Dear All, We are delighted to present the MaPSS Seminar topic of Monday ; please see the abstract below. **This Semester the Seminar will always run on Monday, at 5:00pm in 535A** Following the talk, there will be pizza on offer. Speaker: Robert Tang (Postdoc University of Oklahoma) Title: Wall spaces and CAT(0)-cube complexes Abstract: A wall space is a set X together with a collection W of "walls" -- partitions of X into two non-empty subsets. A simple example is a tree: X is the vertex set, and each edge naturally determines a wall by separating the tree into two components. I will describe a construction due to Sageev which associates to a wall space its dual cube complex C(X,W). This dual cube complex admits some nice metrics, and captures many combinatorial properties of the original wall space geometrically. I will go through several examples and, time permitting, some applications to topology and group theory. Supervisors, please encourage your students to attend. Thanks, MaPSS Organizers