scholarly journals CASIMIR DENSITIES FOR A MASSIVE FERMIONIC QUANTUM FIELD IN A GLOBAL MONOPOLE BACKGROUND WITH SPHERICAL BOUNDARY

2005 ◽  
Vol 20 (11) ◽  
pp. 2380-2387 ◽  
Author(s):  
A. A. SAHARIAN ◽  
E. R. BEZERRA DE MELLO
Keyword(s):  
Energy Momentum Tensor ◽  
Solid Angle ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Momentum Tensor ◽  
Global Monopole ◽  
Expectation Values ◽  
Fermionic Field ◽  
Sphere Center ◽  
Spherical Boundary

We investigate the vacuum expectation value of the energy-momentum tensor associated with a massive fermionic field obeying the MIT bag boundary condition on a spherical shell in the global monopole spacetime. The asymptotic behavior of the vacuum densities is investigated near the sphere center and surface, and at large distances from the sphere. In the limit of strong gravitational field corresponding to small values of the parameter describing the solid angle deficit in global monopole geometry, the sphere-induced expectation values are exponentially suppressed.

The effect of backreaction on inflationary Brans–Dicke cosmology

2016 ◽  
Vol 25 (10) ◽  
pp. 1650097 ◽  
Author(s):  
M. Sahraee ◽  
M. R. Setare
Keyword(s):  
Energy Momentum Tensor ◽  
Equations Of Motion ◽  
Dimensional Regularization ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Momentum Tensor ◽  
Expectation Values ◽  
Quantum Energy ◽  
Expectation Value ◽  
Dimensional Spacetime

In this paper, we study the effect of the quantum backreaction on Brans–Dicke cosmology in inflation era. We consider an inflaton field in the [Formula: see text]-dimensional spacetime in the framework of Brans–Dicke model. We use a new notation for the Brans–Dicke field in terms of the dilaton field. Then we obtain the vacuum expectation value of the full energy–momentum tensor using WKB approximation of the mode functions which satisfy the equations of motion. The obtained vacuum expectation values of energy–momentum tensor are divergent. In order to renormalize it, we introduce a constant cut-off [Formula: see text]. The vacuum expectation value of energy–momentum tensor is separated to the UV and IR parts by using [Formula: see text] cut-off. Then, we use the dimensional regularization method to eliminate divergences by introducing a counterterm action. Also, we calculate the IR contribution of the vacuum expectation value of energy–momentum tensor. Thus, we obtain a physically finite result for the quantum energy–momentum tensor. Finally, we find the effect of backreaction on 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.

BRS ANALYSIS OF THE ENERGY MOMENTUM TENSOR IN TWO-DIMENSIONAL GRAVITY

1991 ◽  
Vol 06 (18) ◽  
pp. 1679-1684
Author(s):  
W. S. L'YI ◽  
YOUNG-JAI PARK ◽  
KEE YONG KIM ◽  
YONGDUK KIM
Keyword(s):  
Gravitational Field ◽  
Energy Momentum Tensor ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Momentum Tensor ◽  
Majorana Fermion ◽  
Two Dimensional ◽  
Expectation Value ◽  
Dimensional Gravity

Majorana fermion coupled to a 2-dimensional background gravitational field is investigated by employing the BRS quantization technique. Upon introduction of a quasicon-formal map ζ determined by the Beltrami differential h, the background gravitational field amazingly disappeared leaving just the free Majorana field ψ and ghosts b, c. In this way the vacuum expectation value of the energy-momentum tensor under the background gravitational field is explicitly computed.

The effect of backreaction on inflationary Starobinsky cosmology

2017 ◽  
Vol 14 (10) ◽  
pp. 1750134 ◽  
Author(s):  
Mohammad Reza Setare ◽  
Mitra Sahraee
Keyword(s):  
Energy Momentum Tensor ◽  
Dimensional Regularization ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Momentum Tensor ◽  
Scale Factor ◽  
Quantum Energy ◽  
Expectation Value ◽  
Trace Anomaly ◽  
Friedmann Robertson Walker

In this paper, we would like to obtain the effect of the quantum backreaction on inflationary Starobinsky cosmology in spatially flat [Formula: see text]-dimensional Friedmann–Robertson–Walker universe. For this purpose, first, we obtain the vacuum expectation value of energy–momentum tensor, which is separated into two parts, UV and IR. To calculate the UV contribution, we use the WKB approximation of the mode function of the equation of motion. Since the obtained value of this contribution of the vacuum expectation value of energy–momentum tensor is divergent, we should renormalize it. Therefore, by using the dimensional regularization and introducing a counterterm action, we eliminate divergences. After that, we calculate the contributions of IR part and trace anomaly. Thus, we obtain the quantum energy density and pressure during inflation era in this model. Finally, we can find the effect of backreaction on scale factor in inflation era, which leads to the new scale factor.

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