47,274 research outputs found
Pop III GRBs: an estimative of the event rate for future surveys
We discuss the theoretical event rate of gamma-ray bursts (GRBs) from the
collapse of massive primordial stars. We construct a theoretical model to
calculate the rate and detectability of these GRBs taking into account all
important feedback and recent results from numerical simulations of pristine
gas. We expect to observe a maximum of N 0.2 GRBs per year
integrated over at z > 6 with \textit{Swift} and N 10 GRBs per year
integrated over at z > 6 with EXIST.Comment: 6 pages, 2 figures, published in Proceedings of the Gamma-Ray Bursts
2012 Conference (GRB 2012
Discrete and finite Genral Relativity
We develop the General Theory of Relativity in a formalism with extended
causality that describes physical interaction through discrete, transversal and
localized pointlike fields. The homogeneous field equations are then solved for
a finite, singularity-free, point-like field that we associate to a ``classical
graviton". The standard Einstein's continuous formalism is retrieved by means
of an averaging process, and its continuous solutions are determined by the
chosen imposed symetry. The Schwarzschild metric is obtained by the imposition
of spherical symmetry on the averaged field.Comment: Modified conform the version to appear in Classical and Quantum
Gravit
AMADA-Analysis of Multidimensional Astronomical Datasets
We present AMADA, an interactive web application to analyse multidimensional
datasets. The user uploads a simple ASCII file and AMADA performs a number of
exploratory analysis together with contemporary visualizations diagnostics. The
package performs a hierarchical clustering in the parameter space, and the user
can choose among linear, monotonic or non-linear correlation analysis. AMADA
provides a number of clustering visualization diagnostics such as heatmaps,
dendrograms, chord diagrams, and graphs. In addition, AMADA has the option to
run a standard or robust principal components analysis, displaying the results
as polar bar plots. The code is written in R and the web interface was created
using the Shiny framework. AMADA source-code is freely available at
https://goo.gl/KeSPue, and the shiny-app at http://goo.gl/UTnU7I.Comment: Accepted for publication in Astronomy & Computin
Random Primordial Magnetic Fields and the Gas Content of Dark Matter Halos
We recently predicted the existence of random primordial magnetic fields
(RPMF) in the form of randomly oriented cells with dipole-like structure with a
cell size and an average magnetic field . Here we investigate models
for primordial magnetic field with a similar web-like structure, and other
geometries, differing perhaps in and . The effect of RPMF on the
formation of the first galaxies is investigated. The filtering mass, , is
the halo mass below which baryon accretion is severely depressed. We show that
these RPMF could influence the formation of galaxies by altering the filtering
mass and the baryon gas fraction of a halo, . The effect is particularly
strong in small galaxies. We find, for example, for a comoving B_0=0.1\muG,
and a reionization epoch that starts at and ends at , for
at , the becomes severely depressed for
M<10^7\msun, whereas for the becomes severely depressed only
for much smaller masses, M<10^5\msun. We suggest that the observation of
and at high redshifts can give information on the intensity and
structure of primordial magnetic fields.Comment: 7 pages, 10 figures, accepted for publication in MNRAS (several
improvements after suggestions of the referee
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