The ε ring, the brightest and most massive of the narrow rings, was shown to maintain an appreciable eccentricity (e = 0.00794) and an azimuthally-varying width; the ring is five times wider and ∼2.5 times brighter in reflected sunlight at apoapsis than at periapsis (French et al. 19881; Karkoschka 2001a2). However, many fundamental parameters about the ring system remain unknown, including the filling factor, composition, thickness,
1French, R. G., Elliot, J. L., French, L. M., et al. 1988, Icarus, 73, 349, doi: 10.1016/0019-1035(88)90104-2
2Karkoschka, E. 2001a, Icarus, 151, 51, doi: 10.1006/icar.2001.6596
I've read in Wikipedia's Rings of Uranus that several rings are expected to be fairly young, and there may be interaction with some small moons, but I am surprised that the rings could maintain a significant eccentricity, and do not circularize or smear out due to collisions.
Question: What kind of dynamical effects can maintain Uranus' rings' eccentricities?
Uranus itself has a huge J2 and so any ring that isn't perfectly equatorial should have an eccentricity-dependent precession. The paper states that the apoapsis of the rings is five times wider than the periapsis, so there's definitely a population of different eccentricities and semi-major axes within the ε ring.