arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2001.10392math.RA
收藏

交换子与非交换多项式的象

Commutators and images of noncommutative polynomials

Matej Brešar

摘要:

设$A$是一个代数,$f$是一个非常数的非交换多项式.本文的第一部分讨论了$A$中算子的线性跨度$[A,A]$与$A$中$f$的象的线性跨度$f(A)$之间的关系。特别是,我们表明,$[A,A]=A$意味着跨度$f(A)=A$。在第二部分中,我们建立了多项式象的一些Waring型结果。例如,我们证明了如果$C$是特征为$0$的域$F$上的交换酉代数,$A$是矩阵代数$M_n(C)$,多项式$f$既不是$M_n(F)$的单位元也不是中心多项式,则$A$中的每个交换子都可以写为两个元素的差,其中每个是来自$f(A)$的$7788$元素的和(如果$C=F$是代数闭域,则$4$元素就足够了)。对于其他一些代数,特别是Hilbert空间$H$上的所有有界线性算子的代数$B(H)$,也得到了类似的结果。

英文摘要:

Let $A$ be an algebra and let $f$ be a nonconstant noncommutative polynomial. In the first part of the paper, we consider the relationship between $[A,A]$, the linear span of commutators in $A$, and span$f(A)$, the linear span of the image of $f$ in $A$. In particular, we show that $[A,A]=A$ implies span$f(A)=A$. In the second part, we establish some Waring type results for images of polynomials. For example, we show that if $C$ is a commutative unital algebra over a field $F$ of characteristic $0$, $A$ is the matrix algebra $M_n(C)$, and the polynomial $f$ is neither an identity nor a central polynomial of $M_n(F)$, then every commutator in $A$ can be written as a difference of two elements, each of which is a sum of $7788$ elements from $f(A)$ (if $C=F$ is an algebraically closed field, then $4$ elements suffice). Similar results are obtained for some other algebras, in particular for the algebra $B(H)$ of all bounded linear operators on a Hilbert space $H$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑