Abstract
In even-dimensional phase spaces, we give examples of analytic systems of differential equations that have isolated equilibria and admit nonanalytic first integrals. These integrals are positive definite in a neighborhood of the equilibria, which proves the stability of the equilibria (on the entire time axis). However, such systems of differential equations do not admit nontrivial first integrals in the form of formal power series at all. In particular, the Lyapunov stability of equilibria of analytic systems does not imply their formal stability. In the case of an odd-dimensional phase space, all isolated equilibria are apparently unstable.
REFERENCES
Lyapunov, A.M., Obshchaya zadacha ob ustoichivosti dvizheniya (General Problem of Motion Stability), Moscow–Leningrad: GITTL, 1950.
Siegel, C.L. and Moser, J.K., Lectures on Celestial Mechanics, Berlin–Heidelberg–New York: Springer-Verlag, 1971. Translated under the title: Lektsii po nebesnoi mekhanike, Moscow-Izhevsk: R & C Dynamics, 2001.
Nemytskii, V.V. and Stepanov, V.V., Kachestvennaya teoriya differentsial’nykh uravnenii (Qualitative Theory of Differential Equations), Moscow–Leningrad: GITTL, 1949.
Brunella, M., Instability of equilibria in dimension three, Ann. Inst. Fourier (Grenoble), 1998, vol. 48, no. 5, pp. 1345–1357.
Kozlov, V.V. and Treshchev, D.V., Instability of isolated equilibria of dynamical systems with invariant measure in spaces of odd dimension, Math. Notes, 1999, vol. 65, no. 5, pp. 565–570.
Kozlov, V.V., First integrals and asymptotic trajectories, Sb. Math., 2020, vol. 211, no. 1, pp. 29–54.
Markeev, A.P., Tochki libratsii v nebesnoi mekhanike i kosmodinamike (Libration Points in Celestial Mechanics and Cosmodynamics), Moscow: Nauka, 1978.
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Translated by V. Potapchouck
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Kozlov, V.V. Nonanalytic First Integrals of Analytic Systems of Differential Equations in a Neighborhood of Stable Equilibria. Diff Equat 59, 862–865 (2023). https://doi.org/10.1134/S0012266123060137
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DOI: https://doi.org/10.1134/S0012266123060137