Stopping distance for high energy jets in weakly-coupled quark-gluon plasmas

We derive a simple formula for the stopping distance for a high-energy quark traveling through a weakly-coupled quark gluon plasma. The result is given to next-to-leading-order in an expansion in inverse logarithms ln(E/T), where T is the temperature of the plasma. We also define a stopping distance for gluons and give a leading-log result. Discussion of stopping distance has a theoretical advantage over discussion of energy loss rates in that stopping distances can be generalized to the case of strong coupling, where one may not speak of individual partons.Comment: 20 pages, 4 figures [change from v1: fixed embarrassing reference error

Political preferences and threat perception: opportunities for neuroimaging and developmental research

People have preferences for how their social environment is organized and governed. One influential explanation of variation in these preferences focuses on individual differences in sensitivity to threats. Recent research demonstrates that this relationship is a function not only of the degree of sensitivity (greater or lesser), but also of the danger in question (i.e. immigration or climate change) and the kind of potential harm it poses (i.e. physical pain or contamination). Since many political issues are not unambiguously of one kind, the structure of an individual's reactions to perceived political threats is also uncertain. We argue that future research should (i) use functional neuroimaging to test these structures and (ii) investigate the role of social learning in their transmission

Three-dimensional Roton-Excitations and Supersolid formation in Rydberg-excited Bose-Einstein Condensates

We study the behavior of a Bose-Einstein condensate in which atoms are weakly coupled to a highly excited Rydberg state. Since the latter have very strong van der Waals interactions, this coupling induces effective, nonlocal interactions between the dressed ground state atoms, which, opposed to dipolar interactions, are isotropically repulsive. Yet, one finds partial attraction in momentum space, giving rise to a roton-maxon excitation spectrum and a transition to a supersolid state in three-dimensional condensates. A detailed analysis of decoherence and loss mechanisms suggests that these phenomena are observable with current experimental capabilities.Comment: 4 pages, 5 figure

The Nazi holocaust

The Nazi Holocaust represents an original, interdisciplinary contribution to the field of education, with special reference to the teaching of the humanities in general, and history in particular. Its claim to originality lies in its overall educational conception, in its approach to understanding and transmitting the memory' and lessons of the Holocaust and in its filling a palpable gap. Before the publication of my work, despite hundreds of volumes devoted at various levels to the subject - from fields as disparate as history, psychology, sociology, theology, moral philosophy, literature and jurisprudence - there was no single accessible, multidimensional volume for the many hundreds of teachers who were faced - often suddenly, as in the case of Britain - with the intimidating task of teaching this most complex of subjects; under-informed and under-resourced, they were often resigned to teaching it badly or not at all. Those works that were available were either too simplistic or were too narrowly focused, over-scholasticised and sometimes shrouded in mystification: they generally failed to take sufficient stock of the fact that the Holocaust had historical and ideological antecedents, such decontextualisation being, perhaps, the single most glaring educational problem I identified; virtually all 'historical' works failed even to ask, let alone address, the serious moral and psychological questions raised by the subject, and - most seriously - often formed part of an extremist, partisan and passionate literature, seemingly unable or unwilling to grapple with its broader educational meaning [a meaning that I would argue in my book went way beyond the world of its Jewish victims]. My work set out to make good these shortcomings, and to attempt a breakthrough in the transmission of its most salient messages for all. In a clear, educationally provocative, yet scholarly fashion, I sought to mediate between a vast, often unapproachable literature, and the hard-pressed teacher and student who wrestle with its meaning. By examining it from different disciplinary perspectives, I also wanted to demonstrate that no one discipline can claim an educational monopoly on this subject. My work aimed to break new ground in the educational sphere by locating theHolocaust within a number of historically important and educationally desirable contexts: namely Jewish history, modem German history, genocide in the modem age, and the larger story of human indifference, bigotry and the triumph of ideology over conscience. It examined the impact and aftermath of the Holocaust, considering its implications not only for the surviving Jewish world (including the State of Israel) but for all humanity. In such a highly-charged emotional and intellectual arena, my work aimed, uniquely, to strike an enlightened balance between various Scyllas and Charybdises, standing, as it were, in the educational and historiographical crossfire of often diametrically opposed views. The philosophical starting-point of my work is that the Holocaust, though unquestionably a unique historical event, should not be cordoned off from the rest of human experience and imprisoned within the highly-charged realm of 'Jewish experience' . It offers a new educational perspective by stressing that the attempt to understand even so appalling a tragedy as the Holocaust is, like all good education, ultimately about the making, and not the breaking, of connections. In short, the Holocaust as educational theme is both unique and universal

Relativistic viscoelastic fluid mechanics

A detailed study is carried out for the relativistic theory of viscoelasticity which was recently constructed on the basis of Onsager's linear nonequilibrium thermodynamics. After rederiving the theory using a local argument with the entropy current, we show that this theory universally reduces to the standard relativistic Navier-Stokes fluid mechanics in the long time limit. Since effects of elasticity are taken into account, the dynamics at short time scales is modified from that given by the Navier-Stokes equations, so that acausal problems intrinsic to relativistic Navier-Stokes fluids are significantly remedied. We in particular show that the wave equations for the propagation of disturbance around a hydrostatic equilibrium in Minkowski spacetime become symmetric hyperbolic for some range of parameters, so that the model is free of acausality problems. This observation suggests that the relativistic viscoelastic model with such parameters can be regarded as a causal completion of relativistic Navier-Stokes fluid mechanics. By adjusting parameters to various values, this theory can treat a wide variety of materials including elastic materials, Maxwell materials, Kelvin-Voigt materials, and (a nonlinearly generalized version of) simplified Israel-Stewart fluids, and thus we expect the theory to be the most universal description of single-component relativistic continuum materials. We also show that the presence of strains and the corresponding change in temperature are naturally unified through the Tolman law in a generally covariant description of continuum mechanics.Comment: 52pages, 11figures; v2: minor corrections; v3: minor corrections, to appear in Physical Review E; v4: minor change

Relativistic magnetohydrodynamics in one dimension

We derive a number of solution for one-dimensional dynamics of relativistic magnetized plasma that can be used as benchmark estimates in relativistic hydrodynamic and magnetohydrodynamic numerical codes. First, we analyze the properties of simple waves of fast modes propagating orthogonally to the magnetic field in relativistically hot plasma. The magnetic and kinetic pressures obey different equations of state, so that the system behaves as a mixture of gases with different polytropic indices. We find the self-similar solutions for the expansion of hot strongly magnetized plasma into vacuum. Second, we derive linear hodograph and Darboux equations for the relativistic Khalatnikov potential, which describe arbitrary one-dimensional isentropic relativistic motion of cold magnetized plasma and find their general and particular solutions. The obtained hodograph and Darboux equations are very powerful: system of highly non-linear, relativistic, time dependent equations describing arbitrary (not necessarily self-similar) dynamics of highly magnetized plasma reduces to a single linear differential equation.Comment: accepted by Phys. Rev.

Equilibrium topology of the intermediate state in type-I superconductors of different shapes

High-resolution magneto-optical technique was used to analyze flux patterns in the intermediate state of bulk Pb samples of various shapes - cones, hemispheres and discs. Combined with the measurements of macroscopic magnetization these results allowed studying the effect of bulk pinning and geometric barrier on the equilibrium structure of the intermediate state. Zero-bulk pinning discs and slabs show hysteretic behavior due to geometric barrier that results in a topological hysteresis -- flux tubes on penetration and lamellae on flux exit. (Hemi)spheres and cones do not have geometric barrier and show no hysteresis with flux tubes dominating the intermediate field region. It is concluded that flux tubes represent the equilibrium topology of the intermediate state in reversible samples, whereas laminar structure appears in samples with magnetic hysteresis (either bulk or geometric). Real-time video is available in http://www.cmpgroup.ameslab.gov/supermaglab/video/Pb.html NOTE: the submitted images were severely downsampled due to Arxiv's limitations of 1 Mb total size