Spherical delta-rings

par Edith Hübner (Universität Münster)

mardi 9 juin 2026, 14:00 → 15:00 Europe/Paris

IMT 1R2 207 (Salle Pellos)

Joyal’s notion of a delta-ring has lately gained much prominence in the context of prismatic cohomology. Extensions of the notion to derived algebra have been considered among others by Bhatt, Lurie and Scholze, however, there is currently no analog of the theory of delta-rings in spectral algebra. In this talk, I’ll speak about a possible definition of delta-rings over the sphere - given by E-infinity rings equipped with a suitably defined lift of the Tate-valued Frobenius.
I will discuss some (non-)examples, show that pi_0 of a spherical delta-ring is an ordinary delta-ring and point out some subtleties which distinguish the theory of spherical delta-rings from animated and derived delta-rings. This is joint work in progress with Thomas Nikolaus.