C-symmetry

C-symmetry is the symmetry of physical laws over a charge-inversion transformation. The laws of electromagnetism, both classical and quantum are invariant under this transformation, ie., if all charges (q's) were replaced with charges of negative sign (-q's), in all the equations of electromagnetism, still the laws would preserve the same form. But, evidently this symmetry is violated in observation, owing to the fact that our physical universe is made up of matter and not anti-matter. Though in principle, a positive charge is in all respects identical to that of a negative charge (the choice of 'positiveness' or 'negativeness' being only a convention, as one can say), in reality it isn't. Thus, the violation of C-symmetry was realized to be a fundamental physical property of the universe. It was believed for some time that this along with the parity inversion transformation (see P-symmetry) would preserve a CP-symmetry. Even this symmetry was found to be violated later. Now, a stronger symmetry CPT-symmetry that includes time-reversal too into the picture is believed to be preserved.