HELP Why CS is topological? Why BF is topological?

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SUMMARY

The discussion centers on the topological nature of Chern-Simons (CS) theory and BF theory, emphasizing that the CS Lagrangian is a topological invariant independent of the chosen connection. The participant questions how CS theory can be classified as topological given that a topological field theory (TFT) does not depend on the metric, and raises concerns about the CS Lagrangian being a 3-form rather than a scalar. The participant seeks clarification on demonstrating the topological nature of CS and BF theories through the relationship between constraints and degrees of freedom.

PREREQUISITES
  • Understanding of Chern-Simons theory and its properties
  • Familiarity with topological field theories (TFTs)
  • Knowledge of differential forms, particularly 3-forms
  • Concepts of constraints and degrees of freedom in field theories
NEXT STEPS
  • Research the mathematical foundations of Chern-Simons theory
  • Study the properties of topological field theories (TFTs)
  • Learn about the role of differential forms in theoretical physics
  • Explore the relationship between constraints and degrees of freedom in gauge theories
USEFUL FOR

The discussion is beneficial for theoretical physicists, mathematicians studying topology, and students interested in advanced field theories, particularly those focusing on Chern-Simons and BF theories.

astros
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Hello,
I know that the CS Lagrangian is a topological invariant, in the sense that it does not depend on the connection we choose. OK, but a TFT is a field theory whose Lagrangian and all other observables do not depend on the metric, a connection in general is not uniquely defined by a metric! Then how can I see CS theory as topological? Another problem, CS Lagrangian is a 3-forme, normally; a Lagrangian must be a scalar!? After that, can I see that CS is topological by showing that the number of constraints is equal to the number of degrees of freedom? If yes HOW! The same for BF! Please help me RANI N’NAGER!
 
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