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Speaker:
Qiuyu Ren
Affiliation:
UC Berkeley
Date:
Thu, 17/07/2025 - 11:00 - 12:00
Location:
MPIM Lecture Hall
Parent event:
Low-dimensional topology seminar Skein lasagna modules (with 0-dimensional inputs) are 4-manifold invariants introduced by Morrison-Walker-Wedrich. In this context, a skein is a properly embedded surface in a 4-manifold minus a disjoint union of 4-balls, and the lasagna comes from a TQFT for links in S^3 (satisfying mild conditions). In this talk, we introduce skein lasagna modules with 1-dimensional inputs, where a skein is a properly embedded surface in a 4-manifold minus a tubular neighborhood of an embedded graph, and the lasagna comes from a TQFT for links in \#(S^1\times S^2) and link cobordisms between them in a particular class of 4-manifolds. We present (a subset of) four key ingredients which enable us to show that the Khovanov homology of links in \#(S^1\times S^2), as defined by Rozansky and Willis, has excellent functoriality properties sufficient to supply the lasagna input TQFT. The ingredients are:
0. A lasagna interpretation of Rozansky-Willis homology by Sullivan-Zhang;
1. A calculation of the diffeomorphism group (rel boundary, modulo local diffeomorphisms) of the complement of any graph in S^4;
2. A Khovanov lasagna naturality property of the Gluck twist operation;
3. A naturality result for the Khovanov-Rozansky gl_2-homology of singular gl_2-foams between gl_2-webs in S^3.
This is joint work with I. Sullivan, P. Wedrich, M. Willis, M. Zhang.
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