Abstract
We compute the exact value of the essential p-dimension of the normalizer of a split maximal torus for most simple connected linear algebraic groups. These values give new upper bounds on the essential p-dimension of some simple groups, including some exceptional groups. For each connected simple algebraic group, we also give an upper bound on the essential p-dimension of any torus contained in that group. These results are achieved by a detailed case-by-case analysis.
Similar content being viewed by others
References
G. Berhuy, G. Favi, Essential dimension: a functorial point of view (after A. Merkurjev). Doc. Math. 8 (2003), 279–330.
A. Borel, Linear Algebraic Groups, 2nd ed., Graduate Texts in Mathematics, Vol. 126, Springer-Verlag, New York, 1991.
N. Bourbaki, Groupes et Algèbres de Lie, Chaps. IV–VI, Hermann, Paris, 1968. Russian transl.: Н. Бурбаки, Группы и алгебры Ли, главы IV–VI, Мир, M., 1972.
J. Buhler, Z. Reichstein, On the essential dimension of a finite group, Compositio Math. 106 (1997), no. 2, 159–179.
V. Chernousov, Another proof of Totaro's theorem on E 8 -torsors, Canad. Math. Bull. 49 (2006), no. 2, 196–202.
V. Chernousov, A. S. Merkurjev, Essential p-dimension of split simple groups of type A n , preprint: http://www.mathematik.uni-bielefeld.de/LAG/man/429.html.
J. H. Conway, N. J. A. Sloane, Low-dimensional lattices, I. Quadratic forms of small determinant, Proc. Roy. Soc. London Ser. A 418 (1988), no. 1854, 17–41.
J. H. Conway, N. J. A. Sloane, Low-dimensional lattices, II. Subgroups of \( {\text{GL}}\left( {n,\mathbb{Z}} \right) \), Proc. Roy. Soc. London Ser. A 419 (1988), no. 1856, 29–68.
J. H. Conway, N. J. A. Sloane, Sphere Packings, Lattices and Groups, Springer-Verlag, New York (1993). Russian transl.: Дж. Конвей, Н. Слоэн, Упаковки щаров, рещетки и группы, тт. I, II, Мир, M., 1990.
A. Duncan, Essential dimensions of A 7 and S 7, Math. Res. Lett. 17 (2010), no. 2, 263–266.
G. Favi, M. Florence, Tori and essential dimension, J. Algebra 319 (2008), no. 9, 3885–3900.
P. Gille, Type des tores maximaux des groupes semi-simples, J. Ramanujan Math. Soc. 19 (2004), no. 3, 213–230.
J. E. Humphreys, Reflection groups and Coxeter groups, Cambridge Studies in Advanced Mathematics, Vol. 29. Cambridge University Press, Cambridge, 1992.
J.C. Jantzen, Representations of Algebraic Groups, Pure and Applied Mathematics, Vol. 131. Academic Press, Inc., Boston, MA, 1987.
N. A. Karpenko, A. S. Merkurjev, Essential dimension of finite p-groups, Invent. Math. 172 (2008), no. 3, 491–508.
N. Lemire, Essential dimension of algebraic groups and integral representations of Weyl groups, Transform. Groups 9 (2004), no. 4, 337–379.
R. Lötscher, M. L. MacDonald, A. Meyer, Z. Reichstein, Essential p-dimension of algebraic tori, preprint: http://www.math.uni-bielefeld.de/LAG/man/363.html.
R. Lötscher, M. L. MacDonald, A. Meyer, Z. Reichstein, Essential dimension of algebraic tori, preprint: http://www.math.uni-bielefeld.de/LAG/man/399.html.
M.L. MacDonald, Cohomological invariants of odd degree Jordan algebras, Math. Proc. Cambridge Philos. Soc. 145 (2008), no. 2, 295–303.
A. Meyer, Z. Reichstein, The essential dimension of the normalizer of a maximal torus in the projective linear group, Algebra Number Theory 3 (2009), no. 4, 467–487.
A. Meyer, Z. Reichstein, Some Consequences of the Karpenko-Merkurjev theorem, Documenta Math. Extra Volume: Andrei A. Suslin’s Sixtieth Birthday (2010), 445–457.
M. S. Raghunathan, Tori in quasi-split-groups, J. Ramanujan Math. Soc. 19 (2004), no. 4, 281–287.
Z. Reichstein, Essential dimension, Proceedings of ICM 2010, to appear, preprint: http://www.mathematik.uni-bielefeld.de/LAG/man/393.html.
Z. Reichstein, B. Youssin, Essential dimensions of algebraic groups and a resolution theorem for G-varieties, with an appendix by J. Kollár and E. Szabó. Canad. J. Math. 52 (2000), no. 5, 1018–1056.
J.-P. Serre, Galois Cohomology, Springer Monographs in Mathematics, Springer-Verlag, Berlin, 2002.
J. Tits, Classification of algebraic semisimple groups, in: Algebraic Groups and Discontinuous Subgroups, Proc. Sympos. Pure Math., Vol. IX, Amer. Math. Soc., Providence, R.I., 1966, pp. 33–62.
В. Е. Воскресенский, Максималные торы без аффекта в полупростых алгебраических группах, Мат. заметки 44 (1988), no. 3, 309–318, 410. Engl. transl.: V. E. Voskresenskii, Maximal tori without affect in semisimple algebraic groups, Math. Notes 44 (1988), nos. 3–4, 651–655 (1989).
V. E. Voskresenskii, Algebraic Groups and Their Birational Invariants, Translations of Mathematical Monographs, Vol. 179, American Mathematical Society, Providence, RI, 1998.
W. C. Waterhouse, Introduction of Affine Group Schemes, Graduate Texts in Mathematics, Vol. 66. Springer-Verlag, New York, 1991.
Author information
Authors and Affiliations
Corresponding author
Additional information
Partially supported by an NSERC Postdoctoral Fellowship. (Mark L. MacDonald)
Rights and permissions
About this article
Cite this article
MacDonald, M.L. Essential p-dimension of the normalizer of a maximal torus. Transformation Groups 16, 1143–1171 (2011). https://doi.org/10.1007/s00031-011-9157-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00031-011-9157-2