We discuss the near singularity region of the linear mass Vaidya metric for massless particles with nonzero angular momentum. In particular we look at massless geodesics near the vanishing point of a special subclass of linear mass Vaidya metrics. We also investigate this same structure in the numerical solutions for the scattering of the Maxwell field from the singularity. In both cases we find that the null-singularity effectively becomes repulsive close to the final vanishing point leading us to argue that this metric could be plausibly used as a semi-classical model for the endpoint of black hole evaporation.
COBISS.SI-ID: 3722491
To interpret the mean depth of cosmic ray air shower maximum and its dispersion, we parametrize those two observables as functions of the first two moments of the ln A distribution. We examine the goodness of this simple method through simulations of test mass distributions. The application of the parameterization to Pierre Auger Observatory data allows one to study the energy dependence of the mean ln A and of its variance under the assumption of selected hadronic interaction models. We discuss possible implications of these dependencies in term of interaction models and astrophysical cosmic ray sources.
COBISS.SI-ID: 2692859
The surface detector array of the Pierre Auger Observatory provides information about the longitudinal development of the muonic component of extensive air showers. Using the timing information from the flash analogtodigital converter traces of surface detectors far from the shower core, it is possible to reconstruct a muon production depth distribution. We characterize the goodness of this reconstruction for zenith angles around 60° and different energies of the primary particle. From these distributions, we define Xμ max as the depth along the shower axis where the production of muons reaches maximum. We explore the potentiality of Xμ max as a useful observable to infer the mass composition of ultrahighenergy cosmic rays. Likewise, we assess its ability to constrain hadronic interaction models.
COBISS.SI-ID: 3494395
We revisit the theory of null shells in general relativity, with a particular emphasis on null shells placed at horizons of black holes. We study in detail the considerable freedom that is available in the case that one solders two metrics together across null hypersurfaces (such as Killing horizons) for which the induced metric is invariant under translations along the null generators.
COBISS.SI-ID: 4159995
Neutrinos in the cosmic ray flux with energies near 1 EeV and above are detectable with the Surface Detector array (SD) of the Pierre Auger Observatory. We report here on searches through Auger data from 1 January 2004 until 20 June 2013. No neutrino candidates were found, yielding a limit to the diffuse flux of ultrahigh energy neutrinos that challenges the Waxman-Bahcall bound predictions.
COBISS.SI-ID: 3928571