Published online by Cambridge University Press: 21 September 2020
A finite group whose irreducible complex characters are rational-valued is called a rational group. The aim of this paper is to determine the rational almost simple and rational quasi-simple groups.
The first-named author gladly acknowledges the financial support of the University of Tehran during the course of this work. The research of the first-named author was also in part supported by a grant from IPM (No. 99200027). The third-named author was in part supported by the Grant No. 98012009 from the Iranian National Science Foundation (INSF).