Fine projection complex and subsurface homeomorphisms with positive stable commutator length

Abstract

Drawing inspiration from [BBF15], we construct a family of unbounded quasi-trees for a connected closed oriented surface \(S_g\) of genus \(g\geq 2\), upon which the group \(\Homeo_0(S_g)\) acts coboundedly by isometries. As an application, we show that some surface homeomorphisms preserving a non-sporadic essential subsurface or an essential subsurface homeomorphic to a once-bordered torus can have positive stable commutator length in \(\Homeo_0(S_g)\). Moreover, we provide a version of projection complex that does not require the finiteness conditions.