Alternatives to quintessence model building

Avelino, P. P.; Beça, L. M. G.; Carvalho, J. P. M. de; Martins, C. J. A. P.; Pinto, Philip A.

doi:10.1103/physrevd.67.023511

Cited by 93 publications

(75 citation statements)

References 32 publications

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“…The case, where the Chaplygin gas is mixed with CDM, has been considered in a number of papers [23,24,25,26,27,28,29,30]. Here, the Chaplygin gas simply plays the role of DE.…”

Section: Introductionmentioning

confidence: 99%

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Cosmological tachyon condensation

2009

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We consider the prospects for dark matter/energy unification in k-essence type cosmologies. General mappings are established between the k-essence scalar field, the hydrodynamic and braneworld descriptions. We develop an extension of the general relativistic dust model that incorporates the effects of both pressure and the associated acoustic horizon. Applying this to a tachyon model, we show that this inhomogeneous "variable Chaplygin gas" does evolve into a mixed system containing cold dark matter like gravitational condensate in significant quantities. Our methods can be applied to any dark energy model, as well as to mixtures of dark energy and traditional dark matter.

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“…The case, where the Chaplygin gas is mixed with CDM, has been considered in a number of papers [23,24,25,26,27,28,29,30]. Here, the Chaplygin gas simply plays the role of DE.…”

Section: Introductionmentioning

confidence: 99%

“…In keeping with the quartessence philosophy, it would be preferred if CDM could be replaced by droplets of Chaplygin gas condensate, as in [31]. Homogeneous world models, containing a mixture of CDM and Chaplygin gas, have been successfully confronted with lensing statistics [23,24] as well as with supernova and other tests [25,26].…”

Section: Introductionmentioning

confidence: 99%

Cosmological tachyon condensation

2009

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“…In this short paper we apply that diagnostic to Chaplygin cosmological models (the direct comparison of the already available supernova data with the Chaplygin gas model was also undertaken recently in [16,17]). We consider both the one-fluid pure Chaplygin gas model and a two-fluid model where dust is present as well.…”

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confidence: 99%

Can the Chaplygin gas be a plausible model for dark energy?

2003

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In this note two cosmological models representing the flat Friedmann Universe filled with a Chaplygin fluid, with or without dust, are analyzed in terms of the recently proposed "statefinder" parameters [1]. Trajectories of both models in the parameter plane are shown to be significantly different w.r.t. "quiessence" and "tracker" models. The generalized Chaplygin gas model with an equation of state of the form p = −A/ρ α is also analyzed in terms of the statefinder parameters. PACS numbers: 98.80. Es, 98.80.Cq, 98.80.Hw In the search for cosmological models describing the observed cosmic acceleration [2,3,4], the inspiration coming from inflation has suggested mainly models making use of scalar fields [5,6,7,8,9]. There are of course alternatives; in particular, in [10,11,12] an elementary model has been presented describing a Friedmann universe filled with a perfect fluid obeying the Chaplygin equation of statewhere A is a positive constant (for a thorough review see Ref.[13]). The interesting feature of this model is that it naturally provides a universe that undergoes a transition from a decelerating phase, driven by dust-like matter, to a cosmic acceleration at later stages of its evolution (see [10] for details). An interesting attempt to justify this model [14] makes use of an effective field theory for a three-brane universe [15]. In the flat case, the model can be equivalently described in terms of a homogeneous minimally coupled scalar field φ, with potential [10]However, since models trying to provide a description (if not an explanation) of the cosmic acceleration are proliferating, there exists the problem of discriminating between the various contenders. To this aim a new proposal introduced in [1] makes use of a pair of parameters {r, s}, called "statefinder". The relevant definition is as follows:where H ≡ȧ a is the Hubble constant and q ≡ −ä aH 2 is the deceleration parameter. The new feature of the statefinder is that it involves the third derivative of the cosmological radius.

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“…The repulsive nature of Λ could be responsible for the acceleration of the universe as demonstrated in (14). Although introduced into physics in 1917, the physical basis for a cosmological constant remained a bit of a mystery until the 1960's, when it was realised that zero-point vacuum fluctuations must respect Lorenz invariance and therefore have the form T ik = Λg ik [214].…”

Section: The Cosmological Constant and Vacuum Energymentioning

confidence: 99%

“…(The constant α regulates the transition time in the equation of state.) WMAP, supernovae and large scale sructure data have all been used to test Chaplygin gas models; see [27,65,78,9,14,22,115,128,56,25]. …”

Section: Chaplygin Gasmentioning

confidence: 99%

The Physics of the Early Universe

Papantonopoulos¹

2005

Lecture Notes in Physics

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Abstract. I briefly review our current understanding of dark matter and dark energy. The first part of this paper focusses on issues pertaining to dark matter including observational evidence for its existence, current constraints and the 'abundance of substructure' and 'cuspy core' issues which arise in CDM. I also briefly describe MOND. The second part of this review focusses on dark energy. In this part I discuss the significance of the cosmological constant problem which leads to a predicted value of the cosmological constant which is almost 10 123 times larger than the observed value Λ/8πG ≃ 10 −47 GeV 4 . Setting Λ to this small value ensures that the acceleration of the universe is a fairly recent phenomenon giving rise to the 'cosmic coincidence' conundrum according to which we live during a special epoch when the density in matter and Λ are almost equal. Anthropic arguments are briefly discussed but more emphasis is placed upon dynamical dark energy models in which the equation of state is time dependent. These include Quintessence, Braneworld models, Chaplygin gas and Phantom energy. Model independent methods to determine the cosmic equation of state and the Statefinder diagnostic are also discussed. The Statefinder has the attractive property ... a /aH 3 = 1 for LCDM, which is helpful for differentiating between LCDM and rival dark energy models. The review ends with a brief discussion of the fate of the universe in dark energy models.

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Alternatives to quintessence model building

Cited by 93 publications

References 32 publications

Cosmological tachyon condensation

Cosmological tachyon condensation

Can the Chaplygin gas be a plausible model for dark energy?

The Physics of the Early Universe

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