The combination of
Charge and
Parity in
physics.
While a combined Charge, Parity, and Time (
CPT) transformation leaves a system invariant
some systems are not invariant under a combination
of just CP transformations. This was first proposed
by
T.D. Lee and
C. N. Yang in the
1950's
and experimentally verified by
C.S. Wu a few years later.
Lee and Yang recieved the
Nobel prize for this work.
A charge transformation is when you take the charge of a particle and swap it's sign
e ---} -e
A parity transformation is when you change the sign of
the space coordinate of the particle
x ---} -x
A time transformation ,well go on guess.