The Topos Oxford Seminar is a weekly, informal seminar, hosting informal talks that are broadly aligned with the research themes of the Topos Institute.
Owen Lynch
(Topos)
Feb 14, 2025
TBA
David Jaz Myers
(Topos)
Jan 31, 2025
If universal algebra is the study of sets equipped with the structure of some operations satisfying universally quantified equations, then 2-algebra is the study of *categories* equipped with the structure of some operations, some natural transformations between these operations, and some equations between these. Examples of 2-algebras include symmetric monoidal categories and categories with finite products. Just as the functorial semantics (due to Lawvere) for algebra lets us interpret algebraic theories in categories other than sets (so long as they have finite products), the functorial semantics for 2-algebra (due to Power, Lack, and others) lets us interpret 2-algebraic structure in 2-categories other than Cat. For example, instead of symmetric monoidal categories, we can consider symmetric monoidal double categories. Any strict 2-functor that preserves finite products will push forward 2-algebraic structure. But 2-functors are often only functorial up to coherent isomorphism. What 2-algebraic structure do such cartesian pseudo-functors preserve? In this talk, we'll ask the question and put forward an answer: so long as the 2-algebraic theory is *flexible*, in the sense that it only asks for equations between transformations and not between operations, then it will be preserved by cartesian pseudo-functors.