Coherent and squeezed states in black-hole evaporation

In earlier Letters, we adopted a complex approach to quantum processes in the formation and evaporation of black holes. Taking Feynman's $+i\epsilon$ prescription, rather than than one of the more usual approaches, we calculated the quantum amplitude (not just the probability density) for final weak-field configurations following gravitational collapse to a black hole with subsequent evaporation. What we have done is to find quantum amplitudes relating to a pure state at late times following black-hole matter collapse. Such pure states are then shown to be susceptible to a description in terms of coherent and squeezed states - in practice, this description is not very different from that for the well-known highly-squeezed final state of the relic radiation background in inflationary cosmology. The simplest such collapse model involves Einstein gravity with a massless scalar field. The Feynman approach involves making the boundary-value problem for gravity and a massless scalar field well-posed. To define this, let T be the proper-time separation, measured at spatial infinity, between two space-like hypersurfaces on which initial (collapse) and final (evaporation) data are posed. Then, in this approach, one rotates T by a complex phase exp(-i\delta) into the lower half-plane. In an adiabatic approximation, the resulting quantum amplitude may be expressed in terms of generalised coherent states of the quantum oscillator, and a physical interpretation is given. A squeezed-state representation, as above, then follows

On the cohomology rings of tree braid groups

Let $\Gamma$ be a finite connected graph. The (unlabelled) configuration space $UC^n \Gamma$ of $n$ points on $\Gamma$ is the space of $n$-element subsets of $\Gamma$. The $n$-strand braid group of $\Gamma$, denoted $B_n\Gamma$, is the fundamental group of $UC^n \Gamma$. We use the methods and results of our paper "Discrete Morse theory and graph braid groups" to get a partial description of the cohomology rings $H^*(B_n T)$, where $T$ is a tree. Our results are then used to prove that $B_n T$ is a right-angled Artin group if and only if $T$ is linear or $n<4$. This gives a large number of counterexamples to Ghrist's conjecture that braid groups of planar graphs are right-angled Artin groups.Comment: 25 pages, 7 figures. Revised version, accepted by the Journal of Pure and Applied Algebr

Potential for a new muon g-2 experiment

A new experiment to measure the muon g-2 factor is proposed. We suppose the sensitivity of this experiment to be about 0.03 ppm. The developed experiment can be performed on an ordinary storage ring with a noncontinuous field created by usual magnets. When the total length of straight sections of the ring is appropriate, the spin rotation frequency becomes almost independent of the particle momentum. In this case, a high-precision measurement of an average magnetic field can be carried out with polarized proton beams. A muon beam energy can be arbitrary. Possibilities to avoid a betatron resonance are analyzed and corrections to the g-2 frequency are considered.Comment: 5 pages, 1 figur

Demons, devils and witches: the occult in heavy metal music

Heavy Metal has developed from a British fringe genre of rock music in the late 1960s to a global mass market consumer-good in the early twenty-first century. Early proponents of the musical style, such as Black Sabbath, Deep Purple, Judas Priest, Saxon, Uriah Heep and Iron Maiden, were mostly seeking to reach a young male audience. Songs were often filled with violent, sexist and nationalistic themes but were also speaking to the growing sense of deterioration in social and professional life. At the same time, however, Heavy Metal was seriously indebted to the legacies of blues and classical music as well as to larger literary and cultural themes. The genre also produced mythological concept albums and rewritings of classical poems. In other words, Heavy Metal tried from the beginning to locate itself in a liminal space between pedestrian mass culture and a rather elitist adherence to complexity and musical craftsmanship, speaking from a subaltern position against the hegemonic discourse. This collection of essays provides a comprehensive and multi-disciplinary look at British Heavy Metal from its beginning through The New Wave of British Heavy Metal up to the increasing internationalization and widespread acceptance in the late 1980s. The individual chapter authors approach British Heavy Metal from a textual perspective, providing critical analysis of the politics and ideology behind the lyrics, images and performances. Rather than focus on individual bands or songs, the essays collected here argue with the larger system of Heavy Metal music in mind, providing comprehensive analysis that relate directly to the larger context of British life and culture. The wide range of approaches should provide readers from various disciplines with new and original ideas about the study of this phenomenon of popular culture

Amachi In Brief

This first issue in P/PV's In Brief series focuses on the Amachi program, which partners faith-based organizations with public agencies and nonprofit service providers to identify the children of prisoners and match them with caring adult volunteers.Amachi In Brief touches on the program's development and recruiting strategies, its early results and its expansion into new cities