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Geometry of third order ODE systems

Alexandr Medvedev (2010)

Archivum Mathematicum

We compute cohomology spaces of Lie algebras that describe differential invariants of third order ordinary differential equations. We prove that the algebra of all differential invariants is generated by 2 tensorial invariants of order 2, one invariant of order 3 and one invariant of order 4. The main computational tool is a Serre-Hochschild spectral sequence and the representation theory of semisimple Lie algebras. We compute differential invariants up to degree 2 as application.

Germes de difféomorphismes et de champs de vecteurs en classe de différentiabilité finie

F. Dumortier, Robert Roussarie (1983)

Annales de l'institut Fourier

Pour tout triplet d’entiers s , k , ℓ tels que 0 ≤ s ≤ k ≤ ℓ , se pose la question d’étudier les germes de difféomorphismes ou de champs de vecteurs sur R n , de classe ℓ , k -déterminés en classe s , c’est-à-dire respectivement conjugués ou équivalents en classe s , à tout germe ayant la même classe ℓ et le même k -jet. Cette question est abordée ici, avec quelque généralité en dimension 2 et pour les germes de champs de vecteurs de codimension 2, en dimension 3 et 4. Une conséquence de cette dernière étude est l’existence...

Global asymptotic stability for half-linear differential systems with coefficients of indefinite sign

Jitsuro Sugie, Masakazu Onitsuka (2008)

Archivum Mathematicum

This paper is concerned with the global asymptotic stability of the zero solution of the half-linear differential system x ' = - e ( t ) x + f ( t ) φ p * ( y ) , y ' = - g ( t ) φ p ( x ) - h ( t ) y , where p > 1 , p * > 1 ( 1 / p + 1 / p * = 1 ), and φ q ( z ) = | z | q - 2 z for q = p or q = p * . The coefficients are not assumed to be positive. This system includes the linear differential system 𝐱 ' = A ( t ) 𝐱 with A ( t ) being a 2 × 2 matrix as a special case. Our results are new even in the linear case ( p = p * = 2 ). Our results also answer the question whether the zero solution of the linear system is asymptotically stable even when Coppel’s condition does not hold...

Global attractor of a differentiable autonomous system on the plane

Nguyen Van Chau (1995)

Annales Polonici Mathematici

We study the structure of a differentiable autonomous system on the plane with non-positive divergence outside a bounded set. It is shown that under certain conditions such a system has a global attractor. The main result here can be seen as an improvement of the results of Olech and Meisters in [7,9] concerning the global asymptotic stability conjecture of Markus and Yamabe and the Jacobian Conjecture.

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