The absence of a universal upper bound for the first eigenvalue in terms of inradius
The absence of a universal upper bound for the first eigenvalue in terms of inradius
Let be a unilateral metric graph with Dirichlet set , let denote its first eigenvalue, and define the inradius relative to the Dirichlet set by
Inradius upper-bound conjecture. There is no universal constant such that
for all unilateral metric graphs. This is presented as a weaker version of the mean-distance conjecture. The source explains that a uniform lower bound in terms of inradius alone cannot hold, while the proposed uniform upper bound is left as an open conjecture.
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Sources & referencesView supporting material
Primary source
Delio Mugnolo, “The role of expanders in the spectral geometry of metric graphs”, arXiv:2607.14312 (2026).
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