Attractors and isocurvature perturbations in quintessence models

Abramo, L. Raul; Finelli⋆, F.

doi:10.1103/physrevd.64.083513

Cited by 47 publications

(49 citation statements)

References 42 publications

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“…(9) shows that the growing mode of perturbation during the scaling regime accompanies the adiabatic (δ v ) as well as the isocurvature (S rφ ) modes; this is in contrast with the assumption made in [23], and the result in [31] * . * The work in [31] was made in the zero-shear gauge which fixes the scalar-type shear of the normal hypersurface χ equal to zero [36,40]. δ f in the zero-shear gauge is the same as δ f χ ≡ δ f +3(1+w)Hχ.…”

Section: Perturbed Equationscontrasting

confidence: 46%

“…Although the scaling by itself cannot explain the acceleration in the present epoch, since the scaling works as an attractor we find many implementation of quintessence idea having such an attractor in the early evolution stage. The evolution of perturbation during the scaling regime as well as the following quintessential development has been actively studied in recent literature [3,5,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34].…”

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Quintessential perturbations during scaling regime

2001

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The scalar field with an exponential potential allows a scaling solution where the the density of the field follows the density of the dominating fluid. Such a scaling regime is often used as an important ingredient in many models of quintessence. We analyse evolution of perturbations while the background follows the scaling. As the results, the perturbed scalar field also scales with the perturbed fluid, and the perturbations accompany the adiabatic as well as the isocurvature mode between the fluid and the field.PACS numbers: 98.80. Hw, Recent observational advances in high redshift supernovae, and the small angular-scale CMBR temperature anisotropy had spurred renewed interest in the possible acceleration of the present day universe. The cosmological constant would be the first available and historically well studied explanation for such an unexpected state of the present universe. In order to make the universe to start accelerating only in the latest moment in logarithmic time interval we need high level of fine tuning of the amount of the cosmological constant. In a way to avoid such a fine tuning a new paradigm of simulating the late acceleration based on a minimally coupled scalar field has been proposed, with such a field termed a quintessence. Although the prime motivation of reducing the fine tuning problem has not been quite successful, we notice a variety of roles the field with different potential could achieve diverse evolutions of the world model [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].It has been known that an exponential potential supports a scaling attractor regime where the density of the field follows the density of the dominating fluid in the background [1][2][3][4]. Although the scaling by itself cannot explain the acceleration in the present epoch, since the scaling works as an attractor we find many implementation of quintessence idea having such an attractor in the early evolution stage. The evolution of perturbation during the scaling regime as well as the following quintessential development has been actively studied in recent literature [3,5,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34].In this paper we study the evolution of perturbations in a fluid-field system with an exponential field potential. We will show that the conventional growing and decaying solutions of the fluid without the field remain valid with two additional decaying solutions due to the coupling, eqs. (7,13,16). The perturbed scalar field also scales the perturbed density field of the fluid, eqs. (8,14,17). As a result we show that while the background evolution follows the scaling solution the perturbations accompany both the adiabatic and the isocurvature modes, eqs. (9,15,18). In order to make the paper self contained, and for future convenient usage, the notations and basic set of equations are summarized in the Appendix. Perturbed equations:The pressureless matter (c) or the radiation (r) dominated eras in three component system (r, c and a scalar field φ) can be hand...

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Section: Perturbed Equationscontrasting

confidence: 46%

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confidence: 99%

Quintessential perturbations during scaling regime

2001

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“…If the field is a tracker, the initial conditions may indeed be irrelevant also for the perturbed field. However, for minimally coupled fields it has been shown that in some instances this is not the case [41,42], while isocurvature perturbations in coupled quintessence remain to be systematically studied.…”

Section: B Perturbation Evolutionmentioning

confidence: 99%

Growth of perturbations in dark matter coupled with quintessence

2005

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We consider the evolution of linear perturbations in models with a nonminimal coupling between dark matter and scalar field dark energy. Growth of matter inhomogeneities in two examples of such models proposed in the literature are investigated in detail. Both of these models are based on a low-energy limit of effective string theory action, and have been previously shown to naturally lead to late acceleration of the universe. However, we find that these models can be ruled out by taking properly into account the impact of the scalar field coupling on the formation of structure in the dark matter density. In particular, when the transition to acceleration in these models begins, the interaction with dark energy enchances the small scale clustering in dark matter much too strongly. We discuss also the role of an effective small scale sound speed squared and the issue of adiabatic initial conditions in models with a coupled dark sector.

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“…This becomes a source of the CMB anisotropy through the Sachs-Wolfe effect. When the slow-roll condition is satisfied for the quintessence,δ Q (k) is approximated as 9) and it changes its behavior at the scale k phys ∼ H 0 or at k phys ∼ Λ 2 /f Q , as a consequence of the scale dependence ofq. Now, we consider the CMB anisotropy in the case with the isocurvature mode.…”

Section: Isocurvature Modementioning

confidence: 99%

“…[6]. #2 Abramo and Finelli [9] studied the isocurvature fluctuations for tracker-type quintessence models without considering the evolution of the tracker field and its fluctuations during inflation.…”

Section: Introductionmentioning

confidence: 99%

Cosmic microwave background anisotropy with cosine-type quintessence

2001

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We study the Cosmic Microwave Background (CMB) anisotropies produced by cosine-type quintessence models. In our analysis, effects of the adiabatic and isocurvature fluctuations are both taken into account. For purely adiabatic fluctuations with scale invariant spectrum, we obtain a stringent constraint on the model parameters using the CMB data from COBE, BOOMERanG and MAXIMA. Furthermore, it is shown that isocurvature fluctuations have significant effects on the CMB angular power spectrum at low multipoles in some parameter space, which may be detectable in future satellite experiments. Such a signal may be used to test the cosine-type quintessence models.

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Attractors and isocurvature perturbations in quintessence models

Cited by 47 publications

References 42 publications

Quintessential perturbations during scaling regime

Quintessential perturbations during scaling regime

Growth of perturbations in dark matter coupled with quintessence

Cosmic microwave background anisotropy with cosine-type quintessence

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