Particle creation and quadratic deceleration parameter in Lyra geometry

New Astronomy ◽  
2021 ◽  
Vol 85 ◽  
pp. 101563
Author(s):  
Binaya K. Bishi ◽  
Pratik V. Lepse
Author(s):  
Kalyani Desikan

Cosmological models with linearly varying deceleration parameter in the cosmological theory based on Lyra’s geometry have been discussed. Exact solutions have been obtained for a spatially flat FRW model by considering a time dependent displacement field. We have also obtained the time periods during which the universe undergoes decelerated and accelerated expansions for a matter-dominated universe.


2010 ◽  
Vol 25 (18n19) ◽  
pp. 3825-3834 ◽  
Author(s):  
C. P. SINGH ◽  
A. BEESHAM

We study spatially homogeneous and anisotropic Bianchi-V perfect fluid cosmological model with variable G and Λ. Exact solutions to the field equations in the case of particle creation and in the absence of particle creation are obtained by assuming a constant deceleration parameter. The model has a big-bang-type singularity at the initial time t = 0. We find that a constant value of deceleration parameter is reasonable for a description of the present day universe. We also observe that the variable G does not necessarily imply particle creation. The behavior of observationally important parameters such as the expansion scalar, mean anisotropic parameter and shear scalar are discussed. It is observed that the solutions are compatible with the results of recent observations.


2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Supriya Pan ◽  
Subenoy Chakraborty

The paper deals with nonequilibrium thermodynamics based on adiabatic particle creation mechanism with the motivation of considering it as an alternative choice to explain the recent observed accelerating phase of the universe. Using Friedmann’s equations, it is shown that the deceleration parameter (q) can be obtained from the knowledge of the particle production rate (Γ). Motivated by thermodynamical point of view, cosmological solutions are evaluated for the particle creation rates in three cosmic phases, namely, inflation, matter dominated era, and present late time acceleration. The deceleration parameter (q) is expressed as a function of the redshift parameter (z), and its variation is presented graphically. Also, statefinder analysis has been presented graphically in three different phases of the universe. Finally, two noninteracting fluids with different particle creation rates are considered as cosmic substratum, and deceleration parameter (q) is evaluated. Whether more than one transition ofqis possible or not is examined by graphical representations.


2016 ◽  
Vol 31 (02n03) ◽  
pp. 1641031 ◽  
Author(s):  
S. P. Gavrilov ◽  
D. M. Gitman

We consider QED with strong external backgrounds that are concentrated in restricted space areas. The latter backgrounds represent a kind of spatial x-electric potential steps for charged particles. They can create particles from the vacuum, the Klein paradox being closely related to this process. We describe a canonical quantization of the Dirac field with x-electric potential step in terms of adequate in- and out-creation and annihilation operators that allow one to have consistent particle interpretation of the physical system under consideration and develop a nonperturbative (in the external field) technics to calculate scattering, reflection, and electron-positron pair creation. We resume the physical impact of this development.


Author(s):  
Anil Kumar Yadav ◽  
G. K. Goswami ◽  
Anirudh Pradhan ◽  
Sudhir Kumar Srivastava
Keyword(s):  

2015 ◽  
Vol 92 (4) ◽  
Author(s):  
Christos G. Tsagas ◽  
Miltiadis I. Kadiltzoglou

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