1,495 research outputs found
Phonon-assisted decoherence and tunneling in quantum dot molecules
We study the influence of the phonon environment on the electron dynamics in
a doped quantum dot molecule. A non-perturbative quantum kinetic theory based
on correlation expansion is used in order to describe both diagonal and
off-diagonal electron-phonon couplings representing real and virtual processes
with relevant acoustic phonons. We show that the relaxation is dominated by
phonon-assisted electron tunneling between constituent quantum dots and occurs
on a picosecond time scale. The dependence of the time evolution of the quantum
dot occupation probabilities on the energy mismatch between the quantum dots is
studied in detail.Comment: 4 pages, 2 figures, conference proceeding NOEKS10, to be published in
Phys. Stat. So
Theory of phonon-mediated relaxation in doped quantum dot molecules
A quantum dot molecule doped with a single electron in the presence of
diagonal and off-diagonal carrier-phonon couplings is studied by means of a
non-perturbative quantum kinetic theory. The interaction with acoustic phonons
by deformation potential and piezoelectric coupling is taken into account. We
show that the phonon-mediated relaxation is fast on a picosecond timescale and
is dominated by the usually neglected off-diagonal coupling to the lattice
degrees of freedom leading to phonon-assisted electron tunneling. We show that
in the parameter regime of current electrical and optical experiments, the
microscopic non-Markovian theory has to be employed.Comment: Final extended version, 5 pages, 4 figure
Developing the Business Process Management Performance of an Information System Using the Delphi Study Technique
Information systems are used to manage an organisation’s business process management (BPM), its operations and performance. Thus, organisations will benefit from systematic processes for evaluating their business information systems with the aim of developing BPM and business information systems performance. The Delphi Study Technique (DST) is a structured business study technique that can be used as a systematic and interactive assessment process based on controlled feedback from business experts, professionals, or others with relevant experience. The Delphi study technique (also known as the Delphi method) has produced significant achievements in evaluating and improving BPM through identifying BPM values to be used as key indicators. This paper describes the essential stages for measuring the performance of an information system by combining the Delphi method and BPM values to improve an organisation’s business performance. The paper provides examples of the use of DST and discusses empirical results from the published literature
Discretization of the velocity space in solution of the Boltzmann equation
We point out an equivalence between the discrete velocity method of solving
the Boltzmann equation, of which the lattice Boltzmann equation method is a
special example, and the approximations to the Boltzmann equation by a Hermite
polynomial expansion. Discretizing the Boltzmann equation with a BGK collision
term at the velocities that correspond to the nodes of a Hermite quadrature is
shown to be equivalent to truncating the Hermite expansion of the distribution
function to the corresponding order. The truncated part of the distribution has
no contribution to the moments of low orders and is negligible at small Mach
numbers. Higher order approximations to the Boltzmann equation can be achieved
by using more velocities in the quadrature
Explicit coercivity estimates for the linearized Boltzmann and Landau operators
We prove explicit coercivity estimates for the linearized Boltzmann and
Landau operators, for a general class of interactions including any
inverse-power law interactions, and hard spheres. The functional spaces of
these coercivity estimates depend on the collision kernel of these operators.
They cover the spectral gap estimates for the linearized Boltzmann operator
with Maxwell molecules, improve these estimates for hard potentials, and are
the first explicit coercivity estimates for soft potentials (including in
particular the case of Coulombian interactions). We also prove a regularity
property for the linearized Boltzmann operator with non locally integrable
collision kernels, and we deduce from it a new proof of the compactness of its
resolvent for hard potentials without angular cutoff.Comment: 32 page
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