Interacting Kasner-type cosmologies

Cataldo, Mauricio; Arevalo, Fabiola; Mella, Patricio Oliva

doi:10.1007/s10509-011-0596-y

Cited by 7 publications

(7 citation statements)

References 43 publications

(33 reference statements)

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“…This point has been considered in some detail in Comer et al (2012a, b). It has been suggested Adhav et al 2011;Cataldo et al 2011) that, since Bianchi universes-seen as averaged inhomogeneous and anisotropic spacetimes-can have effective strong energy condition violating stress-energy tensors, they could be part of a backreaction driven acceleration model.…”

Section: Multi-component Cosmologymentioning

confidence: 99%

Relativistic fluid dynamics: physics for many different scales

Andersson

Comer

2021

Living Rev Relativ

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The relativistic fluid is a highly successful model used to describe the dynamics of many-particle systems moving at high velocities and/or in strong gravity. It takes as input physics from microscopic scales and yields as output predictions of bulk, macroscopic motion. By inverting the process—e.g., drawing on astrophysical observations—an understanding of relativistic features can lead to insight into physics on the microscopic scale. Relativistic fluids have been used to model systems as “small” as colliding heavy ions in laboratory experiments, and as large as the Universe itself, with “intermediate” sized objects like neutron stars being considered along the way. The purpose of this review is to discuss the mathematical and theoretical physics underpinnings of the relativistic (multi-) fluid model. We focus on the variational principle approach championed by Brandon Carter and collaborators, in which a crucial element is to distinguish the momenta that are conjugate to the particle number density currents. This approach differs from the “standard” text-book derivation of the equations of motion from the divergence of the stress-energy tensor in that one explicitly obtains the relativistic Euler equation as an “integrability” condition on the relativistic vorticity. We discuss the conservation laws and the equations of motion in detail, and provide a number of (in our opinion) interesting and relevant applications of the general theory. The formalism provides a foundation for complex models, e.g., including electromagnetism, superfluidity and elasticity—all of which are relevant for state of the art neutron-star modelling.

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Section: Multi-component Cosmologymentioning

confidence: 99%

Relativistic fluid dynamics: physics for many different scales

Andersson

Comer

2021

Living Rev Relativ

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“…However, one can consider also gravitational configurations filled with two or more fluids [9]. For example, in cosmology such two-fluid models are widely considered today in order to explain the observed accelerated expansion of the Universe [10].…”

Section: Introductionmentioning

confidence: 99%

Two-fluid evolving Lorentzian wormholes

Cataldo

Campo

2012

Phys. Rev. D

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We investigate the evolution of a family of wormholes sustained by two matter components: one with homogeneous and isotropic properties ρ(t) and another inhomogeneous and anisotropic ρin(t, r). The rate of expansion of these evolving wormholes is only determined by the isotropic and homogeneous matter component ρ(t). Particularly, we consider a family of exact two-fluid evolving wormholes expanding with constant velocity and satisfying the dominant and the strong energy conditions in the whole spacetime. In general, for the case of vanishing isotropic fluid ρ(t) and cosmological constant Λ the space expands with constant velocity, and for ρ(t) = 0 and Λ = 0 the rate of expansion is determined by the cosmological constant. The considered here two-fluid evolving wormholes are a generalization of single fluid models discussed in previous works of the present authors [Phys. Rev. D 78, 104006 (2008)

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“…[22].) For instance, it has been suggested [23][24][25] that since Bianchi universes, seen as averaged inhomogeneous and anisotropic spacetimes, can have effective strong energy condition violating stress-energy tensors, they could be part of a backreaction driven acceleration model.…”

Section: Introductionmentioning

confidence: 99%

Multifluid cosmology: An illustration of fundamental principles

2012

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Our current understanding of the Universe depends on the interplay of several distinct "matter" components, which interact mainly through gravity, and electromagnetic radiation. The nature of the different components, and possible interactions, tends to be based on the notion of coupled perfect fluids (or scalar fields). This approach is somewhat naive, especially if one wants to be able to consider issues involving heat flow, dissipative mechanisms, or Bose-Einstein condensation of dark matter. We argue that a more natural starting point would be the multi-purpose variational relativistic multi-fluid system that has so far mainly been applied to neutron star astrophysics. As an illustration of the fundamental principles involved, we develop the formalism for determining the non-linear cosmological solutions to the Einstein equations for a general relativistic two-fluid model for a coupled system of matter (non-zero rest mass) and "radiation" (zero rest mass). The two fluids are allowed to interpenetrate and exhibit a relative flow with respect to each other, implying, in general, an anisotropic Universe. We use initial conditions such that the massless fluid flux dominates early on so that the situation is effectively that of a single fluid and one has the usual Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime. We find that there is a Bianchi I transition epoch out of which the matter flux dominates. The situation is then effectively that of a single fluid and the spacetime evolves towards the FLRW form. Such a transition opens up the possiblity of imprinting observable consequences at the specific scale corresponding to the transition time.PACS numbers: 97.60. Jd,26.20.+c,47.75.+f,95.30.Sf

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Interacting Kasner-type cosmologies

Cited by 7 publications

References 43 publications

Relativistic fluid dynamics: physics for many different scales

Relativistic fluid dynamics: physics for many different scales

Two-fluid evolving Lorentzian wormholes

Multifluid cosmology: An illustration of fundamental principles

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