Bound on the Photon Charge from the Phase Coherence of Extragalactic Radiation

If the photon possessed a nonzero charge, then electromagnetic waves traveling along different paths would acquire Aharonov-Bohm phase differences. The fact that such an effect has not hindered interferometric astronomy places a bound on the photon charge estimated to be at the 10^(-32) e level if all photons have the same charge and 10^(-46) e if different photons can carry different charges.Comment: 8 pages, new bound added, version appearing in Phys. Rev. Let

SBML Level 3 Package Proposal: Flux

This document describes an easy to implement package for storing information related 
to flux balance analysis of SBML Level 3 models (the FBA package). In addition, 
we provide an example of how this package may be implemented and used as a SBML
Level 2 annotation

Radiatively Induced Lorentz and Gauge Symmetry Violation in Electrodynamics with Varying alpha

A time-varying fine structure constant alpha(t) could give rise to Lorentz- and CPT-violating changes to the vacuum polarization, which would affect photon propagation. Such changes to the effective action can violate gauge invariance, but they are otherwise permitted. However, in the minimal theory of varying alpha, no such terms are generated at lowest order. At second order, vacuum polarization can generate an instability--a Lorentz-violating analogue of a negative photon mass squared -m^2 proportional to alpha [(d alpha/dt) / alpha]^2 log (Lambda^2), where Lambda is the cutoff for the low-energy effective theory.Comment: 14 page

A Bayesian Filtering Algorithm for Gaussian Mixture Models

A Bayesian filtering algorithm is developed for a class of state-space systems that can be modelled via Gaussian mixtures. In general, the exact solution to this filtering problem involves an exponential growth in the number of mixture terms and this is handled here by utilising a Gaussian mixture reduction step after both the time and measurement updates. In addition, a square-root implementation of the unified algorithm is presented and this algorithm is profiled on several simulated systems. This includes the state estimation for two non-linear systems that are strictly outside the class considered in this paper

Limits on Neutron Lorentz Violation from the Stability of Primary Cosmic Ray Protons

Recent evidence appears to confirm that the ultra-high-energy primary cosmic ray spectrum consists mostly of protons. The fact that these protons can traverse large distances to reach Earth allows us to place bounds on Lorentz violations. The protons neither emit vacuum Cerenkov radiation nor $\beta$-decay into neutrons, and this constrains six previously unmeasured coefficients in the neutron sector at the 5 x 10^(-14) level. Among the coefficients bounded here for the first time are those that control spin-independent boost anisotropy for neutrons. This is a phenomenon which could have existed (in light of the preexisting bounds) without additional fine tuning. There are also similar bounds for others species of hadrons. The bounds on Lorentz violation for neutral pions are particularly strong, at the 4 x 10^(-21) level, eleven orders of magnitude better than previous constraints.Comment: 13 pages, version to appear in Phys. Rev.

Does haste make waste? The human factors of overtaking land design

The aim of this research was to improve overtaking safety and efficiency through improvements in road signage, markings, geometry and speed control associated with the placement and layout of passing lanes. The approach of the research was to explore the effects of several types of overtaking lane treatments in the safety and controlled environment of a state-of-the-art driving simulator. It was found that under the most benign conditions there were no differential effects of the three treatments. With poorer visibility or more taxing road geometry, the drivers relied more heavily on the road markings and signage and the effects of the treatments become more pronounced. The sensitivity to the more "challenging" situations was borne out by the greater speed differential between merge area sections at these sites

This is exactly what this study is all about and it is happening right in front of me! Using Participatory action research to awaken a sense of injustice within a privileged institution

Rockport is an elite, all boys, day school in the northeast United States. It educates mostly white, wealthy, young men. Student researchers, faculty researchers and I collaborated to study bullying at Rockport using an approach to research known as participatory action research (PAR). In the process we also gained a better understanding of how privilege, especially gendered privilege, was socialized and (re)produced. The participatory research spaces that emerged in our project - grounded in the experiences of students, teachers, and administrators - facilitated critical awareness of self and context that Deutsch (2006) referred to as awaking the sense of injustice. Over the course of a year, our research at Rockport collected data of local consequence and in doing so, built institutional momentum that has since become a school-wide and ongoing initiative to address bullying. As a result, this work was a form of counter-hegemonic action