EN
Let $𝔽_q[t]$ be the polynomial ring over the finite field $𝔽_q$, and let $𝔾_{N}$ be the subset of $𝔽_q[t]$ containing all polynomials of degree strictly less than N. Define D(N) to be the maximal cardinality of a set $A ⊆ 𝔾_{N}$ for which A-A contains no squares of polynomials. By combining the polynomial Hardy-Littlewood circle method with the density increment technology developed by Pintz, Steiger and Szemerédi, we prove that $D(N) ≪ q^N( log N)^{7}/N$.