Wide nutation: binary black-hole spins repeatedly oscillating from full alignment to full anti-alignment

Understand

Within the framework of 2PN black-hole binary spin precession, we explore configurations where one of the two spins oscillates from being completely aligned with the orbital angular momentum to being completely anti-aligned with it during a single precession cycle.

• This "wide nutation" is the extreme limit of the generic phenomenon of spin nutation in black-hole binaries.
• Crucially, wide nutation happens on the short precession time scale and it is not a secular effect due to gravitational-wave radiation reaction.
• The spins of these binaries, therefore, flip repeatedly as one of these special configurations is entered.