1,369 research outputs found
Spectral properties of one-dimensional Fermi systems after an interaction quench
We show that the single-particle spectral properties of gapless
one-dimensional Fermi systems in the Luttinger liquid state reached at
intermediate times after an abrupt quench of the two-particle interaction are
highly indicative of the unusual nonequilibrium nature of this state. The line
shapes of the momentum integrated and resolved spectral functions strongly
differ from their ground state as well as finite temperature equilibrium
counterparts. Using an energy resolution improved version of radio-frequency
spectroscopy of quasi one-dimensional cold Fermi gases it should be possible to
experimentally identify this nonequilibrium state by its pronounced spectral
signatures.Comment: 5 pages, 3 figure
On the convergence of local expansions of layer potentials
In a recently developed quadrature method (quadrature by expansion or QBX),
it was demonstrated that weakly singular or singular layer potentials can be
evaluated rapidly and accurately on surface by making use of local expansions
about carefully chosen off-surface points. In this paper, we derive estimates
for the rate of convergence of these local expansions, providing the analytic
foundation for the QBX method. The estimates may also be of mathematical
interest, particularly for microlocal or asymptotic analysis in potential
theory
Tuning the thermal conductance of molecular junctions with interference effects
We present an \emph{ab initio} study of the role of interference effects in
the thermal conductance of single-molecule junctions. To be precise, using a
first-principles transport method based on density functional theory, we
analyze the coherent phonon transport in single-molecule junctions based on
several benzene and oligo-phenylene-ethynylene derivatives. We show that the
thermal conductance of these junctions can be tuned via the inclusion of
substituents, which induces destructive interference effects and results in a
decrease of the thermal conductance with respect to the unmodified molecules.
In particular, we demonstrate that these interference effects manifest as
antiresonances in the phonon transmission, whose energy positions can be
controlled by varying the mass of the substituents. Our work provides clear
strategies for the heat management in molecular junctions and more generally in
nanostructured metal-organic hybrid systems, which are important to determine,
how these systems can function as efficient energy-conversion devices such as
thermoelectric generators and refrigerators
Behavior Trees for UAV Mission Management
Behavior trees are a recent development in artificial intelligence for computer games. Their application has been proposed to increase modularity of an unmanned aerial vehicle's control system. This paper first describes advantages of behavior trees for use in mission management. The paper then points out research towards their deployment. Finally, newly developed transient tasks are introduced to behavior trees. These allow for finite-state-machine-like initialization and interruption of tasks. The use of the system is demonstrated with an unmanned aircraft mission simulation
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