4,008 research outputs found
Perturbing exactly tri-bimaximal neutrino mixings with charged lepton mass matrices
We study perturbations of exactly tri-bimaximal neutrino mixings under the
assumption that they are coming solely from the charged lepton mass matrix.
This may be plausible in scenarios where the mass generation mechanisms of
neutrinos and charged leptons/quarks have a different origin. As a working
hypothesis, we assume mass textures which may be generated by the
Froggatt-Nielsen mechanism for the charged lepton and quark sectors, which
generically leads to strong hierarchies, whereas the neutrino sector is exactly
tri-bimaximal with a mild (normal) hierarchy. We find that in this approach,
deviations from maximal atmospheric mixing can be introduced without affecting
theta_13 and theta_12, whereas a deviation of theta_13 or theta_12 from its
tri-bimaximal value will inevitably lead to a similar-sized deviation of the
other parameter. Therefore, the already very precise knowledge of theta_12
points towards small sin^2(2 theta_13) <= 0.01. The magnitude of this deviation
can be controlled by the specific form of the charged lepton texture.Comment: 13 pages, 9 figures; matches published version, changes in notatio
SU(3) Gauge Family Symmetry and Prediction for the Lepton-Flavor Mixing and Neutrino Masses with Maximal Spontaneous CP Violation
A model for the lepton-flavor mixing and CP violation is proposed based on
the SU(3) gauge family symmetry and the Majorana feature of neutrinos. A
consistent prediction for the lepton-flavor mixing and masses is shown to be
resulted from the appropriate vacuum structure of SU(3) gauge symmetry
breaking. By choosing the SU(3) gauge fixing condition to possess a
residual symmetry and requiring the vacuum structure of spontaneous
symmetry breaking to have approximate global U(1) family symmetries, we obtain
naturally the tri-bimaximal mixing matrix and largely degenerate neutrino
masses in the neutrino sector and the small mixing matrix in the charged-lepton
sector. With a simple ansatz that all the smallness due to the approximate
global U(1) family symmetries is characterized by a single Wolfenstein
parameter , and the charged-lepton mixing matrix has a
similar hierarchy structure as the CKM quark mixing matrix, we arrive at a
consistent prediction for the MNSP lepton-flavor mixing with a maximal
spontaneous CP violation: , (),
and
, which agree well
with the current experimental data. The CP-violating Jarlskog-invariant is
obtained to be , which is detectable in next generation neutrino experiment. The
largely degenerate neutrino masses with the normal hierarchy and inverse
hierarchy are discussed and found be at the order eV with a total mass eV, which is testable in future precision astrophysics and cosmology.Comment: 14 pages, it is explicitly shown that the smallness for both the
charged-lepton mixing and neutrino masses with the standard seesaw mechanism
can naturally be explained by the approximate global U(1) family symmetries
of vacuum structure in the SU(3) gauge family model, references added,
published version in PL
Accidental stability of dark matter
We propose that dark matter is stable as a consequence of an accidental Z2
that results from a flavour-symmetry group which is the double-cover group of
the symmetry group of one of the regular geometric solids. Although
model-dependent, the phenomenology resembles that of a generic Higgs portal
dark matter scheme.Comment: 12 pages, final version, published in JHE
Deviation from Tri-Bimaximal Mixing and Large Reactor Mixing Angle
Recent observations for a non-zero have come from various
experiments. We study a model of lepton mixing with a 2-3 flavor symmetry to
accommodate the sizable measurement. In this work, we derive
deviations from the tri-bimaximal (TBM) pattern arising from breaking the
flavor symmetry in the neutrino sector, while the charged leptons contribution
has been discussed in a previous work. Contributions from both sectors towards
accommodating the non-zero measurement are presented.Comment: 25 pages, 12 figures. arXiv admin note: text overlap with
arXiv:1109.232
Do the ends justify the means? Impact of drought progression rate on stress response and recovery in Vitis vinifera
Ordovician tectonics of the South European Variscan Realm: new insights from Sardinia
Although much is known about the Ordovician tectonics of the South European Variscides, aspects of their geodynamic evolution and palaeogeographic reconstruction remain uncertain. In Sardinia, Variscan tectonic units include significant vestiges of Ordovician evolution, such as a fold system that affected only the Cambrian-Lower Ordovician successions, and are cut by a regional angular unconformity. A comparison of the stratigraphy and tectonic structures of the successions below and above the Lower Ordovician unconformity and a reinterpretation of biostratigraphic data allow us to identify significant differences between the stacked tectonic units. The unconformity is sealed as follows: (i) in the Sulcis-Iglesiente Unit (Variscan External Zone, SW Sardinia) by Middle-Upper Ordovician continental and tidal deposits; and (ii) in the Sarrabus and Gerrei units (part of the Variscan Nappe Zone, SE Sardinia) by Middle-Upper Ordovician calc-alkaline volcanic rocks. Therefore, at the same time, one tectonic unit was situated close to a rifting setting and the others were involved in a convergent margin. Of note are the different durations associated with the unconformities in the tectonic units (17 Myr in the Sulcis-Iglesiente Unit, 6 Myr in the Sarrabus and Gerrei units) and the occurrence (or absence) of glacio-marine deposits indicating that the units were located at different palaeo-latitudes during the Ordovician. These results suggest that the SW and SE Sardinia blocks did not share the same geodynamic setting during the Ordovician, implying that they were situated in different palaeogeographic positions at this time and subsequently amalgamated during the Variscan Orogeny. Furthermore, stratigraphic and tectonic correlations with neighbouring areas, such as the eastern Pyrenees, imply alternative palaeogeographic reconstructions to those proposed previously for some peri-Mediterranean Variscan terranes
Tri-Bimaximal Neutrino Mixing and Discrete Flavour Symmetries
We review the application of non-Abelian discrete groups to Tri-Bimaximal
(TB) neutrino mixing, which is supported by experiment as a possible good first
approximation to the data. After summarizing the motivation and the formalism,
we discuss specific models, mainly those based on A4 but also on other finite
groups, and their phenomenological implications, including the extension to
quarks. The recent measurements of \theta_13 favour versions of these models
where a suitable mechanism leads to corrections to \theta_13 that can naturally
be larger than those to \theta_12 and \theta_23. The virtues and the problems
of TB mixing models are discussed, also in connection with lepton flavour
violating processes, and the different approaches are compared.Comment: 26 pages, 5 figures, 4 tables. V3 submitted to add an acknowledgment
to a network. Review written for the special issue on "Flavor Symmetries and
Neutrino Oscillations", published in Fortschritte der Physik - Progress of
Physic
TFH Mixing Patterns, Large and Flavor Symmetry
We perform a comprehensive analysis of the Toorop-Feruglio-Hagedorn (TFH)
mixing patterns within the family symmetry . The general neutrino
mass matrix for the TFH mixing and its symmetry properties are investigated.
The possible realizations of the TFH mixing in are analyzed in the
minimalist approach. We propose two dynamical models which produce the TFH
mixing patterns at leading order. The full flavor symmetries are
and
respectively. The next to leading order terms introduce corrections of order
to the three mixing angles in both models. The allowed mixing
patterns are studied under the condition that the Klein four subgroups and the
cyclic subgroups with are preserved in the neutrino and the
charged lepton sector respectively. We suggest that the deformed tri-bimaximal
mixing is a good leading order approximation to understanding a largish reactor
angle.Comment: 43 pages, 2 figure
If players are sparse social dilemmas are too: Importance of percolation for evolution of cooperation
Spatial reciprocity is a well known tour de force of cooperation promotion. A
thorough understanding of the effects of different population densities is
therefore crucial. Here we study the evolution of cooperation in social
dilemmas on different interaction graphs with a certain fraction of vacant
nodes. We find that sparsity may favor the resolution of social dilemmas,
especially if the population density is close to the percolation threshold of
the underlying graph. Regardless of the type of the governing social dilemma as
well as particularities of the interaction graph, we show that under pairwise
imitation the percolation threshold is a universal indicator of how dense the
occupancy ought to be for cooperation to be optimally promoted. We also
demonstrate that myopic updating, due to the lack of efficient spread of
information via imitation, renders the reported mechanism dysfunctional, which
in turn further strengthens its foundations.Comment: 6 two-column pages, 5 figures; accepted for publication in Scientific
Reports [related work available at http://arxiv.org/abs/1205.0541
Strong coupling, discrete symmetry and flavour
We show how two principles - strong coupling and discrete symmetry - can work
together to generate the flavour structure of the Standard Model. We propose
that in the UV the full theory has a discrete flavour symmetry, typically only
associated with tribimaximal mixing in the neutrino sector. Hierarchies in the
particle masses and mixing matrices then emerge from multiple strongly coupled
sectors that break this symmetry. This allows for a realistic flavour
structure, even in models built around an underlying grand unified theory. We
use two different techniques to understand the strongly coupled physics:
confinement in N=1 supersymmetry and the AdS/CFT correspondence. Both
approaches yield equivalent results and can be represented in a clear,
graphical way where the flavour symmetry is realised geometrically.Comment: 31 pages, 5 figures, updated references and figure
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