The nature of turbulence in OMC1 at the star forming scale: observations and simulations

Aim: To study turbulence in the Orion Molecular Cloud (OMC1) by comparing observed and simulated characteristics of the gas motions. Method: Using a dataset of vibrationally excited H2 emission in OMC1 containing radial velocity and brightness which covers scales from 70AU to 30000AU, we present the transversal structure functions and the scaling of the structure functions with their order. These are compared with the predictions of two-dimensional projections of simulations of supersonic hydrodynamic turbulence. Results: The structure functions of OMC1 are not well represented by power laws, but show clear deviations below 2000AU. However, using the technique of extended self-similarity, power laws are recovered at scales down to 160AU. The scaling of the higher order structure functions with order deviates from the standard scaling for supersonic turbulence. This is explained as a selection effect of preferentially observing the shocked part of the gas and the scaling can be reproduced using line-of-sight integrated velocity data from subsets of supersonic turbulence simulations. These subsets select regions of strong flow convergence and high density associated with shock structure. Deviations of the structure functions in OMC1 from power laws cannot however be reproduced in simulations and remains an outstanding issue.Comment: 12 pages, 8 figures, accepted A&A. Revised in response to referee. For higher resolution, see http://www.astro.phys.au.dk/~maikeng/sim_paper

Derivation of the Lorentz Force Law, the Magnetic Field Concept and the Faraday-Lenz Law using an Invariant Formulation of the Lorentz Transformation

It is demonstrated how the right hand sides of the Lorentz Transformation equations may be written, in a Lorentz invariant manner, as 4--vector scalar products. This implies the existence of invariant length intervals analogous to invariant proper time intervals. This formalism, making essential use of the 4-vector electromagnetic potential concept, provides a short derivation of the Lorentz force law of classical electrodynamics, the conventional definition of the magnetic field, in terms of spatial derivatives of the 4--vector potential and the Faraday-Lenz Law. An important distinction between the physical meanings of the space-time and energy-momentum 4--vectors is pointed out.Comment: 15 pages, no tables 1 figure. Revised and extended version of physics/0307133 Some typos removed and minor text improvements in this versio

'Improper practices' in great war British cinemas

in Hammond, M and Williams, (Eds), British Silent Cinema and the Great War (2011), Palgrave Macmillan; reproduced with permission of Palgrave Macmillan. This extract is taken from the author's original manuscript and has not been edited. The definitive, published, version of record is available here: http://www.palgrave.com/products/title.aspx?pid=493370Analysis of the environment in which films were viewed is essential in order to gain a fuller understanding of the British cinema experience during the Great War. The exhibition context is of particular importance during the war years, as cinema going throughout this period was far from idyllic; in fact, British cinemas were subject to police scrutiny and were a hub of sexual activity that the government strove to suppress. Many critics have located the reports of these activities as part of a wider ‘moral panic’ regarding the cinema and the films exhibited within it, predominantly orchestrated by religious pressure groups and self-styled ‘moral crusaders’. Lise Shapiro Sanders likens this movement to similar campaigns in the nineteenth century, arguing that, like music halls previously, cinemas were subjected to ‘censorship and ideological control in an endeavour to distribute middle-class codes of social practice to the “lower” classes’. Yet this approach has often been based on the findings of a report by the National Council for Public Morals, with little investigation of the actual data supplied to the committee. Even accounts that have used some of this evidence position it as a minor component, exaggerated out of all proportion in order to satisfy the personal objectives of the moral purity campaigners.While there was a concerted effort throughout the Great War to highlight the perceived social ills of the cinema, I have attempted to present a more balanced account, which details the problems faced by cinemas during this period and the measures sought to improve them

Transverse and longitudinal momentum spectra of fermions produced in strong SU(2) fields

We study the transverse and longitudinal momentum spectra of fermions produced in a strong, time-dependent non-Abelian SU(2) field. Different time-dependent field strengths are introduced. The momentum spectra are calculated for the produced fermion pairs in a kinetic model. The obtained spectra are similar to the Abelian case, and they display exponential or polynomial behaviour at high p_T, depending on the given time dependence. We investigated different color initial conditions and discuss the recognized scaling properties for both Abelian and SU(2) cases.Comment: 10 pages, 11 figures; version accepted to PR

'Against the World': Michael Field, female marriage and the aura of amateurism'

This article considers the case of Katherine Bradley and Edith Cooper, an aunt and niece who lived and wrote together as ‘Michael Field’ in the fin-de-siècle Aesthetic movement. Bradley’s bold statement that she and Cooper were ‘closer married’ than the Brownings forms the basis for a discussion of their partnership in terms of a ‘female marriage’, a union that is reflected, as I will argue, in the pages of their writings. However, Michael Field’s exclusively collaborative output, though extensive, was no guarantee for success. On the contrary, their case illustrates the notion, valid for most products of co-authorship, that the jointly written work is always surrounded by an aura of amateurism. Since collaboration defied the ingrained notion of the author as the solitary producer of his or her work, critics and readers have time and again attempted to ‘parse’ the collaboration by dissecting the co-authored work into its constituent halves, a treatment that the Fields too failed to escape

Transition Radiation in QCD matter

In ultrarelativistic heavy ion collisions a finite size QCD medium is created. In this paper we compute radiative energy loss to zeroth order in opacity by taking into account finite size effects. Transition radiation occurs on the boundary between the finite size medium and the vacuum, and we show that it lowers the difference between medium and vacuum zeroth order radiative energy loss relative to the infinite size medium case. Further, in all previous computations of light parton radiation to zeroth order in opacity, there was a divergence caused by the fact that the energy loss is infinite in the vacuum and finite in the QCD medium. We show that this infinite discontinuity is naturally regulated by including the transition radiation.Comment: 21 page, 22 figure