5,483 research outputs found
Study of Unmanned Systems to Evaluate the Martian Environment. Volume IV - Summary
Unmanned space mission to determine Martian environmental factors influencing design of systems for manned space mission to Mars - summary repor
DMRG evaluation of the Kubo formula -- Conductance of strongly interacting quantum systems
In this paper we present a novel approach combining linear response theory
(Kubo) for the conductance and the Density Matrix Renormalization Group (DMRG).
The system considered is one-dimensional and consists of non-interacting tight
binding leads coupled to an interacting nanostructure via weak links. Electrons
are treated as spinless fermions and two different correlation functions are
used to evaluate the conductance.
Exact diagonalization calculations in the non-interacting limit serve as a
benchmark for our combined Kubo and DMRG approach in this limit. Including both
weak and strong interaction we present DMRG results for an extended
nanostructure consisting of seven sites. For the strongly interacting structure
a simple explanation of the position of the resonances is given in terms of
hard-core particles moving freely on a lattice of reduced size.Comment: 7 pages, 2 figures. Minor typos correcte
Mesoscopic Capacitance Oscillations
We examine oscillations as a function of Fermi energy in the capacitance of a
mesoscopic cavity connected via a single quantum channel to a metallic contact
and capacitively coupled to a back gate. The oscillations depend on the
distribution of single levels in the cavity, the interaction strength and the
transmission probability through the quantum channel. We use a Hartree-Fock
approach to exclude self-interaction. The sample specific capacitance
oscillations are in marked contrast to the charge relaxation resistance, which
together with the capacitance defines the RC-time, and which for spin polarized
electrons is quantized at half a resistance quantum. Both the capacitance
oscillations and the quantized charge relaxation resistance are seen in a
strikingly clear manner in a recent experiment.Comment: 9 pages, 2 figure
Fermi-Edge Singularities in the Mesoscopic X-Ray Edge Problem
We study the x-ray edge problem for a chaotic quantum dot or nanoparticle
displaying mesoscopic fluctuations. In the bulk, x-ray physics is known to
produce deviations from the naively expected photoabsorption cross section in
the form of a peaked or rounded edge. For a coherent system with chaotic
dynamics, we find substantial changes and in particular that a photoabsorption
cross section showing a rounded edge in the bulk will change to a slightly
peaked edge on average as the system size is reduced to a mesoscopic (coherent)
scale.Comment: 4 pages, 3 figures, final version as published in PR
Analysis of information systems for hydropower operations
The operations of hydropower systems were analyzed with emphasis on water resource management, to determine how aerospace derived information system technologies can increase energy output. Better utilization of water resources was sought through improved reservoir inflow forecasting based on use of hydrometeorologic information systems with new or improved sensors, satellite data relay systems, and use of advanced scheduling techniques for water release. Specific mechanisms for increased energy output were determined, principally the use of more timely and accurate short term (0-7 days) inflow information to reduce spillage caused by unanticipated dynamic high inflow events. The hydrometeorologic models used in predicting inflows were examined to determine the sensitivity of inflow prediction accuracy to the many variables employed in the models, and the results used to establish information system requirements. Sensor and data handling system capabilities were reviewed and compared to the requirements, and an improved information system concept outlined
- …