Zhang's weak-resonance obstruction conjecture for hyperbolic diffeomorphisms

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Let AA be a hyperbolic matrix in GL(n,R)GL(n,\mathbb R) and let BB be a real logarithm of AA. Let f(z)=O(∣z∣2)f(z)=O(|z|^2) be C∞C^{\infty} (respectively, analytic), and suppose it has a non-vanishing weakly resonant monomial w1m1⋯wnmnejw_1^{m_1}\cdots w_n^{m_n}e_j with respect to BB. The resulting locally hyperbolic diffeomorphism is

φ(z)=Az+f(z).\varphi(z)=Az+f(z).

Zhang's conjecture. The diffeomorphism φ\varphi is not embedded in a C∞C^{\infty} (respectively, analytic) flow.

The conjecture proposes that weak resonances obstruct embedding a hyperbolic diffeomorphism into a smooth or analytic flow. The source states that the conjecture is false and gives two counterexamples consisting of resonant diffeomorphisms.

References

Primary source

Javier Ribón, “Embedding smooth and formal diffeomorphisms through the Jordan-Chevalley decomposition”, arXiv:1107.3601 (2011).

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