9,380 research outputs found
Bethe Ansatz solution of a new class of Hubbard-type models
We define one-dimensional particles with generalized exchange statistics. The
exact solution of a Hubbard-type Hamiltonian constructed with such particles is
achieved using the Coordinate Bethe Ansatz. The chosen deformation of the
statistics is equivalent to the presence of a magnetic field produced by the
particles themselves, which is present also in a ``free gas'' of these
particles.Comment: 4 pages, revtex. Essentially modified versio
Many-body approach to the nonlinear interaction of charged particles with an interacting free electron gas
We report various many-body theoretical approaches to the nonlinear decay
rate and energy loss of charged particles moving in an interacting free
electron gas. These include perturbative formulations of the scattering matrix,
the self-energy, and the induced electron density. Explicit expressions for
these quantities are obtained, with inclusion of exchange and correlation
effects.Comment: 11 pages, 5 figures. To appear in Journal of Physics
A model for the phase separation controlled by doping and the internal chemical pressure in different cuprate superconductors
In the framework of a two-band model, we study the phase separation regime of
different kinds of strongly correlated charge carriers as a function of the
energy splitting between the two sets of bands. The narrow (wide) band
simulates the more localized (more delocalized) type of charge carriers. By
assuming that the internal chemical pressure on the CuO layer due to
interlayer mismatch controls the energy splitting between the two sets of
states, the theoretical predictions are able to reproduce the regime of phase
separation at doping higher than 1/8 in the experimental pressure-doping-
phase diagram of cuprates at large microstrain as it appears in overoxygenated
LaCuO.Comment: 8 pages, 5 figures, submitted to Phys. Rev.
Researching ‘bogus’ asylum seekers, ‘illegal’ migrants and ‘crimmigrants’
Both immigration and criminal laws are, at their core, systems of inclusion and exclusion. They are designed to determine whether and how to include individuals as members of society or exclude them from it, thereby, creating insiders and outsiders (Stumpf 2006). Both are designed to create distinct categories of people — innocent versus guilty, admitted versus excluded or, as majority would say, ‘legal’ versus ‘illegal’ (Stumpf 2006). Viewed in that light, perhaps it is not surprising that these two areas of law have become inextrica- bly connected in the official discourses. When politicians and policy makers (and also law enforcement authorities and tabloid press) seek to raise the barriers for non-citizens to attain membership in society, it is unremarkable that they turn their attention to an area of the law that similarly func- tions to exclude the ‘other’ — transforming immigrants into ‘crimmigrants’.1 As a criminological researcher one then has to rise up to the challenges of disentangling these so-called officially constructed (pseudo) realities, and breaking free from a continued dominance of authoritative discourses, and developing an alternative understanding of ‘crimmigration’ by connecting the processes of criminal is ation and ‘other ing’ with poverty, xe no-racism and other forms of social exclusion (see Institute of Race Relations 1987; Richmond 1994; Fekete 2001; Bowling and Phillips 2002; Sivanandan 2002; Weber and Bowling 2004)
An experimental study of the temporal statistics of radio signals scattered by rain
A fixed-beam bistatic CW experiment designed to measure the temporal statistics of the volume reflectivity produced by hydrometeors at several selected altitudes, scattering angles, and at two frequencies (3.6 and 7.8 GHz) is described. Surface rain gauge data, local meteorological data, surveillance S-band radar, and great-circle path propagation measurements were also made to describe the general weather and propagation conditions and to distinguish precipitation scatter signals from those caused by ducting and other nonhydrometeor scatter mechanisms. The data analysis procedures were designed to provide an assessment of a one-year sample of data with a time resolution of one minute. The cumulative distributions of the bistatic signals for all of the rainy minutes during this period are presented for the several path geometries
Dispersion Instability in Strongly Interacting Electron Liquids
We show that the low-density strongly interacting electron liquid,
interacting via the long-range Coulomb interaction, could develop a dispersion
instability at a critical density associated with the approximate flattening of
the quasiparticle energy dispersion. At the critical density the quasiparticle
effective mass diverges at the Fermi surface, but the signature of this Fermi
surface instability manifests itself away from the Fermi momentum at higher
densities. For densities below the critical density the system is unstable
since the quasiparticle velocity becomes negative. We show that one physical
mechanism underlying the dispersion instability is the emission of soft
plasmons by the quasiparticles. The dispersion instability occurs both in two
and three dimensional electron liquids. We discuss the implications of the
dispersion instability for experiments at low electron densities.Comment: Accepted version for publicatio
On Quantum Groups in the Hubbard Model with Phonons
The correct Hamiltonian for an extended Hubbard model with quantum group
symmetry as introduced by A. Montorsi and M. Rasetti is derived for a
D-dimensional lattice. It is shown that the superconducting SUq(2) holds as a
true quantum symmetry only for D = 1 and that terms of higher order in the
fermionic operators in addition to phonons are required for a quantum symmetric
hamiltonian. The condition for quantum symmetry is "half filling" and there is
no local electron-phonon coupling. A discussion of Quantum symmetries in
general is given in a formalism that should be readily accessible to non
Hopf-algebraists.Comment: latex, 17 page
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