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Homotopical combinatorics

Kyle Ormsby, University of Washington / Reed College
Tuesday, October 25, 2022 - 3:30pm to 4:30pm
PDL C-401
Kyle Ormsby at a lectern holding a paper model of an associahedron

Model structures underpin the modern enterprise of abstract homotopy theory and form presentations of \((\infty,1)\) categories. Despite their fundamental nature, model structures have historically been studied en masse or applied in specific cases, and very little is known about the totality of model structures on a given (complete and cocomplete) category. Homotopical combinatorics is an emerging field that remedies this situation by studying the enumerative combinatorics and structural properties of model structures on finite lattices. Specialized to a finite chain, we find rich connections with Catalan combinatorics, including (intervals in) the Tamari and Kreweras lattices. I will sketch homotopical combinatorics as it currently stands, including the surprising way in which the theory of equivariant \(N_\infty\) operads has enabled recent advances. The talk will not assume prior knowledge of model category theory, though attendees interested in this context are invited to attend the pre-talk. Portions of this work are joint with Balchin, Franchere, Hafeez, MacBrough, Marcus, Osorno, Qin, Roitzheim, and Waugh.

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