English

Cayley unitary elements in group algebras under oriented involutions

Rings and Algebras 2025-02-20 v1

Abstract

Let F\mathbf{F} be a real extension of Q\mathbb{Q}, GG a finite group and FG\mathbf{F}G its group algebra. Given both a group homomorphism σ:G{±1}\sigma:G\rightarrow \{\pm1\} (called an orientation) and a group involution :GG^\ast:G \rightarrow G such that ggN=ker(σ)gg^\ast\in N=ker(\sigma), an oriented group involution \circledast of FG\mathbf{F}G is defined by α=gGαggα=gGαgσ(g)g\alpha=\sum_{g\in G}\alpha_{g}g \mapsto \alpha^\circledast=\sum_{g\in G}\alpha_{g}\sigma(g)g^{\ast}. In this paper, in case the involution on GG is the classical one, xx1x\mapsto x^{-1}, β=x+x1\beta=x+x^{-1} is a skew-symmetric element in FG\mathbf{F}G such that 1+β1+\beta is invertible, for xGx\in G with σ(x)=1\sigma(x)=-1, we consider Cayley unitary elements built out of β\beta. We prove that the coefficients of (1+β)1(1+\beta)^{-1} involve an interesting sequence which is a Fibonacci-like sequence.

Keywords

Cite

@article{arxiv.2502.13796,
  title  = {Cayley unitary elements in group algebras under oriented involutions},
  author = {John H. Castillo and Yzel Wlly Gómez-Espíndola and Alexander Holguín-Villa},
  journal= {arXiv preprint arXiv:2502.13796},
  year   = {2025}
}

Comments

10 pages

R2 v1 2026-06-28T21:50:10.781Z