6,985 research outputs found
Inflationary Cosmology and Oscillating Universes in Loop Quantum Cosmology
We study oscillatory universes within the context of Loop Quantum Cosmology.
We make a comparative study of flat and positively curved universes sourced by
scalar fields with either positive or negative potentials. We investigate how
oscillating universes can set the initial conditions for successful slow-roll
inflation, while ensuring that the semi-classical bounds are satisfied. We
observe rich oscillatory dynamics with negative potentials, although it is
difficult to respect the semi-classical bounds in models of this type.Comment: 7 pages, In Press Int. Mod. Phys.
Probing dark energy beyond with CODEX
Precision measurements of nature's fundamental couplings and a first
measurement of the cosmological redshift drift are two of the key targets for
future high-resolution ultra-stable spectrographs such as CODEX. Being able to
do both gives CODEX a unique advantage, allowing it to probe dynamical dark
energy models (by measuring the behavior of their equation of state) deep in
the matter era and thereby testing classes of models that would otherwise be
difficult to distinguish from the standard CDM paradigm. We illustrate
this point with two simple case studies.Comment: 4 pages, 4 figures; submitted to Phys. Rev.
Western Mediterranean precipitation over the last 300 years from instrumental observations
The paper reports the results of the analysis of the 14 longest precipitation
instrumental series, covering the last 300 years, that have been recovered in six subareas
of the Western Mediterranean basin, i.e., Portugal, Northern and Southern Spain, Southern
France, Northern and Southern Italy. This study extends back by one century our knowledge
about the instrumental precipitation over theWestern Mediterranean, and by two centuries in
some specific subareas. All the time series show repeated swings. No specific trends have been found over the whole period, except in a few cases, but with modest time changes and
sometimes having opposite tendency. The same can be said for the most recent decades
although with some more marked departures from the average. The correlation between the
various Mediterranean subareas is generally not significant, or almost uncorrelated. The
Wavelet Spectral Analysis applied to the precipitation identifies only a minor 56-year cycle
in autumn, i.e., the same return period that has been found in literature for the Sea Surface
Temperature over North Atlantic. A comparison with a gridded dataset reconstruction based on
mixed multiproxy and instrumental observations, shows that the grid reconstruction is in good
agreement with the observed data for the period after 1900, less for the previous period
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