Year: 2026
Type: preprint
Abstract: We disprove Laugesen's conjecture that the ratio of the first two Robin eigenvalues decreases with the positive boundary parameter. On any prescribed compact interval of positive parameters, the ratio is strictly increasing on a suitable connected polyhedral domain in every dimension at least two; in the plane, the domain can be a simply connected polygon. In contrast, we prove strict decrease on every rectangular box. Both results follow from a comparison of the relative growth of interval eigenvalues.
Source: arXiv (Cornell University)
Authors: Dai, Guowei, Sun, Yingxin
Institution: Dalian University of Technology
Language: English
Subfield: Mathematical Physics
Field: Mathematics
Domain: Physical Sciences
Open Access status: green
Award: G4772512679
OpenAlex ID: W7214044985