Together with holonomy corrections, inverse volume terms should be taken into account when studying the primordial universe in loop quantum cosmology. We investigate how the tensor power spectrum is ...modified with respect to the standard general relativistic prediction by those semi-classical corrections. Depending on the values of the free parameters of the model, it is shown that the spectrum can exhibit a very large deviation from its usual shape, in particular with a very red slope and a strong running in the infrared limit.
Loop quantum cosmology with a scalar field is known to be closely linked with an inflationary phase. In this article, we study probabilistic predictions for the duration of slow-roll inflation, by ...assuming a minimalist massive scalar field as the main content of the Universe. The phase of the field in its "prebounce" oscillatory state is taken as a natural random parameter. We find that the probability for a given number of inflationary e-folds is quite sharply peaked around 145, which is consistent with the most favored minimum values. In this precise sense, a satisfactory inflation is therefore a clear prediction of loop gravity. In addition, we derive an original and stringent upper limit on the Barbero-Immirzi parameter. The general picture of inflation, superinflation, deflation, and superdeflation is also much clarified in the framework of bouncing cosmologies.
Using Monte Carlo simulations, we compute the integrated emission spectra of black holes in the framework of Loop Quantum Gravity (LQG). The black hole emission rates are governed by the entropy ...whose value, in recent holographic loop quantum gravity models, was shown to agree at leading order with the Bekenstein-Hawking entropy. Quantum corrections depend on the Barbero-Immirzi parameter γ. Starting with black holes of initial horizon area A ∼ 10 2 in Planck units, we present the spectra for different values of γ. Each spectrum clearly decomposes in two distinct parts: a continuous background which corresponds to the semi-classical stages of the evaporation and a series of discrete peaks which constitutes a signature of the deep quantum structure of the black hole. We show that γ has an effect on both parts that we analyze in details. Finally, we estimate the number of black holes and the instrumental resolution required to experimentally distinguish between the considered models.
Antiprotons from primordial black holes Barrau, A.; Boudoul, G.; Donato, F. ...
Astronomy and astrophysics (Berlin),
06/2002, Letnik:
388, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Primordial black holes (pbhs) have motivated many studies since it was shown that they should evaporate and produce all kinds of particles (Hawking CITE). Recent experimental measurements of cosmic ...rays with great accuracy, theoretical investigations on the possible formation mechanisms and detailed evaporation processes have revived the interest in such astrophysical objects. This article aims to use the latest developments in antiproton propagation models (Maurin et al. CITE; Donato et al. CITE) together with new data from BESS, CAPRICE and AMS experiments to constrain the local amount of pbh dark matter. Depending on the diffusion halo parameters and on the details of the emission mechanisms, we derive an average upper limit of the order of $\rho_{\odot}^{\rm PBH}\approx 1.7\times10^{-33}$g cm-3.
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