1. Apr 21, 2016 #1

   Independent

   

   How does one arrive at the formula 4.8?
   
   
   The Lagrangian (one spatial dimension) is:
   
   

    

   Independent, Apr 21, 2016
2. 
   Phys.org - latest science and technology news stories on Phys.org

   • • Imaged 'jets' reveal cerium's post-shock inner strength
   • • Exciting silicon nanoparticles
   • • How many ways can you arrange 128 tennis balls? Researchers solve an apparently impossible problem
3. Apr 23, 2016 #2

   vanhees71

   

   Science Advisor

   Insights Author

   2016 Award

   That's a special case of Noether's theorem for space-time translations, which is a symmetry of Minkowski space. The corresponding conserved quantities are energy and momentum. For fields it defines the canonical energy-momentum tensor
   $$\Theta^{\mu \nu}=\frac{\partial \mathcal{L}}{\partial (\partial_{\nu} \phi)}\partial^{\mu} \phi-\mathcal{L} g^{\mu \nu}.$$
   The momentum density components are given by ##\Theta^{0j}## (##j \in \{1,2,3 \}##). Now it should be easy to show the above formula.

    

   vanhees71, Apr 23, 2016

• Log in with Facebook
• Log in with Twitter

Your name or email address:

Do you already have an account?

• No, create an account now.
• Yes, my password is:
• Forgot your password?

Stay logged in