CPT symmetry
The CPT theorem ( for eng. Batch, parity, time = charge, parity, time) is a fundamental law of physics, which was founded in 1955 by Wolfgang Pauli ( and also independent of Gerhart Lüders ) erected. It states that any process that emerges from another possible process by exchanging matter with antimatter and additional reflection of the space and reversing the direction of time, also in accordance with the laws of physics is, and thus is possible. This situation is referred to as invariance of physical laws with respect to a CPT transformation. The validity of the CPT theorem is a fundamental property of quantum field theory.
The CPT transformation
A CPT- transformation is effected by successively executing the following three discrete transformations:
- C- transformation: exchange of each particle by its antiparticle, and vice versa. This change, among others the charge sign. Therefore, this transformation is also called charge conjugation.
- P- transformation: inversion of all three spatial coordinates of all the atoms involved, and structures. This transformation is called space reflection or parity transformation. It is ( in the three-dimensional case ) is identical to an ordinary mirror, in which only one spatial coordinate is inverted, and an additional 180 degree rotation around these coordinate axes.
- T- transformation: inversion time coordinates of all the atoms involved, and structures so that the process takes time reversed. This transformation is called time reversal.
Invariance with respect to the individual transformations
The laws of physics that describe processes in which only the gravitational and electromagnetic interactions are involved, stay with each of the three transformations described unchanged ( invariant ). This is particularly the case for all operations of everyday physics. That for each operation are also
- The charge mirrored,
- The mirror image,
- The time-reversed,
And all combinations are possible.
With participation of the weak interaction, however, this is no longer the case. Thus, processes are possible, for example, in elementary particle physics, their mirror images are not compatible with the laws of physics. One speaks in this case of a violation of mirror symmetry, a so-called parity violation. The weak interaction also violates the symmetry with respect to a charge mirroring and symmetry with respect to a time reversal. If one of these symmetries violated, then it is also the combination of the other two. For example, in the weak interaction due to the violation of time symmetry, the CP symmetry violated, which corresponds to a combined use of charge reversal and space reflection.
Whether this individual symmetries can be violated in processes involving the strong interaction is not yet fully understood. However, so far it exist no experimental evidence.
Basics
Although the invariants are compared with the discrete transformations P and CP violated in physics, says the CPT theorem that physics compared to the combined use of all three transformations is invariant.
Wolfgang Pauli showed that every theory is CPT invariant which satisfies the following conditions:
- Invariance with respect to Lorentz transformations (strictly invariant under real orthochroner Poincaré transformation),
- Causality,
- Locality and
- A limited downward Hamiltonian so that there is a quantum-mechanical state of the vacuum.
Experimental verification
As part of the currently achievable accuracy, the CPT theorem is confirmed experimentally. However, there are theories that predict a violation of the CPT theorem below this limit of accuracy, eg some string or quantum gravity theories. New experiments, such as in the in the planning Darmstadt FAIR accelerator complex at CERN or to decide on the validity of such theories.
From a CPT- violation is also a violation of Lorentz invariance and therefore of special relativity would follow, Modern tests of Lorentz invariance see.