Cosmological behavior in extended nonlinear massive gravity

León, Genly; Saavedra, Joel; Saridakis, Emmanuel N.

doi:10.1088/0264-9381/30/13/135001

Cited by 103 publications

(92 citation statements)

References 62 publications

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“…by imposing a dilatation-like symmetry [41] or considering variations of the parameters with a scalar field [42]. Indeed, the resulting cosmological solutions [43][44][45] can still be fully homogeneous and isotropic, with non-zero kinetic terms for perturbations. The perturbation analysis of these extensions will be addressed in a separate work [46].…”

Section: Discussionmentioning

confidence: 99%

Nonlinear stability of cosmological solutions in massive gravity

Felice

Gümrükçüoğlu

Lin

et al. 2013

J. Cosmol. Astropart. Phys.

106

100

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We investigate nonlinear stability of two classes of cosmological solutions in massive gravity: isotropic Friedmann-Lemaître-Robertson-Walker (FLRW) solutions and anisotropic FLRW solutions. For this purpose we construct the linear cosmological perturbation theory around axisymmetric Bianchi type-I backgrounds. We then expand the background around the two classes of solutions, which are fixed points of the background evolution equation, and analyze linear perturbations on top of it. This provides a consistent truncation of nonlinear perturbations around these fixed point solutions and allows us to analyze nonlinear stability in a simple way. In particular, it is shown that isotropic FLRW solutions exhibit nonlinear ghost instability. On the other hand, anisotropic FLRW solutions are shown to be ghost-free for a range of parameters and initial conditions.

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Section: Discussionmentioning

confidence: 99%

Nonlinear stability of cosmological solutions in massive gravity

Felice

Gümrükçüoğlu

Lin

et al. 2013

J. Cosmol. Astropart. Phys.

106

100

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“…To analyse the dynamical system of the interacting polytropic gases considered in this section, one follows to existing scientific literature (see for instance [83]). There is a huge number of articles presenting the phase space analysis of different cosmological models [83][84][85][86][87][88][89][90] (to mention a few).…”

Section: Alternative Look At the Problemmentioning

confidence: 99%

On the Phenomenology of an Accelerated Large-Scale Universe

Khurshudyan

2016

Symmetry

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Abstract:In this review paper, several new results towards the explanation of the accelerated expansion of the large-scale universe is discussed. On the other hand, inflation is the early-time accelerated era and the universe is symmetric in the sense of accelerated expansion. The accelerated expansion of is one of the long standing problems in modern cosmology, and physics in general. There are several well defined approaches to solve this problem. One of them is an assumption concerning the existence of dark energy in recent universe. It is believed that dark energy is responsible for antigravity, while dark matter has gravitational nature and is responsible, in general, for structure formation. A different approach is an appropriate modification of general relativity including, for instance, f (R) and f (T) theories of gravity. On the other hand, attempts to build theories of quantum gravity and assumptions about existence of extra dimensions, possible variability of the gravitational constant and the speed of the light (among others), provide interesting modifications of general relativity applicable to problems of modern cosmology, too. In particular, here two groups of cosmological models are discussed. In the first group the problem of the accelerated expansion of large-scale universe is discussed involving a new idea, named the varying ghost dark energy. On the other hand, the second group contains cosmological models addressed to the same problem involving either new parameterizations of the equation of state parameter of dark energy (like varying polytropic gas), or nonlinear interactions between dark energy and dark matter. Moreover, for cosmological models involving varying ghost dark energy, massless particle creation in appropriate radiation dominated universe (when the background dynamics is due to general relativity) is demonstrated as well. Exploring the nature of the accelerated expansion of the large-scale universe involving generalized holographic dark energy model with a specific Nojiri-Odintsov cut-off is presented to finalize the paper.

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“…Also as was recently shown, study of cosmology within these theories gives rise to additional densities in the Friedmann equation, which can be included in our definition of ρ in Eq. (3) [40][41][42]. Other theoretical approaches also point to graviton mass in this range, [43][44][45].…”

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confidence: 99%

Dark matter and dark energy from a Bose–Einstein condensate

Das

Bhaduri

2015

Class. Quantum Grav.

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We show that Dark Matter consisting of bosons of mass of about 1 eV or less has critical temperature exceeding the temperature of the universe at all times, and hence would have formed a Bose-Einstein condensate at very early epochs. We also show that the wavefunction of this condensate, via the quantum potential it produces, gives rise to a cosmological constant which may account for the correct dark energy content of our universe. We argue that massive gravitons or axions are viable candidates for these constituents. In the far future this condensate is all that remains of our universe.The basic contents of our universe in terms of Dark Matter (DM), Dark Energy (DE), visible matter and radiation, and also its accelerated expansion in recent epochs has been firmly established by a number of observations now [1][2][3][4]. However although DM constitutes about 25% and DE about 70% of all matter-energy content, the constituents of DM and the origin of a tiny cosmological constant, or DE, of the order of 10 −123 in Planck units, which drives this acceleration, remains to be understood. In this paper we show that if DM is assumed to consist of a gas of bosons of mass m, then for m ≤ 1eV , the critical temperature below which they will form a Bose-Einstein condensate (BEC) exceeds the temperature of the universe at all times. Therefore they would form such a condensate at very early epochs, in which a macroscopic fraction of the bosons fall to the ground state with little or no momentum and zero pressure, and therefore may be considered as viable candidates for cold DM (CDM). Further, via the quantum potential that it produces, the macroscopic wavefunction of the condensate gives rise to a positive cosmological constant in the Friedmann equation, whose magnitude depends on m, and for m ≃ 10 −32 eV , one obtains the observed value of the cosmological constant. Therefore bosons with this tiny mass can account for both DM and DE in our universe. We argue that massive gravitons or axions are viable candidates for these bosons. Finally we speculate on the ultimate fate of our universe, and end with some open problems.To compute the critical temperature of an ideal gas of bosons constituting DM, we first note that these must have a mass, however small, and with average interparticle distances (N/V ) −1/3 (where N = total number of bosons in volume V ) comparable or smaller than the * email: saurya.das@uleth.ca † email: bhaduri@physics.mcmaster.ca thermal de Broglie wavelength hc/k B T , such that quantum effects start to dominate. Identifying this temperature of a bosonic gas to the critical temperature T c (below which the condensate forms) we get k B T c ≃ hc(N/V ) 1/3 . A more careful calculation for ultra-relativistic noninteracting bosons with a tiny mass gives [5][6][7] In the above N = N B + N R , N B being the number of bosons in the BEC, and N R outside it, both consisting of bosons of small mass as discussed earlier, η is the polarization factor and ζ(3) ≈ 1.2. Also a is the cosmological scale factor, L = L 0 a i...

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Cosmological behavior in extended nonlinear massive gravity

Cited by 103 publications

References 62 publications

Nonlinear stability of cosmological solutions in massive gravity

Nonlinear stability of cosmological solutions in massive gravity

On the Phenomenology of an Accelerated Large-Scale Universe

Dark matter and dark energy from a Bose–Einstein condensate

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