Dear All, We are delighted to present the MaPSS Seminar topic of Monday 07/08; 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: Becky Armstrong (Sydney University) Title: Group actions, groupoids, and their C*-algebras Abstract: C*-algebras were first introduced in order to model physical observables in quantum mechanics, but are now studied more abstractly in pure mathematics. Much of the current research of C*-algebraists involves constructing interesting classes of C*-algebras from various mathematical objects---such as groups, groupoids, and directed graphs---and studying their properties. Groupoid C*-algebras were introduced by Renault in 1980, and provide a unifying model for C*-algebras associated to groups, group actions, and graphs. In this talk, I will define topological groupoids and examine Renault’s construction of groupoid C*-algebras. I will discuss several examples of groupoids, including group actions and graph groupoids, and will conclude with a brief description of my PhD research. Supervisors, please encourage your students to attend. Thanks, MaPSS Organizers