# CPT symmetry

**CPT symmetry** is a fundamental symmetry of physical laws under transformations that involve the inversions of charge, parity and time simultaneously. Efforts in the late 1950s revealed the violation of P-symmetry by some phenomena that involve weak nuclear force fields, and there are well known violations of C-symmetry and T-symmetry as well. For a short time, the CP-symmetry was believed to be preserved by all physical phenomena, but that was later found to be false too. There is a theorem that derives the preservation of CPT symmetry for all of physical phenomena assuming the correctness of quantum laws.

The implication of CPT symmetry is that a mirror-image of our universe—with all objects having momenta and positions reflected by an imaginary plane (corresponding to a parity inversion), with all matter replaced by antimatter (corresponding to a charge inversion), and reversed in time—would evolve exactly like our universe. At any moment, the two universes would be identical, and the CPT transformation would simply turn one into the other. CPT symmetry is recognized to be a fundamental property of physical laws.

The CPT theorem can be generalized to take into account pin groups.

## See also

- Poincare symmetry and Quantum field theory
- Parity (physics), Charge conjugation and Time reversal symmetry
- CP violation and Kaon

## References

- Griffiths, David J. (1987).
*Introduction to Elementary Particles*, Wiley, John & Sons, Inc. ISBN 0471603864.