ABSTRACT
The charge conjugation (C), the parity (P), and the time-reversal (T ) are the three important discrete symmetries in nature. These symmetries are exactly conserved in the electromagnetic, the strong and the gravitational interactions, although they are violated in the weak interaction. It is also known that the consistency of the eld theory requires that the product CPT should be conserved in any theory. Another product CP plays a special role in particle physics and cosmology.
