219 research outputs found
A physical interpretation of Hubble's law and the cosmological redshift from the perspective of a static observer
We derive explicit and exact expressions for the physical velocity of a free
particle comoving with the Hubble flow as measured by a static observer, and
for the frequency shift of light emitted by a comoving source and received,
again, by a static observer. The expressions make it clear that an
interpretation of the redshift as a kind of Doppler effect only makes sense
when the distance between the observer and the source vanishes exactly.Comment: 5 pages, added references; accepted for publication in General
Relativity and Gravitatio
Revised WMAP constraints on neutrino masses and other extensions of the minimal CDM model
Recently, two issues concerning the three-year WMAP likelihood code were
pointed out. On large angular scales (), a sub-optimal
likelihood approximation resulted in a small power excess. On small angular
scales (), over-subtraction of unresolved point sources produced
a small power deficit. For a minimal six-parameter cosmological model, these
two effects conspired to decrease the value of by . In
this paper, we study the change in preferred parameter ranges for more
extensive cosmological models, including running of , massive neutrinos,
curvature, and the equation of state for dark energy. We also include
large-scale structure and supernova data in our analysis. We find that the
parameter ranges for , and are not much altered by the
modified analysis. For massive neutrinos the upper limit on the sum of the
neutrino masses decreases from eV to eV when using
the modified WMAP code and WMAP data only. We also find that the shift of
to higher values is quite robust to these extensions of the minimal
cosmological model.Comment: 7 pages. Matching version published in Physical Review D. Figures
changed, references added, additional comment
Effects of the Generalized Uncertainty Principle on the Inflation Parameters
We investigate the effects of the generalized uncertainty principle on the
inflationary dynamics of the early universe in both standard and braneworld
viewpoint. We choose the Randall-Sundrum II model as our underlying braneworld
scenario. We find that the quantum gravitational effects lead to a spectral
index which is not scale invariant. Also, the amplitude of density fluctuations
is reduced by increasing the strength of quantum gravitational corrections.
However, the tensor-to-scalar ratio increases by incorporation of these quantum
gravity effects. We outline possible manifestations of these quantum gravity
effects in the recent and future observations.Comment: 11 pages, revised version with new references, Accepted for
publication in IJMP
Last CPT-Invariant Hope for LSND Neutrino Oscillations
It is shown that the 99% confidence limits from the analyses of the data of
cosmological and neutrino experiments imply a small marginally allowed region
in the space of the neutrino oscillation parameters of 3+1 four-neutrino mixing
schemes. This region can be confirmed or falsified by experiments in the near
future.Comment: 6 pages, added predictions for neutrinoless double beta decay and
tritium experiment
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