How Do E²-B² and F_{μν}F^{μν} Relate in Tensor Calculations?

  • Thread starter Thread starter noamriemer
  • Start date Start date
  • Tags Tags
    Gravitation
Click For Summary
SUMMARY

The relationship between \(E^{2} - B^{2}\) and \(F_{\mu\nu} F^{\mu\nu}\) is established through tensor calculations in electromagnetic theory. Specifically, \(F_{\mu\nu}\) represents the electromagnetic field tensor, and its contraction \(F_{\mu\nu} F^{\mu\nu}\) results in a scalar quantity, which is crucial for understanding the invariance of electromagnetic fields. The confusion arises from the expectation of matrix multiplication yielding another matrix, whereas the contraction of indices leads to a scalar, aligning with the formal definitions in tensor calculus.

PREREQUISITES
  • Understanding of tensor calculus and index notation
  • Familiarity with the electromagnetic field tensor \(F_{\mu\nu}\)
  • Knowledge of scalar quantities in physics
  • Basic principles of matrix multiplication and contraction
NEXT STEPS
  • Study the properties of the electromagnetic field tensor \(F_{\mu\nu}\)
  • Learn about tensor contraction and its implications in physics
  • Explore the derivation of scalar quantities from tensor products
  • Investigate the role of invariants in electromagnetic theory
USEFUL FOR

Physicists, students of electromagnetism, and anyone studying tensor calculus in the context of field theory.

noamriemer
Messages
50
Reaction score
0
Hello!
I need to find the relation between E^{2}-B^{2} and F_{\mu\nu} F^{\mu\nu}
Actually, I need to use this relation to determine that the first is a scalar.
What I can't understand is how these notations match the formal definition:
If I multiply a matrix by another (same size) I should be receiving another matrix of the same size. Not a scalar...
But if I use the notations I need to use here:
F_{\mu\nu} F^{\mu\nu}\Rightarrow \Sigma_{i=1}^{3} \Sigma_{j=1}^{3} = F_{00}F^{00}+F_{01}F^{01}+...<br /> and that is not the product I expect it to be...
Could someone explain me how these definitions get along?
Thank you!
 
Physics news on Phys.org
Anybody...? I am lost in here ...
Thanks
 

Similar threads

Replies
7
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
3
Views
2K
  • · Replies 16 ·
Replies
16
Views
4K
  • · Replies 9 ·
Replies
9
Views
1K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 15 ·
Replies
15
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K