Warning’s Second Theorem with restricted variables

Abstract

We present a restricted variable generalization of Warning’s Second Theorem (a result giving a lower bound on the number of solutions of a low degree polynomial system over a finite field, assuming one solution exists). This is analogous to Schauz-Brink’s restricted variable generalization of Chevalley’s Theorem (a result giving conditions for a low degree polynomial system not to have exactly one solution). Just as Warning’s Second Theorem implies Chevalley’s Theorem, our result implies Schauz-Brink’s Theorem. We include several combinatorial applications, enough to show that we have a general tool for obtaining quantitative refinements of combinatorial existence theorems. Let q = p[superscript ℓ] be a power of a prime number p, and let F[subscript q] be “the” finite field of order q. For a[subscript 1],...,a[subscript n], N∈Z[superscript +], we denote by m(a[subscript 1],...,a[subscript n];N)∈Z[superscript +] a certain combinatorial quantity defined and computed in Section 2.1.