# Changing size of greek in mathmode with Times fonts

I'm using mathptmx to write a paper for a conference that wants Times. Everything seems to be working ok, except for the size of the greek letters in mathmode. The greek letters have a larger x-height than the normal text font. Is there a way to adjust the font size of the greek letters to get a closer match?

For example, the following document shows the issue:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{mathptmx}
\begin{document}
x$\epsilon$x$\sigma$x
\end{document}

-

Consider getting the Times fonts by using \usepackage{txfonts} or \usepackage{txfontsb} instead--those packages don't seem to have the same problem.