Cayley unitary elements in group algebras under oriented involutions
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arXiv
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| Formato: | Preprint |
| Publicado: |
2025
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| author | Castillo, John H. Gómez-Espíndola, Yzel Wlly Holguín-Villa, Alexander |
| author_facet | Castillo, John H. Gómez-Espíndola, Yzel Wlly Holguín-Villa, Alexander |
| contents | Let $\mathbf{F}$ be a real extension of $\mathbb{Q}$, $G$ a finite group and $\mathbf{F}G$ its group algebra. Given both a group homomorphism $σ:G\rightarrow \{\pm1\}$ (called an orientation) and a group involution $^\ast:G \rightarrow G$ such that $gg^\ast\in N=ker(σ)$, an oriented group involution $\circledast$ of $\mathbf{F}G$ is defined by $α=\sum_{g\in G}α_{g}g \mapsto α^\circledast=\sum_{g\in G}α_{g}σ(g)g^{\ast}$. In this paper, in case the involution on $G$ is the classical one, $x\mapsto x^{-1}$, $β=x+x^{-1}$ is a skew-symmetric element in $\mathbf{F}G$ such that $1+β$ is invertible, for $x\in G$ with $σ(x)=-1$, we consider Cayley unitary elements built out of $β$. We prove that the coefficients of $(1+β)^{-1}$ involve an interesting sequence which is a Fibonacci-like sequence. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_13796 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Cayley unitary elements in group algebras under oriented involutions Castillo, John H. Gómez-Espíndola, Yzel Wlly Holguín-Villa, Alexander Rings and Algebras 16U60, 16W10, 16S34, 16R50 Let $\mathbf{F}$ be a real extension of $\mathbb{Q}$, $G$ a finite group and $\mathbf{F}G$ its group algebra. Given both a group homomorphism $σ:G\rightarrow \{\pm1\}$ (called an orientation) and a group involution $^\ast:G \rightarrow G$ such that $gg^\ast\in N=ker(σ)$, an oriented group involution $\circledast$ of $\mathbf{F}G$ is defined by $α=\sum_{g\in G}α_{g}g \mapsto α^\circledast=\sum_{g\in G}α_{g}σ(g)g^{\ast}$. In this paper, in case the involution on $G$ is the classical one, $x\mapsto x^{-1}$, $β=x+x^{-1}$ is a skew-symmetric element in $\mathbf{F}G$ such that $1+β$ is invertible, for $x\in G$ with $σ(x)=-1$, we consider Cayley unitary elements built out of $β$. We prove that the coefficients of $(1+β)^{-1}$ involve an interesting sequence which is a Fibonacci-like sequence. |
| title | Cayley unitary elements in group algebras under oriented involutions |
| topic | Rings and Algebras 16U60, 16W10, 16S34, 16R50 |
| url | https://arxiv.org/abs/2502.13796 |