Shor's conjecture on the peak of normalized tree coefficients

Let TT be a tree with n3n\geq 3 vertices. Let dk(T)d_k(T) denote the normalized coefficients of the distance characteristic polynomial, defined from the coefficients δk(T)\delta_k(T) by

dk(T)=δk(T)/2nk2.d_k(T)=|\delta_k(T)|/2^{n-k-2}.

A sequence is unimodal if it is nondecreasing up to some index and nonincreasing thereafter. Shor's conjecture. The normalized coefficients d0(T),,dn2(T)d_0(T),\dots,d_{n-2}(T) are unimodal, with their peak between n/2\left\lfloor n/2\right\rfloor and (11/5)n\left\lceil (1-1/\sqrt{5})n\right\rceil.

This is a revised version attributed by Collins to Peter Shor after the Graham–Lovász peak-location claim was disproved. The survey does not provide evidence that this revised conjecture has been resolved.

Sources & referencesView supporting material

Primary source

Leslie Hogben and Carolyn Reinhart, “Spectra of variants of distance matrices of graphs and digraphs: a survey”, arXiv:2103.00647 (2021).

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