Lie Algebras and Similarity Transformations

Click For Summary
SUMMARY

The discussion centers on the use of similarity transformations to create alternative representations of Lie algebras, specifically in n x n matrix format. Dan notes that both the adjoint representation and the similarity transformation representation utilize a Cartan-Weyl basis, leading to equivalent representations through basis changes. While he acknowledges that this concept is not novel, he seeks to understand the practical advantages of employing similarity transformations over the adjoint representation. The conversation highlights the importance of recognizing multiple representations within Lie algebras, particularly in the context of physics applications.

PREREQUISITES
  • Understanding of Lie algebras and their representations
  • Familiarity with Cartan-Weyl basis
  • Knowledge of similarity transformations in linear algebra
  • Basic concepts of n x n matrices
NEXT STEPS
  • Explore the implications of similarity transformations in Lie algebra representations
  • Investigate the relationship between adjoint representations and physical applications in quantum mechanics
  • Study the structure factors of specific Lie algebras, such as su(2), under similarity transformations
  • Learn about basis changes and their impact on the generators of Lie algebras
USEFUL FOR

Mathematicians, physicists, and students studying Lie algebras, particularly those interested in representation theory and its applications in quantum mechanics.

topsquark
Science Advisor
Homework Helper
Insights Author
MHB
Messages
2,020
Reaction score
843
Say we have an adjoint representation (specifically in n x n matrix format) of a Lie algebra. I have noted that we can create another n x n representation using a similarity transformation on the adjoint rep. I know I haven't discovered anything new but none of my sources mention this. Is there any advantage to using a similarity transformation rep over the adjoint rep?

-Dan

PS: I should perhaps also mention that the adjoint rep is a Cartan-Weyl basis and the similarity transformation rep is as well.
 
Last edited by a moderator:
Physics news on Phys.org
If I'm reading this correctly, what you've done is made an equivalent representation by changing basis from the Cartan-Weyl basis. What was the goal exactly? What kind of result are you looking for?
 
Last edited:
Euge said:
If I'm reading this correctly, what you've done is made an equivalent representation by changing basis from the Cartan-Weyl basis. What was the goal exactly? What kind of result are you looking for?
A little while ago I was having some difficulty with basis changes for the generators of a Lie algebra. I finally figured out what I was doing wrong and in the process of fixing my flawed proofs and ideas I was working with the adjoint representation and discovered the similarity transformation property. For some reason I hadn't expected to find more than one n x n (nontrivial basis change) representation of the Lie algebra. So I was just checking to see if the similarity idea had any particular use.

Oddly enough I did find examples of this today in a Physics text and realized that one of my Lie algebra texts did actually make a brief mention of this for su(2), though in this particular example the structure factors do change under the similarity transformation. (The similarity transformation didn't use the adjoint rep for su(2) but was enough to satisfy my curiosity.)

-Dan
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 20 ·
Replies
20
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 20 ·
Replies
20
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K