Bruhat intervals and parabolic cosets in arbitrary Coxeter groups

Abstract

In [Journal of Pure and Applied Algebra 224 (2020), no 12, 106449], V. Mazorchuk and R. Mrđen (with some help by A. Hultman) prove that, given a Weyl group, the intersection of a Bruhat interval with a parabolic coset has a unique maximal element and a unique minimal element. We show that such intersections are actually Bruhat intervals also in the case of an arbitrary Coxeter group.