https://phys.org/news/2020-10-gravitational-lensing.html Detection of gravitational wave 'lensing' could be some way off: Gravitational wave scientists looking for evidence of "lensing," in which the faintest gravitational wave signals become amplified, are unlikely to make these detections in the near future according to new analysis by scientists at the University of Birmingham. A team in the University's School of Physics and Astronomy and the Institute for Gravitational Wave Astronomy has analyzed currently available gravitational wave data to predict that these elusive signals are likely to remain undetected by the instruments currently operated by the LIGO and Virgo Collaboration. The existence of gravitational lensing was predicted by Einstein and is a well-recognized phenomenon in relation to light waves. Light emitted by distant objects in the Universe is bent by the gravitational pull of other massive objects, such as galaxies when the light source passes behind them. When detected by the earth's telescopes, this distortion might make the light-emitting object seem larger or closer to earth than it actually is. more at link...... the paper: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.141102 ABSTRACT Gravitational waves (GWs) are subject to gravitational lensing in the same way as electromagnetic radiation. However, to date, no unequivocal observation of a lensed GW transient has been reported. Independently, GW observatories continue to search for the stochastic GW signal that is produced by many transient events at high redshift. We exploit a surprising connection between the lensing of individual transients and limits to the background radiation produced by the unresolved population of binary back hole mergers: we show that it constrains the fraction of individually resolvable lensed binary black holes to less than ∼4×10−5 at present sensitivity. We clarify the interpretation of existing, low redshift GW observations (obtained assuming no lensing) in terms of their apparent lensed redshifts and masses and explore constraints from GW observatories at future sensitivity. Based on our results, recent claims of observations of lensed events are statistically disfavored.
