASSLESS FERMIONIC FIELD BY A MAGNETIC FLUX IN THE COSMIC STRING SPACETIME

We calculate the vacuum averages of the energy–momentum tensor associated with a massless left-handed spinor fields due to magnetic fluxes on idealized cosmic string spacetime. In this analysis three distinct configurations of magnetic fields are considered: (i) a homogeneous field inside the tube, (ii) a magnetic field proportional to 1/r, and (iii) a cylindrical shell with δ-function. In these three cases the axis of the infinitely long tubes of radius R coincides with the cosmic string. In order to proceed with these calculations we explicitly obtain the Euclidean Feynman propagators associated with these physical systems. As we shall see, these propagators possess two distinct parts. The first are the standard ones, i.e. corresponding to the spinor Greens functions associated with the massless fermionic fields on the idealized cosmic string spacetime with a magnetic flux running through the line singularity. The second parts are new, they are due to the finite thickness of the radius of the tubes. As we shall see these extra parts provide relevant contributions to the vacuum averages of the energy–momentum tensor.

Relativistic quantum scattering on a cone

In this paper 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. For the idealized cosmic string, an effective two-dimensional delta-function interaction takes place besides the usual topological scattering. In this case the dimensionless coupling parameter must be renormalized in order to make this problem consistent.

Vacuum polarization by a magnetic flux in a cosmic string background

Abstract In this paper we analyse the vacuum polarization effects due to a magnetic flux on massless fermionic fields in a cosmic string background. Three distinct configurations of magnetic fields are considered. In all of them the magnetic fluxes are confined in a long cylindrical tube of finite radius.

VACUUM POLARIZATION BY A MAGNETIC FIELD IN THE COSMIC STRING SPACETIME

In this paper we consider a charged massless scalar quantum field operator in the spacetime of an idealized cosmic string which presents a magnetic field confined in a cylindrical tube of finite radius. Three distinct situations are taken into account in this analysis. In three cases the axis of the infinitely long tube of radius R coincides with the cosmic string. Because we study the combined gravitational and electromagnetic Aharanov-Bohm effect, we calculate the vacuum polarization effects outside the tube.

VACUUM POLARIZATION BY FERMIONIC FIELDS IN HIGHER DIMENSIONAL COSMIC STRING SPACE-TIME

In this paper we investigate vacuum polarization effects associated with charged massive quantum fermionic fields in a six-dimensional cosmic string space-times considering the presence of a magnetic flux running along its core. We have shown that for specific values of the parameters which codify the presence of the cosmic string, and the fractional part of the ratio of the magnetic flux by the quantum one, a closed expression for the respective Green function is obtained. Adopting this result, we explicitly calculate the renormalized vacuum expectation value of the energy-momentum tensor, , and analyse this result in some limiting cases.

Vacuum polarization of a massless scalar field in the background of a global monopole with finite core

In this paper, we analyse the vacuum polarization effects of a massless scalar field in the background of a global monopole considering its inner structure. Specifically we investigate the effect of its structure on the vacuum expectation value of the square of the field operator, , admitting a non-minimal coupling between the field with the geometry: . Also, we calculate the corrections to the vacuum expectation value of the energy–momentum tensor, , due to the inner structure of the monopole. In order to develop these analyses, we calculate the Euclidean Green function associated with the system for points in the region outside the core. As we shall see, for a specific value of the coupling parameter ξ, the corrections caused by the inner structure of the monopole can provide relevant contributions to these vacuum polarizations.

INDUCED ELECTROSTATIC SELF-INTERACTION IN THE SPACE–TIME OF A GLOBAL MONOPOLE WITH INNER STRUCTURE

In this work we analyze the electrostatic self-energy and self-force on a pointlike electric-charged particle induced by a global monopole space–time considering an inner structure for it. In order to develop this analysis we calculate the three-dimensional Green function associated with this physical system. We explicitly show that for points inside and outside the monopoles core the self-energy presents two distinct contributions. The first is induced by the geometry associated with the space–time under consideration, and the second is a correction due to the nonvanishing inner structure attributed to it. Considering specifically the ballpoint pen model for the region inside, we are able to obtain exact expressions for the self-energies in the regions outside and inside the monopoles core.

VACUUM POLARIZATION BY A MAGNETIC FLUX TUBE AT FINITE TEMPERATURE IN THE COSMIC STRING SPACE–TIME

In this paper, we analyze the effect produced by the temperature in the vacuum polarization associated with a charged massless scalar field in the presence of a magnetic flux tube in the cosmic string space–time. Three different configurations of magnetic fields are taken into account: (i) a homogeneous field inside the tube, (ii) a field proportional to 1/r, and (iii) a cylindrical shell with δ-function. In these three cases, the axis of the infinitely long tube of radius R coincides with the cosmic string. Because of the complexity of this analysis in the region inside the tube, we consider the thermal effect in the region outside. In order to develop this analysis, we construct the thermal Green function associated with this system for the three above-mentioned situations considering points in the region outside the tube. We explicitly calculate, in the high-temperature limit, the thermal average of the field square and the energy–momentum tensor.