Hermitian forms graph smallest eigenvalue conjectures

Let Qq(d)Q_q(d) be the Hermitian forms scheme on the d×dd\times d Hermitian matrices over Fq2\mathbb{F}_{q^2}, and let Qj(i)Q_j(i) denote the eigenvalue indexed by ii in its distance-jj graph, for 0i,jd0\leq i,j\leq d.

Hermitian forms eigenvalue conjectures. (i) If jj is odd, then

Qj(1)Qj(i)Q_j(1) \leq Q_j(i)

for 0id0\leq i\leq d. (ii) If jj is even and j2j\geq 2, then

Qj(dj+2)Qj(i)Q_j(d-j+2) \leq Q_j(i)

for 0id0\leq i\leq d.

Both assertions are proved in the paper for q2q\geq 2, d6d\geq 6, and j1j\geq 1.

Sources & referencesView supporting material

Primary source

Sebastian M. Cioabă and Himanshu Gupta, “On the eigenvalues of Grassmann graphs, Bilinear forms graphs and Hermitian forms graphs”, arXiv:2102.10155 (2021).

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