\documentclass[12pt]{article}
\usepackage{amsmath,amssymb,amsfonts}
\begin{document}
We obtain the periods and one-instanton coefficient of the N=2 superrsymmetric Yang-Mills theory with the exceptional gauge group $E_6$. These calculations are based on the $E_6$ spectral curve and the obtained one-instanton coefficient is in agreement with the microscopic results.
\end{document}