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We investigate the evolution of low mass (Md /Mb = 0.005) misaligned gaseousdiscs around eccentric supermassive black hole (SMBH) binaries. These areexpected to form from randomly oriented accretion events onto a SMBH binaryformed in a galaxy merger. When expanding the interaction terms between thebinary and a circular ring to quadrupole order and averaging over the binaryorbit, we expect four non-precessing disc orientations: aligned orcounter-aligned with the binary, or polar orbits around the binary eccentricityvector with either sense of rotation. All other orientations precess aroundeither of these, with the polar precession dominating for high eccentricity.These expectations are borne out by smoothed particle hydrodynamics simulationsof initially misaligned viscous circumbinary discs, resulting in the formationof polar rings around highly eccentric binaries in contrast to the co-planardiscs around circular binaries. Moreover, we observe disc tearing and violentinteractions between differentially precessing rings in the disc significantlydisrupting the disc structure and causing gas to fall onto the binary withlittle angular momentum. While accretion from a polar disc may not promote SMBHbinary coalescence (solving the `final-parsec problem'), ejection of thisinfalling low-angular momentum material via gravitational slingshot is apossible mechanism to reduce the binary separation. Moreover, this process actson dynamical rather than viscous time scales, and so is much faster.

Misaligned gas discs around eccentric black-hole binaries and implications for the final-parsec problem