atlas Library · Script File
springer_table_G.at
for |rd="G2".simply_connected|, the command |orbits(rd)| returns 5 orbits, whose diagrams are, in order, [0,0],[0,1],[1,0],[0,2],[2,2]. The springer map send these respectively to the (full) sign, short-root-reflection sign, triangluar reflection, reflection, and trivial representations of W(G2) (in the numbering of irreducibles fixed in |character_table_G|, numbers 3,1,4,5,0 respectively). The dual map sends the same orbits to just 3 dual orbits, whose stratified diagrams (so the dual Dynkin diagram order is reversed) are respectively [2,2],[0,2],[0,2],[0,2],[0,0]. Below we take an ad hoc approach too the dual map, testing explicitly for the two extreme cases. Since we are supposed to ignore any radical component of |O.H|, we avoid testing |O.H| directly for being zero or |rd.two_rho_check|, computing the diagram instead which will do the required ignoring.
Definitions in source order
springer_table_G
L20
springer_table_G (int n) = SpringerTablealso in this file at line 47
The main challenge for this file is to do the same when |rd| is any root datum with Cartan matrix of type $G_2$. The fact that we do not know the coordinates used by |rd| makes us express the explicit weight/coweight above as linear combinations of simple ones for |rd|L41
springer_table_G
L47
springer_table_G (RootDatum rd) = SpringerTablealso in this file at line 20
Generated from atlas-scripts at commit 648506c (2026-10-13).