– Europe/Lisbon
Room P3.10, Mathematics Building — Online
Topological quantum field theories and homotopy cobordisms
I will begin by explaining the construction of a category $\operatorname{CofCos}$, whose objects are topological spaces and whose morphisms are cofibrant cospans. Here the identity cospan is chosen to be of the form $X\to X\times [0,1] \rightarrow X$, in contrast with the usual identity in the bicategory $\operatorname{Cosp}(V)$ of cospans over a category $V$. The category $\operatorname{CofCos}$ has a subcategory $\operatorname{HomCob}$ in which all spaces are homotopically $1$-finitely generated. There exist functors into $\operatorname{HomCob}$ from a number of categorical constructions which are potentially of use for modelling particle trajectories in topological phases of matter: embedded cobordism categories and motion groupoids for example. Thus, functors from $\operatorname{HomCob}$ into $\operatorname{Vect}$ give representations of the aforementioned categories.
I will also construct a family of functors $Z_G : \operatorname{HomCob} \to \operatorname{Vect}$, one for each finite group $G$, showing that topological quantum field theories previously constructed by Yetter, and an untwisted version of Dijkgraaf-Witten, generalise to functors from $\operatorname{HomCob}$. I will construct this functor in such a way that it is clear the images are finite dimensional vector spaces, and the functor is explicitly calculable.
Additional file
Local participants are invited to join us in room 3.10 (3rd floor, Mathematics Department, Instituto Superior Técnico).