Simultaneous popular differences for polynomial and linear progressions in finite fields

Source abstract

We study simultaneous popular differences for polynomial progressions and linear progressions over finite fields $\mathbb F_p$. For certain families of polynomial progressions of algebraic complexity $1$, such as $(x, x+y, x+2y)$ and $(x, x+y^3, x+2y^3)$, we prove the existence of $y \neq 0$ which is popular simultaneously for both progressions. This extends previous results by Conlon, Dong and Hong who considered complexity $0$ progressions. On the other hand, we construct counterexamples showing that simultaneous popular differences are not guaranteed to exist for $(x, x+y, x+2y)$ and $(x, x+y^2, x+2y^2)$, or for $(x, x+y, x+2y)$ and $(x, x+y, x+3y)$, or for $(x, x+y, x+2y)$ and $(x,x+y,x+2y,x+3y)$, answering questions posed by Conlon, Dong and Hong.