So I was thinking chain rule. Say I have the variational derivative δF/δA(x) and I expand in terms of ∏ derivatives:
$$\frac{\delta F}{\delta A^i}=\frac{\delta \Pi_j}{\delta A^i}\frac{\delta F}{\delta \Pi_j}$$
Of course the sum goes over the ∏s. But in the OP i calculated the variational...
Homework Statement
To calculate a certain Dirac bracket I need to calculate this Poisson bracket (Weinberg QTF 1 p.349 first eq.)
$$[F,\Pi_i(\mathbf{z})]_P$$
where F is any functional of matter fields and their conjugates and pi is the conjugate to the vector potential. It should be zero...
This is a question I have about the textbook discussion, so I'll do away with the standard format.
The author of my QM book (Shankar, Principles of Quantum Mechanics) used the term "negative momentum states," all of a sudden, and I've never heard of it before. He has a little note saying that...