Ray-Tracing Analysis of Anisotropic Neutrino Radiation for Estimating Gravitational Waves in Core-Collapse Supernovae

We propose a ray-tracing method to estimate gravitational waves (GWs) generated by anisotropic neutrino emission in supernova cores. To calculate the gravitational waveforms, we derive analytic formulae in a useful form, which are applicable also for three-dimensional computations. Pushed by evidence of slow rotation prior to core-collapse, we focus on asphericities in neutrino emission and matter motions outside the protoneutron star. Based on the two-dimensional (2D) models, which mimic SASI-aided neutrino heating explosions, we compute the neutrino anisotropies via the ray-tracing method in a post-processing manner and calculate the resulting waveforms. With these computations, it is found that the waveforms exhibit more variety in contrast to the ones previously estimated by the ray-by-ray analysis (e.g., Kotake et al. (2007)). In addition to a positively growing feature, which was predicted to determine the total wave amplitudes predominantly, the waveforms are shown to exhibit large negative growth for some epochs during the growth of SASI. These features are found to stem from the excess of neutrino emission in lateral directions, which can be precisely captured by the ray-tracing calculation. Due to the negative contributions and the neutrino absorptions appropriately taken into account by the ray-tracing method, the wave amplitudes become more than one-order-of magnitude smaller than the previous estimation, thus making their detections very hard for a galactic source.On the other hand, it is pointed out that the GW spectrum from matter motions have its peak near $\sim 100$ Hz, which could be characteristic for the SASI-induced supernova explosions.(abridged)Comment: 30 pages, 17 figures, ApJ in pres

The gravitational wave spectrum from cosmological B - L breaking

Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying ΩGWh2 ~ 10−13–10−8, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO, ET, BBO and DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking

The NINJA-2 project: detecting and characterizing gravitational waveforms modelled using numerical binary black hole simulations

Contains fulltext : 127900.pdf (preprint version ) (Open Access