Find Cartan Subalgebra for Algebra Given Generators

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SUMMARY

The discussion focuses on finding the Cartan subalgebra for a given set of matrices representing generators of an algebra, crucial for reconstructing the algebra. The initial step involves determining the dimension of the Cartan subalgebra, which indicates how many generators can be simultaneously diagonalized. The conversation highlights that for algebraically closed scalar fields of characteristic not two, the Cartan subalgebra is the maximal toral subalgebra, which is Abelian. The discussion also mentions the complexity of algorithms for Lie algebras, particularly when dealing with nilpotency and the Jordan-Chevalley decomposition.

PREREQUISITES
  • Understanding of group theory and Lie algebras
  • Familiarity with linear algebra concepts, particularly diagonalization
  • Knowledge of algebraically closed fields and their characteristics
  • Basic understanding of Jordan-Chevalley decomposition
NEXT STEPS
  • Research algorithms for finding Cartan subalgebras in Lie algebras
  • Study the properties of maximal toral subalgebras
  • Explore the Jordan-Chevalley decomposition in detail
  • Learn about the implications of nilpotency in algebraic structures
USEFUL FOR

This discussion is beneficial for students and researchers in theoretical physics, particularly those studying group theory and its applications in particle physics, as well as mathematicians focusing on Lie algebras.

CuriosusNN
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Hey! I am studying group theory for particle physicists right now and I came across the following general question (Tell me if you think this rather belongs to the homework section, I am new here.)

Say I am given a set of matrices which represent the generators of an algebra, but I don't know which algebra, i.e. I don't know the commutation relations nor anything like roots or similar about the algebra.
Now I wonder how I could reconstruct the algebra in a smart way. I guess the first step is finding the Cartan subalgebra. Once I have that I should be ready to reconstruct all the rest.
So it all boils down to the question: How can I find the Cartan subalgebra, in particular how can I find out what its dimension (i.e. the rank of the algebra) is, so that I know how many generators I can simultaneously diagonalise?
I suppose this is an undergrad linear algebra question, but I would nevertheless appreciate some hint!
 
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Algorithms for Lie algebras given the multiplication table are notoriously a bit more complicated than what we have in the rest of linear algebra, especially if the scalar field isn't real or complex. For algebraic closed scalar fields of characteristic not two, the CAS is the maximal toral subalgebra, i.e. the largest subalgebra which can be simultaneously diagonalized in the adjoint representation. It is also Abelian in this case, which is a strong requirement. However, in general we have only nilpotency. Hence an algorithm should look for the semisimple parts of the Jordan-Chevalley decomposition of the adjoint representation.
 

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