Hello

How to reduce the size of all subscripts in math mode ?

Thanks

Fabrice

\usemodule[tikz]
 \protected\def\vector#1{%
     \starttikzpicture[baseline=(arg.base),>=stealth]
     \node[inner xsep=0pt] (arg) {\m{#1}};
     \draw[thick,->,shorten >=-1pt] (arg.north west) -- (arg.north east);
    \stoptikzpicture%
    }
\starttext
 \m{z_{\vector{U}}}
\stoptext