Vortices in a Thin Film Superconductor with a Spherical Geometry

We report results from Monte Carlo simulations of a thin film superconductor in a spherical geometry within the lowest Landau level approximation. We observe the absence of a phase transition to a low temperature vortex solid phase with these boundary conditions; the system remains in the vortex liquid phase for all accessible temperatures. The correlation lengths are measured for phase coherence and density modulation. Both lengths display identical temperature dependences, with an asymptotic scaling form consistent with a continuous zero temperature transition. This contrasts with the first order freezing transition which is seen in the alternative quasi-periodic boundary conditions. The high temperature perturbation theory and the ground states of the spherical system suggest that the thermodynamic limit of the spherical geometry is the same as that on the flat plane. We discuss the advantages and drawbacks of simulations with different geometries, and compare with current experimental conclusions. The effect of having a large scale inhomogeneity in the applied field is also considered.Comment: This replacment contains substantial revisions: the new article is twice as long with new and different results on the thermodynamic limit on the sphere plus a full discussion on the alternative boundary conditions used in simulations in the LLL approximation. 19 pages, 12 encapsulated PostScript figures, 1 JPEG figure, uses RevTeX (with epsf

Photon Physics in Heavy Ion Collisions at the LHC

Various pion and photon production mechanisms in high-energy nuclear collisions at RHIC and LHC are discussed. Comparison with RHIC data is done whenever possible. The prospect of using electromagnetic probes to characterize quark-gluon plasma formation is assessed.Comment: Writeup of the working group "Photon Physics" for the CERN Yellow Report on "Hard Probes in Heavy Ion Collisions at the LHC", 134 pages. One figure added in chapter 5 (comparison with PHENIX data). Some figures and correponding text corrected in chapter 6 (off-chemical equilibrium thermal photon rates). Some figures modified in chapter 7 (off-chemical equilibrium photon rates) and comparison with PHENIX data adde

Colligative properties of solutions: I. Fixed concentrations

Using the formalism of rigorous statistical mechanics, we study the phenomena of phase separation and freezing-point depression upon freezing of solutions. Specifically, we devise an Ising-based model of a solvent-solute system and show that, in the ensemble with a fixed amount of solute, a macroscopic phase separation occurs in an interval of values of the chemical potential of the solvent. The boundaries of the phase separation domain in the phase diagram are characterized and shown to asymptotically agree with the formulas used in heuristic analyses of freezing point depression. The limit of infinitesimal concentrations is described in a subsequent paper.Comment: 28 pages, 1 fig; see also math-ph/0407035 (both to appear in JSP

Feshbach-Stimulated Photoproduction of a Stable Molecular Condensate

Photoassociation and the Feshbach resonance are, in principle, feasible means for creating a molecular Bose-Einstein condensate from an already-quantum-degenerate gas of atoms; however, mean-field shifts and irreversible decay place practical constraints on the efficient delivery of stable molecules using either mechanism alone. We therefore propose Feshbach-stimulated Raman photoproduction, i.e., a combination of magnetic and optical methods, as a viable means to collectively convert degenerate atoms into a stable molecular condensate with near-unit efficiency.Comment: 5 pages, 3 figures, 1 table; v3 includes few-level diagram of scheme, and added discussion; transferred to PR

Looking backward: From Euler to Riemann

We survey the main ideas in the early history of the subjects on which Riemann worked and that led to some of his most important discoveries. The subjects discussed include the theory of functions of a complex variable, elliptic and Abelian integrals, the hypergeometric series, the zeta function, topology, differential geometry, integration, and the notion of space. We shall see that among Riemann's predecessors in all these fields, one name occupies a prominent place, this is Leonhard Euler. The final version of this paper will appear in the book \emph{From Riemann to differential geometry and relativity} (L. Ji, A. Papadopoulos and S. Yamada, ed.) Berlin: Springer, 2017

Decoherence, einselection, and the quantum origins of the classical

Decoherence is caused by the interaction with the environment. Environment monitors certain observables of the system, destroying interference between the pointer states corresponding to their eigenvalues. This leads to environment-induced superselection or einselection, a quantum process associated with selective loss of information. Einselected pointer states are stable. They can retain correlations with the rest of the Universe in spite of the environment. Einselection enforces classicality by imposing an effective ban on the vast majority of the Hilbert space, eliminating especially the flagrantly non-local "Schr\"odinger cat" states. Classical structure of phase space emerges from the quantum Hilbert space in the appropriate macroscopic limit: Combination of einselection with dynamics leads to the idealizations of a point and of a classical trajectory. In measurements, einselection replaces quantum entanglement between the apparatus and the measured system with the classical correlation.Comment: Final version of the review, with brutally compressed figures. Apart from the changes introduced in the editorial process the text is identical with that in the Rev. Mod. Phys. July issue. Also available from http://www.vjquantuminfo.or

Chronic non-specific low back pain - sub-groups or a single mechanism?

Copyright 2008 Wand and O'Connell; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Background: Low back pain is a substantial health problem and has subsequently attracted a considerable amount of research. Clinical trials evaluating the efficacy of a variety of interventions for chronic non-specific low back pain indicate limited effectiveness for most commonly applied interventions and approaches. Discussion: Many clinicians challenge the results of clinical trials as they feel that this lack of effectiveness is at odds with their clinical experience of managing patients with back pain. A common explanation for this discrepancy is the perceived heterogeneity of patients with chronic non-specific low back pain. It is felt that the effects of treatment may be diluted by the application of a single intervention to a complex, heterogeneous group with diverse treatment needs. This argument presupposes that current treatment is effective when applied to the correct patient. An alternative perspective is that the clinical trials are correct and current treatments have limited efficacy. Preoccupation with sub-grouping may stifle engagement with this view and it is important that the sub-grouping paradigm is closely examined. This paper argues that there are numerous problems with the sub-grouping approach and that it may not be an important reason for the disappointing results of clinical trials. We propose instead that current treatment may be ineffective because it has been misdirected. Recent evidence that demonstrates changes within the brain in chronic low back pain sufferers raises the possibility that persistent back pain may be a problem of cortical reorganisation and degeneration. This perspective offers interesting insights into the chronic low back pain experience and suggests alternative models of intervention. Summary: The disappointing results of clinical research are commonly explained by the failure of researchers to adequately attend to sub-grouping of the chronic non-specific low back pain population. Alternatively, current approaches may be ineffective and clinicians and researchers may need to radically rethink the nature of the problem and how it should best be managed

Doubling of marine dinitrogen-fixation rates based on direct measurements

Biological dinitrogen fixation provides the largest input of nitrogen to the oceans, therefore exerting important control on the ocean’s nitrogen inventory and primary productivity. Nitrogen-isotope data fromocean sediments suggest that the marine-nitrogen inventory has been balanced for the past 3,000 years (ref. 4). Producing a balanced marine-nitrogenbudget based on direct measurements has proved difficult, however, with nitrogen loss exceeding the gain from dinitrogen fixation by approximately 200 TgNyr-1 (refs 5, 6). Here we present data from the Atlantic Ocean and show that the most widely used method of measuring oceanic N2-fixation rates underestimates the contribution of N2-fixing microorganisms (diazotrophs) relative to a newly developed method. Using molecular techniques to quantify the abundance of specific clades of diazotrophs in parallel with rates of 15N2 incorporation into particulate organic matter, we suggest that the difference between N2-fixation rates measured with the established method and those measured with the new method8 can be related to the composition of the diazotrophic community. Our data show that in areas dominated by Trichodesmium, the established method underestimatesN2-fixation rates by an averageof 62%. We also find that the newly developed method yields N2-fixation rates more than six times higher than those from the established method when unicellular, symbiotic cyanobacteria and c-proteobacteria dominate the diazotrophic community. On the basis of average areal rates measured over the Atlantic Ocean, we calculated basin-wide N2-fixation rates of 14+/-1TgNyr-1 and 24+/-1TgNyr-1 for the established and new methods, respectively. If our findings can be extrapolated to other ocean basins, this suggests that the global marine N2-fixation rate derived from direct measurements may increase from 103+/-8TgNyr-1 to 177+/-8TgNyr-1, and that the contribution of N2 fixers other than Trichodesmium is much more significant than was previously thought

An equal right to inherit? Women's land rights, customary law and constitutional reform in Tanzania

This article explores contemporary contestations surrounding women’s inheritance of land in Africa. Legal activism has gained momentum, both in agendas for law reform and in test case litigation, which reached United Nations Committee on the Elimination of Discrimination against Women in ES and SC v. United Republic of Tanzania. Comparing the approach of Tanzania to that of its neighbours, Uganda, Kenya and Rwanda, this article explores patterns of resistance and omission towards enshrining an equal right to inherit in land and succession laws. It identifies two main reasons: neoliberal drivers for land law reform of the 1990s and sociopolitical sensitivity surrounding inheritance of land. It argues that a progressive approach to constitutional and law reform on women’s land rights requires understanding of the realities of claims to family land based on kinship relations. It calls for a holistic approach to land, marriage and inheritance law reform underpinned with constitutional rights to equality and progressive interpretations of living customary law