Zur Klassifikation glatter kompakter C*-Flächen.
A Hilbert-Mumford criterion for SL₂-actions
Let the special linear group G : = SL₂ act regularly on a ℚ-factorial variety X. Consider a maximal torus T ⊂ G and its normalizer N ⊂ G. We prove: If U ⊂ X is a maximal open N-invariant subset admitting a good quotient U → U ⃫N with a divisorial quotient space, then the intersection W(U) of all translates g · U is open in X and admits a good quotient W(U) → W(U) ⃫G with a divisorial quotient space. Conversely, we show that every maximal open G-invariant subset W ⊂ X admitting a good quotient W...
A general Hilbert-Mumford criterion
Let a reductive group act on an algebraic variety . We give a Hilbert-Mumford type criterion for the construction of open -invariant subsets admitting a good quotient by .
A generalization of Mumford's geometric invariant theory.
Multigraded factorial rings and Fano varieties with torus action.
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