Abstract

In the early nineties, the Buonos Aires Cyclic Homology group calculated the Hochschild and cyclic homology of hypersurfaces, in general, and of the coordinate rings of planar cuspical curves, in particular. With Cortiñas' birelative theorem, proved in 2005, this gives a calculation of the relative K-theory of planar cuspical curves over a field of characteristic zero. By a p-adic version of Cortiñas' theorem, proved by Geisser and myself in 2006, the relative K-groups of planar cuspical curves over a perfect field of characteristic p > 0 can similarly be expressed in terms of topological cyclic homology, but the relevant topological cyclic homology groups have resisted calculation. In this talk, I will show that the new setup for topological cyclic homology by Nikolaus and Scholze has made this calculation possible. This is joint work with Nikolaus and similar results have been obtained by Angeltveit.