A positive resolution of the gap-entropy conjecture
Abstract
We prove the gap-entropy conjecture for fixed-confidence best-arm identification with independent unit-variance Gaussian arms, means in [0,1], and a unique optimal arm. For each suboptimal arm i, let Δi=μ*−μi be its gap from the optimal mean, and write H=∑i≠ *Δi−2. Let pr be the fraction of H contributed by arms with 2−(r+1)<Δi≤2−r, and let Ent(I)=∑r:pr>0 prlog(1/pr). Among all algorithms that identify the optimal arm with probability at least 1−δ on every Gaussian instance, the optimal expected number of samples on a given instance, averaged over all permutations of the arm labels, is within absolute constant factors of H(log(1/δ)+Ent(I)). Moreover, there is an algorithm, independent of the instance, whose expected number of samples is bounded by a constant multiple of this quantity plus g−2loglog(ee/g), where g=mini≠ *Δi is the gap to the closest competitor.
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BibTeX
@misc{aronow2026positive,
title = {{A positive resolution of the gap-entropy conjecture}},
author = {P. M. Aronow and Nathan Kallus and Patrick Lopatto},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10529},
eprint = {2609.10529},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.10529},
}
RIS
TY - UNPB
TI - A positive resolution of the gap-entropy conjecture
AU - P. M. Aronow
AU - Nathan Kallus
AU - Patrick Lopatto
PY - 2026
DA - 2026/09/09
PB - arXiv
DO - 10.48550/arxiv.2609.10529
UR - https://arxiv.org/abs/2609.10529
AB - We prove the gap-entropy conjecture for fixed-confidence best-arm identification with independent unit-variance Gaussian arms, means in [0,1], and a unique optimal arm. For each suboptimal arm i, let Δ_i=μ_*−μ_i be its gap from the optimal mean, and write H=∑_i≠ *Δ_i^−2. Let p_r be the fraction of H contributed by arms with 2^−(r+1)<Δ_i≤2^−r, and let Ent(I)=∑_r:p_r>0 p_rlog(1/p_r). Among all algorithms that identify the optimal arm with probability at least 1−δ on every Gaussian instance, the optimal expected number of samples on a given instance, averaged over all permutations of the arm labels, is within absolute constant factors of H(log(1/δ)+Ent(I)). Moreover, there is an algorithm, independent of the instance, whose expected number of samples is bounded by a constant multiple of this quantity plus g^−2loglog(e^e/g), where g=min_i≠ *Δ_i is the gap to the closest competitor.
ER -