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Asylum Policy under New Labour
This article examines New Labour policies on asylum with a focus on changes in welfare provision. The changes that have taken place have resulted in the exclusion of asylum seekers from 'mainstream' provision and have led to an increase in poverty and destitution among some asylum seekers
Phases of lattice hard core bosons in a periodic superlattice
We study by Quantum Monte Carlo simulations the phase diagram of lattice hard
core bosons with nearest-neighbour repulsive interactions, in the presence of a
super-lattice of adsorption sites. For a moderate adsorption strength, the
system forms crystal phases registered with the adsorption lattice; a
"supersolid" phase exists, on both the vacancy and interstitial sides, whereas
at commensuration the superfluid density vanishes. The possible relevance of
these results to experiments on He films adsorbed on graphite is discussed.Comment: 5 pages, 5 figure
Ordered and disordered dynamics in monolayers of rolling particles
We consider the ordered and disordered dynamics for monolayers of rolling
self-interacting particles with an offset center of mass and a non-isotropic
inertia tensor. The rolling constraint is considered as a simplified model of a
very strong, but rapidly decaying bond with the surface, preventing application
of the standard tools of statistical mechanics. We show the existence and
nonlinear stability of ordered lattice states, as well as disturbance
propagation through and chaotic vibrations of these states. We also investigate
the dynamics of disordered gas states and show that there is a surprising and
robust linear connection between distributions of angular and linear velocity
for both lattice and gas states, allowing to define the concept of temperature
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Individual complex Dirac eigenvalue distributions from random matrix theory and lattice QCD at nonzero chemical potential
We analyze how individual eigenvalues of the QCD Dirac operator at nonzero chemical potential are distributed in the complex plane. Exact and approximate analytical results for such distributions are derived from non-Hermitian random matrix theory. When comparing these to lattice QCD spectra close to the origin, excellent agreement is found for zero and nonzero topology at several values of the chemical potential. Our analytical results are also applicable to other physical systems in the same symmetry class
Distributions of individual Dirac eigenvalues for QCD at non-zero chemical potential: RMT predictions and lattice results
For QCD at non-zero chemical potential , the Dirac eigenvalues are scattered in the complex plane. We define a notion of ordering for individual eigenvalues in this case and derive the distributions of individual eigenvalues from random matrix theory (RMT). We distinguish two cases depending on the parameter , where is the volume and is the familiar low-energy constant of chiral perturbation theory. For small , we use a Fredholm determinant expansion and observe that already the first few terms give an excellent approximation. For large , all spectral correlations are rotationally invariant, and exact results can be derived. We compare the RMT predictions to lattice data and in both cases find excellent agreement in the topological sectors
Characteristics of Bose-Einstein condensation in an optical lattice
We discuss several possible experimental signatures of the Bose-Einstein
condensation (BEC) transition for an ultracold Bose gas in an inhomogeneous
optical lattice. Based on the commonly used time-of-flight imaging technique,
we show that the momentum-space density profile in the first Brillouin zone,
supplemented by the visibility of interference patterns, provides valuable
information about the system. In particular, by crossing the BEC transition
temperature, the appearance of a clear bimodal structure sets a qualitative and
universal signature of this phase transition. Furthermore, the momentum
distribution can also be applied to extract the condensate fraction, which may
serve as a promising thermometer in such a system.Comment: 12 pages, 13 figures; Revised version with new figures; Phys. Rev. A
77, 043626 (2008
The Kohn-Luttinger Effect in Gauge Theories
Kohn and Luttinger showed that a many body system of fermions interacting via
short range forces becomes superfluid even if the interaction is repulsive in
all partial waves. In gauge theories such as QCD the interaction between
fermions is long range and the assumptions of Kohn and Luttinger are not
satisfied. We show that in a U(1) gauge theory the Kohn-Luttinger phenomenon
does not take place. In QCD attractive channels always exist, but there are
cases in which the primary pairing channel leaves some fermions ungapped. As an
example we consider the unpaired fermion in the 2SC phase of QCD with two
flavors. We show that it acquires a very small gap via a mechanism analogous to
the Kohn-Luttinger effect. The gap is too small to be phenomenologically
relevant.Comment: 5 pages, 2 figure, minor revisions, to appear in PR
Geometrically constrained magnetic wall
The structure and properties of a geometrically constrained magnetic wall in
a constriction separating two wider regions are investigated theoretically.
They are shown to differconsiderably from those of an unconstrained wall, so
that the geometrically constrained magnetic wall truly constitutes a new kind
of magnetic wall, besides the well known Bloch and Neel walls. In particular,
the width of a constrained wall cann become very small if the characteristic
length of the constriction is small, as is actually the case in an atomic point
contact. This provides a simple, natural explanation for the large
magnetoresistance observed in ferromagnetic atomic point contacts.Comment: RevTeX, 4 pages, 4 eps figures; v2: revised version; v3: ref. adde
Sub-Doppler resonances in the back-scattered light from random porous media infused with Rb vapor
We report on the observation of sub-Doppler resonances on the back-scattered
light from a random porous glass medium with rubidium vapor filling its
interstices. The sub-Doppler spectral lines are the consequence of saturated
absorption where the incident laser beam saturates the atomic medium and the
back-scattered light probes it. Some specificities of the observed spectra
reflect the transient atomic evolution under confinement inside the pores.
Simplicity, robustness and potential miniaturization are appealing features of
this system as a spectroscopic reference.Comment: 6 pages, 4 figure
Remarks on Infrared Dynamics in QED3
In this work we study how the infrared sector of the interaction Hamiltonian
can affect the construction of the S matrix operator of QED in (2+1)
dimensions.Comment: 9 page
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