Expectations for the Difference Between Local and Global Measurements of the Hubble Constant

There are irreducible differences between the Hubble constant measured locally and the global value. They are due to density perturbations and finite sample volume (cosmic variance) and finite number of objects in the sample (sampling variance). We quantify these differences for a suite of COBE-normalized CDM models that are consistent with the observed large-scale structure. For small samples of objects that only extend out to 10,000 km/sec, the variance can approach 4%. For the largest samples of Type Ia supernovae (SNeIa), which include about 40 objects and extend out to almost 40,000 km/sec, the variance is 1-2% and is dominated by sampling variance. Sampling and cosmic variance may be an important consideration in comparing local determinations of the Hubble constant with precision determinations of the global value that will be made from high-resolution maps of CBR anisotropy.Comment: 10 pages, Latex, 2 figures, version accepted for Ap.

Kinetic decoupling of neutralino dark matter

After neutralinos cease annihilating in the early Universe, they may still scatter elastically from other particles in the primordial plasma. At some point in time, however, they will eventually stop scattering. We calculate the cross sections for neutralino elastic scattering from standard-model particles to determine the time at which this kinetic decoupling occurs. We show that kinetic decoupling occurs above a temperature $T\sim$ MeV. Thereafter, neutralinos act as collisionless cold dark matter.Comment: Replaced with revised version, new references adde

Using the acoustic peak to measure cosmological parameters

Recent measurements of the cosmic microwave background radiation by the Boomerang experiment indicate that the universe is spatially flat. Here some simple back-of-the-envelope calculations are used to explain their result. The main result is a simple formula for the angular scale of the acoustic peak in terms of the standard cosmological parameters: l=193*[1+3(1-Omega_0)/5+(1-h)/5+Omega_Lambda/35].Comment: 4 pages, 1 figure, Explanations have been clarifie

Direct Signature of Evolving Gravitational Potential from Cosmic Microwave Background

We show that time dependent gravitational potential can be directly detected from the cosmic microwave background (CMB) anisotropies. The signature can be measured by cross-correlating the CMB with the projected density field reconstructed from the weak lensing distortions of the CMB itself. The cross-correlation gives a signal whenever there is a time dependent gravitational potential. This method traces dark matter directly and has a well defined redshift distribution of the window projecting over the density perturbations, thereby avoiding the problems plaguing other proposed cross-correlations. We show that both MAP and Planck will be able to probe this effect for observationally relevant curvature and cosmological constant models, which will provide additional constraints on the cosmological parameters.Comment: 4 pages, 2 figures. Submitted to PR

Detecting an Invisibly Decaying Higgs Boson at a Hadron Supercollider

We demonstrate that an invisibly decaying Higgs boson with Standard Model coupling strength to top--anti-top can be detected at the LHC for masses up to about 250 GeV.Comment: 7 pages, requires phyzzx.tex and tables.tex, revised to convert results from SSC to LHC and include additional top quark mass cases, full postscript file including embedded figure available via anonymous ftp at ucdhep.ucdavis.edu as [anonymous.gunion]hinvisible_revised.ps, preprint UCD-93-2

Scattering of Ultrasound (Including Rayleigh Waves) by Surface Roughness and by Single Surface Flaws. A Review of the Work Done at Paris 7 University

Since some years our team has worked on the characterization of rough surfaces from a study of the angular and frequency dependence of the backscattered intensity of ultrasonic waves. We shall discuss, in view of our experimental results, the different components of the signature of the surface profile which can be evaluated by these means: r.m.s. roughness h with a precision of the order of 1 μm in the range 6-100 μm influence of the autocorrelation distance L when present, surface periodicities with a precision which can be better than 1%. In the case of quasiperiodic surfaces, we shall present a comparison between the spectra theoretically predicted in the low-frequency approximation for various samples, and the ultrasonic spectra actually observed. Since 1977, we have also used Rayleigh waves to study surface properties and surface cracks in ceramics and metals and we shall give an introduction to the results obtained at the present time. This topic will be developed by B.R. Tittmann in a following paper

The isolation of gravitational instantons: Flat tori V flat R^4

The role of topology in the perturbative solution of the Euclidean Einstein equations about flat instantons is examined.Comment: 15 pages, ICN-UNAM 94-1

Cosmological measurement of neutrino mass in the presence of leptonic asymmetry

We show that even the smallest neutrino mass consistent with the Super--Kamiokande data is relevant for cosmological models of structure formation and cosmic microwave background (CMB) anisotropies, provided that a relic neutrino asymmetry exists. We calculate the precision with which a 0.07 eV neutrino mass could be extracted from CMB anisotropy and large-scale structure data by the future Planck satellite and Sloan Digital Sky Survey. We find that such a mass can be detected, assuming a large relic neutrino asymmetry still allowed by current experimental data. This measurement of the absolute value of the neutrino mass would be crucial for our understanding of neutrino models.Comment: 8 pages, 2 PS figures, version to be publishe