879 research outputs found
Generalized Quantum Theory: Overview and Latest Developments
The main formal structures of Generalized Quantum Theory are summarized.
Recent progress has sharpened some of the concepts, in particular the notion of
an observable, the action of an observable on states (putting more emphasis on
the role of proposition observables), and the concept of generalized
entanglement. Furthermore, the active role of the observer in the structure of
observables and the partitioning of systems is emphasized.Comment: 14 pages, update in reference
Hamiltonian Multivector Fields and Poisson Forms in Multisymplectic Field Theory
We present a general classification of Hamiltonian multivector fields and of
Poisson forms on the extended multiphase space appearing in the geometric
formulation of first order classical field theories. This is a prerequisite for
computing explicit expressions for the Poisson bracket between two Poisson
forms.Comment: 50 page
The Poisson Bracket for Poisson Forms in Multisymplectic Field Theory
We present a general definition of the Poisson bracket between differential
forms on the extended multiphase space appearing in the geometric formulation
of first order classical field theories and, more generally, on exact
multisymplectic manifolds. It is well defined for a certain class of
differential forms that we propose to call Poisson forms and turns the space of
Poisson forms into a Lie superalgebra.Comment: 40 pages LaTe
Interacting particles at a metal-insulator transition
We study the influence of many-particle interaction in a system which, in the
single particle case, exhibits a metal-insulator transition induced by a finite
amount of onsite pontential fluctuations. Thereby, we consider the problem of
interacting particles in the one-dimensional quasiperiodic Aubry-Andre chain.
We employ the density-matrix renormalization scheme to investigate the finite
particle density situation. In the case of incommensurate densities, the
expected transition from the single-particle analysis is reproduced. Generally
speaking, interaction does not alter the incommensurate transition. For
commensurate densities, we map out the entire phase diagram and find that the
transition into a metallic state occurs for attractive interactions and
infinite small fluctuations -- in contrast to the case of incommensurate
densities. Our results for commensurate densities also show agreement with a
recent analytic renormalization group approach.Comment: 8 pages, 8 figures The original paper was splitted and rewritten.
This is the published version of the DMRG part of the original pape
A complex geo-scientific strategy for landslide hazard mitigation ? from airborne mapping to ground monitoring
International audienceAfter a large landslide event in Sibratsgfäll/Austria several exploration methods were evaluated on their applicability to investigate and monitor landslide areas. The resulting optimised strategy consists of the combined application of airborne electromagnetics, ground geoelectrical measurements and geoelectrical monitoring combined with hydrological and geological mapping and geotechnical modelling. Interdisciplinary communication and discussion was the primary key to assess this complicated hazard situation
Correlation-Strength Driven Anderson Metal-Insulator Transition
The possibility of driving an Anderson metal-insulator transition in the
presence of scale-free disorder by changing the correlation exponent is
numerically investigated. We calculate the localization length for
quasi-one-dimensional systems at fixed energy and fixed disorder strength using
a standard transfer matrix method. From a finite-size scaling analysis we
extract the critical correlation exponent and the critical exponent
characterizing the phase transition.Comment: 3 pages; 2 figure
Conservation laws in the continuum systems
We study the conservation laws of both the classical and the quantum
mechanical continuum type systems. For the classical case, we introduce
new integrals of motion along the recent ideas of Shastry and Sutherland (SS),
supplementing the usual integrals of motion constructed much earlier by Moser.
We show by explicit construction that one set of integrals can be related
algebraically to the other. The difference of these two sets of integrals then
gives rise to yet another complete set of integrals of motion. For the quantum
case, we first need to resum the integrals proposed by Calogero, Marchioro and
Ragnisco. We give a diagrammatic construction scheme for these new integrals,
which are the quantum analogues of the classical traces. Again we show that
there is a relationship between these new integrals and the quantum integrals
of SS by explicit construction.Comment: 19 RevTeX 3.0 pages with 2 PS-figures include
Enhanced Charge and Spin Currents in the One-Dimensional Disordered Mesoscopic Hubbard Ring
We consider a one-dimensional mesoscopic Hubbard ring with and without
disorder and compute charge and spin stiffness as a measure of the permanent
currents. For finite disorder we identify critical disorder strength beyond
which the charge currents in a system with repulsive interactions are {\em
larger} than those for a free system. The spin currents in the disordered
repulsive Hubbard model are enhanced only for small , where the magnetic
state of the system corresponds to a charge density wave pinned to the
impurities. For large , the state of the system corresponds to localized
isolated spins and the spin currents are found to be suppressed. For the
attractive Hubbard model we find that the charge currents are always suppressed
compared to the free system at all length scales.Comment: 20 RevTeX 3.0 pages, 8 figures NOT include
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