Cosmology seeking friendship with sterile neutrinos

Recent cosmological measurements favour additional relativistic energy density beyond the one provided by the three active neutrinos and photons of the Standard Model (SM). This is often referred to as "dark radiation", suggesting the need of new light states in the theory beyond those of the SM. In this paper, we study and numerically explore the alternative possibility that this increase comes from the decay of some new form of heavy matter into the SM neutrinos. We study the constraints on the decaying matter density and its lifetime, using data from the Wilkinson Microwave Anisotropy Probe, the South Pole Telescope, measurements of the Hubble constant at present time, the results from high-redshift Type-I supernovae and the information on the Baryon Acoustic Oscillation scale. We, moreover, include in our analysis the information on the presence of additional contributions to the expansion rate of the Universe at the time of Big Bang Nucleosynthesis. We compare the results obtained in this decaying matter scenario with those obtained with the standard analysis in terms of a constant N eff .

Section: +14mentioning

confidence: 99%

Section: +14mentioning

confidence: 99%

Section: +14mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Dark radiation and decaying matter

Gonzalez-Garcia

Niro

Salvadó

2013

“…Depending on the datasets, constraint results on N eff are qualitatively changed. For instance, it is pointed out that the observational deuterium abundance D/H favors the presence of extra radiation [50,51]: N eff = 3.90 ± 0.44. The combining analysis of CMB data from the 7-year WMAP and the Atacama Cosmology Telescope (ACT) gives an excess N eff = 5.3±1.3 [52], and the addition of BAO and H 0 data decreases the value N eff = 4.56 ± 0.75 [52,53].…”

Section: A Unified Model Of Dark Energy and Dark Radiation In Rmcg Comentioning

confidence: 99%

Reduced modified Chaplygin gas cosmology

Geng

et al. 2015

Abstract:In this paper, we study cosmologies containing the reduced modified Chaplygin gas (RMCG) fluid which is reduced from the modified Chaplygin gas p = Aρ − Bρ −α for the value of α = −1/2. In this special case, dark cosmological models can be realized for different values of model parameter A. We investigate the viabilities of these dark cosmological models by discussing the evolutions of cosmological quantities and using the currently available cosmic observations. It is shown that the special RMCG model (A = 0 or A = 1) which unifies the dark matter and dark energy should be abandoned. For A = 1/3, RMCG which unifies the dark energy and dark radiation is the favorite model according to the objective Akaike information criteria. In the case of A < 0, RMCG can achieve the features of the dynamical quintessence and phantom models, where the evolution of the universe is not sensitive to the variation of model parameters.

Phenomenological study of extended seesaw model for light sterile neutrino

Nath¹,

Ghosh²,

Goswami³

et al. 2017

Abstract:We study the zero textures of the Yukawa matrices in the minimal extended type-I seesaw (MES) model which can give rise to ∼ eV scale sterile neutrinos. In this model, three right handed neutrinos and one extra singlet S are added to generate a light sterile neutrino. The light neutrino mass matrix for the active neutrinos, m ν , depends on the Dirac neutrino mass matrix (M D ), Majorana neutrino mass matrix (M R ) and the mass matrix (M S ) coupling the right handed neutrinos and the singlet. The model predicts one of the light neutrino masses to vanish. We systematically investigate the zero textures in M D and observe that maximum five zeros in M D can lead to viable zero textures in m ν . For this study we consider four different forms for M R (one diagonal and three off diagonal) and two different forms of (M S ) containing one zero. Remarkably we obtain only two allowed forms of m ν (m eτ = 0 and m τ τ = 0) having inverted hierarchical mass spectrum. We re-analyze the phenomenological implications of these two allowed textures of m ν in the light of recent neutrino oscillation data. In the context of the MES model, we also express the low energy mass matrix, the mass of the sterile neutrino and the active-sterile mixing in terms of the parameters of the allowed Yukawa matrices. The MES model leads to some extra correlations which disallow some of the Yukawa textures obtained earlier, even though they give allowed one-zero forms of m ν . We show that the allowed textures in our study can be realized in a simple way in a model based on MES mechanism with a discrete Abelian flavor symmetry group Z 8 × Z 2 .