Can Structure Constants Define a Metric in a 10D Lie Algebra?

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SUMMARY

The discussion centers on the possibility of defining a metric in a 10-dimensional Lie algebra using structure constants derived from a field of functions. It highlights the use of the Killing-Cartan Form, which is a symmetric bilinear form that can be non-degenerate for semisimple algebras, expressed through the contraction of structure constants. The conversation emphasizes that the non-degeneracy of the Killing form is crucial for determining the semisimplicity of the Lie algebra, rather than the specific field used. Additionally, it questions the existence of other contractions or tensors that can be formed from structure constants beyond the Killing form.

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  • Understanding of Lie algebras and their structure constants
  • Familiarity with symmetric bilinear forms, specifically the Killing-Cartan Form
  • Knowledge of semisimple algebras and their properties
  • Basic concepts of tensor contraction in mathematical physics
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  • Research the properties of the Killing-Cartan Form in various Lie algebras
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jfy4
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Hi,

Let's say I have a 10 dimensional Lie algebra over some field of functions, something along the lines of at least twice differentiable with twice differentiable inverses. The structure constants have inputs from this field. Is it possible to build a metric from these structure constants?

I have seen that a symmetric bi-linear form (the Killing-Cartan Form) that can also be non-degenerate for semi-simple algebras can be formed through contraction of the structure constants \kappa f^{\alpha\beta}_{\quad\gamma} f^{\delta\gamma}_{\quad\beta}=K^{\alpha\delta}. Are there any other contractions or tensors one can form from structure constants over a field of functions (something other than \mathbb{R} or \mathbb{C})?

Thanks,
 
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The field doesn't matter. What matters is, whether the Killing form is non degenerate or not, i.e. whether the Lie algebra is semisimple or not. I won't call the Killing form a metric on the structure constants, or any other attempt to define a metric on this finite set: Why? The Killing form defines a metric on the root spaces.
See: https://www.physicsforums.com/insights/lie-algebras-a-walkthrough-the-basics/
 

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