Undergrad Question about Haar measures on lie groups

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SUMMARY

The discussion centers on the invariance of the Haar measure when transitioning from the fundamental representation to the adjoint representation of a Lie group. Participants assert that the Haar measure remains unchanged due to its invariance under left and right translations. The integral in question involves the Itzykson-Zuber integral, specifically the expression ∫dU exp(-tr(XUYU†)), where X and Y are n x n Hermitian matrices and U belongs to U(n). The provided link to the AMS Open Math Notes offers additional context and examples relevant to this topic.

PREREQUISITES
  • Understanding of Lie groups and their representations
  • Familiarity with Haar measures in the context of group theory
  • Knowledge of Hermitian matrices and their properties
  • Experience with integrals involving matrix exponentials, specifically the Itzykson-Zuber integral
NEXT STEPS
  • Study the properties of Haar measures on compact Lie groups
  • Explore the adjoint representation of Lie groups in detail
  • Learn about the Itzykson-Zuber integral and its applications
  • Investigate the role of matrix exponentials in quantum mechanics and statistical mechanics
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This discussion is beneficial for mathematicians, theoretical physicists, and researchers working with Lie groups, representation theory, and integrals in quantum field theory.

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I'm not sure if this question belongs to here, but here it goes

Suppose you have to integrate over a lie group in the fundamental representation. If you pass to the adjoint representation of that group, does the Haar measure have to change? I think that it should not change because it is invariant under left and right translations, is it correct?
 
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dextercioby said:
Integrate what?

Some function f: G -> ℝ, where G is the Lie group. For example, the Itzykson-Zuber integral

∫dUexp(-tr(XUYU)), where X, Y are n x n hermitean matrices and U ∈ U(n)
 

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