Influence of particle creation on flat and negative curved FLRW universes

Montani, Giovanni

doi:10.1088/0264-9381/18/1/311

Cited by 20 publications

(18 citation statements)

References 12 publications

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“…Particles creation, which comes out from the rapid time variation of the gravitational field, can explain both an increase of the entropy of the universe 7 and, as shown here, a remarkable stability compared with the cosmological standard model one.…”

Section: Introductionsupporting

confidence: 59%

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Influence of Matter Creation on the Early Universe Stability

Montani

Nescatelli

2008

Int. J. Mod. Phys. A

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The effects of the particles creation processes on the evolution of a spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) universe are investigated. Our approach is involved in the context of open thermodynamics systems choosing a natural phenomenological ansatz for the particles creation rate. There are reasons to believe that this model gives a simple and appropriate description of the gravitational stability concerning the isotropic model for the Early Universe considered both on a small and large scale. The prelude of our study is that the consideration of the particles production processes are supposed to play an relevant role in the perturbation theory arising in the Early Universe dynamics. We show how perturbations damp forwards in time or remain constant (as in the Cosmological Standard Model) and, differently from the standard analysis, we find instability backward in time from an initial condition on scalar perturbation.

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Section: Introductionsupporting

confidence: 59%

“…Following the lines indicated in Ref. 7 we fixed the background dynamics for our perturbation picture. In Sec.…”

Section: Introductionmentioning

confidence: 99%

Influence of Matter Creation on the Early Universe Stability

Montani

Nescatelli

2008

Int. J. Mod. Phys. A

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“…4 A detailed microscopic description of matter creation phenomena should be provided by a fully self-consistent quantum field theory on a curved space time. 5 Many attempts have been made to treat the matter creation process at a phenomenological macroscopic level.…”

Section: 3mentioning

confidence: 99%

Brane World Dynamics and Adiabatic Matter Creation

Gopakumar

Vijayagovindan

2006

Int. J. Mod. Phys. D

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We have treated the adiabatic matter creation process in various three-brane models by applying thermodynamics of open systems. The matter creation rate is found to affect the evolution of scale factor and energy density of the universe. We find modification at early stages of cosmic dynamics. In GB and RS brane worlds, by chosing appropriate parameters we obtain standard scenario, while the warped DGP model has different solutions. During later stages, since the matter creation is negligible the evolution reduces to FRW expansion, in RS and GB models.

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“…In the relativistic limit, dissipative precesses are derived [18], [20], [21], [22] as a correction of the energy-momentum tensor pressure characterizing the matter filling the space-time. In presence of viscosity, the thermostatic pressure p is replaced by a new quantity of the form…”

Section: Motion Equations Of An Unperturbed Viscous Fluidmentioning

confidence: 99%

On the gravitational collapse of a gas cloud in the presence of bulk viscosity

Carlevaro

Montani

2005

Class. Quantum Grav.

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We analyze the effects induced by the bulk (or second) viscosity on the dynamics associated to the extreme gravitational collapse. Aim of the work is to investigate whether the presence of viscous corrections to the evolution of a collapsing gas cloud influence the top-down fragmentation process. To this end, we generalize the approach presented in the Hunter work [1] to include in the dynamics of the (uniform and spherically symmetric) cloud the negative pressure contribution associated to the bulk viscosity phenomenology. Within the framework of a Newtonian approach (whose range of validity is outlined), we extend to the viscous case either the Lagrangian, either the Eulerian motion of the system addressed in [1] and we treat the asymptotic evolution in correspondence to a viscosity coefficient of the form ζ = ζ0 ρ 5/6 (ρ being the cloud density and ζ0 = const.). We show how the adiabatic-like behavior of the gas is deeply influenced by viscous correction when its collapse reaches the extreme regime toward the singularity. In fact the density contrast associated to a given scale of the fragmentation process acquires, asymptotically, a vanishing behavior which prevents the formation of sub-structures. Since in the non-viscous case the density contrasts remain constant, we can conclude that in the adiabatic-like collapse the top down mechanism of structures formation is suppressed as soon as viscous effects are taken into account. Such a feature is not present in the isothermal-like collapse because the sub-structures formation is yet present and outlines the same behavior as in the non-viscous case. We emphasize that in the adiabatic-like collapse the bulk viscosity is also responsible for the appearance of a threshold scale beyond which perturbations begin to increase; this issue, absent in the non-viscous case, is equivalent to deal with a Jeans length. A discussion of the physical character that the choice ν = 5/6 takes place in the present case is provided.PACS numbers: 95.30. Wi, 51.20.+d

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Influence of particle creation on flat and negative curved FLRW universes

Cited by 20 publications

References 12 publications

Influence of Matter Creation on the Early Universe Stability

Influence of Matter Creation on the Early Universe Stability

Brane World Dynamics and Adiabatic Matter Creation

On the gravitational collapse of a gas cloud in the presence of bulk viscosity

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