scholarly journals Electromagnetic Vacuum Densities Induced by a Cosmic String

Particles ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 13 ◽  
Author(s):  
Aram Saharian ◽  
Vardan Manukyan ◽  
Nvard Saharyan
Keyword(s):  
Cosmic String ◽  
Vacuum Expectation ◽  
Momentum Tensor ◽  
Curvature Radius ◽  
De Sitter ◽  
Dimensional Spacetime ◽  
Special Cases ◽  
Electric And Magnetic Fields ◽  
Spatial Dimensions ◽  
Planar Angle

We investigate the influence of a generalized cosmic string in (D+1)-dimensional spacetime on the local characteristics of the electromagnetic vacuum. Two special cases are considered with flat and locally de Sitter background geometries. The topological contributions in the vacuum expectation values (VEVs) of the squared electric and magnetic fields are explicitly separated. Depending on the number of spatial dimensions and on the planar angle deficit induced by the cosmic string, these contributions can be either negative or positive. In the case of the flat bulk, the VEV of the energy–momentum tensor is evaluated as well. For the locally de Sitter bulk, the influence of the background gravitational field essentially changes the behavior of the vacuum densities at distances from the string larger than the curvature radius of the spacetime.

scholarly journals Electromagnetic Casimir densities for a cylindrical shell on de Sitter space

2016 ◽  
Vol 31 (34) ◽  
pp. 1650183 ◽  
Author(s):  
A. A. Saharian ◽  
V. F. Manukyan ◽  
N. A. Saharyan
Keyword(s):  
Cylindrical Shell ◽  
Electric Field ◽  
Energy Momentum Tensor ◽  
Vacuum Expectation ◽  
Vacuum State ◽  
Momentum Tensor ◽  
Curvature Radius ◽  
Perfect Conductor ◽  
De Sitter ◽  
Proper Distance

Complete set of cylindrical modes is constructed for the electromagnetic field inside and outside a cylindrical shell in the background of [Formula: see text]-dimensional dS space–time. On the shell, the field obeys the generalized perfect conductor boundary condition. For the Bunch–Davies vacuum state, we evaluate the vacuum expectation values (VEVs) of the electric field squared and of the energy–momentum tensor. The shell-induced contributions are explicitly extracted. In this way, for points away from the shell, the renormalization is reduced to the one for the VEVs in the boundary-free dS bulk. As a special case, the VEVs are obtained for a cylindrical shell in the [Formula: see text]-dimensional Minkowski bulk. We show that the shell-induced contribution in the electric field squared is positive for both the interior and exterior regions. The corresponding Casimir–Polder forces are directed toward the shell. The vacuum energy–momentum tensor, in addition to the diagonal components, has a nonzero off-diagonal component corresponding to the energy flux along the direction normal to the shell. This flux is directed from the shell in both the exterior and interior regions. For points near the shell, the leading terms in the asymptotic expansions for the electric field squared and diagonal components of the energy–momentum tensor are obtained from the corresponding expressions in the Minkowski bulk replacing the distance from the shell by the proper distance in the dS bulk. The influence of the gravitational field on the local characteristics of the vacuum is essential at distances from the shell larger than the dS curvature radius. The results are extended for confining boundary conditions of flux tube models in QCD.

Electromagnetic Casimir densities for planar boundaries in AdS spacetime

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040029 ◽  
Author(s):  
A. A. Saharian ◽  
A. S. Kotanjyan ◽  
A. A. Saharyan ◽  
H. G. Sargsyan
Keyword(s):  
Boundary Condition ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Momentum Tensor ◽  
Curvature Radius ◽  
Perfect Conductor ◽  
Parallel Plates ◽  
Casimir Forces ◽  
Spatial Dimensions ◽  
Ads Spacetime

We investigate the vacuum expectation value of the energy-momentum tensor and the Casimir forces for the electromagnetic field in AdS spacetime for the geometry of two parallel plates. On the plates the field obeys the boundary condition that generalizes the perfect conductor boundary condition for an arbitrary number of spatial dimensions. The interaction forces between the plates are attractive. At separations larger than the curvature radius of the spacetime they decay exponentially.

The backreaction of massive scalar field on FLRW and de Sitter spaces

2020 ◽  
Vol 17 (03) ◽  
pp. 2050033
Author(s):  
M. R. Setare ◽  
M. Sahraee
Keyword(s):  
Scalar Field ◽  
Energy Momentum Tensor ◽  
Friedmann Equation ◽  
Vacuum Expectation ◽  
Momentum Tensor ◽  
Scale Factor ◽  
Massive Scalar ◽  
De Sitter ◽  
Massive Scalar Field ◽  
Quantum Energy

In this paper, we obtain the effect of backreaction on the scale factor of the Friedmann–Lemaître–Robertson–Walker (FLRW) and de Sitter spaces. We consider a non-minimally coupled massive scalar field to the curvature scalar. For our purpose, we use the results of vacuum expectation values of energy–momentum tensor, which have been obtained previously. By substituting the quantum energy density into the Friedmann equation, we obtain the linear order perturbation of the scale factor. So, the effect of backreaction leads to the new scale factor.

scholarly journals VACUUM POLARIZATION IN A COSMIC STRING SPACETIME INDUCED BY FLAT BOUNDARY

2011 ◽  
Vol 03 ◽  
pp. 434-445
Author(s):  
EUGÊNIO R. BEZERRA DE MELLO ◽  
ARAM A. SAHARIAN
Keyword(s):  
Cosmic String ◽  
Vacuum Polarization ◽  
Energy Momentum Tensor ◽  
Neumann Boundary ◽  
Vacuum Expectation ◽  
Momentum Tensor ◽  
Massive Scalar ◽  
Expectation Values ◽  
Massive Scalar Field ◽  
Higher Dimensional

In this paper we analyze the vacuum expectation values of the field squared and the energy-momentum tensor associated to a massive scalar field in a higher dimensional cosmic string spacetime, obeying Dirichlet or Neumann boundary conditions on the surface orthogonal to the string.

Vacuum polarization in the background of conical singularity

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040030
Author(s):  
Yuri V. Grats ◽  
Pavel Spirin
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Energy Momentum Tensor ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Momentum Tensor ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Dimensional Spacetime ◽  
Higher Dimensional

We consider the gravity-induced effects associated with a massless scalar field living in a higher-dimensional spacetime being the tensor product of Minkowski space and spherically-symmetric space with angle deficit. These spacetimes are considered as simple models for a multidimensional global monopole or cosmic string with flat extra dimensions, where the deficit of solid angle is proportional to Newton constant and tension. Thus, we refer to them as conical backgrounds. In terms of the angular deficit value, we derive the perturbative expression for the scalar Green’s function and compute it to the leading order. With the use of this Green’s function we compute the renormalized vacuum expectation value of the scalar-field’s energy-momentum tensor. We make some general note on the linear-on-curvature part of the trace of even coefficients of Schwinger-deWitt expansion.

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.

scholarly journals QUANTUM EFFECTS IN HIGHER-DIMENSIONAL COSMOLOGICAL MODELS

2012 ◽  
Vol 18 ◽  
pp. 164-173 ◽  
Author(s):  
ARAM A. SAHARIAN
Keyword(s):  
Vacuum Energy ◽  
Vacuum Expectation ◽  
Vacuum Energy Density ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Expectation Values ◽  
Sitter Spacetime ◽  
Higher Dimensional ◽  
Spatial Dimensions ◽  
Robin Boundary

Vacuum energy density and stresses are investigated for a scalar field in de Sitter spacetime with an arbitrary number of toroidally compactified spatial dimensions and in anti-de Sitter spacetime with two parallel branes. On the branes the field obeys the Robin boundary conditions. The behavior of the vacuum expectation values is discussed in various asymptotic regions of the parameters. Applications are given to Randall-Sundrum type braneworlds.

scholarly journals CASIMIR EFFECT IN TOROIDALLY COMPACTIFIED DE SITTER SPACETIME

2009 ◽  
Vol 24 (08n09) ◽  
pp. 1813-1820 ◽  
Author(s):  
A. A. SAHARIAN
Keyword(s):  
Casimir Effect ◽  
Coupling Parameter ◽  
Vacuum Expectation ◽  
Vacuum Energy Density ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Expectation Values ◽  
Sitter Spacetime ◽  
Spatial Dimensions ◽  
Late Stages

Vacuum energy density and stresses are investigated for a scalar field with general curvature coupling parameter in (D + 1)-dimensional de Sitter spacetime with an arbitrary number of toroidally compactified spatial dimensions. The corresponding expectation values are presented in the form of the sum of the vacuum expectation values in uncompactified dS spacetime and the part induced by the non-trivial topology. In the early stages of the cosmological evolution the topological parts dominate. In this limit the behavior of the Casimir densities does not depend on the curvature coupling parameter and coincides with that for a conformally coupled massless field. At late stages of the cosmological expansion the expectation values are dominated by the part corresponding to uncompactified dS spacetime. The vanishing of the topological parts is monotonic or oscillatory in dependence of the mass and the curvature coupling parameter of the field.

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.

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