English

Switchings of semifield multiplications

Combinatorics 2015-06-19 v1

Abstract

Let B(X,Y)B(X,Y) be a polynomial over Fqn\mathbb{F}_{q^n} which defines an Fq\mathbb{F}_q-bilinear form on the vector space Fqn\mathbb{F}_{q^n}, and let ξ\xi be a nonzero element in Fqn\mathbb{F}_{q^n}. In this paper, we consider for which B(X,Y)B(X,Y), the binary operation xy+B(x,y)ξxy+B(x,y)\xi defines a (pre)semifield multiplication on Fqn\mathbb{F}_{q^n}. We prove that this question is equivalent to finding qq-linearized polynomials L(X)Fqn[X]L(X)\in\mathbb{F}_{q^n}[X] such that Trqn/q(L(x)/x)0Tr_{q^n/q}(L(x)/x)\neq 0 for all xFqnx\in\mathbb{F}_{q^n}^*. For n4n\le 4, we present several families of L(X)L(X) and we investigate the derived (pre)semifields. When qq equals a prime pp, we show that if n>12(p1)(p2p+4)n>\frac{1}{2}(p-1)(p^2-p+4), L(X)L(X) must be a0Xa_0 X for some a0Fpna_0\in\mathbb{F}_{p^n} satisfying Trqn/q(a0)0Tr_{q^n/q}(a_0)\neq 0. Finally, we include a natural connection with certain cyclic codes over finite fields, and we apply the Hasse-Weil-Serre bound for algebraic curves to prove several necessary conditions for such kind of L(X)L(X).

Keywords

Cite

@article{arxiv.1406.1067,
  title  = {Switchings of semifield multiplications},
  author = {Xiang-dong Hou and Ferruh Özbudak and Yue Zhou},
  journal= {arXiv preprint arXiv:1406.1067},
  year   = {2015}
}
R2 v1 2026-06-22T04:30:36.151Z