The effects of light propagation in constant magnetic and electric backgrounds are considered in the framework of the effective action approach. We use the exact analytic series representation for the one-loop effective action of QED and apply it to the birefringence effect. Analytical results for the light velocity modes are obtained for weak and strong field regime. We present asymptotic form...

It says in the report by Wang et al. that a negative group velocity u = −c/310 is obtained and that a pulse advancement shift 62-ns is measured. The authors claim that the negative group velocity is associated with superluminal light propagation and that the pulse advancement is not at odds with causality or special relativity. However, it is shown here that their conclusions above are not true...

We present a simple proof, using the conservation equations, that any quantum stress tensor on Kerr space-time which is isotropic in a frame which rotates rigidly with the angular velocity of the event horizon must be divergent at the velocity of light surface. We comment on our result in the light of the absence of a ‘true Hartle-Hawking’ vacuum for Kerr.

introduction: lasers, light emitting diodes (leds) and super luminous diodes (slds) are widely used to treat selected musculoskeletal, integumentary and neurological conditions. the mechanisms underlying the reported treatment effects of light therapy are unclear and the physiologic effect of light on a variety of tissues, particularly neurological, is mostly unknown. a few researchers have rep...

Although research has provided evidence of increased muscular performance following a facilitation set of resistance exercise, this has not been established for use prior to measuring baseball bat velocity. The purpose of this study was to determine the effectiveness of selected weighted bat warm-up protocols to enhance bat velocity in collegiate baseball players. Nineteen collegiate baseball p...

This paper introduces an optical measurement system for shock wave characteristics. The system works by mountinga metal plate attached to spring mounts against the shock wavefront. This set is sealed and can plot the shock wave pressure diagram by measuring plate's displacement, radiation and changing the reflection of light during shock wave conflict, and converting these optical data to volta...

Calcium accumulation by two fractions of sarcoplasmic reticulum presumably derived from longitudinal tubules (light vesicles) and terminal cisternae (heavy vesicles) was examined radiochemically in the presence of various free Mg2+ concentrations. Both fractions of sarcoplasmic reticulum exhibited a Mg2+-dependent increase in phosphate-supported calcium uptake velocity, though half-maximal velo...

Around 1930, both Gregory Breit and Erwin Schrödinger showed that the eigenvalues of the velocity of a particle described by wavepacket solutions to the Dirac equation are simply ±c, the speed of light. This led Schrödinger to coin the term Zitterbewegung, which is German for “trembling motion”, where all particles of matter (fermions) zig-zag back-and-forth at only the speed of light. The resu...

The absolute phase refractive index n relates the phase velocity v in matter to the vacuum light velocity c(n » civ). It is determined by the molecular polarizability of the medium and gives insight to the interaction of light with matter and the structure of substances. 3 Additionally the group refractive index ng is needed to describe light pulse propagation, 4 5 which is defined as the ratio...

We reveal that the reduction of the group velocity of light in periodic waveguides is generically associated with the presence of circulating energy flows or optical vortices. We show that the energy flows are gradually frozen for slow-light at the Brillouin zone edge, whereas vortices persist for slow-light states having non-vanishing phase velocity inside the Brillouin zone. We also demonstra...