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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.
Source
atlas-scripts/springer_table_G.at (74 lines)
Definitions
2
Loads
Loaded by
springer_tables_reductive.at

Definitions in source order

springer_table_G

L20springer_table_G (int n) = SpringerTable

also 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

L47springer_table_G (RootDatum rd) = SpringerTable

also in this file at line 20

Generated from atlas-scripts at commit 648506c (2026-10-13).