Thurston's fragmentation and c-principles

Abstract

In this paper, we generalize the original idea of Thurston for the so called Mather-Thurston's theorem for foliated bundles to prove new variants of this theorem for PL homeomorphisms, contactormorphisms. These versions answer questions posed by Gelfand -Fuks and Greenberg on PL foliations and Rybicki on contactomorphisms. The interesting point about the original Thurston's technique compared to the better known Segal-McDuff's proof of the Mather-Thurston theorem is that it gives a compactly supported c-principle theorem without knowing the relevant local statement on open balls. In the appendix, we show that Thurston's fragmentation implies the non-abelian Poincare duality theorem and its generalization using blob complexes.