Directional limits on persistent gravitational waves using LIGO S5 science data.

The gravitational-wave (GW) sky may include nearby pointlike sources as well as stochastic backgrounds. We perform two directional searches for persistent GWs using data from the LIGO S5 science run: one optimized for pointlike sources and one for arbitrary extended sources. Finding no evidence to support the detection of GWs, we present 90% confidence level (C.

An upper limit on the stochastic gravitational-wave background of cosmological origin.

A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin. It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standard astrophysical observations. Direct measurements of the amplitude of this background are therefore of fundamental importance for understanding the evolution of the Universe when it was younger than one minute.

Proposal for a search for cosmic axions using an optical cavity.

A high finesse optical cavity can be used to search for cosmic axions in the mass range 10;{-6} < m_{a} < 10;{-4} eV. Either a two-arm or a single-arm cavity is suitable, and in either case the signal appears as resonant sidebands imposed on the carrier. Assuming for the local axion density the usual figure of rho_{a} = 500 Mev/cm;{3}, the KSVZ axion line g_{agammagamma}/m_{a} = 0.

Measurement of the thermal contribution to the nonlinear refractive index of air at 1064nm.

The thermal contribution to the nonlinear refractive index of air at 1.064mum was measured with a high-finesse Fabry-Perot cavity and a 500-mW cw laser beam. At room temperature and pressure, the nonlinear refractive-index coefficient of air was found to be n(2)((th))=(-1.

Spatial patterns induced in a laser beam by thermal nonlinearities.

Stable spatial laser patterns were observed in a high-finesse Fabry-Perot cavity containing up to 2 atm of CO(2) and O(2). The gases displayed the same sequence of patterns that obey a scaling law of the form P(beta)p(2), where P is the power stored in the cavity, p is the pressure of the gas, and beta is a material-dependent parameter.

Electro-optic measurement of the wake fields of a relativistic electron beam.

When a relativistic electron bunch traverses a structure, strong electromagnetic fields are induced in its wake. For a 12 nC bunch of duration 4.2 ps FWHM, the peak field is measured >0.