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.

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.

Casimir effect for massive scalar field

2014 ◽  
Vol 29 (31) ◽  
pp. 1450160 ◽  
Author(s):  
S. Mobassem
Keyword(s):  
Scalar Field ◽  
Energy Momentum Tensor ◽  
Casimir Effect ◽  
Momentum Tensor ◽  
Massive Scalar ◽  
Massive Scalar Field ◽  
Fluctuation Dissipation ◽  
Fluctuation Dissipation Theorem ◽  
The Green Function ◽  
Field Quantization

The energy–momentum tensor is used to introduce the Casimir force of the massive scalar field acting on a nonpenetrating surface. This expression can be used to evaluate the vacuum force by employing the appropriate field operators. To simplify our formalism, we also relate the vacuum force expression to the imaginary part of the Green function via the fluctuation–dissipation theorem and Kubo's formula. This allows one to evaluate the vacuum force without resorting to the process of field quantization. These two approaches are used to calculate the attractive force between two nonpenetrating plates. Special attention is paid to the generalization of the formalism to D+1 spacetime dimensions.

CASIMIR-AHARONOV-BOHM EFFECT IN THE COSMIC STRING BACKGROUND

2011 ◽  
Vol 03 ◽  
pp. 574-582
Author(s):  
YU. A. SITENKO ◽  
N. D. VLASII ◽  
O. P. LYASHCHENKO
Keyword(s):  
Scalar Field ◽  
Cosmic String ◽  
Energy Momentum Tensor ◽  
String Tension ◽  
Momentum Tensor ◽  
Massive Scalar ◽  
Massive Scalar Field ◽  
Bohm Effect ◽  
String Background ◽  
Aharonov Bohm

A charged massive scalar field is quantized in the background of a static gauge cosmic string. We find the energy-momentum tensor which is induced in the vacuum. The dependence of the tensor components on the gauge flux, string tension and the coupling to the space-time curvature is comprehensively analyzed.

CASIMIR EFFECT FOR THE ROBIN SURFACES IN STATIC ROBERTSON–WALKER SPACE–TIME

2011 ◽  
Vol 20 (02) ◽  
pp. 161-168 ◽  
Author(s):  
MOHAMMAD R. SETARE ◽  
M. DEHGHANI
Keyword(s):  
Scalar Field ◽  
Energy Momentum Tensor ◽  
Casimir Effect ◽  
Vacuum Expectation ◽  
Robin Boundary Condition ◽  
Momentum Tensor ◽  
Space Time ◽  
Conformally Invariant ◽  
Time Space ◽  
Robin Boundary

We investigate the energy–momentum tensor for a massless conformally coupled scalar field in the region between two curved surfaces in k = -1 static Robertson–Walker space–time. We assume that the scalar field satisfies the Robin boundary condition on the surfaces. Robertson–Walker space–time space is conformally related to Rindler space; as a result we can obtain vacuum expectation values of the energy–momentum tensor for a conformally invariant field in Robertson–Walker space–time space from the corresponding Rindler counterpart by the conformal transformation.

Cosmic acceleration with tachyon field

2018 ◽  
Vol 33 (34) ◽  
pp. 1850199 ◽  
Author(s):  
A. I. Keskin
Keyword(s):  
Scalar Field ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Cosmic Acceleration ◽  
Late Time ◽  
De Sitter ◽  
Tachyon Field ◽  
Minimal Coupling ◽  
Acceleration Of The Universe ◽  
The Universe

In this study, we examine two models of the scalar field, that is, a normal scalar field and a tachyon scalar field in [Formula: see text] gravity to describe cosmic acceleration of the universe, where [Formula: see text], [Formula: see text] and [Formula: see text] are Ricci curvature scalar, trace of energy–momentum tensor and kinetic energy of scalar field [Formula: see text], respectively. Using the minimal-coupling Lagrangian [Formula: see text], for both the scalar models we obtain a viable cosmological system, where [Formula: see text] and [Formula: see text] are real constants. While a normal scalar field gives a system describing expansion from the deceleration to the late-time acceleration, tachyon field together with [Formula: see text] in the system produces a quintessential expansion which is very close to de Sitter point, where we find a new condition [Formula: see text] for inflation.

scholarly journals Strong cosmic censorship under quasinormal modes of non-minimally coupled massive scalar field

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
Bogeun Gwak
Keyword(s):  
Black Holes ◽  
Scalar Field ◽  
Decay Rate ◽  
Small Mass ◽  
Cosmic Censorship ◽  
Massive Scalar ◽  
De Sitter ◽  
Massive Scalar Field ◽  
Strong Cosmic Censorship ◽  
Cosmic Censorship Conjecture

Abstract We investigate the strong cosmic censorship conjecture in lukewarm Reissner–Nordström–de Sitter black holes (and Martínez–Troncoso–Zanelli black holes) using the quasinormal resonance of non-minimally coupled massive scalar field. The strong cosmic censorship conjecture is closely related to the stability of the Cauchy horizon governed by the decay rate of the dominant quasinormal mode. Here, dominant modes are obtained in the limits of small and large mass black holes. Then, we connect the modes by using the WKB approximation. In our analysis, the strong cosmic censorship conjecture is valid except in the range of the small-mass limit, in which the dominant mode can be assumed to be that of the de Sitter spacetime. Particularly, the coupling constant and mass of the scalar field determine the decay rate in the small mass range. Therefore, the validity of the strong cosmic censorship conjecture depends on the characteristics of the scalar field.

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.

scholarly journals On the algebraic quantization of a massive scalar field in anti-de Sitter spacetime

2018 ◽  
Vol 30 (02) ◽  
pp. 1850004 ◽  
Author(s):  
Claudio Dappiaggi ◽  
Hugo R. C. Ferreira
Keyword(s):  
Scalar Field ◽  
De Sitter Spacetime ◽  
Massive Scalar ◽  
De Sitter ◽  
Functional Formalism ◽  
Arbitrary Boundary ◽  
Massive Scalar Field ◽  
Sitter Spacetime ◽  
Hadamard States ◽  
Definition Of

We discuss the algebraic quantization of a real, massive scalar field in the Poincaré patch of the [Formula: see text]-dimensional anti-de Sitter spacetime, with arbitrary boundary conditions. By using the functional formalism, we show that it is always possible to associate to such system an algebra of observables enjoying the standard properties of causality, time-slice axiom and F-locality. In addition, we characterize the wavefront set of the ground state associated to the system under investigation. As a consequence, we are able to generalize the definition of Hadamard states and construct a global algebra of Wick polynomials.

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