Spontaneous Breaking of Flavor Symmetry and Naturalness of Nearly Degenerate Neutrino Masses and Bi-maximal Mixing

The gauge model with $SO(3)_{F}$ flavor symmetry and three Higgs triplets is studied. We show how the intriguing nearly degenerate neutrino mass and bi-maximal mixing scenario comes out naturally after spontaneous breaking of the symmetry. The hierarchy between the neutrino mass-squared differences, which is needed for reconciling both solar and atmospheric neutrino data, is naturally resulted from an approximate permutation symmetry. The model can also lead to interesting phenomena on lepton-flavor violations via the $SO(3)_{F}$ gauge interactions.Comment: 13 pages, latex, no figures, the version appearing in SCIENCE IN CHINA (Series A), Vol.35 No.9 (2000

SO(3) Gauge model for neutrino masses and oscillations

I mainly describe neutrino masses and oscillations in the gauge model with $SO(3)_{F}$ lepton flavor symmetry and with two Higgs triplets. It is shown how the maximal mixing between $\nu_{\mu}$ and $\nu_{\tau}$ neutrinos comes out naturally after spontaneous breaking of the symmetry. The nearly two-flavor mixing scenario is resulted naturally from an approximate permutation symmetry between the two Higgs triplets. The hierarchy between the neutrino mass-squared differences, which is needed for reconciling both solar and atmospheric neutrino data, leads to an almost maximal mixing between $\nu_{e}$ and $\nu_{\mu}$ neutrinos. Thus the model favors the intriguing bi-maximal mixing scenario.The three Majorana neutrino masses are allowed to be nearly degenerate and large enough to play a significant cosmological role. The model can also lead to interesting phenomena on lepton-flavor violations via the $SO(3)_{F}$ gauge interactions.Comment: latex, no figures, invited talk at the Sixth Topical Seminar on Neutrino and Astroparticle Physics, San Miniato, Italy, May 1999, to appear in Nucl. Phys. B (Proc. Suppl.

Magnetic phase diagram in Eu1−x_{1-x}Lax_xFe2_2As2_2 single crystals

We have systematically measured resistivity, susceptibility and specific heat under different magnetic fields (H) in Eu$_{1-x}$La$_x$Fe$_2$As$_2$ single crystals. It is found that a metamagnetic transition from A-type antiferromagnetism to ferromagnetism occurs at a critical field for magnetic sublattice of $Eu^{2+}$. The jump of specific heat is suppressed and shifts to low temperature with increasing H up to the critical value, then shifts to high temperature with further increasing H. Such behavior supports the metamagnetic transition. Detailed H-T phase diagrams for x=0 and 0.15 crystals are given, and possible magnetic structure is proposed. Magnetoresistance measurements indicate that there exists a strong coupling between local moment of $Eu^{2+}$ and charge in Fe-As layer. These results are very significant to understand the underlying physics of FeAs superconductors.Comment: 5 pages, 4 figure

Charge-monopole versus Gravitational Scattering at Planckian Energies

The amplitude for the scattering of a point magnetic monopole and a point charge, at centre-of-mass energies much larger than the masses of the particles, and in the limit of low momentum transfer, is shown to be proportional to the (integer-valued) monopole strength, assuming the Dirac quantization condition for the monopole-charge system. It is demonstrated that, for small momentum transfer, charge-monopole electromagnetic effects remain comparable to those due to the gravitational interaction between the particles even at Planckian centre-of-mass energies.Comment: 9 pages, revtex, IMSc/93-4

Sources of CP Violation in the Two-Higgs Doublet Model

Assuming CP violation arises solely through the Higgs potential, we develop the most general two-Higgs doublet model. There is no discrete symmetry that distinguishes the two Higgs bosons. It is assumed that an approximate global family symmetry sufficiently suppresses flavor-changing neutral scalar interactions. In addition to a CKM phase, neutral boson mixing, and superweak effects, there can be significant CP violation due to charged Higgs boson exchange. The value of $\epsilon'/\epsilon$ due to this last effect could be as large as in the standard model.Comment: 8 pages, RevTex, (appear in Phys. Rev. Lett. 73, (1994) 1762 ), CMU-HEP94-1

Whole genome sequencing of a banana wild relative Musa itinerans provides insights into lineage-specific diversification of the Musa genus

Crop wild relatives are valuable resources for future genetic improvement. Here, we report the de novo genome assembly of Musa itinerans, a disease-resistant wild banana relative in subtropical China. The assembled genome size was 462.1 Mb, covering 75.2% of the genome (615.2Mb) and containing 32, 456 predicted protein-coding genes. Since the approximate divergence around 5.8 million years ago, the genomes of Musa itinerans and Musa acuminata have shown conserved collinearity. Gene family expansions and contractions enrichment analysis revealed that some pathways were associated with phenotypic or physiological innovations. These include a transition from wood to herbaceous in the ancestral Musaceae, intensification of cold and drought tolerances, and reduced diseases resistance genes for subtropical marginally distributed Musa species. Prevalent purifying selection and transposed duplications were found to facilitate the diversification of NBS-encoding gene families for two Musa species. The population genome history analysis of M. itinerans revealed that the fluctuated population sizes were caused by the Pleistocene climate oscillations, and that the formation of Qiongzhou Strait might facilitate the population downsizing on the isolated Hainan Island about 10.3 Kya. The qualified assembly of the M. itinerans genome provides deep insights into the lineage-specific diversification and also valuable resources for future banana breeding

Bailout Embeddings, Targeting of KAM Orbits, and the Control of Hamiltonian Chaos

We present a novel technique, which we term bailout embedding, that can be used to target orbits having particular properties out of all orbits in a flow or map. We explicitly construct a bailout embedding for Hamiltonian systems so as to target KAM orbits. We show how the bailout dynamics is able to lock onto extremely small KAM islands in an ergodic sea.Comment: 3 figures, 9 subpanel

What can the braking indices tell us about pulsars' nature?

As a result of observational difficulties, braking indices of only six rotation-powered pulsars are obtained with certainty, all of which are remarkably smaller than the value ($n=3$) expected for pure magnetodipole radiation model. This is still a real fundamental question not being well answered after nearly forty years of the discovery of pulsar. The main problem is that we are shamefully not sure about the dominant mechanisms that result in pulsars' spin-down. Based on the previous works, the braking index is re-examined, with a conclusion of suggesting a constant gap potential drop for pulsars with magnetospheric activities. New constrains on model parameters from observed braking indices are presented.Comment: 10 pages, 4 figures, submitted to "Advances in Space Research" (Proceedings of COSPAR 2006

Charmless Bs→PP,PV,VVB_s\to PP, PV, VV Decays Based on the six-quark Effective Hamiltonian with Strong Phase Effects II

We provide a systematic study of charmless $B_s \to PP, PV, VV$ decays ($P$ and $V$ denote pseudoscalar and vector mesons, respectively) based on an approximate six-quark operator effective Hamiltonian from QCD. The calculation of the relevant hard-scattering kernels is carried out, the resulting transition form factors are consistent with the results of QCD sum rule calculations. By taking into account important classes of power corrections involving "chirally-enhanced" terms and the vertex corrections as well as weak annihilation contributions with non-trivial strong phase, we present predictions for the branching ratios and CP asymmetries of $B_s$ decays into PP, PV and VV final states, and also for the corresponding polarization observables in VV final states. It is found that the weak annihilation contributions with non-trivial strong phase have remarkable effects on the observables in the color-suppressed and penguin-dominated decay modes. In addition, we discuss the SU(3) flavor symmetry and show that the symmetry relations are generally respected