TY - JOUR
T1 - Increasing the effective number of neutrinos with decaying particles
AU - Ichikawa, Kazuhide
AU - Kawasaki, Masahiro
AU - Nakayama, Kazunori
AU - Senami, Masato
AU - Takahashi, Fuminobu
PY - 2007/5/1
Y1 - 2007/5/1
N2 - We present models of decaying particles for increasing the effective number of neutrinos Nν after big bang nucleosynthesis but before the structure formation begins. We point out that our scenario not only solves the discrepancy between the constraints on Nν from these two epochs, but also provides a possible answer to deeper inconsistency in the estimation of the matter power spectrum amplitude at small scales, represented by σ8, between the WMAP and some small scale matter power measurements such as the Lyman-α forest and weak lensing. We consider (a) saxion decay into two axions; (b) gravitino decay into axino and axion; (c) Dirac right-handed sneutrino decay into gravitino and right-handed neutrino.
AB - We present models of decaying particles for increasing the effective number of neutrinos Nν after big bang nucleosynthesis but before the structure formation begins. We point out that our scenario not only solves the discrepancy between the constraints on Nν from these two epochs, but also provides a possible answer to deeper inconsistency in the estimation of the matter power spectrum amplitude at small scales, represented by σ8, between the WMAP and some small scale matter power measurements such as the Lyman-α forest and weak lensing. We consider (a) saxion decay into two axions; (b) gravitino decay into axino and axion; (c) Dirac right-handed sneutrino decay into gravitino and right-handed neutrino.
KW - Axions
KW - Cosmological neutrinos
KW - Cosmology of theories beyond the SM
UR - http://www.scopus.com/inward/record.url?scp=34547577875&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34547577875&partnerID=8YFLogxK
U2 - 10.1088/1475-7516/2007/05/008
DO - 10.1088/1475-7516/2007/05/008
M3 - Article
AN - SCOPUS:34547577875
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
SN - 1475-7516
IS - 5
M1 - 008
ER -