The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
S. Biswas - One of the best experts on this subject based on the ideXlab platform.
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Fermion Particle Production in a Periodic Potential
General Relativity and Gravitation, 2004Co-Authors: S. Biswas, I. ChowdhuryAbstract:In this paper we study fermion Particle Production in the early universe. The present work is motivated to restudy the fermion Particle Production from the basics and compare the results in the literature through another method developed by one of the present author. One of the authors (SB) has developed a method, known as complex trajectory WKB method, to study Particle Production in curved as well as flat spacetime. In the present work we have tried to compare the CWKB method with that of other works, current in the literature. In this work we have obtained the Particle Production amplitude starting from the basics and test our results through both analytical and numerical calculations. For fermion Particle Production, we first do analytical calculations with a toy example to calculate the Production amplitude and verify the same doing fourth order Runge-Kutta calculation. As most problems relevant to early universe are not amenable to analytical calculations, we then take up to study the Particle Production in periodic potential, generally used in inflationary cosmology. We recheck two recent approaches and obtain almost identical results as that obtained by Greene and Kofman. We also verify the result through CWKB method. Boson Particle Production has been discussed elsewhere, we discuss it briefly in connection with CWKB. In the present work we generalize the CWKB results of boson Production to fermion Production. Our works will enable one to understand the various phenomena in early universe related to Particle Production. Using CWKB we calculate the occupation number and some other results for fermion Particle Production. The present work will help us clarify the variant results of fermion Production current in the literature.
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The CWKB Method of Particle Production in Periodic Potential
General Relativity and Gravitation, 2003Co-Authors: S. Biswas, P. Misra, I. ChowdhuryAbstract:In this work we study the Particle Production in time dependent periodic potential using the method of complex time WKB (CWKB) approximation. In the inflationary cosmology at the end of inflationary stage, the potential becomes time dependent as well as periodic. Reheating occurs due to Particle Production by the oscillating inflaton field. Using CWKB we obtain almost identical results on catastrophic Particle Production as obtained by others.
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The CWKB Method of Particle Production in a Periodic Potential
General Relativity and Gravitation, 2003Co-Authors: S. Biswas, P. Misra, I. ChowdhuryAbstract:In this work we study the Particle Production in time dependent periodic potential using the method of complex time WKB (CWKB) approximation. In the inflationary cosmology at the end of the inflationary stage, the potential becomes time dependent as well as periodic. Reheating occurs due to Particle Production by the oscillating inflaton field. Using CWKB we obtain almost identical results on catastrophic Particle Production as obtained by others.
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The CWKB Method of Particle Production Near Chronology Horizon
arXiv: General Relativity and Quantum Cosmology, 2002Co-Authors: S. Biswas, P. Misra, I. ChowdhuryAbstract:In this paper we investigate the phenomenon of Particle Production of massles scalar field, in a model of spacetime where the chronology horizon could be formrd, using the method of complex time WKB approximation (CWKB). For the purpose, we take two examples in a model of spacetime, one already discussed by Sushkov, to show that the mode of Particle Production near chronology horizon possesses the similar characteristic features as are found while discussing Particle Production in time dependent curved background. We get identical results as that obtained by Sushkov in this direction. We find, in both the examples studied, that the total number of Particles remain finite at the moment of the formation of the chronology horizon.
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Particle Production in Expanding Spacetime
General Relativity and Gravitation, 2002Co-Authors: S. Biswas, A. Shaw, P. MisraAbstract:The complex time WKB (CWKB) approximation has been an effective technique to study Particle Production in expanding space time. The success of the approximation technique both in time and space dependent gauge has motivated us to study the method in relation to the time dependent approximation. In this work we try to understand the adiabatic and non-adiabatic transition within the framework of complex time WKB approximation. We find that the emergence of thermal radiation is due to some topological characteristics of cosmological spacetime that separates the spacetime into Euclidean and non-Euclidean region. This applies also to blackhole spacetime. The complex WKB trajectory approach shows that the Euclidean vacuum fluctuation is root cause of thermal Particle Production and is basically a Hawking effect. We also study here the sensitivity of Particle Production on the rise of scale factor at early times. It is found that the tunneling paths are responsible for the origin of thermal radiation whereas the slope of the scale factor determines the magnitude of the temperature of the thermal Particle Production. We also substantiate Hu's assertion in this connection.
N G Sarkar - One of the best experts on this subject based on the ideXlab platform.
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Particle Production in curved spacetime
Pramana, 1998Co-Authors: N G Sarkar, S. BiswasAbstract:Particle Production in curved spacetime has been discussed through the method of complex time WKB approximation. We consider Dirac equation in non-flat spacetime to understand Particle Production as Particle-antiParticle rotation. The method is also generalized to understand Particle Production through parametric resonance. To understand the method of CWKB we consider Particle Production in Kasner spacetime as an example.
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Particle Production in de Sitter space
Classical and Quantum Gravity, 1995Co-Authors: S. Biswas, J Guha, N G SarkarAbstract:Partial creation in de Sitter spacetime is studied in a complex-time WKB approximation. It is found that the Particle Production parallels the description of Particle creation by a collapsing spherical body. The appropriate vacuum for an inflationary early universe is the Hartle--Hawking vacuum; this is also a general feature of expanding spacetimes. The effect of Particle Production back on the metric is treated in a way that differs from the standard semiclassical approach.
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Effect of Particle Production in Robertson-Walker spacetime
Classical and Quantum Gravity, 1995Co-Authors: J Guha, N G Sarkar, D. Biswas, S. BiswasAbstract:We show that the Dirac equation in Robertson--Walker (RW) spacetime can be written in a two-dimensional equivalent form that parallels the motion of an electron in a time-varying electric field. Using the effect of Particle Production, a RW spacetime that describes a universe which contracts and re-expands almost symmetrically and becomes asymptotically static is simulated. The back-reaction problem is considered only through the quantum behaviour of Particle Production without any reference to Einstein field equations.
P. Foka - One of the best experts on this subject based on the ideXlab platform.
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Strange Particle Production in nuclear collisions
Nuclear Physics A, 1995Co-Authors: P. FokaAbstract:Abstract Strange Particle Production was studied in central collisions of 32S+S, 32S+Ag and 32S+Au. Compared to the negative Particle Production in the same events, it is found that there is an enhancement of strange Particle Production at mid rapidity.
Georg Wolschin - One of the best experts on this subject based on the ideXlab platform.
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Particle Production beyond the thermal model
EPJ Web of Conferences, 2016Co-Authors: Georg WolschinAbstract:The sources of Particle Production in relativistic heavy-ion collisions are investigated from RHIC to LHC energies. Whereas charged-hadron Production in the fragmentation sources follows a ln( s NN / s 0 ) law, Particle Production in the mid-rapidity low- x gluon-gluon source exhibits a much stronger dependence ∝ ln 3 ( s NN / s 0 ), and becomes dominant between RHIC and LHC energies. The equilibration of the three sources is investigated in a relativistic diffusion model (RDM). It agrees with the thermal model only for t → ∞.
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Particle Production sources at LHC energies
Journal of Physics G: Nuclear and Particle Physics, 2013Co-Authors: Georg WolschinAbstract:Particle Production sources at RHIC and LHC energies are investigated in pseudorapidity space. A nonequilibrium-statistical relativistic diffusion model with three sources is applied to the analysis of charged-hadron distributions in AuAu collisions at RHIC energies, in PbPb collisions at the current LHC energy of 2.76 TeV, in p Pb at 5.02 TeV, and in pp . The size of the midrapidity source relative to the fragmentation sources in heavy-ion collisions is investigated as function of incident energy. At LHC energies, the midrapidity value is mostly determined by Particle Production from gluon–gluon collisions.
Stéphane J. M. Houndjo - One of the best experts on this subject based on the ideXlab platform.
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Quantum Particle Production at sudden singularities
Physical Review D, 2008Co-Authors: John D. Barrow, A. B. Batista, Júlio C. Fabris, Stéphane J. M. HoundjoAbstract:We investigate the effects of quantum Particle Production on a classical sudden singularity occurring at finite time in a Friedmann universe. We use an exact solution to describe an initially radiation-dominated universe that evolves into a sudden singularity at finite time. We calculate the density of created Particles exactly and find that it is generally much smaller than the classical background density and pressure which produce the sudden singularity. We conclude that, in the example studied, the quantum Particle Production does not lead to the avoidance or modification to the sudden future singularity. We argue that the effects of small residual anisotropies in the expansion will not change these results and show how they can be related to studies of classical Particle Production using a bulk viscosity. We conclude that we do not expect to see significant observable effects from local sudden singularities on our past light cone.
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Particle Production in an expanding universe dominated by dark energy fluid
Gravitation and Cosmology, 2008Co-Authors: A. B. Batista, Júlio C. Fabris, Stéphane J. M. HoundjoAbstract:We investigate Particle Production in an expanding universe dominated by a perfect fluid with the equation of state p = αρ. The rate of Particle Production, using the Bogoliubov coefficients, is determined exactly for any value of α in the case of a flat universe. When the strong energy condition is satisfied, the Particle Production rate decreases with time; the opposite occurs when the strong energy condition is violated. In the phantom case, the Particle Production rate diverges in a finite time for each mode represented by a wavenumber k. Nevertheless, the energy density associated with the produced Particles tends to zero as the big rip is approached.