3,061 research outputs found
Thermodynamics of an incommensurate quantum crystal
We present a simple theory of the thermodynamics of an incommensurate quantum
solid. The ground state of the solid is assumed to be an incommensurate
crystal, with quantum zero-point vacancies and interstitials and thus a
non-integer number of atoms per unit cell. We show that the low temperature
variation of the net vacancy concentration should be as , and that the
first correction to the specific heat due to this varies as ; these are
quite consistent with experiments on solid He. We also make some
observations about the recent experimental reports of ``supersolidity'' in
solid He that motivate a renewed interest in quantum crystals.Comment: revised, new title, somewhat expande
Marine Protected Areas and commercial fisheries: the existing fishery in potential protected areas, and a modelling study of the impact of protected areas on North Sea Plaice
Dit rapport presenteert resultaten van onderzoek, dat in 2005/2006 is uitgevoerd. In het kader van de Europese Vogel en Habitat Richtlijnen dienen lidstaten te beschermen gebieden op zee aan te wijzen, wat mogelijk zou leiden tot beperkingen van visserijactiviteiten in deze gebieden. De vraag was, welke invloed dit zou hebben op de vis en visserij. In dit onderzoek is enerzijds een statische beschrijving opgesteld van de visserijinspanning en de vangsten in de voorgestelde gebieden, en is anderzijds een eerste analyse (simulatie-model) opgezet van het lange-termijn effect op migrerende vis (schol). Dit onderzoek werd eind 2006 afgerond met een concept-rapport
He Who Came by Water and by Blood - A Summary and Critique of the Majo Interpretations of 1 John 5:6
It has been said that 1 John 5:6 is the most perplexing passage in the Epistle and one of the most perplexing in the New Testament. It is perplexing, if for no other reason, for the variety of interpretations that have been offered. This variety, in turn, hinges on many factors beyond the text itself
Parametric analysis of microwave and laser systems for communication and tracking. Volume 2 - System selection
System selection criteria of microwave and laser systems for communication and tracking - Vol.
Nonlocal Cooper pair Splitting in a pSn Junction
Perfect Cooper pair splitting is proposed, based on crossed Andreev
reflection (CAR) in a p-type semiconductor - superconductor - n-type
semiconductor (pSn) junction. The ideal splitting is caused by the energy
filtering that is enforced by the bandstructure of the electrodes. The pSn
junction is modeled by the Bogoliubov-de Gennes equations and an extension of
the Blonder-Tinkham-Klapwijk theory beyond the Andreev approximation. Despite a
large momentum mismatch, the CAR current is predicted to be large. The proposed
straightforward experimental design and the 100% degree of pureness of the
nonlocal current open the way to pSn structures as high quality sources of
entanglement
Generalization of Gutzwiller Approximation
We derive expressions required in generalizing the Gutzwiller approximation
to models comprising arbitrarily degenerate localized orbitals.Comment: 6 pages, 1 figure, to appear in J.Phys.Soc.Jpn. vol.6
Hubbard physics in the symmetric half-filled periodic Anderson-Hubbard model
Two very different methods -- exact diagonalization on finite chains and a
variational method -- are used to study the possibility of a metal-insulator
transition in the symmetric half-filled periodic Anderson-Hubbard model. With
this aim we calculate the density of doubly occupied sites as a function of
various parameters. In the absence of on-site Coulomb interaction ()
between electrons, the two methods yield similar results. The double
occupancy of levels remains always finite just as in the one-dimensional
Hubbard model. Exact diagonalization on finite chains gives the same result for
finite , while the Gutzwiller method leads to a Brinkman-Rice transition
at a critical value (), which depends on and .Comment: 10 pages, 5 figure
Analytical calculation of the Green's function and Drude weight for a correlated fermion-boson system
In classical Drude theory the conductivity is determined by the mass of the
propagating particles and the mean free path between two scattering events. For
a quantum particle this simple picture of diffusive transport loses relevance
if strong correlations dominate the particle motion. We study a situation where
the propagation of a fermionic particle is possible only through creation and
annihilation of local bosonic excitations. This correlated quantum transport
process is outside the Drude picture, since one cannot distinguish between free
propagation and intermittent scattering. The characterization of transport is
possible using the Drude weight obtained from the f-sum rule, although its
interpretation in terms of free mass and mean free path breaks down. For the
situation studied we calculate the Green's function and Drude weight using a
Green's functions expansion technique, and discuss their physical meaning.Comment: final version, minor correction
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