New answers tagged time-reversal
It is very important to distinguish whether the symmetry is broken explicitly or spontaneously. I think that the sentence "Now when I break this symmetry spontaneously (or explicitly)" indicates that its author isn't quite distinguishing these things. An explicit symmetry breaking generally lifts the degeneracy because the different parts of the multiplets ...
When you perform a time reversal, you have to not only change the sign of $t$ everywhere, but also change the sign of some of the other physical quantities involved. Time reversal symmetry just means that the form of all equations involved is the same after making the appropriate transformations. If two quantities are related by a time derivative, they ...
The magnetic field is a pseudovector and will therefore pick up a minus sign under reflections or time inversion.
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