A while back I learned about systems which could undergo a "full revolution" and end up in the opposite state they were in when they started. Two full revolutions were required in order to return to the origin.
Does anyone know what these systems are called? I would like to look into them further but I can't remember what they were called and I can't find it on Google.
Thanks
These are called spinors. They are used prominently in relativistic quantum mechanics and quantum field theory in physics.