## On the exotic Grassmannian and its nilpotent variety

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- by Lucas Fresse and Kyo Nishiyama
- Represent. Theory
**20**(2016), 451-481 - DOI: https://doi.org/10.1090/ert/489
- Published electronically: November 28, 2016
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## Abstract:

Given a decomposition of a vector space $V=V_1\oplus V_2$, the direct product $\mathfrak {X}$ of the projective space $\mathbb {P}(V_1)$ with a Grassmann variety $\mathrm {Gr}_k(V)$ can be viewed as a double flag variety for the symmetric pair $(G,K)=(\mathrm {GL}(V),\mathrm {GL}(V_1)\times \mathrm {GL}(V_2))$. Relying on the conormal variety for the action of $K$ on $\mathfrak {X}$, we show a geometric correspondence between the $K$-orbits of $\mathfrak {X}$ and the $K$-orbits of some appropriate exotic nilpotent cone. We also give a combinatorial interpretation of this correspondence in some special cases. Our construction is inspired by a classical result of Steinberg (1976) and by the recent work of Henderson and Trapa (2012) for the symmetric pair $(\mathrm {GL}(V),\mathrm {Sp}(V))$.## References

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## Bibliographic Information

**Lucas Fresse**- Affiliation: Université de Lorraine, CNRS, Institut Élie Cartan de Lorraine, UMR 7502, Vandoeuvre-lès-Nancy, F-54506, France
- MR Author ID: 875745
- Email: lucas.fresse@univ-lorraine.fr
**Kyo Nishiyama**- Affiliation: Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe 5-10-1, Sagamihara 252-5258, Japan
- MR Author ID: 207972
- Email: kyo@gem.aoyama.ac.jp
- Received by editor(s): April 6, 2016
- Received by editor(s) in revised form: October 9, 2016
- Published electronically: November 28, 2016
- Additional Notes: The first author was supported by the ISF Grant Nr. 797/14 and by the ANR project NilpOrbRT (ANR-12-PDOC-0031).

The second author was supported by JSPS KAKENHI Grant Numbers #25610008 and #16K05070. - © Copyright 2016 American Mathematical Society
- Journal: Represent. Theory
**20**(2016), 451-481 - MSC (2010): Primary 14L30; Secondary 14L35, 14M15, 17B08
- DOI: https://doi.org/10.1090/ert/489
- MathSciNet review: 3576071