Symmetry, splitting rational places in extensions of function fields and generalization of the Hermitian function field

Abstract

The notion of symmetry in polynomial rings with several indeterminates is generalized to polynomial rings over finite fields. Families of extensions of the projective line over a finite field of constants possessing this property are explicitly constructed. These extensions exhibit complete splitting of all finite rational places. Subcovers of these extensions are also explicitly described. New examples of function fields attaining the Oesterle bounds are obtained. These constructions are compared with class field theoretic constructions achieving similar splitting of rational places. A generalization to the Hermitian function field over fields of non-square cardinality is proposed.