content_image/310380.jpg content_image/310382.jpg content_image/310381.jpg content_image/310383.jpg content_image/310384.jpg
Therefore 

We know that F 2 = 2( ⃗ B 2 + ⃗ E $^{2}$), and since E = − F 0 i we have that 

## Proca 

Let’s now find the stress-energy tensor for the Proca Lagrangian, 

<img src='content_image/310380.jpg'>

<img src='content_image/310382.jpg'>

<img src='content_image/310381.jpg'>

<img src='content_image/310383.jpg'>

<img src='content_image/310384.jpg'>

