Published online by Cambridge University Press: 20 November 2018
Let $R$ be a dense subring of
$\text{End}\left( _{D}V \right)$ , where
$V$ is a left vector space over a division ring
$D$ . If
$\dim{{\,}_{D}}V\,=\,\infty $ , then the range of any nonzero polynomial
$f\left( {{X}_{1}},\,\ldots \,,\,{{X}_{m}} \right)$ on
$R$ is dense in
$\text{End}\left( _{D}V \right)$ . As an application, let
$R$ be a prime ring without nonzero nil one-sided ideals and
$0\,\ne \,a\,\in \,R$ . If
$af{{\left( {{x}_{1}},\ldots ,{{x}_{m}} \right)}^{n\left( {{x}_{i}} \right)}}\,=\,0$ for all
${{x}_{1}},\,\ldots \,,\,{{x}_{m}}\,\in \,R$ , where
$n\left( {{x}_{i}} \right)$ is a positive integer depending on
${{x}_{1}},\,\ldots \,,\,{{x}_{m}}\,\in \,R$ , then
$f\left( {{X}_{1}},\,\ldots \,,\,{{X}_{m}} \right)$ is a polynomial identity of
$R$ unless
$R$ is a finite matrix ring over a finite field.