4,123 research outputs found
Coulomb scattering with remote continuum states in quantum dot devices
Electron capture and emission by Coulomb scattering in self-assembled quantum
dot (QD) devices is studied theoretically. While the dependence of the Coulomb
scattering (Auger) rates on the local wetting layer electron density has been a
topic of intense research, we put special interest on the remote scattering
between QD electrons and continuum electrons originating from a quantum well,
doped bulk layers or metal contacts. Numerical effort is made to include all
microscopic transitions between the Fermi distributed continuum states. The
remote Coulomb scattering is investigated as a function of the electron
density, the distance from the QDs and the temperature. Our results are
compared with experimental observations, considering lifetime limitations in QD
memory structures as well as the electron emission in pn-diodes
Remarks on Alain Connes' approach to the standard model
Our 1992 remarks about Alain Connes' interpretation of the standard model
within his theory of non-commutative riemannian spin manifolds.Comment: 9 pages TeX, dedicated to the memory of E. M. Polivano
Magnetic Monopoles, Center Vortices, Confinement and Topology of Gauge Fields
The vortex picture of confinement is studied. The deconfinement phase
transition is explained as a transition from a phase in which vortices
percolate to a phase of small vortices. Lattice results are presented in
support of this scenario. Furthermore the topological properties of magnetic
monopoles and center vortices arising, respectively, in Abelian and center
gauges are studied in continuum Yang-Mills-theory. For this purpose the
continuum analog of the maximum center gauge is constructed.Comment: talk given by H. Reinhardt on the Int. Workshop ``Hadrons 1999'',
Coimbra, 10.-15. Sept. 199
Diffractive Meson Production and the Quark-Pomeron Coupling
Diffractive meson production at HERA offers interesting possibilities to
investigate diffractive processes and thus to learn something about the
properties of the pomeron. The most succesful phenomenological description of
the pomeron so far assumes it to couple like a isoscalar photon to
single quarks. This coupling leads, however, to problems for exclusive
diffractive reactions. We propose a new phenomenological pomeron vertex, which
leads to very good fits to the known data, but avoids the problems of the old
vertex.Comment: 20 pages, latex with uuencoded postscript, revised versio
Distance-generalized Core Decomposition
The -core of a graph is defined as the maximal subgraph in which every
vertex is connected to at least other vertices within that subgraph. In
this work we introduce a distance-based generalization of the notion of
-core, which we refer to as the -core, i.e., the maximal subgraph in
which every vertex has at least other vertices at distance within
that subgraph. We study the properties of the -core showing that it
preserves many of the nice features of the classic core decomposition (e.g.,
its connection with the notion of distance-generalized chromatic number) and it
preserves its usefulness to speed-up or approximate distance-generalized
notions of dense structures, such as -club.
Computing the distance-generalized core decomposition over large networks is
intrinsically complex. However, by exploiting clever upper and lower bounds we
can partition the computation in a set of totally independent subcomputations,
opening the door to top-down exploration and to multithreading, and thus
achieving an efficient algorithm
QCD sum rules with finite masses
The concept of QCD sum rules is extended to bound states composed of
particles with finite mass such as scalar quarks or strange quarks. It turns
out that mass corrections become important in this context. The number of
relevant corrections is analyzed in a systematic discussion of the IR- and
UV-divergencies, leading in general to a finite number of corrections. The
results are demonstrated for a system of two massless quarks and two heavy
scalar quarks.Comment: 15 pages, including two pictures to be found in an extra file. Latex
neads epsf.st
POPLMark reloaded: Mechanizing proofs by logical relations
We propose a new collection of benchmark problems in mechanizing the metatheory of programming languages, in order to compare and push the state of the art of proof assistants. In particular, we focus on proofs using logical relations (LRs) and propose establishing strong normalization of a simply typed calculus with a proof by Kripke-style LRs as a benchmark. We give a modern view of this well-understood problem by formulating our LR on well-typed terms. Using this case study, we share some of the lessons learned tackling this problem in different dependently typed proof environments. In particular, we consider the mechanization in Beluga, a proof environment that supports higher-order abstract syntax encodings and contrast it to the development and strategies used in general-purpose proof assistants such as Coq and Agda. The goal of this paper is to engage the community in discussions on what support in proof environments is needed to truly bring mechanized metatheory to the masses and engage said community in the crafting of future benchmarks
Oakleaf: an S locus-linked mutation of Primula vulgaris that affects leaf and flower development
•In Primula vulgaris outcrossing is promoted through reciprocal herkogamy with insect-mediated cross-pollination between pin and thrum form flowers. Development of heteromorphic flowers is coordinated by genes at the S locus. To underpin construction of a genetic map facilitating isolation of these S locus genes, we have characterised Oakleaf, a novel S locus-linked mutant phenotype. •We combine phenotypic observation of flower and leaf development, with classical genetic analysis and next-generation sequencing to address the molecular basis of Oakleaf. •Oakleaf is a dominant mutation that affects both leaf and flower development; plants produce distinctive lobed leaves, with occasional ectopic meristems on the veins. This phenotype is reminiscent of overexpression of Class I KNOX-homeodomain transcription factors. We describe the structure and expression of all eight P. vulgaris PvKNOX genes in both wild-type and Oakleaf plants, and present comparative transcriptome analysis of leaves and flowers from Oakleaf and wild-type plants. •Oakleaf provides a new phenotypic marker for genetic analysis of the Primula S locus. We show that none of the Class I PvKNOX genes are strongly upregulated in Oakleaf leaves and flowers, and identify cohorts of 507 upregulated and 314 downregulated genes in the Oakleaf mutant
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