Sebastiao Firmo | Searcharxiv

arXiv2008

Paires de structures de contact sur les variétés de dimension trois

We introduce a notion of positive pair of contact structures on a 3-manifold which generalizes a previous definition of Eliashberg-Thurston and Mitsumatsu. Such a pair gives rise to a locally integrable plane field $λ$. We prove that if $λ$ is uniquely integrable and if both structures of the pair are tight, then the integral foliation of $λ$ doesn't contain any Reeb component whose core curve is homologous to zero. Moreover, the ambient manifold carries a Reebless foliation. We also show a stability theorem "à la Reeb" for positive pairs of tight contact structures.

math.SG↗

arXiv2001

Fixed points of discrete nilpotent group actions on S^2

We prove that for each integer k of at least 2, there is an open neigborhood ν_k of the identity map of the 2-sphere S^2, in C^1-topology such that: if G is a nilpotent subgroup of Diff^1(S^2) with length k of nilpotency, generated by elements in ν_k, then the natural action on S^2 has non-empty fixed point set. Moreover, the G-action has at least two fixed points if the action has a finite non-trivial orbit.

math.GT↗