[Todos] IAFE -COLOQUIOS: "Overview of the CREST and NASA research programs at NCCU with an accent on high energy gamma polarimeter, rigorous few-body calculations, and a new cosmological model"]

[difusion en iafe.uba.ar]

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                       PRÓXIMO COLOQUIO DEL IAFE
                 Instituto de Astronomía y Física del Espacio
                           CONICET-UBA
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"Overview of the CREST and NASA research programs at NCCU with an accent
on high energy gamma polarimeter, rigorous few-body calculations, and a
new cosmological model"

                                  Branislav Vlahovic
Center for Research Excellence (CREST) and NASA University Research
Centers at the North Carolina Central University, Durham NC, US
                          Lunes 11 de marzo 2013, 15:00hs.
                             Aula del Edificio IAFE

After brief overview of the NSF Center for Research Excellence (CREST) and
NASA University Research Centers at the North Carolina Central University,
the presentation will focus on three specific research topics related to
astrophysics: polarimeter for high energy gammas, rigorous few body
calculations, and a new cosmological model.
The CREST is a research center with computational program on
nanotechnology, nuclear physics, robotics, and geophysics. The NASA Center
is complementary to the CREST, supporting experimentally oriented programs
on formation of nanostructures (for photovoltaic cells, biochemical and IR
detector applications), design of new polarimeter for linearly polarized
high energy photons for astrophysics, design of new neutrino detector,
robotics, and the highest intensity positron beam facility that we are
building at Jefferson National Laboratory.
The high energy photons polarization measurements are anticipated to play
a significant role in major discoveries addressing fundamental questions
of thermal and relativistic astrophysics. Presented will be a new
theoretical method that allows improvement in data analysis for the
existing high-energy photon polarimeters, based on pair production, and a
new polarimeter prototype for astrophysics applications that has a
projected analyzing power and efficiency of 10% for MeV to GeV energy
range, which up to now was not investigated at all.
Theoretical predictions of the mean baryon density in the Universe depend
on the cross-sections for eleven key reactions. The first basic reactions
in the pp chain are the weak captures p+p→d+e + ,
He+p→ He+e +  and radiative captures p(n,γ)d, d(p,
γ) He,  He(α,γ) Be,  He(α, γ) Li. These reactions
are crucial for the  H, and  Li yields and also for the solar neutrino
spectrum. Up to now, theoretical studies of these reactions have been
performed by the variational approach, using the empirical two- and
three-body nucleon potentials and either the hyperspherical basis for
trial functions for atomic numbers A=2-4 or the phenomenological wave
functions in the variational Monte-Carlo technique for larger A. Our
theoretical group has a vast experience in the study of light nuclei and
hypernuclei by the Faddeev (F) and Faddeev-Yakubovsky (FY) approach in
configuration space. This technique has an advantage to directly calculate
nuclear wave functions, solving the corresponding Schrödinger equation
point by point. In contrast, variational methods are oriented towards
energy values, which are obtained with a quadratic precision in the error
in the wave function. The wave functions themselves are obtained with a
much lower precision. Presented will be results for the basic reactions
using the F and FY approach, complemented with a cluster technique applied
in the case of nuclei with A>4.
	Presented will be a variant of the cosmological 3-D spherical shell
model, within FRW formalism, that will be compared with the standard
CDM model. The new topological model satisfies cosmological
principles and is consistent with SNe Ia and other observational data,
but it may require new interpretation for some data. In this model
propagation of the light is confined along the shell, which has as a
consequence that observed CMB originated from one point or a limited
space region. It allows to interpret the uniformity of the CMB without
inflation scenario. In addition this removes any constraints on the
uniformity of the universe at the early stage and opens a possibility
that the universe was not uniform and that creation of galaxies and large
structures is due to the inhomogeneities that originated in the Big Bang.