Sakharov criteria

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The three Sakharov criteria are necessary conditions in cosmology for a dynamic generation of baryon asymmetry in the universe during baryogenesis . They are named after their discoverer Andrei Sakharov , who was the first to find them in 1967. Independently of him, they were also discovered in 1970 by Vadim Alexejewitsch Kuzmin .

The three criteria

The different theories about the origin of baryon asymmetry differ in how the following conditions are met in detail.

Violation of the conservation of baryons

In principle, this criterion is fulfilled in the standard model by the Sphaleron processes. Due to the high mass of the Higgs boson , the baryogenesis by this process in the Standard Model cannot be reconciled with the departure from thermodynamic equilibrium, the third Sakharov criterion. With regard to the other criteria, it is met without contradiction by all models that represent an approach to the large unified theory for the unification of strong and electroweak interaction.

Violation of C and CP invariance

C stands for batch here. for charge and CP for charge parity, d. H. Charge and parity . This criterion is already met in the standard model of elementary particle physics. The CP violation during the decay of the neutral kaon was also found experimentally. However, the observed CP violation is far too small to explain today's baryon asymmetry. Since the validity of the CPT invariance is generally assumed (T = time), the T invariance should also be violated - this could also be observed, but is not a necessary condition.

Thermodynamic non-equilibrium

In the thermodynamic equilibrium, an existing baryon asymmetry would inevitably be canceled out again by the inverse reactions of the observed particle decays. In today's theories of baryogenesis, the non-equilibrium is usually explained by a rapid rate of expansion of the universe (faster than the rate of decay of the particle under consideration) at the point in time in question.

Individual evidence

  1. ^ AD Sakharov: Violation of CP Invariance, c Asymmetry, and Baryon Asymmetry of the Universe . In: JETP Lett. tape 5 , no. 1 , 1967, p. 24–27 (English, jetpletters.ac.ru [PDF]).
  2. ^ VA Kuz'min: CP-noninvariance and Baryon Asymmetry of the Universe . In: JETP Lett. tape 12 , no. 6 , p. 228–230 (English, jetpletters.ac.ru [PDF]).
  3. ↑ Werner Bernreuther: CP Violation and Baryogenesis . Lectures given at the International School on CP Violation and related Processes, Prerow, Germany, October 1 - 8, 2000, and at the workshop of the Graduiertenkolleg Elementarteilchenphysik of Humboldt-Universität, Berlin, April 2 - 5, 2001. In: Lect. Notes Phys. No. 591 , 2002, p. 237–293 , arxiv : hep-ph / 0205279 (English).