Spaces with labelled partitions and isometric affine actions on Banach   spaces
  We define the structure of spaces with labelled partitions which generalizes the structure of spaces with measured walls and study the link between actions by automorphisms on spaces with labelled partitions and isometric affine actions on Banach spaces, and more particularly, on $L^p$ spaces. We build natural spaces with labelled partitions for the action of various contructions of groups, namely: direct sum; semi-direct product; wreath product and amalgamated free product. We apply this to prove that the wreath product of a group with property $PL^p$ by a group with Haagerup property has property $PL^p$ and the amalgamated free product over finite subgroups of groups with property $PL^p$ has property $PL^p$. 
Sylvain Arnt
math.GR