Frangible prime gaps
Abstract
A prime gap (pn, pn+1) is \textit{frangible} if the smallest prime divisor of every integer m with pn<m<pn+1 is strictly less than the size of the gap, pn+1−pn. Gafni and Tao recently proved that the number of frangible gaps up to X is ≪ X/log2 X, answering a question of Erdős. They also showed that under the Dickson--Hardy--Littlewood prime tuples conjecture this number is ∼ c X/log2 X for a constant c, for which they obtained a rough estimate. We describe improved methods for estimating this constant under the same hypothesis, and establish that its value lies in $[2.7416, 2.7984]$, confirming a speculation of Gafni and Tao. In addition, we present the results of a complete survey of frangible gaps up to 1017. An ensuing empirical measurement of c matches our estimate very well.
Related
BibTeX
@misc{mossinghoff2026frangible,
title = {{Frangible prime gaps}},
author = {Michael J. Mossinghoff and Timothy S. Trudgian},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.34525},
eprint = {2610.34525},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.34525},
}
RIS
TY - UNPB
TI - Frangible prime gaps
AU - Michael J. Mossinghoff
AU - Timothy S. Trudgian
PY - 2026
DA - 2026/10/25
PB - arXiv
DO - 10.48550/arxiv.2610.34525
UR - https://arxiv.org/abs/2610.34525
AB - A prime gap (p_n, p_n+1) is \textit{frangible} if the smallest prime divisor of every integer m with p_n<m<p_n+1 is strictly less than the size of the gap, p_n+1−p_n. Gafni and Tao recently proved that the number of frangible gaps up to X is ≪ X/log^2 X, answering a question of Erdős. They also showed that under the Dickson--Hardy--Littlewood prime tuples conjecture this number is ∼ c X/log^2 X for a constant c, for which they obtained a rough estimate. We describe improved methods for estimating this constant under the same hypothesis, and establish that its value lies in $[2.7416, 2.7984]$, confirming a speculation of Gafni and Tao. In addition, we present the results of a complete survey of frangible gaps up to 10^17. An ensuing empirical measurement of c matches our estimate very well.
ER -