Rephasing invariance and the neutrino mu-tau symmetry

The vacuum neutrino mixing is known to exhibit an approximate $\mu-\tau$ symmetry, which was shown to be preserved for neutrino propagating in matter. This symmetry reduces the neutrino transition probabilities to very simple forms when expressed in a rephasing invariant parametrization introduced earlier. Applications to long baseline experiments are discussed.Comment: 12 pages, 4 figure

Seventy-One New L and T Dwarfs from the Sloan Digital Sky Survey

We present near-infrared observations of 71 newly discovered L and T dwarfs, selected from imaging data of the Sloan Digital Sky Survey (SDSS) using the i-dropout technique. Sixty-five of these dwarfs have been classified spectroscopically according to the near-infrared L dwarf classification scheme of Geballe et al. and the unified T dwarf classification scheme of Burgasser et al. The spectral types of these dwarfs range from L3 to T7, and include the latest types yet found in the SDSS. Six of the newly identified dwarfs are classified as early- to mid-L dwarfs according to their photometric near-infrared colors, and two others are classified photometrically as M dwarfs. We also present new near-infrared spectra for five previously published SDSS L and T dwarfs, and one L dwarf and one T dwarf discovered by Burgasser et al. from the Two Micron All Sky Survey. The new SDSS sample includes 27 T dwarfs and 30 dwarfs with spectral types spanning the complex L-T transition (L7-T3). We continue to see a large (~0.5 mag) spread in J-H for L3 to T1 types, and a similar spread in H-K for all dwarfs later than L3. This color dispersion is probably due to a range of grain sedimentation properties, metallicity, and gravity. We also find L and T dwarfs with unusual colors and spectral properties that may eventually help to disentangle these effects.Comment: accepted by AJ, 18 pages, 10 figures, 5 tables, emulateapj layou

Domain wall fermion and CP symmetry breaking

We examine the CP properties of chiral gauge theory defined by a formulation of the domain wall fermion, where the light field variables $q$ and $\bar q$ together with Pauli-Villars fields $Q$ and $\bar Q$ are utilized. It is shown that this domain wall representation in the infinite flavor limit $N=\infty$ is valid only in the topologically trivial sector, and that the conflict among lattice chiral symmetry, strict locality and CP symmetry still persists for finite lattice spacing $a$. The CP transformation generally sends one representation of lattice chiral gauge theory into another representation of lattice chiral gauge theory, resulting in the inevitable change of propagators. A modified form of lattice CP transformation motivated by the domain wall fermion, which keeps the chiral action in terms of the Ginsparg-Wilson fermion invariant, is analyzed in detail; this provides an alternative way to understand the breaking of CP symmetry at least in the topologically trivial sector. We note that the conflict with CP symmetry could be regarded as a topological obstruction. We also discuss the issues related to the definition of Majorana fermions in connection with the supersymmetric Wess-Zumino model on the lattice.Comment: 33 pages. Note added and a new reference were added. Phys. Rev.D (in press

Influence of retardation effects on 2D magnetoplasmon spectrum

Within dissipationless limit the magnetic field dependence of magnetoplasmon spectrum for unbounded 2DEG system found to intersect the cyclotron resonance line, and, then approaches the frequency given by light dispersion relation. Recent experiments done for macroscopic disc-shape 2DEG systems confirm theory expectations.Comment: 2 pages,2 figure

A Perturbative Study of a General Class of Lattice Dirac Operators

A perturbative study of a general class of lattice Dirac operators is reported, which is based on an algebraic realization of the Ginsparg-Wilson relation in the form $\gamma_{5}(\gamma_{5}D)+(\gamma_{5}D)\gamma_{5} = 2a^{2k+1}(\gamma_{5}D)^{2k+2}$ where $k$ stands for a non-negative integer. The choice $k=0$ corresponds to the commonly discussed Ginsparg-Wilson relation and thus to the overlap operator. We study one-loop fermion contributions to the self-energy of the gauge field, which are related to the fermion contributions to the one-loop $\beta$ function and to the Weyl anomaly. We first explicitly demonstrate that the Ward identity is satisfied by the self-energy tensor. By performing careful analyses, we then obtain the correct self-energy tensor free of infra-red divergences, as a general consideration of the Weyl anomaly indicates. This demonstrates that our general operators give correct chiral and Weyl anomalies. In general, however, the Wilsonian effective action, which is supposed to be free of infra-red complications, is expected to be essential in the analyses of our general class of Dirac operators for dynamical gauge field.Comment: 30 pages. Some of the misprints were corrected. Phys. Rev. D (in press

Quark Mass Matrices with Four and Five Texture Zeroes, and the CKM Matrix, in terms of Mass Eigenvalues

Using the triangular matrix techniques of Kuo et al and Chiu et al for the four and five texture zero cases, with vanishing (11) elements for U and D matrices, it is shown, from the general eigenvalue equations and hierarchy conditions, that the quark mass matrices, and the CKM matrix can be expressed (except for the phases) entirely in terms of quark masses. The matrix structures are then quite simple and transparent. We confirm their results for the five texture zero case but find, upon closer examination of all the CKM elements which our results provide, that six of their nine patterns for the four texture zero case are not compatible with experiments. In total, only one five-texture zero and three four-texture zero patterns are allowed.Comment: 15 pages, 3 table

Probing neutrino mass hierarchies and ϕ13\phi_{13} with supernova neutrinos

We investigate the feasibility of probing the neutrino mass hierarchy and the mixing angle $\phi_{13}$ with the neutrino burst from a future supernova. An inverse power-law density $\rho \sim r^{n}$ with varying $n$ is adopted in the analysis as the density profile of a typical core-collapse supernova. The survival probabilities of $\nu_{e}$ and $\bar{\nu}_{e}$ are shown to reduce to two-dimensional functions of $n$ and $\phi_{13}$. It is found that in the $n-\sin^{2} \phi_{13}$ parameter space, the 3D plots of the probability functions exhibit highly non-trivial structures that are sensitive to the mass hierarchy, the mixing angle $\phi_{13}$, and the value of $n$. The conditions that lead to observable differences in the 3D plots are established. With the uncertainty of $n$ considered, a qualitative analysis of the Earth matter effect is also included.Comment: 16 pages, 3 figures. Ref [11] added, and some typos correcte

Generalized Ginsparg-Wilson algebra and index theorem on the lattice

Recent studies of the topological properties of a general class of lattice Dirac operators are reported. This is based on a specific algebraic realization of the Ginsparg-Wilson relation in the form $\gamma_{5}(\gamma_{5}D)+(\gamma_{5}D)\gamma_{5} = 2a^{2k+1}(\gamma_{5}D)^{2k+2}$ where $k$ stands for a non-negative integer. The choice $k=0$ corresponds to the commonly discussed Ginsparg-Wilson relation and thus to the overlap operator. It is shown that local chiral anomaly and the instanton-related index of all these operators are identical. The locality of all these Dirac operators for vanishing gauge fields is proved on the basis of explicit construction, but the locality with dynamical gauge fields has not been established yet. We suggest that the Wilsonian effective action is essential to avoid infrared singularities encountered in general perturbative analyses.Comment: 11 pages. Talk given at APCTP-Nankai Joint Symposium on Lattice Statistics and Mathematical Physics, Tianjin, China, 8-11 October, 2001. To be published in the Proceedings and in Int. Jour. Mod. Phys.