Group Theory is intended as a textbook for a one-term course in group theory for senior undergraduate or graduate students. It provides students with good insight into group theory as quickly as possible. Simplicity and working knowledge are emphasized here over mathematical completeness. This book will provide a rigorous proof-based modern treatment of the main results of group theory. As a result, proofs are in great details with a lot of interesting examples.This book can also serve as a reference for professional mathematicians. The book contains 221 carefully selected exercises of varying difficulty which will allow students to practice their own computational and proof-writing skills. Sample solutions to some exercise questions are provided, from which students can learn to write their own solutions and proofs. Besides standard ones, many of the exercises are very interesting.Group Theory includes:basic properties of groupssymmetric groups and alternating groupsisomorphism theorems, commutator subgroups, direct and semi-direct products of groupsgroup action on sets, Cauchy-Frobenius Lemma, symmetries of the regular polyhedronsJordan-Holder Theorem and Sylow Theoremsfree groups, group presentations, finitely generated abelian groupssolvable groups, Hall subgroups, characteristically simple groups, Sylow systems and Sylow basesnilpotent groups, Frattini subgroupsbasic properties of representations of groups on vector spaces, subrepresentations; irreducibility, Schur's Lemma, and Maschke's Theorem
