\documentclass[10pt,ngerman]{scrbook}
\usepackage[utf8]{inputenc}
\usepackage[ngerman]{babel}

\usepackage[xindy]{imakeidx}
\usepackage[xindy,acronym]{glossaries}
\newglossary{symbolslist}{syiX1}{sygX1}{Symbolverzeichnis} 
\makeglossaries
\makeindex
\newglossaryentry{physical_t}{
type=symbolslist,
name={\ensuremath{t}},
description={text t}
}
\newglossaryentry{physical_dt}{
type=symbolslist,
name={\ensuremath{\Delta t}},
description={missing text delta}
}
\newglossaryentry{tau_k}{
type=symbolslist,
name={\ensuremath{\tau_k}},
description={text tau}
}
\newglossaryentry{gamma_k}{
type=symbolslist,
name={\ensuremath{\gamma_k}},
description={missing text gamma}
}
\newacronym{abc}{ABC}{the ABC thing}
\begin{document}
\glsaddall
\printglossary[type=\acronymtype,style=long]
\printglossary[type=symbolslist,style=long]
\end{document}
