Twisted Flavors and Tri/bi-Maximal Neutrino Mixing

A new framework for handling flavor symmetry breaking in the neutrino sector is discussed where the source of symmetry breaking is traced to the global property of right-handed neutrinos in extra-dimensional space. Light neutrino phenomenology has rich and robust predictions such as the tri/bi-maximal form of generation mixing, controlled mass spectrum, and no need of flavor mixing couplings in the theory.Comment: 11 page

Lyman Break Galaxies at z∼5z\sim5: Rest-Frame UV Spectra

We report initial results for spectroscopic observations of candidates of Lyman Break Galaxies (LBGs) at $z\sim5$ in a region centered on the Hubble Deep Field-North by using the Faint Object Camera and Spectrograph attached to the Subaru Telescope. Eight objects with $I_C\leq25.0$ mag, including one AGN, are confirmed to be at $4.5<z<5.2$. The rest-frame UV spectra of seven LBGs commonly show no or weak Lyalpha emission line (rest-frame equivalent width of 0-10\AA) and relatively strong low-ionization interstellar metal absorption lines of SiII $\lambda$1260, OI+SiII $\lambda$1303, and CII $\lambda$1334 (mean rest-frame equivalent widths of them are $-1.2 \sim -5.1$\AA). These properties are significantly different from those of the mean rest-frame UV spectrum of LBGs at $z\sim3$, but are quite similar to those of subgroups of LBGs at $z\sim3$ with no or weak Lyalpha emission. The weakness of Lyalpha emission and strong low-ionization interstellar metal absorption lines may indicate that these LBGs at $z\sim5$ are chemically evolved to some degree and have a dusty environment. Since the fraction of such LBGs at $z\sim5$ in our sample is larger than that at $z\sim3$, we may witness some sign of evolution of LBGs from $z\sim5$ to $z\sim3$, though the present sample size is very small. It is also possible, however, that the brighter LBGs tend to show no or weak Lyalpha emission, because our spectroscopic sample is bright (brighter than $L^{\ast}$) among LBGs at $z\sim5$. More observations are required to establish spectroscopic nature of LBGs at $z\sim5$.Comment: 16 pages, 3 figures, accepted by Ap

Flight Activity and Sex Ratios of a Damselfly, Platycnemis echigoana ASAHINA (Zygoptera, Platycnemididae)

Mark-and-recapture method was applied to a damselfly, Platycnemis echigoana, a rare species among the Platycnemididae in the cool temperate zone of Houshu, Japan. The peak activities of males were observed during 10 : 00-14 : 00, and those of females somewhat delayed. Tandems were also recognized during 11 : 00-14 : 00. Males defended a sunlit point, where the sunlight fell on the forest floor, by perching, and chasing conspecific males. Females encountered the male at the sunlit point, mated and then showed tandem behaviors. They oviposited into plant tissues on the water surface. The size of a mature egg was about 0.19 mm in diameter and 1.14 mm in length. A female seemed to have 250 mature eggs, and then laid about 170 eggs after a mating. A male showed strong residency perching at a sunlit point, while a female did not. Sexual differences in such behaviors were also reflected in the resident ratios