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Proceedings of the 44th Symposium on Ring Theory and ...

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Figure 4. Exchange graph <str<strong>on</strong>g>of</str<strong>on</strong>g> Z/2Z-stable maximal rigid objects<br />

where N is a maximal unipotent subgroup <str<strong>on</strong>g>of</str<strong>on</strong>g> a Kac-Moody group, N − its opposite<br />

unipotent group, B − <str<strong>on</strong>g>the</str<strong>on</strong>g> corresp<strong>on</strong>ding Borel subgroup, <strong>and</strong> w is an element <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

corresp<strong>on</strong>ding Weyl group. In particular, if N is <str<strong>on</strong>g>of</str<strong>on</strong>g> Lie type <strong>and</strong> w is <str<strong>on</strong>g>the</str<strong>on</strong>g> l<strong>on</strong>gest<br />

element, <str<strong>on</strong>g>the</str<strong>on</strong>g>n N(w) = N.<br />

• Partial flag varieties corresp<strong>on</strong>ding to classical Lie groups.<br />

These results were obtained in [5] <strong>and</strong> [6] for <str<strong>on</strong>g>the</str<strong>on</strong>g> simply-laced cases <strong>and</strong> in [2] for <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

n<strong>on</strong> simply-laced cases.<br />

It permits for example to prove in <str<strong>on</strong>g>the</str<strong>on</strong>g>se cases that all <str<strong>on</strong>g>the</str<strong>on</strong>g> cluster m<strong>on</strong>omials (products<br />

<str<strong>on</strong>g>of</str<strong>on</strong>g> elements <str<strong>on</strong>g>of</str<strong>on</strong>g> a same extended cluster) are linearly independent (result which is now<br />

generalized but was new at that time) <strong>and</strong> o<str<strong>on</strong>g>the</str<strong>on</strong>g>r more specific results (for example <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

–41–

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