scholarly journals Induced fermionic current in AdS spacetime in the presence of a cosmic string and a compactified dimension

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
S. Bellucci ◽  
W. Oliveira dos Santos ◽  
E. R. Bezerra de Mello
Keyword(s):  
Magnetic Flux ◽  
Cosmic String ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Axial Current ◽  
De Sitter ◽  
Twisted Field ◽  
Compact Dimension ◽  
Ads Spacetime ◽  
Current Densities

AbstractIn this paper, we consider a massive charged fermionic quantum field and investigate the current densities induced by a magnetic flux running along the core of an idealized cosmic string in the background geometry of a 5-dimensional anti-de Sitter spacetime, assuming that an extra dimension is compactified. Along the compact dimension quasi-periodicity condition is imposed on the field with a general phase. Moreover, we admit the presence of a magnetic flux enclosed by the compactified axis. The latter gives rise to Ahanorov–Bohm-like effect on the vacuum expectation value of the currents. In this setup, only azimuthal and axial current densities take place. The former presents two contributions, with the first one due to the cosmic string in a 5-dimensional AdS spacetime without compact dimension, and the second one being induced by the compactification itself. The latter is an odd function of the magnetic flux along the cosmic string and an even function of the magnetic flux enclosed by the compactified axis with period equal to the quantum flux. As to the induced axial current, it is an even function of the magnetic flux along the string’s core and an odd function of the magnetic flux enclosed by the compactification perimeter. For untwisted and twisted field along compact dimension, the axial current vanishes. The massless field case is presented as well some asymptotic limits for the parameters of the model.

scholarly journals Vacuum bosonic currents induced by a compactified cosmic string in dS background

2020 ◽  
Vol 29 (15) ◽  
pp. 2050103
Author(s):  
E. A. F. Bragança ◽  
E. R. Bezerra de Mello ◽  
A. Mohammadi
Keyword(s):  
Cosmic String ◽  
Axial Current ◽  
Wave Functions ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Fermionic Field ◽  
Sitter Spacetime ◽  
Compact Dimension ◽  
Complete Set ◽  
Current Densities

In this paper, we study the vacuum bosonic currents in the geometry of a compactified cosmic string in the background of the de Sitter spacetime. The currents are induced by magnetic fluxes, one running along the cosmic string and another one enclosed by the compact dimension. To develop the analysis, we obtain the complete set of normalized bosonic wave functions obeying a quasiperiodicity condition. In this context, we calculate the azimuthal and axial current densities and we show that these quantities are explicitly decomposed into two contributions: one originating from the geometry of a straight uncompactified cosmic string and the other induced by the compactification. We also compare the results with the literature in the case of a massive fermionic field in the same geometry.

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

2016 ◽  
Vol 31 (02n03) ◽  
pp. 1641021
Author(s):  
Eugênio R. Bezerra de Mello ◽  
Aram A. Saharian ◽  
Azadeh Mohammadi
Keyword(s):  
Magnetic Flux ◽  
Periodic Function ◽  
Cosmic String ◽  
Finite Temperature ◽  
Chemical Potential ◽  
Vacuum Expectation ◽  
Expectation Values ◽  
Quantum Flux ◽  
Current Densities ◽  
Azimuthal Current

Here we analyze the finite temperature expectation values of the charge and current densities for a massive fermionic quantum field with nonzero chemical potential [Formula: see text], induced by a magnetic flux running along the axis of an idealized cosmic string. These densities are decomposed into the vacuum expectation values and contributions coming from the particles and antiparticles. Specifically the charge density is an even periodic function of the magnetic flux with the period equal to the quantum flux and an odd function of the chemical potential. The only nonzero component of the current density corresponds to the azimuthal current and it is an odd periodic function of the magnetic flux and an even function of the chemical potential. Both analyzed are developed for the cases where [Formula: see text] is smaller than the mass of the field quanta [Formula: see text].

scholarly journals Vacuum fermionic currents in braneworld models on AdS bulk with a cosmic string

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
S. Bellucci ◽  
W. Oliveira dos Santos ◽  
E.R. Bezerra de Mello ◽  
A.A. Saharian
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Current Density ◽  
Cosmic String ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Vacuum State ◽  
Total Current ◽  
De Sitter ◽  
Proper Distance

Abstract We investigate the effects of a brane and magnetic-flux-carrying cosmic string on the vacuum expectation value (VEV) of the current density for a charged fermionic field in the background geometry of (4+1)-dimensional anti-de Sitter (AdS) spacetime. The brane is parallel to the AdS boundary and the cosmic string is orthogonal to the brane. Two types of boundary conditions are considered on the brane that include the MIT bag boundary condition and the boundary conditions in Z2-symmetric braneworld models. The brane divides the space into two regions with different properties of the vacuum state. The only nonzero component of the current density is along the azimuthal direction and in both the regions the corresponding VEV is decomposed into the brane- free and brane-induced contributions. The latter vanishes on the string and near the string the total current is dominated by the brane-free part. At large distances from the string and in the region between the brane and AdS horizon the decay of the brane-induced current density, as a function of the proper distance, is power-law for both massless and massive fields. For a massive field this behavior is essentially different from that in the Minkowski bulk. In the region between the brane and AdS boundary the large-distance decay of the current density is exponential. Depending on the boundary condition on the brane, the brane-induced contribution is dominant or subdominant in the total current density at large distances from the string. By using the results for fields realizing two inequivalent irreducible representations of the Clifford algebra, the vacuum current density is investigated in C - and P -symmetric fermionic models. Applications are given for a cosmic string in the Randall-Sundrum-type braneworld model with a single brane.

scholarly journals Fermionic vacuum polarization around a cosmic string in compactified AdS spacetime

2022 ◽  
Vol 2022 (01) ◽  
pp. 010
Author(s):  
S. Bellucci ◽  
W. Oliveira dos Santos ◽  
E.R. Bezerra de Mello ◽  
A.A. Saharian
Keyword(s):  
Energy Density ◽  
Cosmic String ◽  
Vacuum Energy ◽  
Energy Momentum Tensor ◽  
Minkowski Spacetime ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Momentum Tensor ◽  
Vacuum Energy Density ◽  
Ads Spacetime

Abstract We investigate topological effects of a cosmic string and compactification of a spatial dimension on the vacuum expectation value (VEV) of the energy-momentum tensor for a fermionic field in (4+1)-dimensional locally AdS spacetime. The contribution induced by the compactification is explicitly extracted by using the Abel-Plana summation formula. The mean energy-momentum tensor is diagonal and the vacuum stresses along the direction perpendicular to the AdS boundary and along the cosmic string are equal to the energy density. All the components are even periodic functions of the magnetic fluxes inside the string core and enclosed by compact dimension, with the period equal to the flux quantum. The vacuum energy density can be either positive or negative, depending on the values of the parameters and the distance from the string. The topological contributions in the VEV of the energy-momentum tensor vanish on the AdS boundary. Near the string the effects of compactification and gravitational field are weak and the leading term in the asymptotic expansion coincides with the corresponding VEV in (4+1)-dimensional Minkowski spacetime. At large distances, the decay of the cosmic string induced contribution in the vacuum energy-momentum tensor, as a function of the proper distance from the string, follows a power law. For a cosmic string in the Minkowski bulk and for massive fields the corresponding fall off is exponential. Within the framework of the AdS/CFT correspondence, the geometry for conformal field theory on the AdS boundary corresponds to the standard cosmic string in (3+1)-dimensional Minkowski spacetime compactified along its axis.

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

2009 ◽  
Vol 24 (08n09) ◽  
pp. 1481-1488 ◽  
Author(s):  
J. SPINELLY ◽  
E. R. BEZERRA DE MELLO
Keyword(s):  
Magnetic Flux ◽  
Cosmic String ◽  
Vacuum Polarization ◽  
Fractional Part ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Momentum Tensor ◽  
Closed Expression ◽  
Fermionic Fields ◽  
Tensor Formula

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, [Formula: see text], and analyse this result in some limiting cases.

scholarly journals Induced vacuum bosonic current in a compactified cosmic string spacetime

2016 ◽  
Vol 41 ◽  
pp. 1660117 ◽  
Author(s):  
E. A. F. Bragança ◽  
H. F. Santana Mota ◽  
E. R. Bezerra de Mello
Keyword(s):  
Magnetic Flux ◽  
Cosmic String ◽  
Wave Functions ◽  
Complete Set ◽  
Current Densities

We analyze the bosonic current densities induced by a magnetic flux running along an idealized cosmic string considering that the coordinate along its axis is compactified. We also consider the presence of a magnetic flux enclosed by the compactificatified axis. To develop this analysis, we calculate the complete set of normalized bosonic wave functions obeying a quasiperiodicity condition along the compactified dimension. We show that in this context only the azimuthal and axial currents take place.

scholarly journals Induced Cosmological Constant in Braneworlds with Compact Dimensions

2018 ◽  
pp. 315-326
Author(s):  
A. A. Saharian ◽  
H. G. Sargsyan
Keyword(s):  
Magnetic Flux ◽  
Cosmological Constant ◽  
Function Technique ◽  
Vacuum Energy Density ◽  
De Sitter ◽  
Charged Scalar ◽  
Sitter Spacetime ◽  
Compact Dimension ◽  
Spatial Dimensions ◽  
Aharonov Bohm

We investigate the cosmological constant induced by quantum fluctuations of a bulk charged scalar field on a brane in background of locally anti-de Sitter spacetime with toroidally compact spatial dimensions. Along compact dimension quasiperiodicity conditions are imposed with general phases and, in addition, the presence of a constant gauge field is assumed. The latter gives rise to Aharonov-Bohm type effect on the characteristics of the scalar vacuum. The renormalization of the vacuum energy density on the brane is done by making use of the generalized zeta function technique. The behavior of the cosmological constant is studied as a function of the location of the brane, of the length of the compact dimensions and of the magnetic flux enclosed by the compact dimension. In particular, it is shown that the cosmological constant is a periodic function of the magnetic flux with the period equal to the flux quantum.

scholarly journals Quantum fluctuation of stress tensor in a higher-derivative scalar field theory around a cosmic string

2021 ◽  
pp. 2150150
Author(s):  
Nahomi Kan ◽  
Masashi Kuniyasu ◽  
Kiyoshi Shiraishi
Keyword(s):  
Scalar Field ◽  
Stress Tensor ◽  
Cosmic String ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Scalar Fields ◽  
Vacuum Fluctuation ◽  
Higher Derivative ◽  
Scalar Theories ◽  
Quantum Stress Tensor

In this paper, we calculate the vacuum fluctuation of the stress tensor of a higher-derivative theory around a thin cosmic string. To this end, we adopt the method to obtain the stress tensor from the effective action developed by Gibbons et al. By their method, the quantum stress tensor of higher-derivative scalar theories without self-interaction is expressed as a simple sum of quantum stress tensors of free massive scalar fields. Unlike the vacuum expectation value of the scalar field squared obtained in the similar model, there appears no reduction of the values near the conical singularity.

scholarly journals Effects of Quantum Fields Outside Cosmic Strings

1988 ◽  
Vol 130 ◽  
pp. 565-565
Author(s):  
D. A. Konkowski ◽  
T. M. Helliwell
Keyword(s):  
Cosmic String ◽  
Casimir Effect ◽  
Semiclassical Approximation ◽  
Mass Density ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Energy Tensor ◽  
Parallel Plates ◽  
Vacuum Fluctuations ◽  
Gravitational Influence

The space surrounding a long straight cosmic string is flat but conical. The conical topology implies that such a string focuses light rays or particles passing by opposite sides of the string, which can have important astrophysical effects. The flatness, however, implies that the string has no gravitational influence on matter at rest with respect to the string. The flatness is a consequence of the fact that the tension along a cosmic string is equal to its linear mass density μ. There may be physical effects, however, which destroy the equality of tension and mass density, so that straight strings might after all affect matter at rest. One such effect we and others have calculated is the vacuum fluctuations of fields near the strings induced by the conical topology. Such fluctuation s are physically observable but normally small, as in the Casimir effect between parallel plates. We find the vacuum expectation value of the stress - energy tensor of a conformally coupled scalar field around a cosmic string to be in cylindrical coordinates (t, r, θ, z). The equality of Ttt and Tzz means that the effective tension and mass density of the vacuum fluctuations are equal, so that at least in a semiclassical approximation a string dressed by such fields still has no gravitational influence on matter at rest, even though it has a substantial mass density.

scholarly journals Quantum Effects in the Spacetime of a Magnetic Flux Cosmic String

2003 ◽  
Vol 18 (12) ◽  
pp. 2093-2098 ◽  
Author(s):  
M. E. X. Guimarães ◽  
A. L. N. Oliveira
Keyword(s):  
Scalar Field ◽  
Magnetic Flux ◽  
Cosmic String ◽  
Energy Momentum Tensor ◽  
Vacuum Expectation ◽  
Momentum Tensor ◽  
Expectation Values ◽  
Charged Scalar ◽  
Average Value ◽  
Charged Scalar Field

In this work we compute the vacuum expectation values of the energy-momentum tensor and the average value of a massive, charged scalar field in the presence of a magnetic flux cosmic string for both zero- and finite-temperature cases.

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