Primary cosmic-ray elemental spectra have been measured with the balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment since 2004. The third CREAM payload (CREAM-III) flew for 29 days ...during the 2007-2008 Antarctic season. Energies of incident particles above 1 TeV are measured with a calorimeter. Individual elements are clearly separated with a charge resolution of ∼0.12 e (in charge units) and ∼0.14 e for protons and helium nuclei, respectively, using two layers of silicon charge detectors. The measured proton and helium energy spectra at the top of the atmosphere are harder than other existing measurements at a few tens of GeV. The relative abundance of protons to helium nuclei is 9.53 0.03 for the range of 1 TeV/n to 63 TeV/n. This ratio is considerably smaller than other measurements at a few tens of GeV/n. The spectra become softer above ∼20 TeV. However, our statistical uncertainties are large at these energies and more data are needed.
The primordial spectrum of cosmological tensor perturbations is considered as a possible probe of quantum gravity effects. Together with string theory, loop quantum gravity is one of the most ...promising frameworks to study quantum effects in the early universe. We show that the associated corrections should modify the potential seen by gravitational waves during the inflationary amplification. The resulting power spectrum should exhibit a characteristic tilt. This opens a new window for cosmological tests of quantum gravity.
Cosmic ray antiprotons provide an important probe for the study of the galactic Dark Matter, as they could be produced by exotic sources. On the other hand, antiprotons are anyway produced by ...standard nuclear reactions of cosmic ray nuclei on interstellar matter. This process is responsible for a background flux that must be carefully determined to estimate the detectability of an hypothetical exotic signal. Estimates of this background suffer from potential uncertainties of various origins. The propagation of cosmic antiprotons depends on several physical characteristics of the Galaxy which are poorly known. Antiprotons are created from cosmic protons and helium nuclei whose fluxes were not measured with great accuracy until very recently. Calculations of antiproton fluxes make use of nuclear physics models with their own shortcomings and uncertainties. The goal of this paper is to give a new evaluation of the cosmic antiproton flux along with the associated uncertainties. The propagation parameters were tightly constrained in Maurin et al. 2001 by an analysis of cosmic ray nuclei data in the framework of a two-zone diffusion model and we apply these parameters to the propagation of antiprotons. We use the recently published data on proton and helion fluxes, and we find that this particular source of uncertainty has become negligible. The Monte Carlo program DTUNUC was used to carefully examine nuclear reactions. We find that all the cosmic antiproton fluxes naturally coming out of the calculation are fully compatible with experimental data. Uncertainties in this flux have been strongly reduced. Those related to propagation are less than 25%. All other possible sources of uncertainty have also been studied.
This Letter aims at showing that the observation of evaporating black holes should allow the usual Hawking behavior to be distinguished from loop quantum gravity (LQG) expectations. We present a full ...Monte Carlo simulation of the evaporation in LQG and statistical tests that discriminate between competing models. We conclude that contrarily to what was commonly thought, the discreteness of the area in LQG leads to characteristic features that qualify evaporating black holes as objects that could reveal quantum gravity footprints.
Quantum bound states around black holes Grain, J.; Barrau, A.
The European physical journal. C, Particles and fields,
02/2008, Letnik:
53, Številka:
4
Journal Article
Recenzirano
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Quantum mechanics in the vicinity of black holes is a fascinating field of theoretical physics. It involves both general relativity and particle physics, opening new eras to establish the principles ...of unified theories. In this article, we show that quantum bound states with no classical equivalent – as can easily be seen at the dominant monopolar order – should be formed around black holes for massive scalar particles. We qualitatively investigate some important physical consequences, in particular for the Hawking evaporation mechanism and the associated greybody factors.
The Gauss–Bonnet invariant is one of the most promising candidates for a quadratic curvature correction to the Einstein action in expansions of supersymmetric string theory. We study the evaporation ...of such Schwarzschild–Gauss–Bonnet black holes which could be formed at future colliders if the Planck scale is of order of TeV, as predicted by some modern brane world models. We show that, beyond the dimensionality of space, the corresponding coupling constant could be measured by the LHC. This opens new windows for physics investigation in spite of the possible screening of microphysics due to the event horizon.
Planck star phenomenology Barrau, Aurélien; Rovelli, Carlo
Physics letters. B,
12/2014, Letnik:
739
Journal Article
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It is possible that black holes hide a core of Planckian density, sustained by quantum-gravitational pressure. As a black hole evaporates, the core remembers the initial mass and the final explosion ...occurs at macroscopic scale. We investigate possible phenomenological consequences of this idea. Under several rough assumptions, we estimate that up to several short gamma-ray bursts per day, around 10 MeV, with isotropic distribution, can be expected coming from a region of a few hundred light years around us.
There is a wide consensus on the correct dynamics of the background in loop quantum cosmology. In this article we make a systematic investigation of the duration of inflation by varying what we think ...to be the most important “unknowns” of the model: the way to set initial conditions, the amount of shear at the bounce and the shape of the inflaton potential.
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