EDIT: As pointed out by Asaf Karagila (physics) is an intrinsic tag on physics.SE. This means that if a question being migrated has physics tag before migration, the migration will not be rejected.
I have noticed a few tags which are common for both sites. (I am not sure whether there is an easy way to compile a complete list. I found this ones by looking at the most popular tags on Physics.SE and also on looking on questions that were mentioned in discussions about migration to Physics.SE here on meta.) Here are some such tags: quantum-mechanics, classical-mechanics, quantum-field-theory, general-relativity, special-relativity, fluid-dynamics, fourier-transform, notation, terminology, percolation, data-analysis.