15,930 research outputs found
On the hierarchy of neutrino masses
We present a model of neutrino masses combining the seesaw mechanism and
strong Dirac mass hierarchy and at the same time exhibiting a significantly
reduced hierarchy at the level of active neutrino masses. The heavy Majorana
masses are assumed to be degenerate. The suppression of the hierarchy is due to
a symmetric and unitary operator R whose role is discussed. The model gives
realistic mixing and mass spectrum. The mixing of atmospheric neutrinos is
attributed to the charged lepton sector whereas the mixing of solar neutrinos
is due to the neutrino sector. Small U_e3 is a consequence of the model. The
masses of the active neutrinos are given by
and .Comment: 12 pages; Talk presented by M. Jezabek at 'Supersymmetry and Brane
Worlds,' Fifth European Meeting Planck 02, Kazimierz, Poland, May 25-29,
2002, to appear in Acta Phys. Polon.
Thomas-Fermi approximation to static vortex states in superfluid trapped atomic gases
We revise the Thomas-Fermi approximation for describing vortex states in Bose
condensates of magnetically trapped atoms. Our approach is based on considering
the hbar -> 0 limit rather than the N -> infinity limit as Thomas-Fermi
approximation in close analogy with the Fermi systems. Even for relatively
small numbers of trapped particles we find good agreement between
Gross-Pitaevskii and Thomas-Fermi calculations for the different contributions
to the total energy of the atoms in the condensate. We also discuss the
application of our approach to the description of vortex states in superfluid
fermionic systems in the Ginzburg-Landau regime.Comment: 11 pages, 6 figures, revtex4, substantially revised versio
Full sky harmonic analysis hints at large UHECR deflections
The full-sky multipole coefficients of the ultra-high energy cosmic ray
(UHECR) flux have been measured for the first time by the Pierre Auger and
Telescope Array collaborations using a joint data set with E > 10 EeV. We
calculate these harmonic coefficients in the model where UHECR are protons and
sources trace the local matter distribution, and compare our results with
observations. We find that the expected power for low multipoles (dipole and
quadrupole, in particular) is sytematically higher than in the data: the
observed flux is too isotropic. We then investigate to which degree our
predictions are influenced by UHECR deflections in the regular Galactic
magnetic field (GMF). It turns out that the UHECR power spectrum coefficients
are quite insensitive to the effects of the GMF, so it is unlikely
that the discordance can be reconciled by tuning the GMF model. On the
contrary, a sizeable fraction of uniformly distributed flux (representing for
instance an admixture of heavy nuclei with considerably larger deflections) can
bring simulations and observations to an accord.Comment: 8 pages, 4 figures and one table, JETPL style -- v2 as published in
JETP
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