Weyl character triangularity
Representation theory
For any ,
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The statement is interpreted for a split connected reductive algebraic group G over a field k, with a split maximal torus T of G and a chosen positive-root system for (G,T).
The admissibility condition on is precisely that it is a dominant character of T, , with dominance computed from the chosen positive roots.
For every dominant , the exact module whose character occurs in the formula is the contextually defined canonical module , or a module definitionally equal, isomorphic, or otherwise proved equivalent to that object in a way that preserves its T-weight spaces. A canonical socle construction, including the supremum or sum of the simple algebraic G-subrepresentations of , suffices by itself; it need not be accompanied by a separate theorem certifying that the resulting object is nonzero, G-stable, and simple. An unrelated module selected merely because it has the desired character does not satisfy this requirement.
The formal character is the finitely supported element of whose coefficient at each weight is , with the natural-number dimension embedded in .
The relation is the strict weight order fixed by the chosen positive roots: is a nonnegative integral combination of the positive simple roots and . It is fixed independently of , its support, and the desired equality.
The displayed character equality remains the conclusion to be proved from independent representation-theoretic facts, such as finite weight support, highest-weight multiplicity one, and the upper weight bound, or from mathematically equivalent prior results; the equality itself is not installed as a hypothesis, hidden in a definition, or used circularly.