Particle Creation Mechanism Research Articles

Effects of particle creation rate in two-fluid interacting cosmologies

ABSTRACT In this work, a two-fluid interacting model in a flat FLRW universe has been studied considering particle creation mechanism with a particular form of particle creation rate $\Gamma =\Gamma _0 H+\frac{\Gamma _1}{H}$ from different aspects. Statistical analysis with a combined data set of SNe Ia (Supernovae Type Ia) and Hubble data is performed to achieve the best-fitting values of the model parameters, and the model is compatible with current observational data. We also perform a dynamical analysis of this model to get an overall qualitative description of the cosmological evolution by converting the governing equations into a system of ordinary differential equations considering a proper transformation of variables. We find some non-isolated sets of critical points, among which some usually are normally hyperbolic sets of points that describe the present acceleration of the universe dominated by dark energy mimicking cosmological constant or phantom fluid. Scaling solutions are also obtained from this analysis, and they can alleviate the coincidence problem successfully. Statefinder diagnosis is also carried out for this model to compare it with the ΛCDM, and any other dark energy models byfinding various statefinder parameters. Finally, the thermodynamic analysis shows that the generalized second law of thermodynamics is valid in an irreversible thermodynamic context.

Towards Study of Two-Particle PT Correlations in Hadronic Interactions at NICA

A new method for studying two-particle transverse momentum (PT) correlations in soft hadronic interactions is proposed. It is shown that Monte Carlo models: PYTHIA 6 and Geant4 FTF (FRITIOF), give different predictions for the correlations in proton–proton interactions. The correlations are connected with Schwinger’s mechanism of particle creation. These correlations can be studied in current and future experiments in high energy physics, in particular, at the Nuclotron-based Ion Collider fAcility (NICA).

Impact of trans-Planckian excitations on black-hole radiation in dipolar condensates

We consider a quasi-one-dimensional dipolar condensate in a steplike analog black hole setup. It is shown that the existence of roton excitations leaves significant imprints onto the Hawking radiation spectrum. The emitted radiation depends on the depth of the roton minimum, and is in general more intense. In addition, we find a novel spontaneous particle creation mechanism with no counterpart in nondipolar condensates. Our results establish that dipolar condensates offer a richer and more versatile environment for the simulation of particle production from the quantum vacuum in the presence of horizon interfaces than contact-interaction condensates.

Cosmic aspects of matter creation models in modified gravities

This paper is devoted to study some cosmological models in the scenario of two gravitational theories like fractal universe and dynamical Chern–Simons modified theory in particle creation mechanism. In both theories, we consider three particle creation rate models including constant and variable mode. We use Gibbs equation to find out pressure of particle creation rate using adiabatic matter phenomenon. The Hubble parameter along with its normalized form are constructed for each case. We discuss the deceleration parameter and effective equation of state parameter by taking into account the normalized Hubble parameter and model parameters. The results of these parameters represent consistent behavior with recent observational data.

Particle creation in the context of the emergent universe

We study the mechanism of particle creation in the context of the emergent universe (EU) scenario which is privileged by certain important characteristics such as the absence of time-like singularity. EU asymptotically coincides with an Einstein static model in the infinite past and it approaches to a de Sitter expansion phase at late times. By introducing the conformal time, we obtain the solution of the Klein-Gordon equation and by applying the "in" and "out" states method, the total number of produced particles and the total energy associated with them are determined.

Particle creation in FLRW higher dimensional universe with gravitational and cosmological constants

We study the mechanism of particle creation in the higher dimensional FLRW-type cosmological models by using variable cosmological and gravitational constants. The solution of the corresponding field equations is obtained by assuming a linear function of the Hubble parameter (H) (i.e., q = α + βH) (Dixit et al. Pramana. J. Phys. 94, 25 (2020). doi: 10.1007/s12043-019-1884-2 ), which gives a scale factor [Formula: see text], where k and β are positive constants. Here we consider the time-dependent higher-dimensional field equations, including the general formulation of particle creation and entropy generation mechanisms. We also investigate a few quantities, such as the deceleration parameter q, particle creation rate ψ, the entropy S, the cosmological constant Λ, Newton’s gravitational constant G, and the energy density ρ, and discuss their physical significance. We have observed that all quantities, except the gravitational constant (G) and the entropy (S), decrease with time in all dimensions characteristically. However, the entropy S and the gravitational constant G increase with time. Additionally, we have also discussed the look-back time, luminosity distance, distance modulus, and age of the universe with redshift z and observed the role of particle formation in universe evolution in early and late times. For the derived model, we have calculated various physical parameters, which are in good agreement with the recent observations.

Does emergent scenario in Hořava–Lifshitz gravity demand a ghost field?

The non-singular model of the Universe i.e. emergent scenario is now very well known in cosmology. In Einstein gravity such type of singularity free solution is possible in the context of non-equilibrium thermodynamical prescription (both in first and 2nd order theory) with particle creation mechanism. Also there are various models of emergent scenario in different gravity theories. The present work is a twofold attempt namely (i) it has been examined whether it is possible to have singularity free solution in Hořava–Lifshitz modified gravity theory, (ii) if such singularity free solution exists then whether such solution is thermodynamically viable. It is found that perfect fluid matter distribution with phantom nature can generate such type of solution for closed and flat model. Finally thermodynamical analysis has been studied both at the apparent horizon and at any arbitrary horizon.

A complete cosmological scenario with particle creation

A flat Friedmann-Robertson-Walker (FRW) cosmological model with perfect fluid has been investigated within the framework of the particle creation mechanism. Perfect fluid isentropic particle creation rate as a function of Hubble parameter has been incorporated. By considering a simple parametrization of Hubble parameter, we discuss the cosmological scenarios through time evolution of the cosmological parameters. We examine the different regimes of the universe by studying the phase transition from decelerated to accelerated era. We also explore the classical stability of model and the state-finder diagnostic for highlighting the departure of the considered cosmological model from the $\Lambda$Cold Dark Matter ($\Lambda$CDM) model.

Finsler–Randers cosmology in the framework of a particle creation mechanism: a dynamical systems perspective

The present work deals with the dynamical evolution of Finsler–Randers (FR) cosmological model in the framework of particle creation mechanism. The particle creation mechanism presented the real non-equilibrium thermodynamics of the Universe. We investigate the phase plane analysis of the model. The evolution of cosmological solutions is studied by using dynamical system techniques. We find one additional critical point in FR cosmological model than Riemannian geometry. Stability and viability of the model are discussed. We find the solution of FR cosmological model which provide an acceleration phase of the Universe under some restriction. It is also shown that the evolution of the model at additional critical point is de Sitter Universe and can have stable late time attractor.

Cosmological solutions of the Israel-Stewart transport equation

In this paper we shall consider second-order non-equilibrium thermodynamics in the realm of particle creation mechanism. Here we have considered the second-order theory described by Müller, Israel and Stewart (MIS theory). It is very difficult to solve the Israel-Stewart transport equation in the second-order theory. In this paper we have solved the Israel-Stewart transport equation in terms of particle creation rate with suitable assumptions.

Particle Creation in Friedmann–Robertson–Walker Universe

Using variable gravitational and cosmological constants, the mechanism of particle creation in the universe is studied for Friedmann–Robertson–Walker (FRW) space-times at high dimensions to explain the early deceleration and present accelerating phases. To investigate the dynamics of these phases, we consider two scale factor of the forms $$a(t)=\sqrt{t^\alpha{e^t}}$$ and $$a(t)=\sqrt[m]{{\rm{sin}}h(kt)}$$, which yield two different time-dependent deceleration parameters. Firstly, we modify the d-dimensional time-dependent field equations, including the general formulation of particle creation and entropy generation mechanisms. Then, we investigate the time dependence of a few quantities such as the particle creation rate ψ, the entropy S, the gravitational constant G, the cosmological constant Λ, the energy density ρ, the deceleration parameter q, etc. We show that all constants and quantities, except the gravitational constant G and the entropy S, characteristically decrease with time for two kinds of scale factors in all dimensions. However, the gravitational constant G and the entropy S increase with time. Additionally, we show that the cosmological constant Λ is unexpectedly independent of the particle creation mechanism, unlike G.

Is Cold/Warm inflationary scenario a consequence of particle creation process [formula omitted

The present work describes a model of inflationary scenario with particle creation mechanism, in the frame work of non-equilibrium thermodynamics. In the background of homogeneous and isotropic spatially flat FLRW model of the Universe, the cosmic substratum is chosen as dissipative fluid. Here dissipation in the form of bulk viscous pressure is assumed to be due to particle creation formalism. For constant and slow-roll phases of (cold) inflationary scenario, the particle creation rate has been derived and an analogous inflaton field has been calculated. Finally an equivalence of the warm inflation with the present particle creation mechanism has been shown.

Cosmological consequences in the framework of generalized Rastall theory of gravity

The paper deals with generalized Rastall theory of gravity and its cosmological consequences in the background of homogeneous and isotropic flat FLRW model with perfect fluid as the matter context. The model shows a non singular era (emergent scenario) at the early phase of expansion for a particular choice of the Rastall parameter. Also the model finds to be equivalent to the particle creation mechanism in Einstein gravity in the framework of non-equilibrium thermodynamics. Universal thermodynamics is briefly presented and it is found that the entropy function in Rastall theory is the usual Bekenstein entropy and there is no correction to it. Finally, a complete cosmic history starting from inflation to late time acceleration is presented for suitable choices of the Rastall parameter.

Cosmic scenarios in[formula omitted] gravity: A complete evolution

The paper deals withf(R) gravity theory in the background of inhomogeneous FLRW-type space–time model. With proper choice of the inhomogeneous metric function it is possible to have an emergent scenario for thef(R)-cosmology. Explicit form off(R) is obtained for power law expansion. It has been shown that the presentf(R) gravity model is equivalent to some particle creation mechanism in Einstein gravity. Further a complete cosmic evolution from inflation to present late time acceleration is possible with proper continuous choices of thef(R)-functions. Finally, in the perspective of thermodynamical analysis a form off(R) has been evaluated using the unified first law.

Does particle creation mechanism favour formation of black hole or naked singularity?

The paper deals with collapse dynamics of a spherically symmetric massive star in the framework of non-equilibrium thermodynamic prescription through particle creation mechanism. The matter content in the star is in the form of perfect fluid with barotropic equation of state, and the dissipative phenomena due to non-equilibrium thermodynamics is in the form of bulk viscosity. For simplicity, the thermodynamic system is chosen to be adiabatic so that the effective bulk viscous pressure is linearly related to the particle creation rate. As a result, the evolution of the collapsing star also depends on the particle creation rate. By proper choice of creation rate as a function of the Hubble parameter, it is found that the end state of the collapse may be either a black hole (BH) or a naked singularity (NS).

Thermodynamics of the dissipative cosmic fluid and stability criteria

The work deals with the thermodynamical aspects of the cosmic substratum which is dissipative in nature. For homogeneous and isotropic model of the Universe this dissipative phenomenon is effective bulk viscous pressure in nature and is related to the particle creation mechanism. Finally, the stability criteria for the thermal equilibrium has been analyzed and are presented in tabular form restricting the particle creation parameter or the variation of the equation of state parameter with the volume.

Evolving cosmic scenario in modified Chaplygin gas with adiabatic matter creation

Modified Chaplygin Gas has been successful in describing the cosmic history of the universe from radiation to ΛCDM in standard cosmology, while particle creation mechanism in nonlinear thermodynamics can be used to explain inflation as well as late time acceleration. The present work is an attempt to explore the possibilities of obtaining an alternative explanation to cosmic evolution when modified Chaplygin gas is used in the context of particle creation mechanism.

Emergent Scenario in first and second order non-equilibrium thermodynamics and stability analysis

First and second order non-equilibrium thermodynamics are studied in the context of particle creation mechanism for homogeneous and isotropic FLRW model and a general formulation of the emergent scenario is investigated. Finally, the stability of the non-equilibrium thermodynamics is examined.

Dynamical analysis of an interacting dark energy model in the framework of a particle creation mechanism

In this work we present the cosmological dynamics of interacting dark energy models in the framework of particle creation mechanism. The particle creation mechanism presented here describes the true non equilibrium thermodynamics of the universe. In spatially flat Friedmann-Lema{\^\i}tre-Robertson-Walker universe considered here, the dissipative bulk viscous pressure is due to the non conservation of particle number. For simplicity, we assume that the creation of perfect fluid particles to be isentropic (adiabatic) and consequently the viscous pressure obeys a linear relationship with particle creation rate. Due to complicated nature of the Einstein's field equations, dynamical systems analysis has been performed to understand deeply about the cosmological dynamics. We have found some interesting cosmological scenarios like late-time evolution of universe dominated by dark energy which could mimic quintessence, cosmological constant or phantom field through a dark matter dominated era. We also obtained a possibility of crossing the phantom divide line which is favored by observations.

Anisotropic open system cosmology

In this work, we study a particle creation mechanism at the expense of the energy stored in an extra dimension with the respective process of compactification, and hence the emergence of 4D space. The spacetime resulting can be the Friedmann–Robertson–Walker (FRW) type, but also can be the cosmological term plus cold dark matter (ΛCDM) type, depending on the model’s parameters. Concurrent with the compactification process we have also the homogenization process, since initially the spacetime is anisotropic.