Postinflationary Higgs Relaxation and the Origin of Matter-Antimatter Asymmetry

The recent measurement of the Higgs boson mass implies a relatively slow rise of the standard model Higgs potential at large scales, and a possible second minimum at even larger scales. Consequently, the Higgs field may develop a large vacuum expectation value during inflation. The relaxation of the Higgs field from its large postinflationary value to the minimum of the effective potential represents an important stage in the evolution of the Universe. During this epoch, the time-dependent Higgs condensate can create an effective chemical potential for the lepton number, leading to a generation of the lepton asymmetry in the presence of some large right-handed Majorana neutrino masses. The electroweak sphalerons redistribute this asymmetry between leptons and baryons. This Higgs relaxation leptogenesis can explain the observed matter-antimatter asymmetry of the Universe even if the standard model is valid up to the scale of inflation, and any new physics is suppressed by that high scale.

Figure 1

Some diagrams that contribute to lepton number violation via exchange of a heavy Majorana neutrino.

Figure 2

Numerical solutions for the lepton number asymmetry. The IC-1 scenario is shown by the blue solid line for ${\mathrm{\Lambda }}_I={10}^{15}\mathrm{GeV}$, ${\mathrm{\Gamma }}_I={10}^9\mathrm{GeV}$, and $M_R=9\times {10}^{15}\mathrm{GeV}$, which results in $T_{\max }=6\times {10}^{13}\mathrm{GeV}$, sufficient to destabilize the second minimum. The initial VEV is ${\varphi }_0=1\times {10}^{15}\mathrm{GeV}$. The IC-2 case is shown by the red dashed line for ${\mathrm{\Lambda }}_I={10}^{17}\mathrm{GeV}$, ${\mathrm{\Gamma }}_I={10}^8\mathrm{GeV}$, $M_n=5\times {10}^{12}\mathrm{GeV}$, and $M_R={10}^{16}\mathrm{GeV}$. The maximum temperature during reheating is $T_{\max }=3\times {10}^{14}\mathrm{GeV}$, and ${\varphi }_0=1\times {10}^{15}\mathrm{GeV}$. The vertical blue dot-dashed (IC-1) lines denote the first crossing of zero, the time of maximum reheating, and the beginning of the radiation-dominated era, from left to right. The vertical red dotted (IC-2) lines denote the time of maximum reheating, the first crossing of zero, and the beginning of the radiation-dominated era, from left to right.