Burguet's periodic-point growth conjecture for surface diffeomorphisms

Let ff be a CrC^r diffeomorphism, with r>1r>1, on a compact surface MM. Write htop(f)h_{\rm top}(f) for its topological entropy and λ+(f)\lambda^{+}(f) for the relevant positive Lyapunov-exponent bound. For 0<δ<htop(f)0<\delta<h_{\rm top}(f), let Pδn\mathcal{P}^{n}_{\delta} be the set of nn-periodic points whose Lyapunov exponents are δ\delta-away from zero. Burguet's conjecture. If

htop(f)>λ+(f)r,h_{\rm top}(f)>\frac{\lambda^{+}(f)}{r},

then

htop(f)=lim supn+1nlog#Pδn.h_{\rm top}(f)=\limsup_{n\to+\infty}\frac{1}{n}\log \#\mathcal{P}^{n}_{\delta}.

This extends Burguet's result in the CC^{\infty} setting to finite differentiability. The conjecture concerns whether the exponential growth rate of hyperbolic periodic points recovers the topological entropy under the stated entropy and Lyapunov-exponent condition.

Sources & referencesView supporting material

Primary source

Yuntao Zang, “Entropy formula for surface diffeomorphisms”, arXiv:2602.10033 (2026).

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