Vectorial bent functions and partial difference sets

Abstract

The objective of this article is to broaden the understanding of the connections between bent functions and partial difference sets. Recently, the first two authors showed that the elements which a vectorial dual-bent function with certain additional properties maps to 0, form a partial difference set, which generalizes the connection between Boolean bent functions and Hadamard difference sets, and some later established connections between p-ary bent functions and partial difference sets to vectorial bent functions. We discuss the effects of coordinate transformations. As all currently known vectorial dual-bent functions $F:{\mathbb {F}}_{p^n}\rightarrow {\mathbb {F}}_{p^s}$ are linear equivalent to l-forms, i.e., to functions satisfying $F(\beta x) = \beta ^lF(x)$ for all $\beta \in {\mathbb {F}}_{p^s}$, we investigate properties of partial difference sets obtained from l-forms. We show that they are unions of cosets of ${\mathbb {F}}_{p^s}^*$, which also can be seen as certain cyclotomic classes. We draw connections to known results on partial difference sets from cyclotomy. Motivated by experimental results, for a class of vectorial dual-bent functions from ${\mathbb {F}}_{p^n}$ to ${\mathbb {F}}_{p^s}$, we show that the preimage set of the squares of ${\mathbb {F}}_{p^s}$ forms a partial difference set. This extends earlier results on p-ary bent functions.