The tune of the Universe: the role of plasma in tests of strong-field gravity

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Gravitational-wave (GW) astronomy, together with precise pulsar timing and long baseline interferometry, is changing our ability to perform tests of fundamental physics with astrophysical observations. Some of these tests are based on electromagnetic (EM) probes or electrically charged bodies, and assume an empty Universe. However, the cosmos is filled with plasma, a dilute medium which prevents the propagation of low-frequency, small-amplitude EM waves. We show that the plasma hinders our ability to perform some strong-field gravity tests, in particular: (i) nonlinear plasma effects dramatically quench plasma-driven super-radiant instabilities; (ii) the contribution of EM emission to the inspiral of charged black-hole binaries is strongly suppressed; (iii) EM-driven secondary modes, although present in the spectrum of charged black holes, are excited to negligible amplitude in the GW ringdown signal. The last two effects are relevant also in the case of massive fields that propagate in vacuum and can jeopardize tests of modified theories of gravity containing massive degrees of freedom.

Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Volume503
Issue number1
Pages (from-to)563-573
Number of pages11
ISSN0035-8711
DOIs
Publication statusPublished - 11 Feb 2021
Externally publishedYes

    Research areas

  • binaries: general, ISM: general, gravitational waves, black hole physics, RADIATION

ID: 298633199