\(
\newcommand{\d}{\mathrm{d}}
\newcommand{\bomega}{\vec\omega}
\newcommand{\half}{ {1\over 2} }
\def\mathnot#1{\text{"$#1$"}}
%operators
\newcommand{\diag}{\mathrm{diag}}
\newcommand{\sinc}{\mathrm{sinc}}
\newcommand{\Sh}{ {\large\style{font-family:Times}{\text{Ш}}} }
\newcommand{\res}{\mathrm{Res}}
\)
6. Thermodynamics and Statistical Physics