Topology Seminar

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Topology Seminar talks are generally on Tuesdays at 11am, followed by an (optional) lunch with the speaker. This calendar also includes various learning seminars and meetings of the algebraic topology group.

Shauly Ragimov (U Chicago): Universality of character theory

Event Type
Seminar/Symposium
Sponsor
UIUC Math Department
Location
Altgeld 243
Date
Oct 28, 2025   11:00 am  
Views
65
A key tool in the computation of En-cohomology of π-finite spaces is the transchromatic character, constructed by Hopkins-Kuhn-Ravenel and extended by Stapleton and Lurie. For each 0 ≤ (n − t) ≤ n, the height (n − t)-transchromatic character relates the En-cohomology of a π-finite space to that of its (n − t)-fold p-typical loop space, evaluated with respect to a height t-cohomology theory.
                   

We place this construction into a unified framework of (n − t)-fold character theories ap- plicable to any ∞-commutative monoid. Concretely, for an ∞-commutative monoid R there is a universal (n − t)-fold character map that respects the natural induction and restriction structures of R. In particular, it yields a character theory for every T(n)-local algebra. This universal character enjoys strong structural properties: it exhibits a blue-shift phenomenon by sending T(n)-local algebras to T(t)-local algebras, and it carries primitive height-n roots of unity to primitive height-t roots of unity. In the case of En, it recovers the classical transchro- matic character.

                
            
        

   

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