34,281 research outputs found
The K Band Luminosity Functions of Galaxies in High Redshift Clusters
K band luminosity functions (LFs) of three, massive, high redshift clusters
of galaxies are presented. The evolution of K*, the characteristic magnitude of
the LF, is consistent with purely passive evolution, and a redshift of forma
tion z = 1.5-2.Comment: 3 pages, to appear in Proceedings of IAU Colloquium 195 - Outskirts
of Galaxy Clusters: intense life in the suburb
Semiclassical collision theory. Multidimensional Bessel uniform approximation
A multidimensional Bessel uniform approximation for the semiclassical S matrix is derived for the case of four real stationary phase points. A formula is also developed for the particular case when four stationary phase points may be considered to be well separated in pairs. The latter equation is then used in the treatment of two real and two complex stationary phase points
Semiclassical collision theory. Application of multidimensional uniform approximations to the atom-rigid-rotor system
The multidimensional Bessel and Airy uniform approximations developed earlier in this series for the semiclassical S matrix are applied to the atom rigid−rotor system. The need is shown for (a) using a geoemetrical criterion for determining whether a stationary phase point (s.p.pt) is a maximum, minimum, or saddle point; (b) choosing a proper quadrilateral configuration of the s.p.pts. with the phases as nearly equal as possible; and (c) choosing a unit cell to favor near−separation of variables. (a) and (b) apply both to the Airy and to the Bessel uniform approximations, and (c) to the Bessel. The use of a contour plot both to understand and to facilitate the search in new cases is noted. The case of real and complex−valued stationary phase points is also considered, and the Bessel uniform−in−pairs approximation is applied. Comparison is made with exact quantum results. As in the one−dimensional case, the Bessel is an improvement over the Airy for ’’k = 0’’ transitions, while for other transitions they give similar results. Comparison in accuracy with the results of the integral method is also given. As a whole, the agreement can be considered to be reasonable. The improvement of the present over various more approximate results is shown
Advanced general aviation comparative engine/airframe integration study
The NASA Advanced Aviation Comparative Engine/Airframe Integration Study was initiated to help determine which of four promising concepts for new general aviation engines for the 1990's should be considered for further research funding. The engine concepts included rotary, diesel, spark ignition, and turboprop powerplants; a conventional state-of-the-art piston engine was used as a baseline for the comparison. Computer simulations of the performance of single and twin engine pressurized aircraft designs were used to determine how the various characteristics of each engine interacted in the design process. Comparisons were made of how each engine performed relative to the others when integrated into an airframe and required to fly a transportation mission
Supergravity on R4 x S1/Z2 and singular Calabi-Yaus
We discuss the moduli space singularities that are generally present in
five-dimensional vector-coupled supergravity on a spactime of the form R4 x
S1/Z2, with vector fields surviving on the Z2 fixed planes. The framework of
supergravity is necessarily ambiguous when it comes to the non-singular
embedding theory, so we focus on those models coming from Calabi-Yau
three-folds with wrapped membranes.Comment: 13 p
Exact non-equilibrium solutions of the Einstein-Boltzmann equations. II
We find exact solutions of the Einstein-Boltzmann equations with relaxational
collision term in FRW and Bianchi I spacetimes. The kinematic and thermodynamic
properties of the solutions are investigated. We give an exact expression for
the bulk viscous pressure of an FRW distribution that relaxes towards
collision-dominated equilibrium. If the relaxation is toward collision-free
equilibrium, the bulk viscosity vanishes - but there is still entropy
production. The Bianchi I solutions have zero heat flux and bulk viscosity, but
nonzero shear viscosity. The solutions are used to construct a realisation of
the Weyl Curvature Hypothesis.Comment: 16 pages LaTex, CQG documentstyle (ioplppt
Superpartners at LHC and Future Colliders: Predictions from Constrained Compactified M-Theory
We study a realistic top-down M-theory compactification with low-scale
effective Supersymmetry, consistent with phenomenological constraints. A
combination of top-down and generic phenomenological constraints fix the
spectrum. The gluino mass is predicted to be about 1.5 TeV. Three and only
three superpartner channels, , and
(where are Wino-like), are expected
to be observable at LHC-14. We also investigate the prospects of finding heavy
squarks and Higgsinos at future colliders. Gluino-stop-top,
gluino-sbottom-bottom associated production and first generation squark
associated production should be observable at a 100 TeV collider, along with
direct production of heavy Higgsinos. Within this framework the discovery of a
single sparticle is sufficient to determine uniquely the SUSY spectrum,
yielding a number of concrete testable predictions for LHC-14 and future
colliders, and determination of and thereby other fundamental
quantities.Comment: 19 pages, 4 figure
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