Abstract
We show that an effective action of the one-dimensional torus \({\mathbb G}_m\) on a normal affine algebraic variety X can be extended to an effective action of a semi-direct product \({\mathbb G}_m\rightthreetimes {\mathbb G}_a\) with the same general orbit closures if and only if there is a divisor D on X that consists of \({\mathbb G}_m\)-fixed points. This result is applied to the study of orbits of the automorphism group \({{\,\mathrm{Aut}\,}}(X)\) on X.
Similar content being viewed by others
References
Altmann, K., Hausen, J.: Polyhedral divisors and algebraic torus actions. Math. Ann. 334(3), 557–607 (2006)
Arzhantsev, I.: On actions of reductive groups with one-parameter family of spherical orbits. Sb. Math. 188(5), 639–655 (1997)
Arzhantsev, I.: On rigidity of factorial trinomial hypersurfaces. Int. J. Algebra Comput. 26(5), 1061–1070 (2016)
Arzhantsev, I., Bazhov, I.: On orbits of the automorphism group on an affine toric variety. Cent. Eur. J. Math. 11(10), 1713–1724 (2013)
Arzhantsev, I., Flenner, H., Kaliman, S., Kutzschebauch, F., Zaidenberg, M.: Flexible varieties and automorphism groups. Duke Math. J. 162(4), 767–823 (2013)
Arzhantsev, I., Gaifullin, S.: The automorphism group of a rigid affine variety. Math. Nachr. 290(5–6), 662–671 (2017)
Arzhantsev, I., Kuyumzhiyan, K., Zaidenberg, M.: Flag varieties, toric varieties, and suspensions: three instances of infinite transitivity. Sb. Math. 203(7), 923–949 (2012)
Bialynicki-Birula, A.: Some theorems on actions of algebraic groups. Ann. Math. 98, 480–497 (1973)
Boldyrev, I., Gaifullin, S.: Automorphisms of Nonnormal Toric Varieties. Math. Notes (2021), in print; arXiv:2012.03346
Cox, D., Little, J., Schenck, H.: Toric Varieties. Graduate Studies in Mathematics, vol. 124. AMS, Providence (2011)
Flenner, H., Zaidenberg, M.: On the uniqueness of \(\mathbb{C}^*\)-actions on affine surfaces. In: Affine Algebraic Geometry, Contemporary Mathematics, vol. 369, pp. 97–111. American Mathematical Society, Providence (2005)
Flenner, H., Zaidenberg, M.: Locally nilpotent derivations on affine surfaces with a \({\mathbb{C}}^*\)-action. Osaka J. Math. 42(4), 931–974 (2005)
Freudenburg, G.: Algebraic Theory of Locally Nilpotent Derivations, 2nd edn. Encyclopaedia of Mathematical Sciences, vol. 136. Springer, Berlin (2017)
Fulton, W.: Introduction to Toric Varieties. Annals of Mathematics Studies, vol. 131. Princeton University Press, Princeton (1993)
Gaifullin, S., Shafarevich, A.: Flexibility of normal affine horospherical varieties. Proc. Am. Math. Soc. 147(8), 3317–3330 (2019)
Hausen, J., Wrobel, M.: Non-complete rational T-varieties of complexity one. Math. Nachr. 290(5–6), 815–826 (2017)
Kraft, H.: Automorphism groups of affine varieties and a characterization of affine n-space. Trans. Mosc. Math. Soc. 78, 171–186 (2017)
Liendo, A.: \({\mathbb{G}}\)-actions of fiber type on affine \(\mathbb{T}\)-varieties. J. Algebra 324, 3653–3665 (2010)
Oda, T.: Convex Bodies and Algebraic Geometry: An Introduction to Toric Varieties. A Series of Modern Surveys in Mathematics, vol. 15. Springer, Berlin (1988)
Popov, V., Vinberg, E.: Invariant Theory. Algebraic Geometry IV, Encyclopaedia of Mathematics Sciences, vol. 55, pp. 123–284. Springer, Berlin (1994)
Acknowledgements
The author is grateful to Alvaro Liendo for a fruitful discussion, and to Sergey Gaifullin, Michail Zaidenberg, and two anonymous reviewers for many useful comments, suggestions and references to related results.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
The research was supported by Russian Science Foundation, Grant 19-11-00056.
Rights and permissions
About this article
Cite this article
Arzhantsev, I. Limit points and additive group actions. Ricerche mat 73, 715–724 (2024). https://doi.org/10.1007/s11587-021-00630-z
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11587-021-00630-z