The dynamics of neutron star crusts: Lagrangian perturbation theory for a relativistic superfluid-elastic system

The inner crust of a mature neutron star is composed of an elastic lattice of neutron-rich nuclei penetrated by free neutrons. These neutrons can flow relative to the crust once the star cools below the superfluid transition temperature. In order to model the dynamics of this system, which is relevant for a range of problems from pulsar glitches to magnetar seismology and continuous gravitational-wave emission from rotating deformed neutron stars, we need to understand general relativistic Lagrangian perturbation theory for elastic matter coupled to a superfluid component. This paper develops the relevant formalism to the level required for astrophysical applications.Comment: 31 pages, double spacing, minor typos fixe

An energy-dependent, transient peak in the minute range decay of luminescence, present in CO2-accumulating cells of Scenedesmus obliquus

AbstractPhotosynthetic O2 evolution in the green alga, Scenedesmus obliquus, was shown to be more sensitive to the uncoupler FCCP when assayed in a low Ci medium than in a high Ci medium, indicating the action of an energy-dependent mechanism for Ci uptake. Low Ci adapted algae exhibited characteristic luminescence decay kinetics with a transient peak 20–60 s after excitation. This peak was abolished by addition of FCCP and HCO−3. The effect caused by HCO−3 was partially reversed by methyl viologen. In view of the results obtained, a model is presented in order to discuss the origin of the transient luminescence peak

Elastic Stars in General Relativity: II. Radial perturbations

We study radial perturbations of general relativistic stars with elastic matter sources. We find that these perturbations are governed by a second order differential equation which, along with the boundary conditions, defines a Sturm-Liouville type problem that determines the eigenfrequencies. Although some complications arise compared to the perfect fluid case, leading us to consider a generalisation of the standard form of the Sturm-Liouville equation, the main results of Sturm-Liouville theory remain unaltered. As an important consequence we conclude that the mass-radius curve for a one-parameter sequence of regular equilibrium models belonging to some particular equation of state can be used in the same well-known way as in the perfect fluid case, at least if the energy density and the tangential pressure of the background solutions are continuous. In particular we find that the fundamental mode frequency has a zero for the maximum mass stars of the models with solid crusts considered in Paper I of this series.Comment: 22 pages, no figures, final version accepted for publication in Class. Quantum Grav. The treatment of the junction conditions has been improve

Orbital entanglement and violation of Bell inequalities in mesoscopic conductors

We propose a spin-independent scheme to generate and detect two-particle entanglement in a mesoscopic normal-superconductor system. A superconductor, weakly coupled to the normal conductor, generates an orbitally entangled state by injecting pairs of electrons into different leads of the normal conductor. The entanglement is detected via violation of a Bell inequality, formulated in terms of zero-frequency current cross-correlators. It is shown that the Bell inequality can be violated for arbitrary strong dephasing in the normal conductor.Comment: 4 pages, 2 figure

Charge qubit entanglement in double quantum dots

We study entanglement of charge qubits in a vertical tunnel-coupled double quantum dot containing two interacting electrons. Exact diagonalization is used to compute the negativity characterizing entanglement. We find that entanglement can be efficiently generated and controlled by sidegate voltages, and describe how it can be detected. For large enough tunnel coupling, the negativity shows a pronounced maximum at an intermediate interaction strength within the Wigner molecule regime.Comment: revised version of the manuscript, as published in EPL, 7 pages, 4 figure

Nonequilibrium Josephson current in ballistic multiterminal SNS-junctions

We study the nonequilibrium Josephson current in a long two-dimensional ballistic SNS-junction with a normal reservoir coupled to the normal part of the junction. The current for a given superconducting phase difference $\phi$ oscillates as a function of voltage applied between the normal reservoir and the SNS-junction. The period of the oscillations is $\pi \hbar v_F/L$, with $L$ the length of the junction, and the amplitude of the oscillations decays as $V^{-3/2}$ for $eV \gg \hbar v_{F}/L$ and zero temperature. The critical current $I_c$ shows a similar oscillating, decaying behavior as a function of voltage, changing sign every oscillation. Normal specular or diffusive scattering at the NS-interfaces does not qualitatively change the picture.Comment: Proceeding of MS2000, to appear in Physica

Electrical current noise of a beam splitter as a test of spin-entanglement

We investigate the spin entanglement in the superconductor-quantum dot system proposed by Recher, Sukhorukov and Loss, coupling it to an electronic beam-splitter. The superconductor-quantum dot entangler and the beam-splitter are treated within a unified framework and the entanglement is detected via current correlations. The state emitted by the entangler is found to be a linear superposition of non-local spin-singlets at different energies, a spin-entangled two-particle wavepacket. Colliding the two electrons in the beam-splitter, the singlet spin-state gives rise to a bunching behavior, detectable via the current correlators. The amount of bunching depends on the relative positions of the single particle levels in the quantum dots and the scattering amplitudes of the beam-splitter. The singlet spin entanglement, insensitive to orbital dephasing but suppressed by spin dephasing, is conveniently quantified via the Fano factors. It is found that the entanglement-dependent contribution to the Fano factor is of the same magnitude as the non-entangled, making an experimental detection feasible. A detailed comparison between the current correlations of the non-local spin-singlet state and other states, possibly emitted by the entangler, is performed. This provides conditions for an unambiguous identification of the non-local singlet spin entanglement.Comment: 13 pages, 8 figures, section on quantification of entanglement adde

Virtual experiments in collaborative archival education: constructing a digital laboratory for digital learning

Sustainable archives and preservation education in a global digital society demand collaborative frameworks and multiple, geographically-diverse partnerships. This poses considerable challenges for educators. A consortium between archival education programmes at University College London, Mid Sweden University and Simmons College, Boston, is addressing these challenges within an innovative virtual learning environment developed, built and shared among the three institutions. Participants from each of the three programmes describe, analyse and demonstrate ongoing collaboration, research and curriculum development unified through the Digital Curriculum Laboratory (DCL). They also explore the implications of these types of learning resources and collaborative approaches for supporting archives education internationally

Entanglement in Mesoscopic Structures: Role of Projection

We present a theoretical analysis of the appearance of entanglement in non-interacting mesoscopic structures. Our setup involves two oppositely polarized sources injecting electrons of opposite spin into the two incoming leads. The mixing of these polarized streams in an ideal four-channel beam splitter produces two outgoing streams with particular tunable correlations. A Bell inequality test involving cross-correlated spin-currents in opposite leads signals the presence of spin-entanglement between particles propagating in different leads. We identify the role of fermionic statistics and projective measurement in the generation of these spin-entangled electrons.Comment: 5 pages, 1 figur

Formal support, mental disorders and personal characteristics: a 25-year follow-up study of a total cohort of older people.

The present study was designed to describe the pattern of long-term formal support received by people with mental disorders, and to investigate the relationship between the medical, psychological and social characteristics of the participants and types of formal support. This study is based on a cohort (n = 192) of people born in 1902 and 1903 in a community in Southern Sweden. The research participants were assessed using interviews, psychological tests and medical examinations. Information was collected about the use of primary healthcare and social services. The first assessment took place when the cohort was aged 67 years, and then on eight further occasions until they were 92. The participation rate ranged from 72% to 100%. During the observation period of 25 years, 53% of people with dementia eventually received both home help and institutional care compared to 34% of people with other psychiatric diagnoses and 12% of people with good mental health. The last group had all physical health problems and/or problems with activities of daily living. However, 35% of the dementia group, 46% with other psychiatric diagnoses and 52% of people with good mental health did not receive any formal support. Males and self-employed people were significantly less likely to use formal support. The institutionalised group reported loneliness significantly more often than the other two groups. In a logistic regression analysis, loneliness, low social class, high blood pressure and low problem-solving ability were predictors of formal support use. People with a mental disorder, including dementia, were significantly more likely to use formal support compared to people with good mental health. Social factors were the main factors predicting formal support