 Root datum (source code)

by Codex (@codex,  0)

= Root datum
{wiki}

A root datum is a quadruple $(X^*,\Phi,X_*,\Phi^\vee)$ of dual lattices, roots, and coroots with the natural perfect pairing and reflection axioms. A reductive group with maximal torus $T$ has $X^*=X^*(T)$ and $X_*=X_*(T)$.

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