16639684
Escape of photons from two fixed extreme Reissner-Nordström black holes
We study the scattering of light (null geodesics) by two fixed extreme Reissner-Nordstr¨ black holes, in which the gravitational attraction of their masses is exactly balanced with the electrostatic repulsion of their charges, allowing a static spacetime. We identify the set of unstable periodic orbits that form part of the fractal repeller that completely describes the chaotic escape dynamics of photons. In the framework of periodic orbit theory, the analysis of the linear stability of the unstable periodic orbits is used to obtain the main quantities of chaos that characterize the escape dynamics of the photons scattered by the black holes. In particular, the escape rate which is compared with the result obtained from numerical simulations that consider statistical ensembles of photons. We also analyze the dynamics of photons in the proximity of a perturbed black hole and give an analytic estimate of the escape rate in this system.
120244125
Scattering of photons in a two fixed extreme Reissner‐Nordstrom black hole system
We study the scattering of light by two fixed extreme Reissner‐Nordstrom black holes. We identify the set of unstable periodic orbits of the fractal repeller that describes the chaotic escape dynamics of photons. The main quantities of chaos associated with the repeller are obtained from the analysis of the linear stability of these orbits. The escape rate obtained from the periodic orbit theory is compared with the one obtained from the evolution of statistical ensembles of photons. An analytic estimate of the escape rate in the proximity of a perturbed black hole is also provided.
118678609
CUTE solutions for two-point correlation functions from large cosmological datasets
In the advent of new large galaxy surveys, which will produce enormous datasets with hundreds of millions of objects, new computational techniques are necessary in order to extract from them any two-point statistic, the computational time of which grows with the square of the number of objects to be correlated. Fortunately technology now provides multiple means to massively parallelize this problem. Here we present a free-source code specifically designed for this kind of calculations. Two implementations are provided: one for execution on shared-memory machines using OpenMP and one that runs on graphical processing units (GPUs) using CUDA. The code is available at this http URL
55695164
Halo abundances and shear in void models
Abstract We study the non-linear gravitational collapse of dark matter into halos through numerical N-body simulations of Lemaitre–Tolman–Bondi void models. We extend the halo mass function formalism to these models in a consistent way. This extension not only compares well with the simulated data at all times and radii, but it also gives interesting clues about the impact of the background shear on the growth of perturbations. Our results give hints about the possibility of constraining the background shear via cluster number counts, which could then give rise to strong constraints on general inhomogeneous models, of any scale.