\newcommand{\tr}{\mathrm{tr}\,}
\newcommand{\BC}{\mathbf{C}}
\newcommand{\BS}{\mathbf{S}}
\newcommand{\BE}{\mathbf{E}}
\newcommand{\BI}{\mathbf{I}}
\newcommand{\BBC}{\mathbb{C}}
\newcommand{\CI}{\mathcal{I}}
\newcommand{\de}{\delta}
\newcommand{\Bvep}{\boldsymbol\varepsilon}
\newcommand{\fracpt}[2]{\frac{\partial #1}{\partial #2}}
