Gravitational waves with orbital angular momentum
Abstract
Compact orbiting binaries like the black hole binary system observed in GW150914 carry large amount of orbital angular momentum. The postringdown compact object formed after merger of such a binary configuration has only spin angular momentum, and this results in a large orbital angular momentum excess. One significant possibility is that the gravitational waves generated by the system carry away this excess orbital angular momentum. An estimate of this excess is made. Arguing that plane gravitational waves cannot possibly carry any orbital angular momentum, a case is made in this paper for gravitational wave beams carrying orbital angular momentum, akin to optical beams. Restricting to certain specific beamconfigurations, we predict that such beams may produce a new type of strain, in addition to the longitudinal strains measured at aLIGO for GW150914 and GW170817. Current constraints on postringdown spins, derived within the planewave approximation of gravitational waves, therefore stand to improve. The minimal modification that might be needed on a laserinterferometer detector (like aLIGO or VIRGO) to detect such additional strains is also briefly discussed.
 Publication:

European Physical Journal C
 Pub Date:
 April 2020
 DOI:
 10.1140/epjc/s1005202078812
 arXiv:
 arXiv:1901.08804
 Bibcode:
 2020EPJC...80..326B
 Keywords:

 General Relativity and Quantum Cosmology
 EPrint:
 8 pages, 4 figures Version to appear in EPJC