\def \sphi {\phi}
\let \phi \varphi
\let \epsilon \varepsilon
\def \C {\mathbb{C}}
\def \Re {\ensuremath{\mathfrak{Re}\,}}
\def \F {\ensuremath{\mathcal{F}}}
\def \R {\ensuremath{\mathbb{R}}}
\def \N {\ensuremath{\mathbb{N}}}
\def \Rn {\ensuremath{\mathbb{R}^{n}}}
\def \E {\ensuremath{\mathcal{E}}}
\def \d {\ensuremath{\operatorname{d}\!}}
\def \abs#1{\ensuremath{\left|#1\right|}}