On an infinite limit of BGG categories O

Kevin Coulembier, Ivan Penkov

Published 2018-02-18Version 1

We study a version of the BGG category O for Dynkin Borel subalgebras of root-reductive Lie algebras, such as g=gl(infinity). We prove results about extension fullness and compute the higher extensions of simple modules by Verma modules. We also show that the category is Ringel self-dual and initiate the study of Koszul duality. An important tool in obtaining these results is an equivalence we establish between appropriate Serre subquotients of category O for g and category O for finite dimensional reductive subalgebras of g.