Seminar: Rajan Mehta - Coherent 2D span-valued TQFTs (Oct 28, 2025)

Speaker: Rajan Mehta (Smith College)

Title: Coherent 2D span-valued TQFTs

Time: October 28, Tuesday, 2025 at 18:00 (Istanbul LT)

Place: Online

Meeting ID: 935 6390 4955
Passcode: 699568

Abstract: It is well-known that 2D TQFTs taking values in a category correspond to commutative Frobenius objects in that category. If the target category is the category of spans, it is reasonable to ask if there is a lift to a coherent structure (i.e. a Frobenius pseudomonoid) in the bicategory of spans. Such structures can be neatly described by simplicial sets, equipped with some additional symmetric group actions, and satisfying some conditions known as the "2-Segal conditions". I'll describe this correspondence as well as a construction that produces examples from any commutative monoid. This is joint work with Sophia Marx, building on earlier work with Ivan Contreras and Walker Stern.