26,707 research outputs found
Flavour symmetries in a renormalizable SO(10) model
In the context of a renormalizable supersymmetric SO(10) Grand Unified
Theory, we consider the fermion mass matrices generated by the Yukawa couplings
to a representation
of scalars. We perform a complete investigation of the possibilities of
imposing flavour symmetries in this scenario; the purpose is to reduce the
number of Yukawa coupling constants in order to identify potentially predictive
models. We have found that there are only 14 inequivalent cases of Yukawa
coupling matrices, out of which 13 cases are generated by symmetries,
with suitable , and one case is generated by a symmetry. A
numerical analysis of the 14 cases reveals that only two of them---dubbed A and
B in the present paper---allow good fits to the experimentally known fermion
masses and mixings.Comment: 36 pages, no figures, revised fits using newer data, added fit for
case A, added references, new appendices concerning the SO(10) scalar
potential and inequalities for the vacuum expectation values, conclusions
unchanged; some minor changes, matches published versio
Scotogenic model for co-bimaximal mixing
We present a scotogenic model, i.e. a one-loop neutrino mass model with dark
right-handed neutrino gauge singlets and one inert dark scalar gauge doublet
, which has symmetries that lead to co-bimaximal mixing, i.e. to an
atmospheric mixing angle and to a -violating phase
, while the mixing angle remains arbitrary.
The symmetries consist of softly broken lepton numbers (), a non-standard symmetry, and three symmetries. We
indicate two possibilities for extending the model to the quark sector. Since
the model has, besides , three scalar gauge doublets, we perform a
thorough discussion of its scalar sector. We demonstrate that it can
accommodate a Standard Model-like scalar with mass , with
all the other charged and neutral scalars having much higher masses.Comment: v2 - 23 pages, 5 figures, minor changes requested by refere
Two-component mixture of charged particles confined in a channel: melting
The melting of a binary system of charged particles confined in a {\it
quasi}-one-dimensional parabolic channel is studied through Monte Carlo
simulations. At zero temperature the particles are ordered in parallel chains.
The melting is anisotropic and different melting temperatures are obtained
according to the spatial direction, and the different types of particles
present in the system. Melting is very different for the single-, two- and
four-chain configurations. A temperature induced structural phase transition is
found between two different four chain ordered states which is absent in the
mono-disperse system. In the mixed regime, where the two types of particles are
only slightly different, melting is almost isotropic and a thermally induced
homogeneous distribution of the distinct types of charges is observed.Comment: To appear in Journal of Physics: condensed matter ; (13 pages, 12
figures
Fundamental Oscillation Periods of the Interlayer Exchange Coupling beyond the RKKY Approximation
A general method for obtaining the oscillation periods of the interlayer
exchange coupling is presented. It is shown that it is possible for the
coupling to oscillate with additional periods beyond the ones predicted by the
RKKY theory. The relation between the oscillation periods and the spacer Fermi
surface is clarified, showing that non-RKKY periods do not bear a direct
correspondence with the Fermi surface. The interesting case of a FCC(110)
structure is investigated, unmistakably proving the existence and relevance of
non-RKKY oscillations. The general conditions for the occurrence of non-RKKY
oscillations are also presented.Comment: 34 pages, 10 figures ; to appear in J. Phys.: Condens. Mat
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