5,345 research outputs found
Nonextensivity in the solar magnetic activity during the increasing phase of solar Cycle 23
In this paper we analyze the behavior of the daily Sunspot Number from the
Sunspot Index Data Center (SIDC), the mean Magnetic Field strength from the
National Solar Observatory/Kitt Peak (NSO/KP) and Total Solar Irradiance means
from Virgo/SoHO, in the context of the --Triplet which emerges within
nonextensive statistical mechanics. Distributions for the mean solar Magnetic
Field show two different behaviors, with a --Gaussian for scales of 1 to 16
days and a Gaussian for scales longer than 32 days. The latter corresponds to
an equilibrium state. Distributions for Total Solar Irradiance also show two
different behaviors (approximately Gaussian) for scales of 128 days and longer,
consistent with statistical equilibrium and --Gaussian for scales 128
days. Distributions for the Sunspot Number show a --Gaussian independent of
timescales, consistent with a nonequilibrium state. The values obtained
("--Triplet",,)
demonstrate that the Gaussian or --Gaussian behavior of the aforementioned
data depends significantly on timescales. These results point to strong
multifractal behavior of the dataset analyzed, with the multifractal level
decreasing from Sunspot Number to Total Solar Irradiance. In addition, we found
a numerically satisfied dual relation between and .Comment: 6 pages, 4 figure
On the link between rotation, chromospheric activity and Li abundance in subgiant stars
The connection rotation-CaII emission flux-lithium abundance is analyzed for
a sample of bona fide subgiant stars, with evolutionary status determined from
HIPPARCOS trigonometric parallax measurements and from the Toulouse-Geneva
code.Comment: 9 pages, 8 figure
Geometrical CP violation in multi-Higgs models
We introduce several methods to obtain calculable phases with geometrical
values that are independent of arbitrary parameters in the scalar potential.
These phases depend on the number of scalars and on the order of the discrete
non-Abelian group considered. Using these methods we present new geometrical CP
violation candidates with vacuum expectation values that must violate CP (the
transformation that would make them CP conserving is not a symmetry of the
potential). We also extend to non-renormalisable potentials the proof that more
than two scalars are needed to obtain these geometrical CP violation
candidates.Comment: 8 pages, 2 figures. v2: table added, accepted by JHE
Towards a complete SUSY GUT
We propose a renormalisable model based on family symmetry with an
grand unified theory (GUT) which leads to the minimal supersymmetric
standard model (MSSM) with a two right-handed neutrino seesaw mechanism.
Discrete symmetry provides the fermion mass
hierarchy in both the quark and lepton sectors, while symmetry
is broken to , identified as usual R-parity. Proton decay is
highly suppressed by these symmetries. We discuss both the and
symmetry breaking sectors, including doublet-triplet splitting, Higgs mixing
and the origin of the term. The model provides an excellent fit (better
than one sigma) to all quark and lepton (including neutrino) masses and mixing
with spontaneous CP violation. With the vacuum alignments, and
, the model predicts the entire PMNS mixing matrix with no free
parameters, up to a relative phase, selected to be from a choice of
the nine complex roots of unity, providing a direct link between neutrino
oscillations and leptogenesis.Comment: 30 pages, 17 figures, 7 tables; Minor changes, references added,
version accepted in JHE
Power-law statistics and stellar rotational velocities in the Pleiades
In this paper we will show that, the non-gaussian statistics framework based
on the Kaniadakis statistics is more appropriate to fit the observed
distributions of projected rotational velocity measurements of stars in the
Pleiades open cluster. To this end, we compare the results from the
and -distributions with the Maxwellian.Comment: 13 pages, 3 figure
Observational constraints for Lithium depletion before the RGB
Precise Li abundances are determined for 54 giant stars mostly evolving
across the Hertzsprung gap. We combine these data with rotational velocity and
with information related to the deepening of the convective zone of the stars
to analyse their link to Li dilution in the referred spectral region. A sudden
decline in Li abundance paralleling the one already established in rotation is
quite clear. Following similar results for other stellar luminosity classes and
spectral regions, there is no linear relation between Li abundance and
rotation, in spite of the fact that most of the fast rotators present high Li
content. The effects of convection in driving the Li dilution is also quite
clear. Stars with high Li content are mostly those with an undeveloped
convective zone, whereas stars with a developed convective zone present clear
sign of Li dilution.Comment: 5 pages, 4 figures. accepted for publicatio
Leptogenesis in minimal predictive seesaw models
We estimate the Baryon Asymmetry of the Universe (BAU) arising from
leptogenesis within a class of minimal predictive seesaw models involving two
right-handed neutrinos and simple Yukawa structures with one texture zero. The
two right-handed neutrinos are dominantly responsible for the "atmospheric" and
"solar" neutrino masses with Yukawa couplings to proportional to and , respectively, where
is a positive integer. The neutrino Yukawa matrix is therefore characterised by
two proportionality constants with their relative phase providing a
leptogenesis-PMNS link, enabling the lightest right-handed neutrino mass to be
determined from neutrino data and the observed BAU. We discuss an SUSY
GUT example, where vacuum alignment provides the required Yukawa
structures with , while a symmetry fixes the relatives
phase to be a ninth root of unity.Comment: 16 pages, 2 tables. v2: minor changes, references added, version
accepted in JHE
Causal Structure and Birefringence in Nonlinear Electrodynamics
We investigate the causal structure of general nonlinear electrodynamics and
determine which Lagrangians generate an effective metric conformal to
Minkowski. We also proof that there is only one analytic nonlinear
electrodynamics presenting no birefringence.Comment: 11 pages, no figure
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