59 research outputs found
Flavor coupled with chiral oscillations in the presence of an external magnetic field
By reporting to the Dirac wave-packet prescription where it is formally
assumed the {\em fermionic} nature of the particles, we shall demonstrate that
chiral oscillations implicitly aggregated to the interference between positive
and negative frequency components of mass-eigenstate wave-packets introduce
some small modifications to the standard neutrino flavor conversion formula.
Assuming the correspondent spinorial solutions of a ``modified'' Dirac
equation, we are specifically interested in quantifying flavor coupled with
chiral oscillations for a {\em fermionic} Dirac-{\em type} particle (neutrino)
non-minimally coupling with an external magnetic field {\boldmath}. The
viability of the intermediate wave-packet treatment becomes clear when we
assume {\boldmath} orthogonal/parallel to the direction of the propagating
particle.Comment: 21 page
Equilibrium and stability of neutrino lumps as TOV solutions
We report about stability conditions for static, spherically symmetric
objects that share the essential features of mass varying neutrinos in
cosmological scenarios. Compact structures of particles with variable mass are
held together preponderantly by an attractive force mediated by a background
scalar field. Their corresponding conditions for equilibrium and stability are
given in terms of the ratio between the total mass-energy and the spherical
lump radius, . We show that the mass varying mechanism leading to lump
formation can modify the cosmological predictions for the cosmological neutrino
mass limits. Our study comprises Tolman-Oppenheimer-Volkoff solutions of
relativistic objects with non-uniform energy densities. The results leave open
some questions concerning stable regular solutions that, to an external
observer, very closely reproduce the preliminary conditions to form
Schwarzschild black holes.Comment: 20 pages, 5 figure
Reproducing neutrino effects on the matter power spectrum through a degenerate Fermi gas approach
Modifications on the predictions about the matter power spectrum based on the
hypothesis of a tiny contribution from a degenerate Fermi gas (DFG) test-fluid
to some dominant cosmological scenario are investigated. Reporting about the
systematic way of accounting for all the cosmological perturbations, through
the Boltzmann equation we obtain the analytical results for density
fluctuation, , and fluid velocity divergence, , of the DFG.
Small contributions to the matter power spectrum are analytically obtained for
the radiation-dominated background, through an ultra-relativistic
approximation, and for the matter-dominated and -dominated eras,
through a non-relativistic approximation. The results can be numerically
reproduced and compared with those of considering non-relativistic and
ultra-relativistic neutrinos into the computation of the matter power spectrum.
Lessons concerning the formation of large scale structures of a DFG are
depicted, and consequent deviations from standard CDM predictions for
the matter power spectrum (with and without neutrinos) are quantified.Comment: 28 pages, 06 figure
Coupling active and sterile neutrinos in the cosmon plus seesaw framework
The cosmological evolution of neutrino energy densities driven by cosmon-type
field equations is introduced assuming that active and sterile neutrinos are
intrinsically connected by cosmon fields through the {\em seesaw} mechanism.
Interpreting sterile neutrinos as dark matter adiabatically coupled with dark
energy results in a natural decoupling of (active) mass varying neutrino
(MaVaN) equations. Identifying the dimensionless scale of the {\em seesaw}
mechanism, , with a power of the cosmological scale factor, , allows
for embedding the resulting masses into the generalized Chaplygin gas (GCG)
scenario for the dark sector. Without additional assumptions, our findings
establish a precise connection among three distinct frameworks: the cosmon
field dynamics for MaVaN's, the {\em seesaw} mechanism for dynamical mass
generation and the GCG scenario. Our results also corroborate with previous
assertions that mass varying particles can be the right responsible for the
stability issue and for the cosmic acceleration of the universe.Comment: 12 pages, 2 figure
Dynamical dispersion relation for ELKO dark spinor fields
An intrinsic mass generation mechanism for exotic ELKO dark matter fields is
scrutinized, in the context of the very special relativity (VSR). Our results
are reported on unraveling inequivalent spin structures that educe an
additional term on the associated Dirac operator. Contrary to the spinor fields
of mass dimension 3/2, this term is precluded to be absorbed as a shift of some
gauge vector potential, regarding the equations for the dark spinor fields. It
leads to some dynamical constraints that can be intrinsically converted into a
dark spinor mass generation mechanism, with the encoded symmetries maintained
by the VSR. The dynamical mass is embedded in the VSR framework through a
natural coupling to the kink solution of a \lambda \phi^{4} theory for a scalar
field \phi. Our results evince the possibility of novel effective scenarios,
derived from exotic couplings among dark spinor fields and scalar field
topological solutions.Comment: 6 pages, to appear in Phys.Lett.
The Exact Correspondence between Phase Times and Dwell Times in a Symmetrical Quantum Tunneling Configuration
The general and explicit relation between the phase time and the dwell time
for quantum tunneling or scattering is investigated. Considering a symmetrical
collision of two identical wave packets with an one-dimensional barrier, here
we demonstrate that these two distinct transit time definitions give connected
results where, however, the phase time (group delay) accurately describes the
exact position of the scattered particles. The analytical difficulties that
arise when the stationary phase method is employed for obtaining phase
(traversal) times are all overcome. Multiple wave packet decomposition allows
us to recover the exact position of the reflected and transmitted waves in
terms of the phase time, which, in addition to the exact relation between the
phase time and the dwell time, leads to right interpretation for both of them.Comment: 11 pages, 2 figure
Testing the interaction of dark energy to dark matter through the analysis of virial relaxation of clusters Abell Clusters A586 and A1689 using realistic density profiles
Interaction between dark energy and dark matter is probed through deviation
from the virial equilibrium for two relaxed clusters: A586 and A1689. The
evaluation of the virial equilibrium is performed using realistic density
profiles. The virial ratios found for the more realistic density profiles are
consistent with the absence of interaction.Comment: 16pp 1 fig; accepted by GeR
Dirac Equation Studies in the Tunnelling Energy Zone
We investigate the tunnelling zone V0 < E < V0+m for a one-dimensional
potential within the Dirac equation. We find the appearance of superluminal
transit times akin to the Hartman effect.Comment: 12 pages, 4 figure
Potential Scattering in Dirac Field Theory
We develop the potential scattering of a spinor within the context of
perturbation field theory. As an application, we reproduce, up to second order
in the potential, the diffusion results for a potential barrier of quantum
mechanics. An immediate consequence is a simple generalization to arbitrary
potential forms, a feature not possible in quantum mechanics.Comment: 7 page
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