PreprintCC BY 4.0arXiv
The fractional Faber--Krahn inequality in sharp quantitative form
Abstract
We prove that the first Dirichlet eigenvalue of the fractional Laplacian satisfies the sharp quantitative Faber--Krahn inequality. This was conjectured by Brasco, Cinti and Vita, who proved the inequality with a sub-optimal exponent. The proof adapts to the non-local setting the level-set argument recently introduced by Guerra, Machado and Ramos for the Laplacian. It is carried out on the horizontal level sets of the Caffarelli--Silvestre extension of the torsion function, where the asymmetry appears only as a boundary value at the corner of the extension variables.
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BibTeX
@misc{goldman2026fractional,
title = {{The fractional Faber--Krahn inequality in sharp quantitative form}},
author = {Michael Goldman and Matteo Novaga and Berardo Ruffini},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.40232},
eprint = {2610.40232},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.40232},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The fractional Faber--Krahn inequality in sharp quantitative form
AU - Michael Goldman
AU - Matteo Novaga
AU - Berardo Ruffini
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2610.40232
UR - https://arxiv.org/abs/2610.40232
AB - We prove that the first Dirichlet eigenvalue of the fractional Laplacian satisfies the sharp quantitative Faber--Krahn inequality. This was conjectured by Brasco, Cinti and Vita, who proved the inequality with a sub-optimal exponent. The proof adapts to the non-local setting the level-set argument recently introduced by Guerra, Machado and Ramos for the Laplacian. It is carried out on the horizontal level sets of the Caffarelli--Silvestre extension of the torsion function, where the asymmetry appears only as a boundary value at the corner of the extension variables.
ER -