On an Erd\H{o}s-type conjecture on $\mathbb{F}_q[x]$

Abstract

P. Erd\H{o}s conjectured in 1962 that on the ring $\mathbb{Z}$, every set of $n$ congruence classes in $\mathbb{Z}$ that covers the first $2^n$ positive integers also covers the ring $\mathbb{Z}$. This conjecture was first confirmed in 1970 by R. B. Crittenden and C. L. Vanden Eynden. Later, in 2019, P. Balister, B. Bollob\'{a}s, R. Morris, J. Sahasrabudhe, and M. Tiba provided a more transparent proof. In this paper, we follow the approach used by R. B. Crittenden and C. L. Vanden Eynden to prove the generalized Erd\H{o}s' conjecture in the setting of polynomial rings over finite fields. We prove that every set of $n$ cosets of ideals in $\mathbb F_q[x]$ that covers all polynomials whose degree is less than $n$ covers the ring $\mathbb{F}_q[x]$.