English

Clique number of xor-powers of Kneser graphs

Combinatorics 2025-10-03 v1

Abstract

Let f(n,k)f_\ell(n, k) denote the clique number of the xor-product of \ell isomorphic Kneser graphs KG(n,k). Alon and Lubetzky investigated the case of complete graphs as a coding theory problem and showed f(n,1)n+1f_\ell(n,1)\leq \ell n +1. Imolay, Kocsis, and Schweitzer proved that f2(n,k)n/k+c(k)f_2(n,k)\leq n/k +c(k). Here, the order of magnitude of c(k)c(k) is determined to be Θ(k(2kk))\Theta\left( k \binom{2k}{k} \right). By explicit constructions and by an algebraic proof, it is shown that n21f(n,1)n+1\ell n- 2\ell-1 \leq f_\ell(n,1)\leq \ell n-\ell+1 (for all n1n \geq 1 and 3\ell\geq 3). Finally, it is proved that the order of magnitude of ff lies between Ω(nlog2(+1))\Omega\left(n^{\left\lfloor \log_2(\ell+1)\right\rfloor}\right) and O(n+12)O\left(n^{\left\lfloor \frac{\ell+1}{2} \right\rfloor} \right) (as \ell, kk are given and nn\to \infty). We conjecture that the lower bound gives the correct exponent.

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Cite

@article{arxiv.2510.01509,
  title  = {Clique number of xor-powers of Kneser graphs},
  author = {Zoltán Füredi and András Imolay and Ádám Schweitzer},
  journal= {arXiv preprint arXiv:2510.01509},
  year   = {2025}
}

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11 pages