Thickness of the strangelet-crystal crust of a strange star

It has recently been pointed out that if the surface tension of quark matter is low enough, the surface of a strange star will be a crust consisting of a crystal of charged strangelets in a neutralizing background of electrons. This affects the behavior of the surface, and must be taken into account in efforts to observationally rule out strange stars. We calculate the thickness of this ``mixed phase'' crust, taking into account the effects of surface tension and Debye screening of electric charge. Our calculation uses a generic parametrization of the equation of state of quark matter. For a reasonable range of quark matter equations of state, and surface tension of order a few MeV/fm^2, we find that the preferred crystal structure always involves spherical strangelets, not rods or slabs of quark matter. We find that for a star of radius 10 km and mass 1.5 Msolar, the strangelet-crystal crust can be from zero to hundreds of meters thick, the thickness being greater when the strange quark is heavier, and the surface tension is smaller. For smaller quark stars the crust will be even thicker.Comment: 10 pages, LaTe

Analysis of Quark Mixing Using Binary Tetrahedral Flavor Symmetry

Using the binary tetrahedral group $T^{'}$, the three angles and phase of the quark CKM mixing matrix are pursued by symmetry-breaking which involves $T^{'}$-doublet VEVs and the Chen-Mahanthappa CP-violation mechanism. The NMRT$^{'}$M, Next-to-Minimal-Renormalizable -T$^{'}$-Model is described, and its one parameter comparison to experimental data is explored.Comment: 14 pages latex. Two .eps figures include

Binary Tetrahedral Flavor Symmetry

A study of the T' Model and its variants utilizing Binary Tetrahedral Flavor Symmetry. We begin with a description of the historical context and motivations for this theory, together with some conceptual background for added clarity, and an account of our theory's inception in previous works. Our model endeavors to bridge two categories of particles, leptons and quarks, a unification made possible by the inclusion of additional Higgs particles, shared between the two fermion sectors and creating a single coherent system. This is achieved through the use of the Binary Tetrahedral symmetry group and an investigation of the Tribimaximal symmetry evidenced by neutrinos. Our work details perturbations and extensions of this T' Model as we apply our framework to neutrino mixing, quark mixing, unification, and dark matter. Where possible, we evaluate model predictions against experimental results and find excellent matching with the atmospheric and reactor neutrino mixing angles, an accurate prediction of the Cabibbo angle, and a dark matter candidate that remains outside the limits of current tests. Additionally, we include mention of a number of unanswered questions and remaining areas of interest for future study. Taken together, we believe these results speak to the promising potential of finite groups and flavor symmetries to act as an approximation of nature.Comment: PhD thesis, University of North Carolina at Chapel Hill, April 201

Quartification with T' Flavor

In the simplest (non-quiver) unified theories, fermion families are often treated sequentially and a flavor symmetry may act similarly. As an alternative with non-sequential flavor symmetry, we consider a model based on the group (T'*Z_2)_global * [SU(3)^4]_local which combines the predictions of T' flavor symmetry with the features of a unified quiver gauge theory. The model accommodates the relationships between mixing angles separately for neutrinos, and for quarks, which have been previously predicted with T'. This quiver unification theory makes predictions of several additional gauge bosons and bifundamental fermions at the TeV scale.Comment: 8 pages, LaTex; added references and clarifie

Nonzero theta_13 signals nonmaximal atmospheric neutrino mixing

From recent groundbreaking experiments, it is now known that the Pontecorvo-Maki-Nakagawa-Sakata mixing differs significantly from the tribimaximal model in which theta_13=0 and theta_23=pi/4. Flavor symmetry can require that the departures from these two equations are linearly related. T' and A_4, which successfully accommodated the pre-T2K Pontecorvo-Maki-Nakagawa-Sakata matrix, predict that 38.07 deg.< theta_23 <39.52 deg. at 95% C.L.. The best fit values, combining the model predictions with T2K, MINOS, Double Chooz, Daya Bay, and RENO data, are theta_23=38.7 deg. and theta_13=8.9 deg.

Dark matter from binary tetrahedral flavor symmetry

The minimal renormalizable T' x Z2model (MRT'M) is slightly extended in its Higgs scalar sector such that the abelian part of the flavor symmetry enlarges to (Z2x Z'2). All standard model and original MRT'M states will transform trivially under Z'2. Inspired by the Valencia group's A4model building, we propose a T' WIMP candidate as the lightest Z'2odd scalar. This extension of the prior MRT'M model maintains the successful predictions for the neutrino mixing matrix and the Cabibbo angle, and provides an attractive candidate for dark matter ((ΦWIMP) with MΦ≃780 GeV

Predictions of Neutrino Mixing Angles in a T'Model

Flavor symmetry ($T^{'} \times Z_2$) where $T^{'}$ is the binary tetrahedral group predicts for neutrino mixing angles $\theta_{13} = \sqrt{2} (\frac{\pi}{4} - \theta_{23})$ and, with one phenomenological input, provides upper and lower bounds on both $\theta_{13}$ and $\theta_{23}$. The predictions arise from the deviation of the Cabibbo angle $\Theta_{12}$ from its lowest-order value $\tan 2\Theta_{12} = (\sqrt{2})/3$ and from the $T^{'}$ mechanism which relates mixing of $(\nu_{\tau}, \nu_{\mu}, \nu_e)$ neutrinos to mixing of $(s, d)$ quarks.Comment: Typos. Reference adde

Nonzero theta_13 signals nonmaximal atmospheric neutrino mixing

From recent groundbreaking experiments, it is now known that the Pontecorvo-Maki-Nakagawa-Sakata mixing differs significantly from the tribimaximal model in which theta_13=0 and theta_23=pi/4. Flavor symmetry can require that the departures from these two equations are linearly related. T' and A_4, which successfully accommodated the pre-T2K Pontecorvo-Maki-Nakagawa-Sakata matrix, predict that 38.07 deg.< theta_23 <39.52 deg. at 95% C.L.. The best fit values, combining the model predictions with T2K, MINOS, Double Chooz, Daya Bay, and RENO data, are theta_23=38.7 deg. and theta_13=8.9 deg..Comment: 4 pages, 1 figure. Published version Phys. Rev.

Evaluating older drivers’ skills

The Contracting Officer's Technical Representative for this project was Dr. Kathy Sifrit.Research has demonstrated that older drivers pose a higher risk of involvement in fatal crashes at intersections than younger drivers. Age-triggered restrictions are problematic as research shows that the majority of older people have unimpaired driving performance. Thus, it has become important to be able to identify which drivers are at risk of crashes and apply driving limitations based on this risk (instead of age alone). The objective of this project was to review the report from the 2003 University of Florida Consensus Conference as well as other important documents on similar topics, and to interview experts to obtain information about the strengths and weaknesses of these specialist-administered screening and assessment tools, self-screening instruments and training methods. This report will help to guide future research by highlighting tools and methods commonly used by clinicians that have not yet been adequately evaluated and those which may already be recommended for use. The goal was not to reach consensus but to provide a rich background from the literature combined with expert opinions in an attempt to guide decisions and research goals related to these evaluation tools.National Highway Traffic Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/98832/1/102948.pd

Christian-Muslim Relations in a State Church Situation: Politics of Religion and Interfaith Dialogue

No abstract availabl