Twisted Frobenius-Schur Indicators and Character Degree Sums in Dihedral Groups

Abstract

Let $G$ be a finite group and $T(G)$ be the sum of the degrees of its irreducible complex representations. We investigate the relationship between $T(G)$ and the number of twisted involutions $m_{\sigma }=|\{g\in G\mid \sigma (g)=g^{-1}\}|$ for an automorphism $\sigma$. While it is known that $T(G)=m_e$ for the identity automorphism $e$ in certain cases (e.g., real characters), we analyze this relation for non-identity automorphisms of groups of order $p,2p,p^2$. We prove that for the family of Dihedral groups $D_n$, the inequality $T(D_n)\ge m_{\sigma }$ holds for all $\sigma \in \mathrm{Aut}(D_n)$. We provide a complete classification of $m_{\sigma }$ using number-theoretic properties of the automorphism parameters.