85 research outputs found
An alternative singularity-free cosmological scenario from cusp geometries
We study an alternative geometrical approach on the problem of classical
cosmological singularity. It is based on a generalized function which consists of a cusped coupled isosurface.
Such a geometry is computed and discussed into the context of Friedmann
singularity-free cosmology where a pre-big bang scenario is considered.
Assuming that the mechanism of cusp formation is described by non-linear
oscillations of a pre-big bang extended very high energy density field (), we show that the action under the gravitational
field follows a tautochrone of revolution, understood here as the primary
projected geometry that alternatively replaces the Friedmann singularity in the
standard big bang theory. As shown here this new approach allows us to
interpret the nature of both matter and dark energy from first geometric
principles.Comment: Proceedings of Sixth International School on Field Theory and
Gravitation-2012 - by American Institute of Physic
Value-at-Risk and Tsallis statistics: risk analysis of the aerospace sector
In this study, we analyze the aerospace stocks prices in order to
characterize the sector behavior. The data analyzed cover the period from
January 1987 to April 1999. We present a new index for the aerospace sector and
we investigate the statistical characteristics of this index. Our results show
that this index is well described by Tsallis distribution. We explore this
result and modify the standard Value-at-Risk (VaR), financial risk assessment
methodology in order to reflect an asset which obeys Tsallis non-extensive
statistics.Comment: 10 pages, 4 figures, 1 table, to appear in Physica
A new gravitational N-body simulation algorithm for investigation of cosmological chaotic advection
Recently alternative approaches in cosmology seeks to explain the nature of
dark matter as a direct result of the non-linear spacetime curvature due to
different types of deformation potentials. In this context, a key test for this
hypothesis is to examine the effects of deformation on the evolution of large
scales structures. An important requirement for the fine analysis of this pure
gravitational signature (without dark matter elements) is to characterize the
position of a galaxy during its trajectory to the gravitational collapse of
super clusters at low redshifts. In this context, each element in an
gravitational N-body simulation behaves as a tracer of collapse governed by the
process known as chaotic advection (or lagrangian turbulence). In order to
develop a detailed study of this new approach we develop the COsmic LAgrangian
TUrbulence Simulator (COLATUS) to perform gravitational N-body simulations
based on Compute Unified Device Architecture (CUDA) for graphics processing
units (GPUs). In this paper we report the first robust results obtained from
COLATUS.Comment: Proceedings of Sixth International School on Field Theory and
Gravitation-2012 - by American Institute of Physic
Stellar Population Properties of ETGs in Compact Groups of Galaxies
We present results on the study of the stellar population in Early-Type
galaxies (ETGs) belonging to 151 Compact Groups (CGs). We also selected a field
sample composed of 846 ETGs to investigate environmental effects on galaxy
evolution. We find that the dependences of mean stellar ages, [Z/H] and
[/Fe] on central stellar velocity dispersion are similar, regardless
where the ETG resides, CGs or field. When compared to the sample of centrals
and satellites from the literature, we find that ETGs in GCs behave similarly
to centrals, especially those embedded in low-mass haloes (). Except for the low-mass limit, where field galaxies present
a Starforming signature, not seen in CGs, the ionization agent of the gas in CG
and field galaxies seem to be similar and due to hot, evolved low-mass stars.
However, field ETGs present an excess of H emission relative to ETGs in
CGs. Additionally, we performed a dynamical analysis, which shows that CGs
present a bimodality in the group velocity dispersion distribution - a high and
low- mode. Our results indicate that high- groups have a
smaller fraction of spirals, shorter crossing times, and a more luminous
population of galaxies than the low groups. It is important to
emphasize that our findings point to a small environmental impact on galaxies
located in CGs. The only evidence we find is the change in gas content,
suggesting environmentally-driven gas loss.Comment: 21 pages, 18 Figure
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