2,212 research outputs found
String Theory and Cosmology
We discuss the main cosmological implications of considering string-loop
effects and a potential for the dilaton in the lowest order string effective
action. Our framework is based on the effective model arising from regarding
homogeneous and isotropic dilaton, metric and Yang-Mills field configurations.
The issues of inflation, entropy crisis and the Polonyi problem as well as the
problem of the cosmological constant are discussed.Comment: 7 pages, plain Tex, no figure
Generalized Chaplygin Gas Model: Dark Energy - Dark Matter Unification and CMBR Constraints
The generalized Chaplygin gas (GCG) model allows for an unified description
of the recent accelerated expansion of the Universe and the evolution of energy
density perturbations. This dark energy - dark matter unification is achieved
through an exotic background fluid whose equation of state is given by , where is a positive constant and .
Stringent constraints on the model parameters can be obtained from recent WMAP
and BOOMERanG bounds on the locations of the first few peaks and troughs of the
Cosmic Microwave Background Radiation (CMBR) power spectrum as well as SNe Ia
data.Comment: 9 pages, 2 figures; essay selected for an honorable mention by the
Gravity Research Foundation, 200
WMAP Constraints on the Generalized Chaplygin Gas Model
The generalized Chaplygin gas (GCG) model explains the recent accelerated
expansion of the Universe via an exotic background fluid whose equation of
state is given by p=-A/\rho^\alpha, where A is a positive constant and
0<\alpha\le 1. The model is an interesting alternative to scenarios involving
scalar field potentials, with the ensuing unnatural fine tuning conditions for
the underlying particle physics theories. We derive constraints on the
parameter space of the model from bounds on the location of the first few peaks
and troughs of the the Cosmic Microwave Background Radiation (CMBR) power
spectrum arising from recent WMAP and BOOMERanG data.Comment: 18 pages, 5 figures, version to appear in Phys. Lett.
WMAP Constraints on a Quintessence Model
We use the results from the Wilkinson Microwave Anisotropy Probe (WMAP) for
the locations of peaks and troughs of the Cosmic Microwave Background (CMB)
power spectrum, together with constraints from large-scale structure, to study
a quintessence model in which the pure exponential potential is modified by a
polynomial factor. Our analysis, in the cosmological
parameters space shows that this quintessence model is favoured compared to
CDM for and relatively high values of early
quintessence; for , quintessence and CDM give similar results,
except for high values of early quintessence, in which case CDM is
favoured.Comment: 3 pages. Talk presented by N. M. C. Santos at the Tenth Marcel
Grossmann Meeting on General Relativity, Rio de Janeiro, July 200
Functional analysis of novel genes differentially expressed genes in heart/hemangioblast precursor cells (H/HPC)
info:eu-repo/semantics/publishedVersio
Supernovae constraints on dark energy and modified gravity models
We use the Type Ia Supernova gold sample to constrain the parameters of dark
energy models namely the Cardassian, Dvali-Turner (DT) and generalized
Chaplygin gas (GCG) models. In our best fit analysis for these dark energy
proposals we consider flat and the non-flat priors. For all models, we find
that relaxing the flatness condition implies that data favors a positive
curvature; moreover, the GCG model is nearly flat, as required by Cosmic
Microwave Background (CMB) observations.Comment: 6 pages, Latex file + 9 eps figures + (jpconf.cls,jpconf11.clo), to
appear in the Proceedings of the Fourth Meeting on Constrained Dynamics and
Quantum Gravity (QG05), Cala Gonone (Italy) September 12-16 200
Internet of Things: an Applied Research on Automation for Lock Shield
This study presents results obtained in applied research, involving controller boards (Arduino), at the Nove de Julho higher education institution, in the courses of Computer Science in São Paulo. In 2018, focusing mainly on the positive and negative points presented by the statistical data of the public security office. The methodology used to obtain the data was experimental research based on results obtained in the newspaper Estadão of June 25, 2017. Every hour, a house is invaded in the State of São Paulo, according to data of the Public Security Secretariat, focusing mainly in the qualitative and quantitative results, seeking greater security for homes with tilting gates, avoiding fraud and cloning of locks. Creating new automation equipment, focused on security, its assembly is more complex and more structured than the simple control boards and controls for swing gates. Thus obtaining a safer drive with a high power against fraud, since the system is mounted on top of the controller boards (Arduino), this system achieved a higher degree of reliability than conventional systems
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