A Cohomological Proof that Real Representations of Semisimple Lie Algebras Have Q-Forms

• Published in: Symmetry, Integrability and Geometry: Methods and Applications
• Date: 2015
• Main Author: Morris, D.W.
• Format: Article
• Language: English
• Published: Інститут математики НАН України 2015
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/147011
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: A Cohomological Proof that Real Representations of Semisimple Lie Algebras Have Q-Forms / D.W. Morris // Symmetry, Integrability and Geometry: Methods and Applications. — 2015. — Т. 11. — Бібліогр.: 12 назв. — англ.

A Lie algebra gQ over Q is said to be R-universal if every homomorphism from gQ to gl(n,R) is conjugate to a homomorphism into gl(n,Q) (for every n). By using Galois cohomology, we provide a short proof of the known fact that every real semisimple Lie algebra has an R-universal Q-form. We also provi...