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 $\mathbf{10} \oplus \mathbf{120} \oplus \bar{\mathbf{126}}$ 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 $Z_n$ symmetries, with suitable $n$, and one case is generated by a $Z_2 \times Z_2$ 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 $\eta$, which has symmetries that lead to co-bimaximal mixing, i.e. to an atmospheric mixing angle $\theta_{23} = 45^\circ$ and to a $CP$-violating phase $\delta = \pm \pi/2$, while the mixing angle $\theta_{13}$ remains arbitrary. The symmetries consist of softly broken lepton numbers $L_\alpha$ ($\alpha = e,\mu,\tau$), a non-standard $CP$ symmetry, and three $Z_2$ symmetries. We indicate two possibilities for extending the model to the quark sector. Since the model has, besides $\eta$, 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 $125\, \mathrm{GeV}$, 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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