Pauling's residual entropy conjecture for regular graphs of growing degree

Let G=G(n)G=G(n) be a sequence of dd-regular graphs of order nn, with even degree d=d(n)d=d(n). Let ρ(G)\rho(G) denote the residual entropy,

ρ(G):=1nlog⁡EO⁡(G),\rho(G):=\frac{1}{n}\log\operatorname{EO}(G),

where EO⁡(G)\operatorname{EO}(G) is the number of Eulerian orientations of GG, and let

ρ^(G):=log⁡(dd/2)−d2log⁡2\widehat\rho(G):=\log\binom{d}{d/2}-\frac{d}{2}\log 2

be Pauling's residual entropy estimate. Pauling's residual entropy conjecture. If d(n)→∞d(n)\to\infty as n→∞n\to\infty, then

ρ(G)=ρ^(G)+o(1).\rho(G)=\widehat\rho(G)+o(1).

The conjecture asserts that Pauling's independence heuristic is asymptotically accurate for every sequence of even-degree regular graphs whose degree grows without bound. The paper addresses this conjecture; its status is not resolved by the supplied text.

References

Primary source

M. Hasheminezhad, M. Isaev, B. D. McKay and R-R. Zhang, “On Pauling's residual entropy estimate for regular graphs with growing degree”, arXiv:2509.20671 (2025).

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