ABSTRACT
General relativity provides us with an extremely powerful tool to extract at the same time astrophysical and cosmological information from the stochastic gravitational-wave backgrounds (SGWBs): the cross-correlation with other cosmological tracers, since their anisotropies share a common origin and the same perturbed geodesics. In this Letter we explore the cross-correlation of the cosmological and astrophysical SGWBs with cosmic microwave background (CMB) anisotropies, showing that future GW detectors, such as LISA or BBO, have the ability to measure such cross-correlation signals. We also present, as a new tool in this context, constrained realization maps of the SGWBs extracted from the high-resolution CMB Planck maps. This technique allows, in the low-noise regime, to faithfully reconstruct the expected SGWB map by starting from CMB measurements.
ABSTRACT
There has recently been renewed interest in the possibility that the dark matter in the Universe consists of primordial black holes (PBHs). Current observational constraints leave only a few PBH mass ranges for this possibility. One of them is around 10^{-12} M_{â}. If PBHs with this mass are formed due to an enhanced scalar-perturbation amplitude, their formation is inevitably accompanied by the generation of gravitational waves (GWs) with frequency peaked in the mHz range, precisely around the maximum sensitivity of the LISA mission. We show that, if these primordial black holes are the dark matter, LISA will be able to detect the associated GW power spectrum. Although the GW source signal is intrinsically non-Gaussian, the signal measured by LISA is a sum of the signal from a large number of independent sources suppressing the non-Gaussianity at detection to an unobservable level. We also discuss the effect of the GW propagation in the perturbed Universe. PBH dark matter generically leads to a detectable, purely isotropic, Gaussian and unpolarized GW signal, a prediction that is testable with LISA.
ABSTRACT
We report the results of a joint analysis of data from BICEP2/Keck Array and Planck. BICEP2 and Keck Array have observed the same approximately 400 deg^{2} patch of sky centered on RA 0 h, Dec. -57.5°. The combined maps reach a depth of 57 nK deg in Stokes Q and U in a band centered at 150 GHz. Planck has observed the full sky in polarization at seven frequencies from 30 to 353 GHz, but much less deeply in any given region (1.2 µK deg in Q and U at 143 GHz). We detect 150×353 cross-correlation in B modes at high significance. We fit the single- and cross-frequency power spectra at frequencies ≥150 GHz to a lensed-ΛCDM model that includes dust and a possible contribution from inflationary gravitational waves (as parametrized by the tensor-to-scalar ratio r), using a prior on the frequency spectral behavior of polarized dust emission from previous Planck analysis of other regions of the sky. We find strong evidence for dust and no statistically significant evidence for tensor modes. We probe various model variations and extensions, including adding a synchrotron component in combination with lower frequency data, and find that these make little difference to the r constraint. Finally, we present an alternative analysis which is similar to a map-based cleaning of the dust contribution, and show that this gives similar constraints. The final result is expressed as a likelihood curve for r, and yields an upper limit r_{0.05}<0.12 at 95% confidence. Marginalizing over dust and r, lensing B modes are detected at 7.0σ significance.
ABSTRACT
A novel approach for the delivery of 166Ho (t1/2 = 26.6 h) to tissue is via the in vivo decay of its 81.5 h parent, 166Dy-an in vivo generator system. A critical question for the in vivo 166Dy/166Ho generator system is whether translocation of the daughter nucleus occurs. The in vitro and in vivo integrity of the [166Dy]Dy/166Ho-DTPA complex was investigated and results indicated that no translocation of the daughter nucleus occurs subsequent to beta- decay of 166Dy. Biodistribution studies of [166Dy]Dy-DTPA showed that the ratio of 166Dy/166Ho in bone remains constant (+/- 7%) over a 20 h period, indicating no significant in vivo loss of 166Ho from the complex. Increasing the in vivo residence time of [166Dy]Dy-DTPA complex attached to HSA gave similar results.
