Interactions in scalar field cosmology

Billyard, Andrew; Coley, A. A.

doi:10.1103/physrevd.61.083503

Cited by 221 publications

(260 citation statements)

References 39 publications

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“…One is the scalar potential and the other one contains products of the derivatives of the scalar field, both going as 1/r 2 . Furthermore, as (Φ ,r ) 2 ∼ 1/r 2 , this means that Φ ∼ ln(r), implying that the scalar potential is exponential V ∼ exp(2αΦ) such as has been found useful for structure formation scenarios [9,10] and scaling solutions with a primordial scalar field in the cosmological context [9][10][11][12] including quintessential scenarios [13]. Thus, the particular solution for the system (10 -13) that we are considering is…”

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confidence: 89%

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Spherical scalar field halo in galaxies

2000

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We study a spherically symmetric fluctuation of scalar dark matter in the cosmos and show that it could be the dark matter in galaxies, provided that the scalar field has an exponential potential whose overall sign is negative and whose exponent is constrained observationally by the rotation velocities of galaxies. The local space-time of the fluctuation contains a three dimensional space-like hypersurface with surplus of angle.PACS numbers: 95.35.+d, 95.35.G.The existence of dark matter in the Universe has been firmly established by astronomical observations at very different length-scales, ranging from single galaxies, to clusters of galaxies, up to cosmological scale (see for example [1]). A large fraction of the mass needed to produce the observed dynamical effects in all these very different systems is not seen. At the galactic scale, the problem is clearly posed: The measurements of rotation curves (tangential velocities of objects) in spiral galaxies show that the coplanar orbital motion of gas in the outer parts of these galaxies keeps a more or less constant velocity up to several luminous radii [2], forming a radii independent curve in the outer parts of the rotational curves profile; a motion which does not correspond to the one due to the observed matter distribution, hence there must be present some type of dark matter causing the observed motion. The flat profile of the rotational curves is maybe the main feature observed in many galaxies. It is believed that the dark matter in galaxies has an almost spherical distribution which decays like 1/r 2 . With this distribution of some kind of matter it is possible to fit the rotational curves of galaxies quite well [3]. Nevertheless, the main question of the dark matter problem remains; which is the nature of the dark matter in galaxies? The problem is not easy to solve, it is not sufficient to find out an exotic particle which could exist in galaxies in the low energy regime of some theory. It is necessary to show as well, that this particle (baryonic or exotic) distributes in a very similar manner in all these galaxies, and finally, to give some reason for its existence in galaxies.In previous works it has been explored, with considerable success, the possibility that scalar fields could be the dark matter in spiral galaxies by assuming that the scalar dark matter distributes as an axially symmetric halo [4,5]. The idea of these works is to explore whether a scalar field can fluctuate along the history of the Universe and thus forming concentrations of scalar field density. If, for example, the scalar field evolves with a scalar field potential V (Φ) ∼ Φ 2 , the evolution of this scalar field will be similar to the evolution of a perfect fluid with equation of state p = 0, i.e., it would evolve as cold dark matter [6]. However, it is not clear whether a spherical scalar field fluctuation can serve as dark matter in galaxies. In this letter we show that this could be the case. We assume that the halo of a galaxy is a spherical fluctuation of cosmologica...

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confidence: 89%

“…In order to solve equations (11)(12)(13), observe that the combination of the previous equations [(2 − l)(eq. 11)−4 (eq.…”

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confidence: 99%

Spherical scalar field halo in galaxies

2000

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“…these equations together with (12) close the problem to find the potential V and the scalar field φ as functions of t. Expressing the potential (17) and field (18) in terms of the cosmological time, that is V = Ω φa (3H 2 +Ḣ) anḋ φ 2 = −2Ω φaḢ , it is easy to find for the superattractor solution…”

Section: Qddm Superattractor Scenariomentioning

confidence: 99%

“…Perfect fluid behavior occurs in the limit ν → ∞, and a consistent hydrodynamical description of the fluids requires ν > 1. Rewriting (12) in terms of the field baryotropic index γ φ , we get…”

Section: Qddm Superattractor Scenariomentioning

confidence: 99%

Quintessence dissipative superattractor cosmology

Chimento¹,

Jakubi²,

Zuccalá³

2001

Phys. Rev. D

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We investigate the simplest quintessence dissipative dark matter attractor cosmology characterized by a constant quintessence baryotropic index and a power-law expansion. We show that a class of accelerated coincidence-solving attractor solutions converge into this asymptotic behavior. Despite of its simplicity, such "superattractor" regime provides a model of the recent universe that also exhibits an excellent fit to supernovae luminosity observations and no age conflict. Our best fit gives α = 1.71 ± 0.29 for the power-law exponent. We calculate for this regime the evolution of density and entropy fluctuations. PACS number(s): 98.80.Hw, 04.20Jb 1

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“…In this work we assume that w = const, as we want to consider the simplest possible setup, in order to understand the basic effects of dark energy. The extension to the full time-varying w and/or time-varying cosmological constant [42][43][44][45][46], as well as the incorporation of possible dark-energy dark-matter interactions [47][48][49][50] and the corresponding complicated analysis, will follow in a subsequent work.…”

Section: Thermodynamic Instabilities and Dark Energymentioning

confidence: 99%

Galaxy clusters and structure formation in quintessence versus phantom dark energy universe

et al. 2014

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The self-gravitating gas in the Newtonian limit is studied in the presence of dark energy with a linear and constant equation of state. Entropy extremization associates to the isothermal Boltzmann distribution an effective density that includes 'dark energy particles', which either strengthen or weaken mutual gravitational attraction, in case of quintessence or phantom dark energy, respectively, that satisfy a linear equation of state. Stability is studied for microcanonical (fixed energy) and canonical (fixed temperature) ensembles. Compared to the previously studied cosmological constant case, in the present work it is found that quintessence increases, while phantom dark energy decreases the instability domain under gravitational collapse. Thus, structures are more easily formed in a quintessence rather than in a phantom dominated Universe. Assuming that galaxy clusters are spherical, nearly isothermal and in hydrostatic equilibrium we find that dark energy with a linear and constant equation of state, for fixed radius, mass and temperature, steepens their total density profile! In case of a cosmological constant, this effect accounts for a 1.5% increase in the density contrast, that is the center to edge density ratio of the cluster. We also propose a method to constrain phantom dark energy.

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Interactions in scalar field cosmology

Cited by 221 publications

References 39 publications

Spherical scalar field halo in galaxies

Spherical scalar field halo in galaxies

Quintessence dissipative superattractor cosmology

Galaxy clusters and structure formation in quintessence versus phantom dark energy universe

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