39 research outputs found
GUTs and String-GUTs
We look for a connection between string theories and Grand Unified Theories
(GUTs), with the aim to look for new insights in the existing four dimensional
string-GUT problems. We argue that the construction of consistent string-GUT
models could require the use of non canonical affine levels. We list the most
common level values related to realistic GUTs.Comment: 8 pages, Latex file, no figures. Acepted for publication in
Europhysics Letter
Dirac neutrino mixings from hidden symmetry
We explore masses and mixings for Dirac neutrinos in models where lepton
number is conserved, under the guidance of a hidden, but broken,
exchange symmetry, that makes itself evident in the squared hermitian mass
matrix. We study the parameter space in the most general theory as allowed by
current neutrino oscillation experiment data. By using a general
parameterization of the mass matrix which contains only observable parameters
we stablish that the amount of breaking of the symmetry is in the range of the
atmospheric mass scale, without regard to the neutrino hierarchy, the absolute
neutrino mass and the Dirac CP phase. An estimate of the invisible branching
ratio for a Higgs boson decaying into Dirac neutrinos,
, is given and compared to recent measurements
in this context.Comment: Some references adde
Leptonic CP phases near the symmetric limit
The neutrino masses and mixings indicated by current neutrino oscillation
experiments suggest that the neutrino mass matrix possesses an approximate
exchange symmetry. In this study, we explore the neutrino parameter
space and show that if a small symmetry breaking is considered, the
Majorana phases must be unequal and non-zero independently of the neutrino
mass scale. Moreover, a small symmetry breaking favors
quasi-degenerate masses. We also show that Majorana phases are strongly
correlated with the Dirac violating phase. Within this framework, we
obtain robust predictions for the values of the Majorana phases when the
experimental indications for the Dirac phase are used.Comment: 13 pages, 3 figures. Version accepted for publication in PL
Baryogenesis in theories with large extra spatial dimensions
We describe a simple and predictive scenario for baryogenesis in theories
with large extra dimensions which resembles Affleck-Dine baryogenesis. The
Affleck-Dine field is a complex scalar field carrying a charge
which is dynamically broken after the end of inflation. This generates an
excess of over , which then decays into Standard Model
fermions to produce an excess of baryons over anti-baryons. Our model is very
constrained because the Affleck-Dine field has to be sufficiently flat during
inflation. It is also a source for density fluctuations which can be tested in
the coming satellite and balloon experiments.Comment: LaTeX file, 24 pages, no figure