2,619 research outputs found
A dark energy multiverse
We present cosmic solutions corresponding to universes filled with dark and
phantom energy, all having a negative cosmological constant. All such solutions
contain infinite singularities, successively and equally distributed along
time, which can be either big bang/crunchs or big rips singularities.
Classicaly these solutions can be regarded as associated with multiverse
scenarios, being those corresponding to phantom energy that may describe the
current accelerating universe
Tensorial perturbations in the bulk of inflating brane worlds
In this paper we consider the stability of some inflating brane-world models
in quantum cosmology. It is shown that whereas the singular model based on the
construction of inflating branes from Euclidean five-dimensional anti-de Sitter
space is unstable to tensorial cosmological perturbations in the bulk, the
nonsingular model which uses a five-dimensional asymptotically anti-de Sitter
wormhole to construct the inflating branes is stable to these perturbations.Comment: 4 pages, RevTex, to appear in Phys. Rev.
A microscopic NN to NN*(1440) potential
By means of a NN to NN*(1440) transition potential derived in a
parameter-free way from a quark-model based NN potential, we determine
simultaneously the and coupling constants.
We also present a study of the target Roper excitation diagram contributing to
the reaction.Comment: Talk presented at the Fourth International Conference on Perspectives
in Hadronic Physics (ICTP, Trieste, Italy, May 2003). To appear in EPJA. 6
pages, 9 figures, needs svepj.clo and svjour.cl
Anti-de Sitter wormhole kink
The metric describing a given finite sector of a four-dimensional
asymptotically anti-de Sitter wormhole can be transformed into the metric of
the time constant sections of a Tangherlini black hole in a five-dimensional
anti-de Sitter spacetime when one allows light cones to tip over on the
hypersurfaces according to the conservation laws of an one-kink. The resulting
kinked metric can be maximally extended, giving then rise to an instantonic
structure on the euclidean continuation of both the Tangherlini time and the
radial coordinate. In the semiclassical regime, this kink is related to the
existence of closed timelike curves.Comment: 10 pages, to appear in IJMP
A graceful multiversal link of particle physics to cosmology
In this paper we work out a multiverse scenario whose physical
characteristics enable us to advance the following the conjecture that whereas
the physics of particles and fields is confined to live in the realm of the
whole multiverse formed by finite-time single universes, that for our
observable universe must be confined just in one of the infinite number of
universes of the multiverse when such a universe is consistently referred to an
infinite cosmic time. If this conjecture is adopted then some current
fundamental problems that appear when one tries to make compatible particle
physics and cosmology- such as that for the cosmological constant, the arrow of
time and the existence of a finite proper size of the event horizon- can be
solved.Comment: 10 pages, LaTe
Kinematics of gas and stars in circumnuclear star-forming regions of early type spirals
(Abbr.) We present high resolution (R~20000) spectra in the blue and the far
red of cicumnuclear star-forming regions (CNSFRs) in three early type spirals
(NGC3351, NGC2903 and NGC3310) which have allowed the study of the kinematics
of stars and ionized gas in these structures and, for the first time, the
derivation of their dynamical masses for the first two. In some cases these
regions, about 100 to 150 pc in size, are seen to be composed of several
individual star clusters with sizes between 1.5 and 4.9 pc estimated from
Hubble Space Telescope (HST) images. The stellar dispersions have been obtained
from the Calcium triplet (CaT) lines at 8494,8542,8662 \AA,
while the gas velocity dispersions have been measured by Gaussian fits to the
H and [OIII] 5007 \AA lines on the high dispersion
spectra. Values of the stellar velocity dispersions are between 30 and 68 km/s.
We apply the virial theorem to estimate dynamical masses of the clusters,
assuming that systems are gravitationally bounded and spherically symmetric,
and using previously measured sizes. The measured values of the stellar
velocity dispersions yield dynamical masses of the order of 10 to 10
solar masses for the whole CNSFRs. Stellar and gas velocity dispersions are
found to differ by about 20 to 30 km/s with the H emission lines being
narrower than both the stellar lines and the [OIII] 5007 \AA
lines. The twice ionized oxygen, on the other hand, shows velocity dispersions
comparable to those shown by stars, in some cases, even larger. We have found
indications of the presence of two different kinematical components in the
ionized gas of the regions...Comment: 4 pages, proceeding of the meeting "Young massive star clusters -
Initial conditions and environments", Granada, Spain, 200
Decoherence in an accelerated universe
In this paper we study the decoherence processes of the semiclassical
branches of an accelerated universe due to their interaction with a scalar
field with given mass. We use a third quantization formalism to analyze the
decoherence between two branches of a parent universe caused by their
interaction with the vaccum fluctuations of the space-time, and with other
parent unverses in a multiverse scenario.Comment: 11 pages, 2 figure
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