Multifrequency Method for Mapping Active Galactic Nuclei with Allowance for the Frequency-Dependent Image Shift

We consider the problem of multifrequency VLBA image synthesis and spectral-index mapping for active galactic nuclei related to the necessity of taking into account the frequency-dependent image shift. We describe our generalized multifrequency synthesis algorithm with a spectral correction based on the maximum entropy method. The results of our processing of multifrequency VLBI data for the radio sources J2202+4216, J0336+3218, and J1419+5423 are presented.Comment: 12 pages, 2 tables, 6 figure

A Bayesian Variable Selection Approach to Major League Baseball Hitting Metrics

Numerous statistics have been proposed for the measure of offensive ability in major league baseball. While some of these measures may offer moderate predictive power in certain situations, it is unclear which simple offensive metrics are the most reliable or consistent. We address this issue with a Bayesian hierarchical model for variable selection to capture which offensive metrics are most predictive within players across time. Our sophisticated methodology allows for full estimation of the posterior distributions for our parameters and automatically adjusts for multiple testing, providing a distinct advantage over alternative approaches. We implement our model on a set of 50 different offensive metrics and discuss our results in the context of comparison to other variable selection techniques. We find that 33/50 metrics demonstrate signal. However, these metrics are highly correlated with one another and related to traditional notions of performance (e.g., plate discipline, power, and ability to make contact)

Improved Limit on theta_{13} and Implications for Neutrino Masses in Neutrino-less Double Beta Decay and Cosmology

We analyze the impact of a measurement, or of an improved bound, on theta_{13} for the determination of the effective neutrino mass in neutrino-less double beta decay and cosmology. In particular, we discuss how an improved limit on (or a specific value of) theta_{13} can influence the determination of the neutrino mass spectrum via neutrino-less double beta decay. We also discuss the interplay with improved cosmological neutrino mass searches.Comment: 22 pages, 5 figures. Minor corrections, matches version in PR

Magnetoconductivity in the presence of Bychkov-Rashba spin-orbit interaction

A closed-form analytic formula for the magnetoconductivity in the diffusive regime is derived in the presence of Bychkov-Rashba spin-orbit interaction in two dimensions. It is shown that at low fields B << B_{so}, where B_{so} is the characteristic field associated with spin precession, D'yakonov-Perel' mechanism leads to spin relaxation, while for B >> B_{so} spin relaxation is suppressed and the resulting spin precession contributes a Berry phase-like spin phase to the magnetoconductivity. The relative simplicity of the formula greatly facilitates data fitting, allowing for the strength of the spin-orbit coupling to be easily extracted

Majorana Fermions in Strongly Interacting Helical Liquids

Majorana fermions were proposed to occur at edges and interfaces of gapped one-dimensional systems where phases with different topological character meet due to an interplay of spin-orbit coupling, proximity-induced superconductivity and external magnetic fields. Here we investigate the effect of strong particle interactions, and show that the helical liquid offers a mechanism that protects the very existence of Majorana edge states: whereas moderate interactions close the proximity gap which supports the edge states, in helical liquids the gap re-opens due to two-particle processes. However, gapless fermionic excitations occur at spatial proximity to the Majorana states at interfaces and may jeopardize their long term Majorana coherence.Comment: 7 pages, 4 figure

Getting a kick out of the stellar disk(s) in the galactic center

Recent observations of the Galactic center revealed a nuclear disk of young OB stars, in addition to many similar outlying stars with higher eccentricities and/or high inclinations relative to the disk (some of them possibly belonging to a second disk). Binaries in such nuclear disks, if they exist in non-negligible fractions, could have a major role in the evolution of the disks through binary heating of this stellar system. We suggest that interactions with/in binaries may explain some (or all) of the observed outlying young stars in the Galactic center. Such stars could have been formed in a disk, and later on kicked out from it through binary related interactions, similar to ejection of high velocity runaway OB stars in young clusters throughout the galaxy.Comment: 2 pages, 2 figs. To be published in the proceedings of the IAU 246 symposium on "Dynamical evolution of dense stellar systems