Neutron Stars as Type-I Superconductors

In a recent paper by Link, it was pointed out that the standard picture of the neutron star core composed of a mixture of a neutron superfluid and a proton type-II superconductor is inconsistent with observations of a long period precession in isolated pulsars. In the following we will show that an appropriate treatment of the interacting two-component superfluid (made of neutron and proton Cooper pairs), when the structure of proton vortices is strongly modified, may dramatically change the standard picture, resulting in a type-I superconductor. In this case the magnetic field is expelled from the superconducting regions of the neutron star leading to the formation of the intermediate state when alternating domains of superconducting matter and normal matter coexist.Comment: 4 page

Quantitative analysis of numerical estimates for the permeability of porous media from lattice-Boltzmann simulations

During the last decade, lattice-Boltzmann (LB) simulations have been improved to become an efficient tool for determining the permeability of porous media samples. However, well known improvements of the original algorithm are often not implemented. These include for example multirelaxation time schemes or improved boundary conditions, as well as different possibilities to impose a pressure gradient. This paper shows that a significant difference of the calculated permeabilities can be found unless one uses a carefully selected setup. We present a detailed discussion of possible simulation setups and quantitative studies of the influence of simulation parameters. We illustrate our results by applying the algorithm to a Fontainebleau sandstone and by comparing our benchmark studies to other numerical permeability measurements in the literature.Comment: 14 pages, 11 figure

The source ambiguity problem: Distinguishing the effects of grammar and processing on acceptability judgments

Judgments of linguistic unacceptability may theoretically arise from either grammatical deviance or significant processing difficulty. Acceptability data are thus naturally ambiguous in theories that explicitly distinguish formal and functional constraints. Here, we consider this source ambiguity problem in the context of Superiority effects: the dispreference for ordering a wh-phrase in front of a syntactically “superior” wh-phrase in multiple wh-questions, e.g., What did who buy? More specifically, we consider the acceptability contrast between such examples and so-called D-linked examples, e.g., Which toys did which parents buy? Evidence from acceptability and self-paced reading experiments demonstrates that (i) judgments and processing times for Superiority violations vary in parallel, as determined by the kind of wh-phrases they contain, (ii) judgments increase with exposure, while processing times decrease, (iii) reading times are highly predictive of acceptability judgments for the same items, and (iv) the effects of the complexity of the wh-phrases combine in both acceptability judgments and reading times. This evidence supports the conclusion that D-linking effects are likely reducible to independently motivated cognitive mechanisms whose effects emerge in a wide range of sentence contexts. This in turn suggests that Superiority effects, in general, may owe their character to differential processing difficulty

Overview on numerical studies of reconnection and dissipation in the solar wind

In this work, recent advances in numerical studies of local reconnection events in the turbulent plasmas are reviewed. Recently [1], the nonlinear dynamics of magnetic reconnection in turbulence has been investigated through high resolution numerical simulations. Both fluid (MHD and Hall MHD) and kinetic (HybridVlasov) 2D simulations reveal the presence of a large number of X-type neutral points, where magnetic reconnection locally occurs. The associated reconnection rates are distributed over a wide range of values and they depend on the local geometry of the diffusion region. This new approach to the study of magnetic reconnection has broad applications to the turbulent solar wind (SW). Strong magnetic SW discontinuities are in fact strongly related to these intermittent processes of reconnection [2, 3]. Methods employed to identify sets of possible reconnection events along a one-dimensional path through the turbulent field (emulating experimental sampling by a single detector in a highspeed flow) are here reviewed. These local reconnection/discontinuity events may be the main sites of heating and particle acceleration processes [4]. Results from hybrid-Vlasov kinetic simulations support these observations [5, 6]. In the turbulent regime, in fact, kinetic effects manifest through a deformation of the ion distribution function. These patterns of non-Maxwellian features are concentrated in space nearby regions of strong magnetic activity. These results open a new path on the study of kinetic processes such as heating, particle acceleration, and temperature anisotropy, commonly observed in astrophysics.Fil: Donato, S.. Università della Calabria; ItaliaFil: Servidio, S.. Università della Calabria; ItaliaFil: Dmitruk, Pablo Ariel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Valentini, F.. Università della Calabria; ItaliaFil: Greco, A.. Università della Calabria; ItaliaFil: Veltri, P.. Università della Calabria; ItaliaFil: Wan, M.. University of Delaware. Department of Physics and Astronomy; Estados UnidosFil: Shay, M. A.. University of Delaware. Department of Physics and Astronomy; Estados UnidosFil: Cassak, P. A.. West Virginia University. Department of Physics; Estados UnidosFil: Matthaeus, W. H.. University of Delaware. Department of Physics and Astronomy; Estados Unido

Entropic Dynamics, Time and Quantum Theory

Quantum mechanics is derived as an application of the method of maximum entropy. No appeal is made to any underlying classical action principle whether deterministic or stochastic. Instead, the basic assumption is that in addition to the particles of interest x there exist extra variables y whose entropy S(x) depends on x. The Schr\"odinger equation follows from their coupled dynamics: the entropy S(x) drives the dynamics of the particles x while they in their turn determine the evolution of S(x). In this "entropic dynamics" time is introduced as a device to keep track of change. A welcome feature of such an entropic time is that it naturally incorporates an arrow of time. Both the magnitude and the phase of the wave function are given statistical interpretations: the magnitude gives the distribution of x in agreement with the usual Born rule and the phase carries information about the entropy S(x) of the extra variables. Extending the model to include external electromagnetic fields yields further insight into the nature of the quantum phase.Comment: 29 page

Vortons in the SO(5) model of high temperature superconductivity

It has been shown that superconducting vortices with antiferromagnetic cores arise within Zhang's SO(5) model of high temperature supercondictivity. Similar phenomena where the symmetry is not restored in the core of the vortex was discussed by Witten in the case of cosmic strings. It was also suggested that such strings can form stable vortons, which are closed loops of such vortices. Motivated by this analogy, in following we will show that loops of such vortices in the SO(5) model of high T_c superconductivity can exist as classically stable objects, stabilized by the presence of conserved charges trapped on the vortex core. These objects carry angular momentum which counteracts the effect of the string tension that causes the loops to shrink. The existence of such quasiparticles, which are called vortons, could be interesting for the physics of high temperature superconductors. We also speculate that the phase transition between superconducting and antiferromagnetic phases at zero external magnetic field when the doping parameter changes is associated with vortons.Comment: 11 page

"Nonbaryonic" Dark Matter as Baryonic Color Superconductor

We discuss a novel cold dark matter candidate which is formed from the ordinary quarks during the QCD phase transition when the axion domain wall undergoes an unchecked collapse due to the tension in the wall. If a large number of quarks is trapped inside the bulk of a closed axion domain wall, the collapse stops due to the internal Fermi pressure. In this case the system in the bulk, may reach the critical density when it undergoes a phase transition to a color superconducting phase with the ground state being the quark condensate, similar to the Cooper pairs in BCS theory. If this happens, the new state of matter representing the diquark condensate with a large baryon number $B \sim 10^{32}$ becomes a stable soliton-like configuration. Consequently, it may serve as a novel cold dark matter candidate.Comment: Title changed. Two figures and Appendix added. Part on baryogenesis is removed and posted as a separate paper hep-ph/030908

International Coercion, Emulation and Policy Diffusion: Market-Oriented Infrastructure Reforms, 1977-1999

Why do some countries adopt market-oriented reforms such as deregulation, privatization and liberalization of competition in their infrastructure industries while others do not? Why did the pace of adoption accelerate in the 1990s? Building on neo-institutional theory in sociology, we argue that the domestic adoption of market-oriented reforms is strongly influenced by international pressures of coercion and emulation. We find robust support for these arguments with an event-history analysis of the determinants of reform in the telecommunications and electricity sectors of as many as 205 countries and territories between 1977 and 1999. Our results also suggest that the coercive effect of multilateral lending from the IMF, the World Bank or Regional Development Banks is increasing over time, a finding that is consistent with anecdotal evidence that multilateral organizations have broadened the scope of the “conditionality” terms specifying market-oriented reforms imposed on borrowing countries. We discuss the possibility that, by pressuring countries into policy reform, cross-national coercion and emulation may not produce ideal outcomes.http://deepblue.lib.umich.edu/bitstream/2027.42/40099/3/wp713.pd