Continuity conjecture for the Rényi entropy rate at order one

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Let Z={Zn}n=1∞Z=\{Z_n\}_{n=1}^{\infty} be a stationary ergodic process over a finite alphabet Z\mathcal{Z}. Its Shannon entropy rate is

H(Z)≜lim⁡n→∞H(Z1n)n,H(Z)\triangleq \lim_{n\rightarrow\infty}\frac{H(Z_1^n)}{n},

and, when the limit exists, its α\alpha-th order Rényi entropy rate is

Hα(Z)≜lim⁡n→∞Hα(Z1n)n.H_{\alpha}(Z)\triangleq \lim_{n\rightarrow\infty}\frac{H_{\alpha}(Z_1^n)}{n}.

Continuity conjecture. For every stationary ergodic process ZZ,

lim⁡α→1Hα(Z)=H(Z).\lim_{\alpha\rightarrow 1}H_{\alpha}(Z)=H(Z).

The conjecture is a natural rate-level analogue of the finite-block identity lim⁡α→1Hα(Z1n)=H(Z1n)\lim_{\alpha\rightarrow 1}H_{\alpha}(Z_1^n)=H(Z_1^n), but the existence of the Rényi entropy rate itself is not known for general stationary ergodic processes. The source reports this conjecture as neither proved nor disproved in the literature.

References

Primary source

Chengyu Wu, Yonglong Li, Li Xu and Guangyue Han, “Renyi Entropy Rate of Stationary Ergodic Processes”, arXiv:2207.07554 (2022).

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