Sample Variance of the Higher-Order Cumulants of Cosmic Density and Velocity Fields

If primordial fluctuation is Gaussian distributed, higher-order cumulants of the cosmic fields reflect nonlinear mode coupling and provide useful information of gravitational instability picture of structure formation. We show that their expected deviation (sample variance) from the universal values is nonvanishing even in linear theory in the case where observed volume is finite. As a result, we find that the relative sample variance of the skewness of the smoothed velocity divergence field remains as large as $\sim 30$ even if the survey depth is as deep as $\sim 150h^{1}Mpc$.Comment: 8 pages including 1 figure, aas.te

Measuring a Parity Violation Signature in the Early Universe via Ground-based Laser Interferometers

We show that pairs of widely separated interferometers are advantageous for measuring the Stokes parameter V of a stochastic background of gravitational waves. This parameter characterizes asymmetry of amplitudes of right- and left-handed waves and generation of the asymmetry is closely related to parity violation in the early universe. The advantageous pairs include LIGO(Livingston)-LCGT and AIGO-Virgo that are relatively insensitive to Omega_GW (the simple intensity of the background). Using at least three detectors, information of the intensity Omega_GW and the degree of asymmetry V can be separately measured.Comment: 6 pages, 3 figures, accepted for publication in PR