- 1,182

- 8

Why is this? I don't understnad . My thoughts would be pictruing the set up needing to be rotationally invariant, and since E and B are perpendicular a linear term alone wouldn't do this, but this wouldnt explaiin why E.E and B.B are invariant, I dont really know what I'm talking about, as you can tell

many thanks in advance

http://www.damtp.cam.ac.uk/user/tong/qhe/five.pdf , page 145 David Tong notes QHE , chapter 5 (eq. 5.5)