10,096 research outputs found
Phonon origin of low energy and high energy kinks in high temperature cuprate superconductors
Eliashberg theory generalized for the account of the electron-hole
nonequivalence and electron correlations in the vertex function is used. The
phonon contribution to the nodal electron Green function in cuprates is viewed.
At non- zero temperatures the singularities (kinks) in the frequency behavior
of a real and imaginary part of an electron nodal Green function, and also in
the nodal part of the density of the electron states modified by an
electron-phonon interaction are studied. It is shown that near the optimal
doping both the low-energy and high-energy nodal Green function kinks and also
the abnormal broadening of a band in cuprates are reproduced with the
electron-phonon interaction in the extended Eliashberg theory.Comment: 11 pages, 3 figure
NN Interaction JISP16: Current Status and Prospect
We discuss realistic nonlocal NN interactions of a new type - J-matrix
Inverse Scattering Potential (JISP). In an ab exitu approach, these
interactions are fitted to not only two-nucleon data (NN scattering data and
deuteron properties) but also to the properties of light nuclei without
referring to three-nucleon forces. We discuss recent progress with the ab
initio No-core Shell Model (NCSM) approach and respective progress in
developing ab exitu JISP-type NN-interactions together with plans of their
forthcoming improvements.Comment: 9 pages, 3 figures, to be published in Proceedings of Few-body 19
conferenc
Twisting commutative algebraic groups
If is a commutative algebraic group over a field , is a
commutative ring that acts on , and is a finitely generated free
-module with a right action of the absolute Galois group of , then there
is a commutative algebraic group over , which is a twist of
a power of . These group varieties have applications to cryptography (in the
cases of abelian varieties and algebraic tori over finite fields) and to the
arithmetic of abelian varieties over number fields. For purposes of such
applications we devote this article to making explicit this tensor product
construction and its basic properties.Comment: To appear in Journal of Algebra. Minor changes from original versio
Eclipsing Binaries in the OGLE Variable Star Catalog.III. Long-Period Contact Systems
A sample of contact binaries discovered by the OGLE project in Baade's
Window, with orbital periods longer than one day and with available color and
light-curve data, has been analyzed. It consists of only 32 systems, in
contrast to 388 WUMa-type systems with shorter periods which were analyzed
before. Most systems are very distant and are probably located close to or in
the galactic Bulge. Two groups of contact binaries are seen in the sample: (1)
a continuation of the WUMa-type sequence, extending up to the orbital periods
of 1.3 - 1.5 day, but rather sharply ending in this period range; (2) an
inhomogeneous group of rare systems with long periods up to 26 days, all with
red colors and relatively shallow eclipses. While the systems of the first
group share most of the characteristics of the typical WUMa-type systems
(except that they are on the average brighter and more distant, hence more
reddened), the long-period systems do not seem to form an early-type extension
of contact binaries, but may consist of a mixture of late-type objects,
including tidally distorted red giants with invisible companions.Comment: 24 pages including 10 figures (inserted with psfig) and one table;
submitted to A
Comparison of FDMA and CDMA for second generation land-mobile satellite communications
Code Division Multiple Access (CDMA) and Frequency Division Multiple Access (FDMA) (both analog and digital) systems capacities are compared on the basis of identical link availabilities and physical propagation models. Parameters are optimized for a bandwidth limited, multibeam environment. For CDMA, the benefits of voice activated carriers, antenna discrimination, polarization reuse, return link power control and multipath suppression are included in the analysis. For FDMA, the advantages of bandwidth efficient modulation/coding combinations, voice activated carriers, polarization reuse, beam placement, and frequency staggering were taken into account
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