Astrometric Properties of a Stochastic Gravitational Wave Background

Abstract

[evdate 2011-05-31] IAS Conference on Cosmology since Einstein.IAS title: Talk 13: 'Astrometric Effects of a Stochastic Gravitational Wave Background'.

Abstract: A stochastic gravitational wave background causes the apparent positions of distant sources to fluctuate, with angular deflections of order the characteristic strain amplitude of the gravitational waves. These fluctuations may be detectable with high precision astrometry, as first suggested byBraginsky et al. in 1990. Several researchers have made order of magnitude estimates of the upper limits obtainable on the gravitational wave spectrum \Omega_gw(f), at frequencies of order f ~ 1 yr^‐1, both for the future space‐based optical interferometry missions GAIA and SIM, and for VLBI interferometry in radio wavelengths with the SKA. For GAIA, tracking N ~ 10^6 quasars over a time of T ~ 1 yr with an angular accuracy of \Delta \theta ~ 10 \mu as would yield a sensitivity level of \Omega_gw ~ (\Delta \theta)^2/(N T^2 H_0^2) ~ 10^‐6, which would be roughly comparable with pulsar timing. Prof Flanagan takes a first step toward firming up these estimates by computing in detail the statistical properties of the angular deflections caused by a stochastic background. He computes analytically the two point correlation function of the deflections on the sphere, and the spectrum as a function of frequency and angular scale. The fluctuations are concentrated at low frequencies (for a scale invariant stochastic background), and at large angular scales, starting with the quadrupole. The magnetic‐type and electric‐type pieces of the fluctuations have equal amounts of power. [based on Laura Book, EF, Phys. Rev. D 83, 024024 (2011)]

Duration: 39 min.