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Working paper

Weyl's Formula as the Brion Theorem for Gelfand-Tsetlin Polytopes

We exploit the idea that the character of an irreducible finite dimensional gln-module is the sum of certain exponents of integer points in a Gelfand-Tsetlin polytope and can thus be calculated via Brion's theorem. In order to show how the result of such a calculation matches Weyl's character formula we prove some interesting combinatorial traits of Gelfand-Tsetlin polytopes. Namely, we show that under the relevant substitution the integer point transforms of all but n! vertices vanish, the remaining ones being the summands in Weyl's formula.