56,663 research outputs found

    Search for sterile neutrinos in holographic dark energy cosmology: Reconciling Planck observation with the local measurement of the Hubble constant

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    We search for sterile neutrinos in the holographic dark energy cosmology by using the latest observational data. To perform the analysis, we employ the current cosmological observations, including the cosmic microwave background temperature power spectrum data from the Planck mission, the baryon acoustic oscillation measurements, the type Ia supernova data, the redshift space distortion measurements, the shear data of weak lensing observation, the Planck lensing measurement, and the latest direct measurement of H0H_0 as well. We show that, compared to the Λ\LambdaCDM cosmology, the holographic dark energy cosmology with sterile neutrinos can relieve the tension between the Planck observation and the direct measurement of H0H_0 much better. Once we include the H0H_0 measurement in the global fit, we find that the hint of the existence of sterile neutrinos in the holographic dark energy cosmology can be given. Under the constraint of the all-data combination, we obtain Neff=3.76±0.26N_{\rm eff}= 3.76\pm0.26 and mν,sterileeff<0.215eVm_{\nu,\rm sterile}^{\rm eff}< 0.215\,\rm eV, indicating that the detection of ΔNeff>0\Delta N_{\rm eff}>0 in the holographic dark energy cosmology is at the 2.75σ2.75\sigma level and the massless or very light sterile neutrino is favored by the current observations.Comment: 10 pages, 4 figures; typos corrected, published in PR

    Neutrinos in the holographic dark energy model: constraints from latest measurements of expansion history and growth of structure

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    The model of holographic dark energy (HDE) with massive neutrinos and/or dark radiation is investigated in detail. The background and perturbation evolutions in the HDE model are calculated. We employ the PPF approach to overcome the gravity instability difficulty (perturbation divergence of dark energy) led by the equation-of-state parameter ww evolving across the phantom divide w=1w=-1 in the HDE model with c<1c<1. We thus derive the evolutions of density perturbations of various components and metric fluctuations in the HDE model. The impacts of massive neutrino and dark radiation on the CMB anisotropy power spectrum and the matter power spectrum in the HDE scenario are discussed. Furthermore, we constrain the models of HDE with massive neutrinos and/or dark radiation by using the latest measurements of expansion history and growth of structure, including the Planck CMB temperature data, the baryon acoustic oscillation data, the JLA supernova data, the Hubble constant direct measurement, the cosmic shear data of weak lensing, the Planck CMB lensing data, and the redshift space distortions data. We find that mν<0.186\sum m_\nu<0.186 eV (95\% CL) and Neff=3.750.32+0.28N_{\rm eff}=3.75^{+0.28}_{-0.32} in the HDE model from the constraints of these data.Comment: 18 pages, 5 figures; revised version accepted for publication in JCA

    Revisiting the holographic dark energy in a non-flat universe: alternative model and cosmological parameter constraints

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    We propose an alternative model for the holographic dark energy in a non-flat universe. This new model differs from the previous one in that the IR length cutoff LL is taken to be exactly the event horizon size in a non-flat universe, which is more natural and theoretically/conceptually concordant with the model of holographic dark energy in a flat universe. We constrain the model using the recent observational data including the type Ia supernova data from SNLS3, the baryon acoustic oscillation data from 6dF, SDSS-DR7, BOSS-DR11, and WiggleZ, the cosmic microwave background data from Planck, and the Hubble constant measurement from HST. In particular, since some previous studies have shown that the color-luminosity parameter β\beta of supernovae is likely to vary during the cosmic evolution, we also consider such a case that β\beta in SNLS3 is time-varying in our data fitting. Compared to the constant β\beta case, the time-varying β\beta case reduces the value of χ2\chi^2 by about 35 and results in that β\beta deviates from a constant at about 5σ\sigma level, well consistent with the previous studies. For the parameter cc of the holographic dark energy, the constant β\beta fit gives c=0.65±0.05c=0.65\pm 0.05 and the time-varying β\beta fit yields c=0.72±0.06c=0.72\pm 0.06. In addition, an open universe is favored (at about 2σ\sigma) for the model by the current data.Comment: 8 pages, 4 figure