Erdős–Ko–Rado conjecture for k-intersecting invertible matrices

Let qq be a prime power, let kNk\in\mathbb{N}, and let Γ=GL(n,Fq)\Gamma=\operatorname{GL}(n,\mathbb{F}_q). Define

Xq,n,k={AGL(n,Fq):rank(AI)>nk},Gq,n,k=Cay(Γ,Xq,n,k).X_{q,n,k}=\{A\in\operatorname{GL}(n,\mathbb{F}_q):\operatorname{rank}(A-I)>n-k\},\qquad G_{q,n,k}=\operatorname{Cay}(\Gamma,X_{q,n,k}).

The graph's independent sets are the kk-intersecting families of invertible matrices, and α(G)\alpha(G) and ϑ(G)\vartheta(G) denote its independence number and Lovász theta-number. Erdős–Ko–Rado conjecture. For each q,kNq,k\in\mathbb{N}, there exists n0=n0(q,k)Nn_0=n_0(q,k)\in\mathbb{N} such that for all nn0n\geq n_0,

ϑ(Gq,n,k)=α(Gq,n,k)=i=kn1(qnqi).\vartheta(G_{q,n,k})=\alpha(G_{q,n,k})=\prod_{i=k}^{n-1}(q^n-q^i).

The product is achieved by matrices fixing pointwise a chosen kk-dimensional subspace. Computational evidence supports the assertion for small values of nn and qq, but the stated asymptotic result remains open.

Sources & referencesView supporting material

Primary source

Evan DeCorte, David de Laat and Frank Vallentin, “Fourier analysis on finite groups and the Lovász theta-number of Cayley graphs”, arXiv:1307.5703 (2013).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.