Abstract
We start by considering the production rates of sphalerons with different size $\rho$ in the symmetric phase, $T>T_{EW}$. At small $\rho$, the distribution is cut off by the growing mass $M\sim 1/\rho$, and at large $\rho$ by the magnetic screening mass. In the broken phase, $T<T_{EW}$ the scale is set by the Higgs VEV $v(T)$. We introduce the concept of "Sphaleron freezeout" whereby the sphaleron production rate matches the Hubble Universe expansion rate. At freezeout the sphalerons are out of equilibrium. Sphaleron explosions generate sound and even gravity waves, when nonzero Weinberg angle make them non-spherical. We revisit CP violation during the sphaleron explosions. We assess its magnitude using the Standard Model CKM quark matrix, first for nonzero and then zero Dirac eigenstates. We find that its magnitude is maximal at the sphaleron freezeout condition with $T\approx 130\, GeV$. We proceed to estimate the amount of CP violation needed to generate the observed magnitude of baryon asymmetry of Universe. The result is about an order of magnitude below our CKM-based estimates. We also relate the baryon asymmetry to the generation of $U(1)$ magnetic chirality, which is expected to be conserved and perhaps visible in polarized intergalactic magnetic fields.
Highlights
One of the central unsolved problems of physics and cosmology is baryogenesis, the explanation of the apparent baryon asymmetry (BAU) in the Universe
The common setting is the cosmological electroweak phase transition (EWPT), whereby the universe undergoes a transition from a symmetric phase to a broken phase with a nonzero vacuum expectation value (VEV) for the Higgs field
As we will detail below, baryogenesis driven by CP violation is biased toward sphalerons of sizes larger than average, while the gravity wave signal and seeds of magnetic clouds are biased to smaller sizes
Summary
One of the central unsolved problems of physics and cosmology is baryogenesis, the explanation of the apparent baryon asymmetry (BAU) in the Universe. The so-called leptogenesis scenarios use superheavy neutrino decays, occurring at very high scales, and satisfying both large CP and out-ofequilibrium requirements, with large lepton asymmetry transformed into the baryon asymmetry by the electroweak sphalerons at TEW While one of these BSM scenarios may well turn out to be the explanation for BAU, they still remain purely hypothetical at this time, lacking any support from current experiments. Our main point is that the sphaleron-induced BAU must be related with the chiral imbalance of quarks and leptons produced in sphaleron transitions This chiral imbalance is transferred to linkage of magnetic fields.
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