scholarly journals Annihilation of the scalar pair into a photon in a de Sitter universe

2016 ◽  
Vol 31 (14n15) ◽  
pp. 1650081 ◽  
Author(s):  
Mihaela-Andreea Băloi
Keyword(s):  
Photon Emission ◽  
Total Probability ◽  
De Sitter ◽  
Expansion Factor ◽  
Scalar Particles ◽  
Gravitational Fields ◽  
Klein Gordon ◽  
De Sitter Universe ◽  
Mass Expansion ◽  
Strong Gravitational Fields

The annihilation of massive scalar particles in one photon in de Sitter expanding universe is studied, using perturbative QED. The amplitude and probability corresponding to this process is computed using the exact solutions of the Klein–Gordon and Maxwell equations on de Sitter geometry. Our results show that the expression of the total probability of photon emission is a function dependent on the ratio mass/expansion factor. We perform a graphical study of the total probability in terms of the parameter mass/expansion factor, showing that this effect is significant only in strong gravitational fields. We also obtain that the total probability for this process vanishes in the Minkowski limit.

scholarly journals Fermion production by a dependent of time electric field in de Sitter universe

2017 ◽  
Vol 32 (36) ◽  
pp. 1750208 ◽  
Author(s):  
Mihaela-Andreea Băloi ◽  
Cosmin Crucean
Keyword(s):  
Electric Field ◽  
Pair Production ◽  
External Electric Field ◽  
Early Universe ◽  
Total Probability ◽  
De Sitter ◽  
Expansion Factor ◽  
Gravitational Fields ◽  
De Sitter Universe ◽  
Strong Gravitational Fields

Fermion production in external electric field on de Sitter expanding universe is analyzed. The amplitude and probability of pair production are computed. We obtain from our calculations that the modulus of the momentum is no longer conserved. The rate of pair production in an electric field is found to be important in the early universe when the expansion factor was large comparatively with the particle mass. A computation of the total probability is presented in a particular case and the result proves to be nonvanishing only in strong gravitational fields.

scholarly journals Perturbative approach to the problem of particle production in electric field on de Sitter universe

2016 ◽  
Vol 31 (13) ◽  
pp. 1650082 ◽  
Author(s):  
Cosmin Crucean ◽  
Mihaela-Andreea Băloi
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Particle Production ◽  
Transition Amplitude ◽  
Scalar Particle ◽  
Total Probability ◽  
De Sitter ◽  
Expansion Factor ◽  
Perturbative Approach ◽  
De Sitter Universe

In this paper, we study the problem of scalar particle production in external electric field in de Sitter geometry. The total probability is calculated using the previously obtained result in [M. A. Băloi, Mod. Phys. Lett. A 29, 1450138 (2014)] for transition amplitude in external electric field on de Sitter space. Then we make a graphical study of the total probability in terms of the ratio mass of the particle/expansion factor. Our results show that the probability depend on the direction in which the particles are emitted and that the probability becomes maximum when particles are emitted on the direction of the electric field. In the Minkowski limit, we obtain that the probability is vanishing.

scholarly journals Radiation of inertial scalar particles in the de Sitter universe

2015 ◽  
Vol 30 (11) ◽  
pp. 1550062 ◽  
Author(s):  
Robert Blaga
Keyword(s):  
Transition Probability ◽  
Order Term ◽  
Photon Emission ◽  
Scalar Particle ◽  
De Sitter ◽  
Qualitative Comparison ◽  
Scalar Particles ◽  
Radiated Energy ◽  
S Matrix ◽  
De Sitter Universe

We investigate the radiation of an inertial scalar particle evolving in a de Sitter (dS) expanding Universe. In the context of scalar QED, the process is generated by the first-order term in the perturbation theory expansion of the S-matrix. The partial transition probability is obtained and analyzed, and soft-photon emission is found to dominate overall. It has been argued that an inertial particle evolving in dS spacetime loses physical momentum just as a decelerated particle in Minkowski space does. It is thus expected that an inertial charge will radiate in a similar way. We investigate the radiated energy and make a qualitative comparison of the angular distribution of the energy with the radiation pattern in the latter case.

scholarly journals On the Schwarzschild-Anti-de Sitter black hole with an f(R) global monopole

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
H. S. Vieira
Keyword(s):  
Black Hole ◽  
Gordon Equation ◽  
Global Monopole ◽  
De Sitter ◽  
Scalar Particles ◽  
Black Hole Radiation ◽  
Effective Cosmological Constant ◽  
Klein Gordon ◽  
Physical Phenomena

AbstractIn this work, we follow the recently revisited f(R) theory of gravity for studying the interaction between quantum scalar particles and the gravitational field of a generalized black hole with an f(R) global monopole. This background has a term playing the role of an effective cosmological constant, which permits us to call it as Schwarzschild-Anti-de Sitter (SAdS) black hole with an f(R) global monopole. We examine the separability of the Klein–Gordon equation with a non-minimal coupling and then we discuss both the massless and massive cases for a conformal coupling. We investigate some physical phenomena related to the asymptotic behavior of the radial function, namely, the black hole radiation, the quasibound states, and the wave eigenfunctions.

FRACTIONAL ANALYSIS OF WAVE PACKET PROPAGATION AND SOME ASPECTS OF VSL WITH GUP

Fractals ◽  
2008 ◽  
Vol 16 (01) ◽  
pp. 33-42 ◽  
Author(s):  
S. HAMID MEHDIPOUR ◽  
KOUROSH NOZARI ◽  
S. DAVOOD SADATIAN
Keyword(s):  
Wave Packet ◽  
Gordon Equation ◽  
Generalized Uncertainty Principle ◽  
De Sitter ◽  
Modified Dispersion Relation ◽  
Fractional Analysis ◽  
Klein Gordon ◽  
De Sitter Universe ◽  
Klein Gordon Equation ◽  
Wave Packet Broadening

In this paper, we consider the problem of wave packet broadening in the framework of the Generalized Uncertainty Principle (GUP) of quantum gravity. Then we find a fractal Klein-Gordon equation to further analyze the wave packet broadening in a foamy spacetime. We derive a Modified Dispersion Relation (MDR) in the context of GUP which shows an extra broadening due to gravitational induced uncertainty. As a result of these dispersion relations, a generalized Klein-Gordon equation can be obtained. We solve this generalized equation under certain conditions to find both analytical and numerical results. We show that GUP can lead to a variation of the fundamental constants such as speed of light. With this novel properties, we find a time-dependent equation of state for perfect fluid in de Sitter universe and we interpret its physical implications.

scholarly journals Interaction between Maxwell field and charged scalar field in de Sitter universe

2015 ◽  
Vol 30 (16) ◽  
pp. 1550088 ◽  
Author(s):  
Cosmin Crucean ◽  
Mihaela-Andreea Băloi
Keyword(s):  
Scalar Field ◽  
Particle Production ◽  
Perturbation Expansion ◽  
Maxwell Field ◽  
De Sitter ◽  
Charged Scalar ◽  
Gravitational Fields ◽  
Sitter Background ◽  
Charged Scalar Field ◽  
De Sitter Universe

We study the theory of interaction between charged scalar field and Maxwell field in de Sitter background. Solving the equation of interacting fields, we define the in–out fields as asymptotic free fields and construct the reduction formalism for scalar field. Then we derive the perturbation expansion of the scattering operator. The first-order transition amplitudes corresponding to particle production from de Sitter vacuum and pair production in an external field are analyzed. We show that all these effects are important only in strong gravitational fields and vanish in the flat limit.

scholarly journals On quantum corrections to geodesics in de-Sitter spacetime

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Viacheslav A. Emelyanov
Keyword(s):  
Wave Packet ◽  
Gordon Equation ◽  
Plane Waves ◽  
Hubble Constant ◽  
De Sitter ◽  
Field Mass ◽  
Sitter Spacetime ◽  
Klein Gordon ◽  
De Sitter Universe ◽  
Positive Frequency

AbstractWe find a coordinate-independent wave-packet solution of the massive Klein–Gordon equation with the conformal coupling to gravity in the de-Sitter universe. This solution can locally be represented through the superposition of positive-frequency plane waves at any space-time point, assuming that the scalar-field mass M is much bigger than the de-Sitter Hubble constant H. The solution is also shown to be related to the two-point function in the de-Sitter quantum vacuum. Moreover, we study the wave-packet propagation over cosmological times, depending on the ratio of M and H. In doing so, we find that this wave packet propagates like a point-like particle of the same mass if $$M \ggg H$$ M ⋙ H , but, if otherwise, the wave packet behaves highly non-classically.

scholarly journals Rest frame vacua of massive Klein–Gordon fields on spatially flat FLRW spacetimes

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
Ion I. Cotăescu
Keyword(s):  
State Space ◽  
Rest Frame ◽  
Particle Creation ◽  
Time Dependent ◽  
Massive Scalar ◽  
De Sitter ◽  
Rest Energy ◽  
Dynamic Vacuum ◽  
Scalar Particles ◽  
Klein Gordon

Abstract We propose a method of projecting the quantum states from a state space of a given geometry into another state space generated by a different geometry, taking care of the correct normalization which is crucial in interpreting the quantum theory. Thanks to this method we can define on any spatially flat FLRW spacetime states in which genuine Minkowskian parameters are measured. We use these Minkowskian states for separating the frequencies in the rest frames of the massive scalar particles defining thus the scalar rest frame vacuum. We show that this vacuum is stable on the de Sitter expanding universe where the energy is conserved. In contrast, on a spatially flat FLRW spacetime with a Milne-type scale factor this vacuum is found to be dynamic, corresponding to a time-dependent rest energy interpreted as an effective mass. This dynamic vacuum gives rise to cosmological particle creation which is significant only in the early Milne-type universe considered here. Some interesting features of this new effect are pointed out in a brief analysis.

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