Collisional Energy Loss of Fast Charged Particles in Relativistic Plasmas

Following an argument by Kirzhnits we rederive an exact expression for the energy loss of a fast charged particle in a relativistic plasma using the quantum field theoretical language. We compare this result to perturbative calculations of the collisional energy loss of an energetic electron or muon in an electron-positron plasma and of an energetic parton in the quark-gluon plasma.Comment: 9 pages, LATEX, 2 PostScript figure

Decay of a Yukawa fermion at finite temperature and applications to leptogenesis

We calculate the decay rate of a Yukawa fermion in a thermal bath using finite temperature cutting rules and effective Green's functions according to the hard thermal loop resummation technique. We apply this result to the decay of a heavy Majorana neutrino in leptogenesis. Compared to the usual approach where thermal masses are inserted into the kinematics of final states, we find that deviations arise through two different leptonic dispersion relations. The decay rate differs from the usual approach by more than one order of magnitude in the temperature range which is interesting for the weak washout regime. We discuss how to arrive at consistent finite temperature treatments of leptogenesis.Comment: 16 pages, 5 figure

The Judiciary in Virginia: Changes and Challenges in Virginia: One Trial Judge\u27s Perspective

With the convening of the 2014 Virginia General Assembly, members of the Senate and House received the anticipated 2013 Judicial Workload Assessment Report-a weighted case load study produced by the National Center for State Courts and commissioned by the legislature during its 2012 session. The purpose of the study was to help guide both the future selection of judges and the allocation of the political boundaries to be served by those judges. The results of the weighted caseload study as contained in the 2013 Report would validate many of those concerns expressed earlier by the 2011 Judicial Boundary Realignment Committee appointed by the Supreme Court. In addition, the 2013 Report would include a myriad of comments and concerns voiced by legislators, lawyers, judges, court personnel, law enforcement, and the general public concerning judicial need in the Commonwealth. This article will seek to describe the results of the 2013 Virginia Judicial Workload Assessment Report within the context of an evolving dialogue in the Virginia General Assembly concerning judicial resources. It is a dialogue that has taken place since the beginning of the Commonwealth and became a focal point during the General Assembly\u27s 2014 session. This dialogue intensified when House Bill 1990 and Senate Bill 1240 were introduced during the General Assembly\u27s 2011 session

The Judiciary in Virginia: Changes and Challenges in Virginia: One Trial Judge\u27s Perspective

With the convening of the 2014 Virginia General Assembly, members of the Senate and House received the anticipated 2013 Judicial Workload Assessment Report-a weighted case load study produced by the National Center for State Courts and commissioned by the legislature during its 2012 session. The purpose of the study was to help guide both the future selection of judges and the allocation of the political boundaries to be served by those judges. The results of the weighted caseload study as contained in the 2013 Report would validate many of those concerns expressed earlier by the 2011 Judicial Boundary Realignment Committee appointed by the Supreme Court. In addition, the 2013 Report would include a myriad of comments and concerns voiced by legislators, lawyers, judges, court personnel, law enforcement, and the general public concerning judicial need in the Commonwealth. This article will seek to describe the results of the 2013 Virginia Judicial Workload Assessment Report within the context of an evolving dialogue in the Virginia General Assembly concerning judicial resources. It is a dialogue that has taken place since the beginning of the Commonwealth and became a focal point during the General Assembly\u27s 2014 session. This dialogue intensified when House Bill 1990 and Senate Bill 1240 were introduced during the General Assembly\u27s 2011 session

Single session and repeated anodal transcranial direct current stimulation over the right dorsolateral prefrontal cortex increases reflective thinking but not working memory updating performance

Background Anodal transcranial direct current stimulation (tDCS) over the right dorsolateral prefrontal cortex (DLPFC) has shown to have effects on different domains of cognition yet there is a gap in the literature regarding effects on reflective thinking performance. Objective The current study investigated if single session and repeated anodal tDCS over the right DLPFC induces effects on judgment and decision-making performance and whether these are linked to working memory (updating) performance or cognitive inhibition. Methods Participants received anodal tDCS over the right DLPFC once (plus sham tDCS in a second session) or twice (24 h apart). In the third group participants received a single session of sham stimulation only. Cognitive characteristic measures were administered pre-stimulation (thinking disposition, impulsivity, cognitive ability). Experimental tasks included two versions of the Cognitive Reflection Test (numeric vs verbal-CRT), a set of incongruent base-rate vignettes, and two working memory tests (Sternberg task and n-back task). Forty-eight participants (mean age = 26.08 ± 0.54 years; 27 females) were recruited. Results Single sessions of tDCS were associated with an increase in reflective thinking performance compared to the sham conditions, with stimulation improving scores on incongruent base rate tasks as well as marginally improving numeric CRT scores (compared to sham), but not thinking tasks without a numeric component (verbal-CRT). Repeated anodal stimulation only improved numeric CRT scores. tDCS did not increase working memory (updating) performance. These findings could not be explained by a practice effect or a priori differences in cognitive characteristics or impulsivity across the experimental groups. Conclusion The current results demonstrate the involvement of the right DLPFC in reflective thinking performance which cannot be explained by working memory (updating) performance or general cognitive characteristics of participants

Photon-Photon Interaction in a Photon Gas

Using the effective Lagrangian for the low energy photon-photon interaction the lowest order photon self energy at finite temperature and in non-equilibrium is calculated within the real time formalism. The Debye mass, the dispersion relation, the dielectric tensor, and the velocity of light following from the photon self energy are discussed. As an application we consider the interaction of photons with the cosmic microwave background radiation.Comment: REVTEX, 7 pages, 1 PostSrcipt figur

Conserved Density Fluctuation and Temporal Correlation Function in HTL Perturbation Theory

Considering recently developed Hard Thermal Loop perturbation theory that takes into account the effect of the variation of the external field through the fluctuations of a conserved quantity we calculate the temporal component of the Euclidian correlation function in the vector channel. The results are found to be in good agreement with the very recent results obtained within the quenched approximation of QCD and small values of the quark mass ($\sim 0.1T$) on improved lattices of size $128^3\times N_\tau$ at ($N_\tau=40, \ T=1.2T_C$), ($N_\tau=48, \ T=1.45T_C$), and ($N_\tau=16, \ T=2.98T_C$), where $N_\tau$ is the temporal extent of the lattice. This suggests that the results from lattice QCD and Hard Thermal Loop perturbation theory are in close proximity for a quantity associated with the conserved density fluctuation.Comment: 16 pages, 4 figures; One para added in introduction, Fig 1 modified; Accepted in Phys. Rev.

Interference phenomena in the JP=1/2−J^P=1/2^--wave in η\eta photoproduction

The recent precise experimental results for the photoproduction of $\eta$-mesons off the neutron measured with the Crystal Ball/TAPS calorimeter at the MAMI accelerator have been investigated in detail in the framework of the Bonn-Gatchina coupled channel model. The main result is that the narrow structure observed in the excitation function of $\gamma n \rightarrow n\eta$ can be reproduced fully with a particular interference pattern in the $J^P=1/2^-$ partial wave. Introduction of the narrow resonance $N(1685)$ with the properties reported in earlier publications deteriorates the quality of the fit.Comment: 10 pages, 13 figures, accepted for publication in EPJ