TY - JOUR
T1 - U(1)B -L symmetry restoration and effective neutrino species
AU - Ishida, Hiroyuki
AU - Takahashi, Fuminobu
N1 - Funding Information:
We thank Kwang Sik Jeong for discussion on the mini-thermal inflation. F.T. thanks Kazunori Nakayama for useful discussion on the dissipation processes of the Higgs field. This work was supported by JSPS Grant-in-Aid for Scientific Research on Innovative Areas (No. 24111702 , No. 21111006 , and No. 23104008 ) [F.T.], Scientific Research (A) (No. 22244030 and No. 21244033 ) [F.T.], and JSPS Grant-in-Aid for Young Scientists (B) (No. 24740135 ) [F.T.], and Inoue Foundation for Science [H.I. and F.T.]. This work was also supported by World Premier International Center Initiative (WPI Program), MEXT , Japan [F.T.].
PY - 2014/6/27
Y1 - 2014/6/27
N2 - The U(1)B -L symmetry could be restored during inflation, since the BICEP2 results suggest a GUT-scale inflation with the Hubble parameter, Hinf ≃1014GeV, close to the U(1)B -L breaking scale. We consider a scenario in which the B - L Higgs field dominates the Universe after inflation, and mainly decays into the U(1)B -L gauge bosons, whose subsequent decays reheat the Universe. Interestingly, if one of the right-handed neutrinos is extremely light and behaves as dark radiation or hot dark matter, its abundance is determined by the B - L charge assignment and the relativistic degree of freedom in plasma. We find that δNeff takes discrete values between 0.188 and 0.220 in the standard model plus three right-handed neutrinos, depending on whether the decay into heavier right-handed neutrinos is kinematically accessible or not. In the fiveness U(1)5 case, we find that δNeff takes discrete values between 0.313 and 0.423. The tension between BICEP2 and Planck can be partially relaxed by dark radiation.
AB - The U(1)B -L symmetry could be restored during inflation, since the BICEP2 results suggest a GUT-scale inflation with the Hubble parameter, Hinf ≃1014GeV, close to the U(1)B -L breaking scale. We consider a scenario in which the B - L Higgs field dominates the Universe after inflation, and mainly decays into the U(1)B -L gauge bosons, whose subsequent decays reheat the Universe. Interestingly, if one of the right-handed neutrinos is extremely light and behaves as dark radiation or hot dark matter, its abundance is determined by the B - L charge assignment and the relativistic degree of freedom in plasma. We find that δNeff takes discrete values between 0.188 and 0.220 in the standard model plus three right-handed neutrinos, depending on whether the decay into heavier right-handed neutrinos is kinematically accessible or not. In the fiveness U(1)5 case, we find that δNeff takes discrete values between 0.313 and 0.423. The tension between BICEP2 and Planck can be partially relaxed by dark radiation.
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U2 - 10.1016/j.physletb.2014.05.048
DO - 10.1016/j.physletb.2014.05.048
M3 - Article
AN - SCOPUS:84901492664
VL - 734
SP - 183
EP - 187
JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
SN - 0370-2693
ER -