CPT symmetry, also known as the CPT theorem, is a fundamental principle in theoretical physics that combines three different symmetries: Charge conjugation (C), Parity reversal (P), and Time reversal (T). The CPT symmetry states that the laws of physics are invariant under the combined operation of these three symmetries.
Individually, these symmetries have the following meanings:
Charge conjugation (C): It involves reversing the signs of all particle charges. For example, an electron with a negative charge would be transformed into a positron with a positive charge.
Parity reversal (P): It involves spatial inversion or flipping the direction of all spatial coordinates. Essentially, it reflects the system across a mirror plane. For instance, left-handedness would become right-handedness.
Time reversal (T): It involves reversing the direction of time. The flow of time is reversed, and processes occur backward.
The CPT symmetry combines all three symmetries, implying that if you simultaneously perform charge conjugation, parity reversal, and time reversal on a physical system, the resulting system should be physically equivalent to the original.
The CPT theorem has deep implications in physics, particularly in quantum field theory. It is considered a fundamental symmetry of nature and has been extensively tested in various experiments, including particle physics experiments. Violation of CPT symmetry would have profound consequences for our understanding of the laws of physics.
It's worth noting that while the individual symmetries (C, P, and T) can be violated in certain phenomena, the CPT symmetry, as a combined operation, is believed to be an exact symmetry of our universe based on experimental observations and theoretical considerations.