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Résumé |
The NANOGrav pulsar timing collaboration has recently reported strong evidence for
a new stochastic common-spectrum process affecting the pulsar timing residuals in
its 12.5-year data set. If confirmed in the future, this signal may turn out to be
the first glimpse of a stochastic gravitational-wave background at nanohertz
frequencies. In the first half of this talk, I will review the NANOGrav
experiment, discuss the properties of the observed signal, and comment on its
astrophysical interpretation in terms of inspiraling supermassive black-hole
binaries. In the second half of the talk, I will then turn to possible
explanations based on physics beyond the standard model, including first-order
phase transitions, primordial black holes, and cosmic strings. I will conclude by
giving an outlook on the future of gravitational-wave astronomy in general and
pulsar timing measurements in particular in view of the NANOGrav result. My own
work on the NANOGrav signal is contained in 2009.06607 and 2009.10649, which I
will also briefly discuss. |
