24,731 research outputs found
Cosmology with running parameters
The experimental evidence that the equation of state (EOS) of the dark energy
(DE) could be evolving with time/redshift (including the possibility that it
might behave phantom-like near our time) suggests that there might be dynamical
DE fields that could explain this behavior. We propose, instead, that a
variable cosmological term (including perhaps a variable Newton's gravitational
coupling too) may account in a natural way for all these features.Comment: Talk given at TAUP 2005, Zaragoza, Spain, 10-14 Sep 200
Quantum corrections to gravity and their implications for cosmology and astrophysics
The quantum contributions to the gravitational action are relatively easy to
calculate in the higher derivative sector of the theory. However, the
applications to the post-inflationary cosmology and astrophysics require the
corrections to the Einstein-Hilbert action and to the cosmological constant,
and those we can not derive yet in a consistent and safe way. At the same time,
if we assume that these quantum terms are covariant and that they have relevant
magnitude, their functional form can be defined up to a single free parameter,
which can be defined on the phenomenological basis. It turns out that the
quantum correction may lead, in principle, to surprisingly strong and
interesting effects in astrophysics and cosmology.Comment: 15 pages, LaTeX, WS style, contribution to the Proceedings of the
QFEXT-2011 conference in the Centro de Ciencias de Benasque Pedro Pasqual,
Spai
Spin-orbit correlation energy in neutron matter
We study the relevance of the energy correlation produced by the two-body
spin-orbit coupling present in realistic nucleon-nucleon potentials. To this
purpose, the neutron matter Equation of State (EoS) is calculated with the
realistic two-body Argonne potential. The shift occuring in the EoS when
spin-orbit terms are removed is taken as an estimate of the spin-orbit
correlation energy. Results obtained within the Bethe-Brueckner-Goldstone
expansion, extended up to three hole-line diagrams, are compared with other
many-body calculations recently presented in the literature. In particular,
excellent agreement is found with the Green's function Monte-Carlo method. This
agreement indicates the present theoretical accuracy in the calculation of the
neutron matter EoS.Comment: 5 pages, 2 figures, 2 tables; to appear in Phys. Rev.
Glaciological and volcanological studies in the Wrangell Mountains, Alaska
There are no author-identified significant results in this report
Disk and elliptical galaxies within renormalization group improved gravity
The paper is about possible effects of infrared quantum contributions to
General Relativity on disk and elliptical galaxies. The Renormalization Group
corrected General Relativity (RGGR model) is used to parametrize these quantum
effects. The new RGGR results presented here concern the elliptical galaxy NGC
4374 and the dwarf disk galaxy DDO 47. Using the effective approach to Quantum
Field Theory in curved background, one can argue that the proper RG energy
scale, in the weak field limit, should be related to the Newtonian potential.
In the context of galaxies, this led to a remarkably small variation of the
gravitational coupling G, while also capable of generating galaxy rotation and
dispersion curves of similar quality to the the best dark matter profiles
(i.e., the profiles that have a core).Comment: 5 pages. This paper is based on a talk given by D.C. Rodrigues at the
I CosmoSul meeting (Rio de Janeiro, RJ - Brazil. August, 01-05, 2011). To be
published in AIP conference Proceeding
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