20,277 research outputs found
Linear kinetic Sunyaev-Zel'dovich effect and void models for acceleration
There has been considerable recent interest in cosmological models in which
the current apparent acceleration is due to a very large local underdensity, or
void, instead of some form of dark energy. Here we examine a new proposal to
constrain such models using the linear kinetic Sunyaev-Zel'dovich (kSZ) effect
due to structure within the void. The simplified "Hubble bubble" models
previously studied appeared to predict far more kSZ power than is actually
observed, independently of the details of the initial conditions and evolution
of perturbations in such models. We show that the constraining power of the kSZ
effect is considerably weakened (though still impressive) under a fully
relativistic treatment of the problem, and point out several theoretical
ambiguities and observational shortcomings which further qualify the results.
Nevertheless, we conclude that a very large class of void models is ruled out
by the combination of kSZ and other methods.Comment: 15 pages, 9 figures; minor changes, version published in CQG focus
section "Inhomogeneous Cosmological Models and Averaging in Cosmology
Effects of environmental exposures on silicon solar cells
Effect of environmental tests on mechanical and electrical properties of silicon solar cell
Environmental effects on silicon solar cells
Test results indicate that solder coating cells produces protective or deleterious effect, depending on the environment. Major problem for solder coated cells is in control of solder thickness and uniformity. Problem area for non-solder coated cells is not identified
Dilepton Production at Fermilab and RHIC
Some recent results from several fixed-target dimuon production experiments
at Fermilab are presented. In particular, we discuss the use of Drell-Yan data
to determine the flavor structure of the nucleon sea, as well as to deduce the
energy-loss of partons traversing nuclear medium. Future dilepton experiments
at RHIC could shed more light on the flavor asymmetry and possible
charge-symmetry-violation of the nucleon sea. Clear evidence for scaling
violation in the Drell-Yan process could also be revealed at RHIC.Comment: 5 pages, talk presented at the RIKEN-BNL Workshop on 'Hard Parton
Physics in Nucleus-Nucleus collisions, March 199
Tilted Physics: A Cosmologically Dipole-Modulated Sky
Physical constants and cosmological parameters could vary with position. On
the largest scales such variations would manifest themselves as gradients
across our Hubble volume, leading to dipole-modulation of the cosmic microwave
anisotropies. This generically leads to a correlation between adjacent
multipoles in the spherical harmonics expansion of the sky, a distinctive
signal which should be searched for in future data sets.Comment: 4 pages, 3 figure
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