What does it mean to say "internal symmetry"? Let me try to express the way I see it, so you can have it as a starting point.
There are spacetime symmetries, which are global since any Lorentz transformation, at any point in spacetime, will be invariant. On the other hand there are also internal symmetries (which I understand as local), which are only invariant in a certain region of the spacetime.
- Does this make sense?
- Could anyone give examples of internal symmetries?
PS: I'm currently studying Classical Field Theory. That's where I see the terminology.