CPT violation and particle-antiparticle asymmetry in cosmology
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ELEMENTARY PARTICLES AND FIELDS
CP T Violation and Particle–Antiparticle Asymmetry in Cosmology* A. D. Dolgov** Dipartimento di Fisica, Universita` degli Studi di Ferrara, Italy; Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, Italy; Institute of Theoretical and Experimental Physics, Moscow, Russia Received July 3, 2009
Abstract—General features of generation of the cosmological charge asymmetry in CP T noninvariant world are discussed. If the effects of CP T violation manifest themselves only in mass differences of particles and antiparticles, the baryon asymmetry of the Universe hardly can be explained solely by breaking of CP T invariance. However, CP T noninvariant theories may lead to a new effect of distorting the usual equilibrium distributions. If this takes place, CP T violation may explain the baryon asymmetry of the Universe. DOI: 10.1134/S1063778810040022
The generally accepted mechanism of generation of cosmological charge asymmetry is based on three general principles put forward by Sakharov in 1967 [1]: (1) Nonconservation of baryon number. (2) Breaking of C and CP . (3) Deviation from thermal equilibrium. It is established long ago by experiment that P , C, and CP are broken. Big bang cosmology unambiguously states that massive particles should be out of thermal equilibrium in the cosmological plasma. Nonconservation of baryons is predicted by electroweak and grand unified theories and “experimentally” proven by existence of our universe. So the Sakharov baryogenesis seems to be in a pretty good shape, though some efforts are needed to obtain sufficiently large cosmological baryon asymmetry. In this connection it may be interesting to explore other possibilities. For more details about the standard baryogenesis and the list of references see, e.g., reviews [2]. Since all three symmetries C, P , and T are known to be broken, it is tempting to explore consequences of breaking of the combined CP T symmetry. There is of course a drastic difference between anyone of the single symmetry transformations or any pair of them and the combined action of the three. According to the celebrated CP T theorem [3], any local Lorenz invariant theory with hermitian Hamiltonian, with positive definite energy or, better to say, with the canonical relation between spin and statistics is ∗ **
The text was submitted by the author in English. E-mail: [email protected]
invariant with respect to CP T transformation. On the other hand, there are absolutely no theoretical arguments in favor of invariance with respect to separate P , C, and T transformations and they are, indeed, only approximate. If we trust CP T theorem, then we should conclude that any pair CP , P T , and T C are also broken. In fact, historically first was discovered that CP is broken and hence T should be broken as well. The study of phenomenological manifestations of CP T violation has a long history. I will mention here only some selected contributions by L.B. Okun [4–9]. For recent works and review of the literature on CP T violation see [10–12]. In
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