any of several principles that find the physical trajectory of a system by minimizing or maximizing some value computed over the proposed path (for instance geometric optics can be reproduced by insisting on a minimum time principle).
0
votes
0answers
33 views
Derivation of Dirac equation using the Lagrangian density for Dirac field
How can I find Dirac equation using the Lagrangian density for Dirac field?
0
votes
0answers
67 views
Minimum energy magnetic field has zero current?
Following section 9.2 of Bellan's "Fundamentals of Plasma Physics" suppose we have some domain (I assume simply connected) $D$ with a magnetic field $\mathbf{B}$ inside, but no electrostatic field. ...
0
votes
0answers
67 views
What are the details of this variational calculus solution?
This answer includes the problem:
Suppose you have a 2-d bullet going very fast through a 2-d gas. The gas molecules reflects specularly off the bullet, making glancing collisions. What shape of ...
