Ref HAL: hal-00009471_v1
Ref Arxiv: astro-ph/0404043
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

We consider Double Quintessence models for which the Dark Energy sector consists of two coupled scalar fields. We study in particular the possibility to have a transient acceleration in these models. In both Double Quintessence models studied here, it is shown that if acceleration occurs, it is necessarily transient. We consider also the possibility to have transient acceleration in two one-field models, the Albrecht-Skordis model and the pure exponential. Using separate conservative constraints (marginalizing over the other parameters) on the effective equation of state $w_{eff}$, the relative density of the Dark Energy $\\Omega_{Q,0}$ and the present age of the universe, we construct scenarios with a transient acceleration that has already ended at the present time, and even with no acceleration at all, but a less conservative analysis using the CMB data rules out the last possibility. The scenario with a transient acceleration ended by today, can be implemented for the range of cosmological parameters $\\Omega_{m,0}\\gtrsim 0.35$ and $h\\lesssim 0.68$.

Commentaires: 22 pages, 10 figures, 4 tables

Ref HAL: hal-00008562_v1
Ref Arxiv: astro-ph/0303330
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

Depending on various assumptions on the energy scale of inflation and assuming a primordial power spectrum of a Broken Scale Invariance (BSI) type, we explore the possibility for Primordial Black Holes (PBH) and Planck relics to contribute substantially to cold dark matter in the Universe. A recently proposed possibility to produce planck relics in 4-dimensional string gravity is considered. Possible experimental detection through gravitational waves is further explored. We stress that inflation with a low energy scale, and also possibly when Planck relics are produced, leads unavoidably to relics originating from PBHs that are not effectively classical during their formation, rendering the usual formalism inadequate for them.

Commentaires: 10 pages

Ref HAL: hal-00008561_v1
Ref Arxiv: astro-ph/0210149
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

We consider the observational constraints from the detection of antiprotons in the Galaxy on the amount of Primordial Black Holes (PBH) produced from primordial power spectra with a bumpy mass variance. Though essentially equivalent at the present time to the constraints from the diffuse $\\gamma$-ray background, they allow a widely independent approach and they should improve sensibly in the nearby future. We discuss the resulting constraints on inflationary parameters using a Broken Scale Invariance (BSI) model as a concrete example.

Commentaires: 10 pages, 3 figures

Ref Arxiv: astro-ph/0206262
DOI: 10.1103/PhysRevD.67.024024
WoS: 000181015700048
Ref. & Cit.: NASA ADS
52 Citations
Résumé:

We perform an accurate computation of the production rate for primordial black holes (PBHs). The reason is that the underlying mass variance had been overestimated systematically, as was shown recently. For scale-free powerlaw primordial spectra, and for a Universe with critical density, the mass variance is less than 34% of its value thought earlier for the spectral index in the range $1\leq n\leq 1.3$. We then extend our study to spectra with a characteristic scale and find the accurate shape of the corresponding mass variance. For a pure step in the primordial spectrum, the step in the variance is smoothed around the characteristic scale $k_s$. For a spectrum with large oscillations near $k_s$, we find a pronounced bump in the variance. This could yield a significant part of the cold dark matter in the form of PBHs with mass $M$ in the range $5\times 10^{15} {\rm g}\lesssim M \lesssim 10^{21} {\rm g}$.

Ref Arxiv: astro-ph/0203520
DOI: 10.1016/S0370-2693(02)01803-8
WoS: 000176094400003
Ref. & Cit.: NASA ADS
63 Citations
Résumé:

The computation of PBH (primordial black hole) production from primordial perturbations has recently been improved by considering a more accurate relation between the primordial power spectrum and the PBH mass variance. We present here exact expressions which are valid for primordial spectra of arbitrary shape and which allow accurate numerical calculations. We then consider the possibility to have a significant part of dark matter in the form of PBHs produced by a primordial spectrum of inflationary origin possessing a characteristic scale. We show that in this model the relevant PBH mass is constrained to lie in the range $5\times 10^{15} {\rm g}\lesssim M \lesssim 10^{21} {\rm g}$. This is much less than the mass range coming from the QCD phase transition, allowing the two mechanisms to be easily distinguished.

Ref Arxiv: astro-ph/0112328
DOI: 10.1016/S0370-2693(02)01200-5
WoS: 000174479000004
Ref. & Cit.: NASA ADS
9 Citations
Résumé:

General expressions are given for the generation of Primordial Black Holes (PBH) in a universe with a presently accelerated expansion due to a(n effective) cosmological constant. We give expressions both for a powerlaw scalefree primordial spectrum and for spectra which are not of that type. Specializing to the case of a pure cosmological constant $\Lambda$ and assuming flatness, we show that a comological constant with $\Omega_{\Lambda,0}=0.7$ will decrease the mass variance at the PBH formation time by about 15% compared with a critical density universe.

Ref Arxiv: astro-ph/0109404
DOI: 10.1103/PhysRevD.65.024008
WoS: 000173402500044
Ref. & Cit.: NASA ADS
33 Citations
Résumé:

We review the formalism of primordial black holes (PBHs) production and show that the mass variance at horizon crossing has been systematically overestimated in previous studies. We derive the correct expression. The difference is maximal at the earliest formation times and still very significant for PBH masses $\sim 10^{15}$g, an accurate estimate requiring numerical calculations. In particular, this would lead to weaker constraints on the spectral index $n$. We then derive constraints on inflationary models from the fact that primordial black holes must not overclose the Universe. This is done both for the scale-free case of the power spectrum studied earlier and for the case where a step in the mass variance is superimposed. In the former case we find various constraints on $n$, depending on the parameters. In the latter case these limits can be much more strengthened, so that one could find from an observational limit on $n$ a constraint on the allowed height of the step.