Abstract:
We consider a specific class of coadjoint orbits of maximal unipotent subgroups in classical groups over a finite field, i.e., orbits associated with orthogonal subsets in root systems. We derive a formula for the dimension of these orbits in terms of the Weyl group and construct polarizations for canonical forms on the orbits. As a consequence, we describe all possible dimensions of irreducible representations of such unipotent groups.
Keywords:
root system, coadjoint orbits, unipotent group, polarization, Weyl group, irreducible representation, irreducible complex character, polarization of linear forms.
Citation:
M. V. Ignat'ev, “Orthogonal Subsets of Classical Root Systems and Coadjoint Orbits of Unipotent Groups”, Mat. Zametki, 86:1 (2009), 65–80; Math. Notes, 86:1 (2009), 65–80
\Bibitem{Ign09}
\by M.~V.~Ignat'ev
\paper Orthogonal Subsets of Classical Root Systems and Coadjoint Orbits of Unipotent Groups
\jour Mat. Zametki
\yr 2009
\vol 86
\issue 1
\pages 65--80
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\transl
\jour Math. Notes
\yr 2009
\vol 86
\issue 1
\pages 65--80
\crossref{https://doi.org/10.1134/S0001434609070074}
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Linking options:
https://www.mathnet.ru/eng/mzm6356
https://doi.org/10.4213/mzm6356
https://www.mathnet.ru/eng/mzm/v86/i1/p65
This publication is cited in the following 10 articles:
Mikhail V. Ignatev, “Gradedness of the set of rook placements in A n-1”, Communications in Mathematics, 29:2 (2021), 171
Ignatyev M.V., “Centrally Generated Primitive Ideals of U(N) in Types B and D”, Transform. Groups, 24:4 (2019), 1067–1093
Mikhail V. Ignatyev, Progress in Mathematics, 330, Representations and Nilpotent Orbits of Lie Algebraic Systems, 2019, 331
Ignatyev M.V., Penkov I., “Infinite Kostant cascades and centrally generated primitive ideals of U(n) in types A∞,C∞”, J. Algebra, 447 (2016), 109–134
Bochkarev M.A., Ignatyev M.V., Shevchenko A.A., “Tangent cones to Schubert varieties in types An, Bn and Cn”, J. Algebra, 465 (2016), 259–286
M. V. Ignatyev, A. A. Shevchenko, “On tangent cones to Schubert varieties in type Dn”, St. Petersburg Math. J., 27:4 (2016), 609–623
M. V. Ignatyev, A. S. Vasyukhin, “Rook placements in aN and combinatorics of B-orbit closures”, J. Lie Theory, 24:4 (2014), 931–956
Ignatyev M.V., “Combinatorics of B-orbits and Bruhat-Chevalley order on involutions”, Transform. Groups, 17:3 (2012), 747–780
M. V. Ignat'ev, “The Bruhat–Chevalley order on involutions of the hyperoctahedral group and combinatorics of B-orbit closures”, J. Math. Sci. (N. Y.), 192:2 (2013), 220–231
M. V. Ignat'ev, “Orthogonal subsets of root systems and the orbit method”, St. Petersburg Math. J., 22:5 (2011), 777–794