Etingof's Introduction to Representation Theory
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Free PDF lecture notes, top rec in r/math for beginners.
More resources on Group Representations
nLab: Representation Theory
Comprehensive wiki page with references.
Representation Theory of Finite Groups
Learn representation theory of finite groups with this course by Richard Borcherds. Explore group representations and their applications!
mathworld.wolfram.com
MathWorld is an extensive online mathematics encyclopedia offering concise, authoritative articles on topics across math, including group theory and representation theory. Each article provides definitions, theorems, formulas, and examples with links to related concepts.
Representation Theory: A First Course
Representation Theory: A First Course - A book resource
ocw.mit.edu
MIT OpenCourseWare is a free online repository of MIT course materials from a wide range of disciplines. It offers lecture notes, assignments, exams, and sometimes video lectures from actual MIT courses, including mathematics content related to group representations.
ncatlab.org
nLab is a collaborative, research-focused wiki for advanced mathematics, physics, and philosophy, featuring extensive articles, definitions, and discussions—especially in category theory, algebra, topology, and related areas. It includes detailed entries on group representations and representation theory, with cross-references to related concepts and topics.