Conjecture on eigenvector coordinate averages for large S-regular matrices

Let TT be a large SS-regular matrix, and let TT^\ast be the corresponding SS-regular matrix on TS\operatorname{\mathcal{T}}_S. Let UViU\subset V_i be a sufficiently large subset of the ii-th partition cell of the underlying graph of TT. Let ϕ\phi be a normalized eigenvector of TT with eigenvalue λ\lambda, and let μi\mu_i be defined as in the paper's vertex-distribution proposition. Write ci=Vi/Vc_i=|V_i|/|V|.

Eigenvector coordinate conjecture. With high probability,

vUϕ(u)0,\sum_{v\in U}\phi(u)\approx 0,

and

VUvU(ϕ(u))2μi(λ)jkcjμj(λ).\frac{|V|}{|U|}\sum_{v\in U}\left(\phi(u)\right)^2\approx\frac{\mu_i(\lambda)}{\sum_j^k c_j\mu_j(\lambda)}.

Here the conjecture predicts that most eigenvectors have approximately zero mean on a large subset of a partition cell, while their average squared coordinates are governed by the limiting spectral measures. The preceding results provide the limiting cumulative distributions, but the asserted coordinate-level approximations remain conjectural.

Sources & referencesView supporting material

Primary source

Matthew B. Crawford, David J. Marchette, William Maxwell and Samuel S. Mendelson, “Spectral properties of random graphs with fixed equitable partition”, arXiv:2311.07675 (2023).

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