- #1
Trave11er
- 71
- 0
For free EM field:
L=-[itex]\frac{1}{4}[/itex]FabFab
Then the stress-energy tensor is given by:
Tmn=-Fml∂vAl+[itex]\frac{1}{4}[/itex]gmnFabFab
The author then redefines Tmn - he adds ∂lΩlmn to it,
where Ωlmn=-Ωmln.
The redefined tensor is:
Tmn=-FmlFvl+gmv[itex]\frac{1}{4}[/itex]FabFab
It is gauge invariant and still satisfies ∂mTmn=0.
The question: is why the addition is allowed? - to my uneducated mind the procedure seems like changing the energy-momentum tensor arbitrarily.
L=-[itex]\frac{1}{4}[/itex]FabFab
Then the stress-energy tensor is given by:
Tmn=-Fml∂vAl+[itex]\frac{1}{4}[/itex]gmnFabFab
The author then redefines Tmn - he adds ∂lΩlmn to it,
where Ωlmn=-Ωmln.
The redefined tensor is:
Tmn=-FmlFvl+gmv[itex]\frac{1}{4}[/itex]FabFab
It is gauge invariant and still satisfies ∂mTmn=0.
The question: is why the addition is allowed? - to my uneducated mind the procedure seems like changing the energy-momentum tensor arbitrarily.