CPT theorem

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The CPT Theorem (. ENGL c harge, p arity, t ime = charge , parity , time , also known as CPT invariance of the laws of physics referred to) is a fundamental law of physics, the 1954 by Gerhart Lüders and 1955 by Wolfgang Pauli placed has been. It states that any operation that of another possible process by swapping of matter with antimatter and additional reflection of the room as well as a reversal of the direction of time is apparent is also in line with the laws of physics, making it possible.

The validity of the CPT theorem is a fundamental property of quantum field theory .

The CPT transformation

A CPT transformation is effected by executing the following three discrete transformations one after the other :

  • C transformation: exchange of each particle by its antiparticle and vice versa. This changes u. a. the charge the sign. Therefore this transformation is also called charge conjugation .
  • P-transformation: inversion of all three space coordinates of all involved particles and structures. This transformation is called spatial reflection or parity transformation. It is (in the three-dimensional case) identical to a normal mirroring in which only one spatial coordinate is inverted, and an additional 180 ° rotation around this coordinate axis .
  • T-transformation: inversion of the time coordinates of all involved particles and structures, so that the process is reversed in time. This transformation is called time reversal .

Invariance with regard to the individual transformations

The laws of physics, which describe processes in which only gravity and electromagnetic interaction are involved, remain unchanged (invariant) for each of the three described transformations. This is particularly the case with all processes in everyday physics. In other words, there are also

  • the charge-mirrored,
  • the mirror image,
  • the reverse of time

as well as all combinations possible.

However , this is no longer the case if the weak interaction is involved. In elementary particle physics , for example, processes are possible whose mirror images are not compatible with the laws of physics. In this case one speaks of a violation of the mirror symmetry, a so-called parity violation . The weak interaction also violates the symmetry with respect to charge mirroring and the symmetry with respect to time reversal. If one of these symmetries is violated, then so is the combination of the other two. For example, in the weak interaction, because of the violation of the time symmetry, the CP symmetry is also violated , which corresponds to a combined application of charge reversal and space reflection.

Whether these individual symmetries can be violated in processes involving the strong interaction has not yet been conclusively clarified. So far, however, there is no experimental evidence for this.

Basics

Although the invariances towards the discrete transformations P and CP are violated in physics, the CPT theorem states that physics is invariant towards the combined application of all three transformations.

Wolfgang Pauli showed that every theory is CPT-invariant if it fulfills the following requirements:

Experimental review

Within the accuracy that can be achieved today , the CPT theorem has been confirmed experimentally. However, there are theories that predict a violation of the CPT theorem below this limit of accuracy, e.g. B. some quantum gravity - or string theories. New experiments, such as at the Darmstadt accelerator complex FAIR, which is currently being planned, or at CERN , are to subject the validity of such theories to a further examination.

A CPT violation would also result in a violation of the Lorentz invariance and thus the special theory of relativity , see Modern Tests of Lorentz invariance .

See also

Web links

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  1. ↑ P. Bloch: CPT invariance tests in neutral kaon decay. CERN, June 2006. ( PDF; 0.2 MB; Particle Data Group on CPT tests with kaons, English).
  2. ^ Don Colladay, Alan Kostelecky: CPT Violation and the Standard Model. In: Physical Review D. Volume 55, 1996, pp. 6760-6774, doi : 10.1103 / PhysRevD.55.6760 (English).
  3. ^ J. Bernabeu, NE Mavromatos, J. Papavassiliou: Novel type of CPT violation for correlated EPR states. In: Physical Review Letters. Volume 92, 2004, 131601, doi : 10.1103 / PhysRevLett.92.131601 (English).
  4. ↑ Rainer Scharf: CPT test with antiprotonic helium. In: pro-physik.de. March 2, 2007.
  5. ↑ Kjeld Eikema: The Anti Hydrogen Project: The CPT theorem and antimatter. Max Planck Institute for Quantum Optics (MPQ), March 20, 2000 (English, introductory text to CPT experiments with anti-hydrogen).
  6. ^ OW Greenberg: CPT Violation Implies Violation of Lorentz Invariance. In: Physical Review Letters. Volume 89, January 28, 2002, 231602, doi : 10.1103 / PhysRevLett.89.231602 (English).