Neutrino masses and mixings from an SMG \times U(1)^2 model

A natural solution to the fermion mass hierarchy problem suggests the existence of a partially conserved chiral symmetry. We show that this can lead to a reasonably natural solution to the solar and atmospheric neutrino problems without fine-tuning or the addition of new low energy fermions. The atmospheric neutrino atmospheric neutrino anomaly is given by large mixing between $\nu_{\mu}$ and $\nu_{\tau}$, with \Delta m^2_{atm} \sim 10^{-3} \eV^2, and the solar neutrino deficit is due to nearly maximal electron neutrino vacuum oscillations. We present an explicit model for the neutrino masses which is an anomaly free Abelian extension of the standard model that also yields a realistic charged fermion spectrum.Comment: 16 pages, 2 figures. Figures use FeynTeX package.Minor modifications made. Version to appear in Phys.Lett.

Quark Mixings in SU(6)×SU(2)RSU(6)\times SU(2)_R and Suppression of VubV_{ub}

The quark mixing matrix $V_{CKM}$ is studied in depth on the basis of superstring inspired $SU(6)\times SU(2)_R$ model with global flavor symmetries. The sizable mixings between right-handed down-type quark $D^c$ and colored Higgs field $g^c$ potentially occur but no such mixings in up-type quark sector. In the model the hierarchical pattern of $V_{CKM}$ is understood systematically. It is shown that due to large $D^c$-$g^c$ mixings $V_{ub}$ is naturally suppressed compared to $V_{td}$. It is pointed out that the observed suppression of $V_{ub}$ is in favor of the presence of $SU(2)_R$ gauge symmetry but not in accord with generic SU(5) GUT.Comment: 10pages with no figure, Latex fil

A General Analysis of Corrections to the Standard See-saw Formula in Grand Unified Models

In realistic grand unified models there are typically extra vectorlike matter multiplets at the GUT scale that are needed to explain the family hierarchy. These contain neutrinos that, when integrated out, can modify the usual neutrino see-saw formula. A general analysis is given. It is noted that such modifications can explain why the neutrinos do not exhibit a strong family hierarchy like the other types of fermions.Comment: 30 page

Phase transition in gauge theories, monopoles and the Multiple Point Principle

This review is devoted to the Multiple Point Principle (MPP), according to which several vacuum states with the same energy density exist in Nature. The MPP is implemented to the Standard Model (SM), Family replicated gauge group model (FRGGM) and phase transitions in gauge theories with/without monopoles. Lattice gauge theories are reviewed. The lattice results for critical coupling constants are compared with those of the Higgs Monopole Model (HMM), in which the lattice artifact monopoles are replaced by the point-like Higgs scalar particles with a magnetic charge. Considering our (3+1)-dimensional space-time as discrete, for example, as a lattice with a parameter a=\lambda_P, equal to the Planck length, we have investigated the additional contributions of monopoles to beta-functions of renormalization group equations in the FRGGM extended beyond the SM at high (the Planck scale) energies. We have reviewed that, in contrast to the Anti-grand unified theory (AGUT), there exists a possibility of unification of all gauge interactions (including gravity) near the Planck scale due to monopoles. The unifications [SU(5)]^3 and [SO(10)]^3 at the GUT-scale \sim 10^{18} GeV are briefly discussed.Comment: 100 pages, 25 figures, typos correcte

UV Exposed Optical Fibers with Frequency Domain Reflectometry for Device Tracking in Intra-Arterial Procedures

Shape tracking of medical devices using strain sensing properties in optical fibers has seen increased attention in recent years. In this paper, we propose a novel guidance system for intra-arterial procedures using a distributed strain sensing device based on optical frequency domain reflectometry (OFDR) to track the shape of a catheter. Tracking enhancement is provided by exposing a fiber triplet to a focused ultraviolet beam, producing high scattering properties. Contrary to typical quasi-distributed strain sensors, we propose a truly distributed strain sensing approach, which allows to reconstruct a fiber triplet in real-time. A 3D roadmap of the hepatic anatomy integrated with a 4D MR imaging sequence allows to navigate the catheter within the pre-interventional anatomy, and map the blood flow velocities in the arterial tree. We employed Riemannian anisotropic heat kernels to map the sensed data to the pre-interventional model. Experiments in synthetic phantoms and an in vivo model are presented. Results show that the tracking accuracy is suitable for interventional tracking applications, with a mean 3D shape reconstruction errors of 1.6 +/- 0.3 mm. This study demonstrates the promising potential of MR-compatible UV-exposed OFDR optical fibers for non-ionizing device guidance in intra-arterial procedures

Neutrino Masses and Bimaximal Mixing

Solar and atmospheric neutrino anomalies are described by bimaximal mixing of three neutrinos. Neutrino oscillations in appearance nu_e nu_mu,nu_tau and in disappearance nu_e long baseline and atmospheric experiments are sensitive to deviations from the ideal bimaximal mixing. It is suggested that these deviations may be dominated by a rotation in the electron--muon plane of the generation space. Simple seesaw models are described supporting this idea. The rotation angle is estimated from Fritzsch's relation. Predictions are presented for oscillations in long baseline experiments, for solar neutrinos, and for the rates of neutrinoless double beta decays.Comment: Latex, 13 p., no figure

The Origin of Mass

The quark-lepton mass problem and the ideas of mass protection are reviewed. The hierarchy problem and suggestions for its resolution, including Little Higgs models, are discussed. The Multiple Point Principle is introduced and used within the Standard Model to predict the top quark and Higgs particle masses. Mass matrix ans\"{a}tze are considered; in particular we discuss the lightest family mass generation model, in which all the quark mixing angles are successfully expressed in terms of simple expressions involving quark mass ratios. It is argued that an underlying chiral flavour symmetry is responsible for the hierarchical texture of the fermion mass matrices. The phenomenology of neutrino mass matrices is briefly discussed.Comment: 33 pages, 7 figures, to be published in the Proceedings of the XXXI ITEP Winter School, Moscow, Russia, 18 - 26 February 200

Dicyclic Horizontal Symmetry and Supersymmetric Grand Unification

It is shown how to use as horizontal symmetry the dicyclic group $Q_6 \subset SU(2)$ in a supersymmetric unification $SU(5)\otimes SU(5)\otimes SU(2)$ where one $SU(5)$ acts on the first and second families, in a horizontal doublet, and the other acts on the third. This can lead to acceptable quark masses and mixings, with an economic choice of matter supermultiplets, and charged lepton masses can be accommodated.Comment: 10 pages, LaTe

Baryogenesis from the Kobayashi-Maskawa Phase

The Standard Model fulfills the three Sakharov conditions for baryogenesis. The smallness of quark masses suppresses, however, the CP violation from the Kobayashi-Maskawa phase to a level that is many orders of magnitude below what is required to explain the observed baryon asymmetry. We point out that if, as a result of time variation in the Yukawa couplings, quark masses were large at the time of the electroweak phase transition, then the Kobayashi-Maskawa mechanism could be the source of the asymmetry. The Froggatt-Nielsen mechanism provides a plausible framework where the Yukawa couplings could all be of order one at that time, and settle to their present values before nucleosynthesis. The problems related to a strong first order electroweak phase transition may also be alleviated in this framework. Our scenario reveals a loophole in the commonly held view that the Kobayashi-Maskawa mechanism cannot be the dominant source of CP violation to play a role in baryogenesis.Comment: 4 page