Observational tests for strings and gravitational waves: Pulsar timings and cosmological microwave background radiation

Abstract

We discuss the constraints placed on the stronger sources of the cosmological gravitational wave background detectable by millisecond pulsar timings (in particular PSR 1937 + 21) at frequencies of about 10 −7–10 −8 Hz and by binary pulsar timings (PSR 1913 + 16) in the frequency range 10 −13 Hz < ω < 10 −8: upper bounds on the dimentionless gravity wave energy Ω g , on the superconducting and ordinary cosmic string parameter Gμ during t f∼10 −32s≤t≤10 13s and on the anisotropy Δof the CQD transition phase at t ∼ 10 −6s. We study anisotropies and distortions (ΔT/T) in the cosmological background radiation due to cosmic and superconducting strings:(i) temperature angular anisotropy by loop decay into gravitational waves and (ii) spectral distortions due to electromagnetic energy emission. This allows us to cover a wide range of the frequency spectrum. We confront these predictions with observations in particular with the submillimeter excess recently observed by the Nagoya-Berkeley experiment.