Strange expectations in affine Weyl groups

Our main result is a generalization, to all affine Weyl groups, of P. Johnson’s proof of D. Armstrong’s conjecture for the expected number of boxes in a simultaneous core. This extends earlier results by the second and third authors in simply-laced type. We do this by modifying and refining the appropriate notion of the “size” of a simultaneous core. In addition, we provide combinatorial core-like models for the coroot lattices in classical type and type <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>G</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:math> .