Variation of quotients according to Ressayre, I -- Bart Van Steirteghem, April 8, 2011

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As a warm-up we will first apply the Hilbert-Mumford criterion to the diagonal action of SL(2) on (P^1)^N. We will then use what the criterion tells us to describe the so-called GIT-fan for this SL(2)-variety as a first example of the results described in [N. Ressayre, The GIT-equivalence for G-line bundles, Geom. Dedicata 81, 295--324, 2000].
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