Neutrino Masses in a 5D SU(3)WSU(3)_W TeV Unification Model

We study the generation of neutrino masses in the $SU(3)_W$ electroweak unified theory in $M_4\times S_1/(Z_2\times Z'_2)$ spacetime. By appropriate orbifolding, the bulk symmetry $SU(3)_W$ is broken into $SU(2)_L \times U(1)_Y$ at one of the fixed points, where the quarks reside. The leptons form $SU(3)_W$ triplets, localized at the other symmetric fixed point. The fermion masses arise from the bulk Higgs sector containing a triplet and an anti-sextet. We construct neutrino Majorana masses via 1-loop quantum corrections by adding a parity odd bulk triplet scalar. No right-handed neutrino is needed. The neutrino mass matrix is of the inverted hierarchy type. We show that the model can easily accommodate the bi-large mixing angle solution favored by the recent neutrino experiments without much fine tuning of parameters. The constraints from \mu\ra 3e transition and neutrinoless double beta decays are discussed.Comment: 14 pages, 4 figure

Renormalization Group Study of the Minimal Majoronic Dark Radiation and Dark Matter Model

We study the 1-loop renormalization group equation running in the simplest singlet Majoron model constructed by us earlier to accommodate the dark radiation and dark matter content in the universe. A comprehensive numerical study was performed to explore the whole model parameter space. A smaller effective number of neutrinos $\triangle N_{eff}\sim 0.05$, or a Majoron decoupling temperature higher than the charm quark mass, is preferred. We found that a heavy scalar dark matter, $\rho$, of mass $1.5-4$ TeV is required by the stability of the scalar potential and an operational type-I see-saw mechanism for neutrino masses. A neutral scalar, $S$, of mass in the $10-100$ GeV range and its mixing with the standard model Higgs as large as $0.1$ is also predicted. The dominant decay modes are $S$ into $b\bar{b}$ and/or $\omega\omega$. A sensitive search will come from rare $Z$ decays via the chain $Z\rightarrow S+ f\bar{f}$, where $f$ is a Standard Model fermion, followed by $S$ into a pair of Majoron and/or b-quarks. The interesting consequences of dark matter bound state due to the sizable $S\rho \rho$-coupling are discussed as well. In particular, shower-like events with an apparent neutrino energy at $M_\rho$ could contribute to the observed effective neutrino flux in underground neutrino detectors such as IceCube.Comment: 33 pages,11 figures, published versio

Acyclic orientations on the Sierpinski gasket

We study the number of acyclic orientations on the generalized two-dimensional Sierpinski gasket $SG_{2,b}(n)$ at stage $n$ with $b$ equal to two and three, and determine the asymptotic behaviors. We also derive upper bounds for the asymptotic growth constants for $SG_{2,b}$ and $d$-dimensional Sierpinski gasket $SG_d$.Comment: 20 pages, 8 figures and 6 table

Relativistic Conic Beams and Spatial Distribution of Gamma-Ray Bursts

We study the statistics of gamma-ray bursts, assuming that gamma-ray bursts are cosmological and they are beamed in the form of a conical jet with a large bulk Lorentz factor $\sim 100$. In such a conic beam, the relativistic ejecta may have a spatial variation in the bulk Lorentz factor and the density distribution of gamma-ray emitting jet material. An apparent luminosity function arises because the axis of the cone is randomly oriented with respect to the observer's line of sight. The width and the shape of the luminosity function are determined by the ratio of the beam opening angle of the conical jet to the inverse of the bulk Lorentz factor, when the bulk Lorentz factor and the jet material density is uniform on the photon emitting jet surface. We calculate effects of spatial variation of the Lorentz factor and the spatial density fluctuations within the cone on the luminosity function and the statistics of gamma-ray bursts. In particular, we focus on the redshift distribution of the observed gamma-ray bursts. The maximum distance to and the average redshift of the gamma-ray bursts are strongly affected by the beaming-induced luminosity function. The bursts with the angle-dependent Lorentz factor which peaks at the center of the cone have substantially higher average gamma-ray burst redshifts. When both the jet material density and the Lorentz factor are inhomogeneous in the conical beam, the average redshift of the bursts could be 5 times higher than that of the case in which relativistic jet is completely homogeneous and structureless. Even the simplest models for the gamma-ray burst jets and their apparent luminosity distributions have a significant effect on the redshift distribution of the gamma-ray bursts.Comment: 15 pages, 4 figures, submitted to ApJ

Speaker-normalized sound representations in the human auditory cortex

The acoustic dimensions that distinguish speech sounds (like the vowel differences in “boot” and “boat”) also differentiate speakers’ voices. Therefore, listeners must normalize across speakers without losing linguistic information. Past behavioral work suggests an important role for auditory contrast enhancement in normalization: preceding context affects listeners’ perception of subsequent speech sounds. Here, using intracranial electrocorticography in humans, we investigate whether and how such context effects arise in auditory cortex. Participants identified speech sounds that were preceded by phrases from two different speakers whose voices differed along the same acoustic dimension as target words (the lowest resonance of the vocal tract). In every participant, target vowels evoke a speaker-dependent neural response that is consistent with the listener’s perception, and which follows from a contrast enhancement model. Auditory cortex processing thus displays a critical feature of normalization, allowing listeners to extract meaningful content from the voices of diverse speakers