scholarly journals Quantum Scalar Field in the FRW Universe with a Constant Electromagnetic Background

1997 ◽  
Vol 12 (27) ◽  
pp. 4837-4867 ◽  
Author(s):  
S. P. Gavrilov ◽  
D. M. Gitman ◽  
S. D. Odintsov
Keyword(s):  
Electromagnetic Field ◽  
Scalar Field ◽  
Effective Action ◽  
Proper Time ◽  
Back Reaction ◽  
De Sitter ◽  
Frw Universe ◽  
Massive Scalar Field ◽  
Mean Values ◽  
Constant Electromagnetic Field

We discuss a massive scalar field with conformal coupling in the Friedmann–Robertson–Walker (FRW) Universe of a special type with a constant electromagnetic field. Treating an external gravitational–electromagnetic background exactly, at the first time the proper-time representations for out–in, in–in and out–out scalar Green functions are explicitly constructed as proper-time integrals over the corresponding (complex) contours. The vacuum-to-vacuum transition amplitudes and the number of created particles are found and vacuum instability is discussed. The mean values of the current and the energy–momentum tensor are evaluated, and different approximations for them are investigated. The back reaction of the particles created to the electromagnetic field is estimated in different regimes. The connection between the proper-time method and the effective action is outlined. The effective action in scalar QED in the weakly curved FRW Universe (de Sitter space) with a weak constant electromagnetic field is found as a derivative expansion over curvature and electromagnetic field strength. Possible further applications of the results are mentioned.

scholarly journals QUANTUM SPINOR FIELD IN THE FRW UNIVERSE WITH A CONSTANT ELECTROMAGNETIC BACKGROUND

2001 ◽  
Vol 16 (26) ◽  
pp. 4235-4259 ◽  
Author(s):  
S. P. GAVRILOV ◽  
D. M. GITMAN ◽  
A. E. GONÇALVES
Keyword(s):  
Spinor Field ◽  
Proper Time ◽  
Particle Creation ◽  
Transition Amplitude ◽  
Momentum Tensor ◽  
Back Reaction ◽  
Frw Universe ◽  
Mean Values ◽  
Constant Electromagnetic Field ◽  
Massive Spinor

This paper is a natural continuation of our paper Quantum Scalar Field in FRW Universe with Constant Electromagnetic Background, Int. J. Mod. Phys.A12, 4837 (1997). We generalize our previous work to the case of a massive spinor field, which is placed in a FRW universe of a special type with a constant electromagnetic field. So as to achieve this, special sets of exact solutions of the Dirac equation in the background under consideration are constructed and classified. Using these solutions representations for out–in, in–in, and out–out spinor Green functions are explicitly constructed as proper-time integrals over the corresponding contours in the complex proper-time plane. The vacuum-to-vacuum transition amplitude and the number of created particles are found and vacuum instability is discussed. The mean values of the current and of the energy–momentum tensor are evaluated, and different approximations for them are presented. The back reaction related to particle creation and to unstable vacuum polarization is estimated in different regimes.

scholarly journals PROBING THE VACUUM STRUCTURE OF SPACETIME

2012 ◽  
Vol 12 ◽  
pp. 310-319 ◽  
Author(s):  
SANG PYO KIM
Keyword(s):  
Scalar Field ◽  
Effective Action ◽  
Particle Production ◽  
Constant Electric Field ◽  
Massive Scalar ◽  
De Sitter ◽  
Charged Scalar ◽  
Massive Scalar Field ◽  
Vacuum Structure ◽  
Gravitational Analog

We explore the question of how to probe the vacuum structure of space time by a massive scalar field through interaction with background gravitons. Using the Γ-regularization for the in-/out-state formalism, we find the effective action of a scalar field in a conformally, asymptotically flat spacetime and a four-dimensional de Sitter space, which is a gravitational analog of the Heisenberg-Euler and Schwinger effective action for a charged scalar in a constant electric field. The effective action is nonperturbative in that it sums all one-loop diagrams with arbitrary number of external lines of gravitons. The massive scalar field becomes unstable due to particle production, the effective action has an imaginary part that determines the decay rate of the vacuum, and the out-vacuum is unitarily inequivalent to the in-vacuum.

Noncommutative scalar field in de Sitter space–time and pair creation process

2021 ◽  
Vol 36 (02) ◽  
pp. 2150011
Author(s):  
Nabil Mehdaoui ◽  
Lamine Khodja ◽  
Salah Haouat
Keyword(s):  
Scalar Field ◽  
Chemical Potential ◽  
De Sitter Space ◽  
Space Time ◽  
Pair Creation ◽  
De Sitter ◽  
Creation Process ◽  
Scalar Particles ◽  
Constant Electromagnetic Field

In this work, we address the process of pair creation of scalar particles in [Formula: see text] de Sitter space–time in presence of a constant electromagnetic field by applying the noncommutativity on the scalar field up to first-order in [Formula: see text]. We calculate the density of particles created in the vacuum by the mean of the Bogoliubov transformations. In contrast to a previous result, we show that noncommutativity contributes to the pair creation process. We find that the noncommutativity plays the same role of chemical potential and gives an important interest for studies at high energies.

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 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 EULER–HEISENBERG LAGRANGIAN THROUGH KREIN REGULARIZATION

2013 ◽  
Vol 28 (14) ◽  
pp. 1350056 ◽  
Author(s):  
A. REFAEI
Keyword(s):  
Electromagnetic Field ◽  
Effective Action ◽  
Light Cone ◽  
Krein Space ◽  
Renormalization Procedure ◽  
Constant Electromagnetic Field ◽  
Kreĭn Space ◽  
The One ◽  
Convergent Solution ◽  
Krein Regularization

The Euler–Heisenberg effective action at the one-loop for a constant electromagnetic field is derived in Krein space quantization with Ford's idea of fluctuated light-cone. In this work, we present a perturbative but convergent solution of the effective action. Without using any renormalization procedure, the result coincides with the famous renormalized Euler–Heisenberg action.

scholarly journals ANALYTIC RESULTS FOR THE EFFECTIVE ACTION

1991 ◽  
Vol 06 (30) ◽  
pp. 5409-5433 ◽  
Author(s):  
STEVEN K. BLAU ◽  
MATT VISSER ◽  
ANDREAS WIPF
Keyword(s):  
Electromagnetic Field ◽  
Asymptotic Expansion ◽  
Zeta Function ◽  
Effective Action ◽  
Strong Field ◽  
Weak Field ◽  
Four Dimensions ◽  
Effective Lagrangian ◽  
Constant Electromagnetic Field ◽  
The One

Motivated by the seminal work of Schwinger, we obtain explicit closed-form expressions for the one-loop effective action in a constant electromagnetic field. We discuss both massive and massless charged scalars and spinors in two, three and four dimensions. Both strong-field and weak-field limits are calculable. The latter limit results in an asymptotic expansion whose first term reproduces the Euler-Heinsenberg effective Lagrangian. We use the prescription of zeta-function renormalization, and indicate its relationship to Schwinger’s renormalized effective action.

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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