Category O for shifted Yangians and the bi-infinite Bott-Samelson variety
Shifted Yangians admit a family of coproducts which makes the direct sum of Grothendieck groups of their category Os into a ring, K(Osh). On the other hand, the Grothedieck groups of category O for truncated shifted Yangians (which are Coulomb branch algebras for ADE quiver gauge theories) carry G- actions. I will explain the interaction between the ring structure and the G-action. In particular, we show that K(Osh) is isomorphic to the Cox ring of a bi-infinite Bott-Samelson variety. Along the way, I will explain the proofs of some conjectures of Hernandez and co-authors. This is joint work with Antoine Labelle, Alexis Leroux-Lapierre, Th´eo Pinet, and Alex Weekes.