79,179 research outputs found
Controlled Shock Shells and Intracluster Fusion Reactions in the Explosion of Large Clusters
The ion phase-space dynamics in the Coulomb explosion of very large ( atoms) deuterium clusters can be tailored using two consecutive
laser pulses with different intensities and an appropriate time delay. For
suitable sets of laser parameters (intensities and delay), large-scale shock
shells form during the explosion, thus highly increasing the probability of
fusion reactions within the single exploding clusters. In order to analyze the
ion dynamics and evaluate the intracluster reaction rate, a one-dimensional
theory is used, which approximately accounts for the electron expulsion from
the clusters. It is found that, for very large clusters (initial radius
100 nm), and optimal laser parameters, the intracluster fusion yield becomes
comparable to the intercluster fusion yield. The validity of the results is
confirmed with three-dimensional particle-in-cell simulations.Comment: 25 pages, 11 figures, to appear in Physical Review
Wigner-Moyal description of free variable mass Klein-Gordon fields
A system of coupled kinetic transport equations for the Wigner distributions
of a free variable mass Klein-Gordon field is derived. This set of equations is
formally equivalent to the full wave equation for electromagnetic waves in
nonlinear dispersive media, thus allowing for the description of broadband
radiation-matter interactions and the associated instabilities. The standard
results for the classical wave action are recovered in the short wavelength
limit of the generalized Wigner-Moyal formalism for the wave equation.Comment: 9 pages, accepted for publication in Journal of Mathematical Physic
Formation of Dark Matter Haloes in a Homogeneous Dark Energy Universe
Several independent cosmological tests have shown evidences that the energy
density of the Universe is dominated by a dark energy component, which cause
the present accelerated expansion. The large scale structure formation can be
used to probe dark energy models, and the mass function of dark matter haloes
is one of the best statistical tools to perform this study. We present here a
statistical analysis of mass functions of galaxies under a homogeneous dark
energy model, proposed in the work of Percival (2005), using an observational
flux-limited X-ray cluster survey, and CMB data from WMAP. We compare, in our
analysis, the standard Press-Schechter (PS) approach (where a Gaussian
distribution is used to describe the primordial density fluctuation field of
the mass function), and the PL (Power Law) mass function (where we apply a
nonextensive q-statistical distribution to the primordial density field). We
conclude that the PS mass function cannot explain at the same time the X-ray
and the CMB data (even at 99% confidence level), and the PS best fit dark
energy equation of state parameter is , which is distant from the
cosmological constant case. The PL mass function provides better fits to the
HIFLUGCS X-ray galaxy data and the CMB data; we also note that the
parameter is very sensible to modifications in the PL free parameter, ,
suggesting that the PL mass function could be a powerful tool to constrain dark
energy models.Comment: 4 pages, 2 figures, Latex. Accepted for publication in the
International Journal of Modern Physics D (IJMPD)
Nonextensive Quantum H-Theorem
A proof of the quantum -theorem taking into account nonextensive effects
on the quantum entropy is shown. The positiveness of the time variation
of combined with a duality transformation implies that the nonextensive
parameter lies in the interval [0,2]. It is also shown that the equilibrium
states are described by quantum -power law extensions of the Fermi-Dirac and
Bose-Einstein distributions. Such results reduce to the standard ones in the
extensive limit, thereby showing that the nonextensive entropic framework can
be harmonized with the quantum distributions contained in the quantum
statistics theory.Comment: 5 pages, LaTe
Opening the Pandora's box of quantum spinor fields
Lounesto's classification of spinors is a comprehensive and exhaustive
algorithm that, based on the bilinears covariants, discloses the possibility of
a large variety of spinors, comprising regular and singular spinors and their
unexpected applications in physics and including the cases of Dirac, Weyl, and
Majorana as very particular spinor fields. In this paper we pose the problem of
an analogous classification in the framework of second quantization. We first
discuss in general the nature of the problem. Then we start the analysis of two
basic bilinear covariants, the scalar and pseudoscalar, in the second quantized
setup, with expressions applicable to the quantum field theory extended to all
types of spinors. One can see that an ampler set of possibilities opens up with
respect to the classical case. A quantum reconstruction algorithm is also
proposed. The Feynman propagator is extended for spinors in all classes.Comment: 18 page
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