4,165 research outputs found
Fully Constrained Majorana Neutrino Mass Matrices Using
In 2002, two neutrino mixing ansatze having trimaximally-mixed middle
() columns, namely tri-chi-maximal mixing () and
tri-phi-maximal mixing (), were proposed. In 2012, it was
shown that with as well as
with leads to the solution,
, consistent with the
latest measurements of the reactor mixing angle, . To obtain
and
, the type~I see-saw
framework with fully constrained Majorana neutrino mass matrices was utilised.
These mass matrices also resulted in the neutrino mass ratios,
.
In this paper we construct a flavour model based on the discrete group
and obtain the aforementioned results. A Majorana neutrino
mass matrix (a symmetric matrix with 6 complex degrees of freedom)
is conveniently mapped into a flavon field transforming as the complex 6
dimensional representation of . Specific vacuum alignments
of the flavons are used to arrive at the desired mass matrices.Comment: 20 pages, 1 figure. arXiv admin note: substantial text overlap with
arXiv:1402.085
Deviations from Tribimaximal Neutrino Mixing using a Model with Symmetry
We present a model of neutrino mixing based on the flavour group
in order to account for the observation of a non-zero reactor mixing angle
(). The model provides a common flavour structure for the
charged-lepton and the neutrino sectors, giving their mass matrices a
`circulant-plus-diagonal' form. Mass matrices of this form readily lead to
mixing patterns with realistic deviations from tribimaximal mixing, including
non-zero . With the parameters constrained by existing
measurements, our model predicts an inverted neutrino mass hierarchy. We obtain
two distinct sets of solutions in which the atmospheric mixing angle lies in
the first and the second octants. The first (second) octant solution predicts
the lightest neutrino mass, ()
and the phase, (), offering the possibility of large observable violating
effects in future experiments.Comment: 9 pages, 3 figure
Non-Abelian Discrete Symmetries and Neutrino Masses: Two Examples
Two recent examples of non-Abelian discrete symmetries (S_3 and A_4) in
understanding neutrino masses and mixing are discussed.Comment: 16 pages, no figure, invited contribution to NJP focus issue on
neutrino
A Simplest A4 Model for Tri-Bimaximal Neutrino Mixing
We present a see-saw model for Tri-Bimaximal mixing which is based on a
very economical flavour symmetry and field content and still possesses all the
good features of models. In particular the charged lepton mass
hierarchies are determined by the flavour symmetry itself
without invoking a Froggatt-Nielsen U(1) symmetry. Tri-Bimaximal mixing is
exact in leading order while all the mixing angles receive corrections of the
same order in next-to-the-leading approximation. As a consequence the predicted
value of is within the sensitivity of the experiments which will
take data in the near future. The light neutrino spectrum, typical of
see-saw models, with its phenomenological implications, also including
leptoproduction, is studied in detail.Comment: 20 pages, 2 figure
A See-Saw model for fermion masses and mixings
We present a supersymmetric see-saw model giving rise to the most
general neutrino mass matrix compatible with Tri-Bimaximal mixing. We adopt the
flavour symmetry, broken by suitable vacuum expectation values
of a small number of flavon fields. We show that the vacuum alignment is a
natural solution of the most general superpotential allowed by the flavour
symmetry, without introducing any soft breaking terms. In the charged lepton
sector, mass hierarchies are controlled by the spontaneous breaking of the
flavour symmetry caused by the vevs of one doublet and one triplet flavon
fields instead of using the Froggatt-Nielsen U(1) mechanism. The next to
leading order corrections to both charged lepton mass matrix and flavon vevs
generate corrections to the mixing angles as large as .
Applied to the quark sector, the symmetry group can give a
leading order proportional to the identity as well as a matrix with
coefficients in the Cabibbo submatrix. Higher order
corrections produce non vanishing entries in the other entries which
are generically of .Comment: 30 pages, 3 figures, minor changes to match the published versio
Localized Basis for Effective Lattice Hamiltonians: Lattice Wannier Functions
A systematic method is presented for constructing effective Hamiltonians for
general phonon-related structural transitions. The key feature is the
application of group theoretical methods to identify the subspace in which the
effective Hamiltonian acts and construct for it localized basis vectors, which
are the analogue of electronic Wannier functions. The results of the symmetry
analysis for the perovskite, rocksalt, fluorite and A15 structures and the
forms of effective Hamiltonians for the ferroelectric transition in
and , the oxygen-octahedron rotation transition in , the
Jahn-Teller instability in and the
antiferroelectric transition in are discussed. For the oxygen-
octahedron rotation transition in , this method provides an
alternative to the rotational variable approach which is well behaved
throughout the Brillouin zone. The parameters appearing in the Wannier basis
vectors and in the effective Hamiltonian, given by the corresponding invariant
energy expansion, can be obtained for individual materials using first-
principles density-functional-theory total energy and linear response
techniques, or any technique that can reliably calculate force constants and
distortion energies. A practical approach to the determination of these
parameters is presented and the application to ferroelectric
discussed.Comment: extensive revisions in presentation, 32 pages, Revtex, 7 Postscript
figure
Esperanto for histones : CENP-A, not CenH3, is the centromeric histone H3 variant
The first centromeric protein identified in any species was CENP-A, a divergent member of the histone H3 family that was recognised by autoantibodies from patients with scleroderma-spectrum disease. It has recently been suggested to rename this protein CenH3. Here, we argue that the original name should be maintained both because it is the basis of a long established nomenclature for centromere proteins and because it avoids confusion due to the presence of canonical histone H3 at centromeres
Characteristic Energy of the Coulomb Interactions and the Pileup of States
Tunneling data on crystals confirm
Coulomb interaction effects through the dependence of the
density of states. Importantly, the data and analysis at high energy, E, show a
pileup of states: most of the states removed from near the Fermi level are
found between ~40 and 130 meV, from which we infer the possibility of universal
behavior. The agreement of our tunneling data with recent photoemission results
further confirms our analysis.Comment: 4 pages, 4 figures, submitted to PR
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