3,690 research outputs found
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
The velocity anisotropy - density slope relation
One can solve the Jeans equation analytically for equilibrated dark matter
structures, once given two pieces of input from numerical simulations. These
inputs are 1) a connection between phase-space density and radius, and 2) a
connection between velocity anisotropy and density slope, the \alpha-\beta
relation. The first (phase-space density v.s. radius) has already been analysed
through several different simulations, however the second (\alpha-\beta
relation) has not been quantified yet. We perform a large set of numerical
experiments in order to quantify the slope and zero-point of the \alpha-\beta
relation. We find strong indication that the relation is indeed an attractor.
When combined with the assumption of phase-space being a power-law in radius,
this allows us to conclude that equilibrated dark matter structures indeed have
zero central velocity anisotropy \beta_0 = 0, central density slope of \alpha_0
= -0.8, and outer anisotropy of \beta_\infty = 0.5.Comment: 15 pages, 7 figure
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
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
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
Superior olivary complex organization and cytoarchitecture may be correlated with function and catarrhine primate phylogeny
In the mammalian auditory system, the medial nucleus of the trapezoid body and the lateral superior olive (MNTB-LSO system) contribute to binaural intensity processing and lateralization. Localization precision varies with the sound frequencies. As recency of common ancestry with human beings increases, primates have improved low-frequency sensitivity and reduced sensitivity to higher frequencies. The medial part of the MNTB is devoted to higher frequency processing. Thus, its high-frequency-dependent function is nearly lost in humans and its role in binaural processing as part of the contralateral pathway to the LSO remains questionable. Here, Nissl-stained sections of the superior olivary complex of man (Homo sapiens), bonobo (Pan paniscus), chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla), orangutan (Pongo pygmaeus), gibbon (Hylobates lar), and macaque (Macaca fascicularis) were compared to reveal differences and coincidences. From chimpanzees to humans, the size of the LSO decreased, and the MNTB as a compact nucleus nearly disappears. From chimpanzees to humans, the LSO/MNTB ratio increases dramatically too, whereas the LSO/MSO ratio remains 1.1; a finding that probably corresponds to the phylogenetic proximity between the species
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
Contribution to the understanding of tribological properties of graphite intercalation compounds with metal chloride
Intrinsic tribological properties of lamellar compounds are usually attributed to the presence of van der Waals gaps in their structure through which interlayer interactions are weak. The controlled variation of the distances and interactions between graphene layers by intercalation of electrophilic species in graphite is used in order to explore more deeply the friction reduction properties of low-dimensional compounds. Three graphite intercalation compounds with antimony pentachloride, iron trichloride and aluminium trichloride are studied. Their tribological properties are correlated to their structural parameters, and the interlayer interactions are deduced from ab initio bands structure calculations
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