13,088 research outputs found
Search for rare leptonic B decays at the Tevatron
Results of a search for the Flavor-Changing Neutral Current decay using collision data at TeV
collected at Fermilab Tevatron collider by the CDF and D{\O}detectors are
presented. CDF reports upper limits on and
at the 95% C.L. using 171 pb. The D{\O}Collaboration used 240 pb
to set an even more stringent limit on the branching ratio for of at the 95% C.L.Comment: 5 pages, 2 figures, submitted to DPF 2004 conference proceedings, UC
Riverside, C
Microstrip antenna array with parasitic elements
Discussed is the design of a large microstrip antenna array in terms of subarrays consisting of one fed patch and several parasitic patches. The potential advantages of this design are discussed. Theoretical radiation patterns of a subarray in the configuration of a cross are presented
Key polynomials for simple extensions of valued fields
Let be a simple transcendental extension
of valued fields, where is equipped with a valuation of rank 1. That
is, we assume given a rank 1 valuation of and its extension to
. Let denote the valuation ring of . The purpose
of this paper is to present a refined version of MacLane's theory of key
polynomials, similar to those considered by M. Vaqui\'e, and reminiscent of
related objects studied by Abhyankar and Moh (approximate roots) and T.C. Kuo.
Namely, we associate to a countable well ordered set the are called {\bf key
polynomials}. Key polynomials which have no immediate predecessor are
called {\bf limit key polynomials}. Let .
We give an explicit description of the limit key polynomials (which may be
viewed as a generalization of the Artin--Schreier polynomials). We also give an
upper bound on the order type of the set of key polynomials. Namely, we show
that if then the set of key polynomials has
order type at most , while in the case
this order type is bounded above by , where stands
for the first infinite ordinal.Comment: arXiv admin note: substantial text overlap with arXiv:math/060519
Ballistic Localization in Quasi-1D Waveguides with Rough Surfaces
Structure of eigenstates in a periodic quasi-1D waveguide with a rough
surface is studied both analytically and numerically. We have found a large
number of "regular" eigenstates for any high energy. They result in a very slow
convergence to the classical limit in which the eigenstates are expected to be
completely ergodic. As a consequence, localization properties of eigenstates
originated from unperturbed transverse channels with low indexes, are strongly
localized (delocalized) in the momentum (coordinate) representation. These
eigenstates were found to have a quite unexpeted form that manifests a kind of
"repulsion" from the rough surface. Our results indicate that standard
statistical approaches for ballistic localization in such waveguides seem to be
unappropriate.Comment: 5 pages, 4 figure
Impurity Effects in Two-Electron Coupled Quantum Dots: Entanglement Modulation
We present a detailed analysis of the electronic and optical properties of
two-electron quantum dots with a two-dimensional Gaussian confinement
potential. We study the effects of Coulomb impurities and the possibility of
manipulate the entanglement of the electrons by controlling the confinement
potential parameters. The degree of entanglement becomes highly modulated by
both the location and charge screening of the impurity atom, resulting two
regimes: one of low entanglement and other of high entanglement, with both of
them mainly determined by the magnitude of the charge. It is shown that the
magnitude of the oscillator strength of the system could provide an indication
of the presence and characteristics of impurities that could largely influence
the degree of entanglement of the system.Comment: Regular Article (Journal of Physics B, in press), 9 pages, 10 figure
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