We present cosmological bounds on the thermal axion mass in an extended cosmological scenario in ... more We present cosmological bounds on the thermal axion mass in an extended cosmological scenario in which the primordial power spectrum of scalar perturbations differs from the usual power-law shape predicted by the simplest inflationary models. The power spectrum is instead modeled by means of a "piecewise cubic Hermite interpolating polynomial" (PCHIP). When using Cosmic Microwave Background measurements combined with other cosmological data sets, the thermal axion mass constraints are degraded only slightly. The addition of the measurements of $\sigma_8$ and $\Omega_m$ from the 2013 Planck cluster catalogue on galaxy number counts relaxes the bounds on the thermal axion mass, mildly favouring a $\sim 1$~eV axion mass, regardless of the model adopted for the primordial power spectrum.However, in general, such a preference disappears if the sum of the three active neutrino masses is also considered as a free parameter in our numerical analyses, due to the strong correlation between the masses of these two hot thermal relics.
The recent discovery of B-modes in the polarization pattern of the Cosmic Microwave Background by... more The recent discovery of B-modes in the polarization pattern of the Cosmic Microwave Background by the BICEP2 experiment has important implications for neutrino physics. We revisit cosmological bounds on light sterile neutrinos and show that they are compatible with all current cosmological data provided that the mass is relatively low. Using CMB data, including BICEP-2, we find an upper bound of m s < 0.85 eV (2σ Confidence Level). This bound is strengthened to 0.48 eV when HST measurements of H 0 are included. However, the inclusion of SZ cluster data from the Planck mission and weak gravi-tational measurements from the CFHTLenS project favours a non-zero sterile neutrino mass of 0.44 +0.11 −0.16 eV. Short baseline neutrino oscillations, on the other hand, indicate a new mass state around 1.2 eV. This mass is highly incompatible with cosmological data if the sterile neutrino is fully thermalised (∆χ 2 > 10). However, if the sterile neutrino only partly thermalises it can be compatible with all current data, both cosmological and terrestrial.
We investigate a phenomenological non-gravitational coupling between dark energy and dark matter,... more We investigate a phenomenological non-gravitational coupling between dark energy and dark matter, where the interaction in the dark sector is parameterized as an energy transfer either from dark matter to dark energy or the opposite. The models are constrained by a whole host of updated cosmological data: cosmic microwave background temperature anisotropies and polarization, high-redshift supernovae, baryon acoustic oscillations, redshift space distortions and gravitational lensing. Both models are found to be compatible with all cosmological observables, but in the case where dark matter decays into dark energy, the tension with the independent determinations of H 0 and σ 8 , already present for standard cosmology, increases: this model in fact predicts lower H 0 and higher σ 8 , mostly as a consequence of the higher amount of dark matter at early times, leading to a stronger clustering during the evolution. Instead, when dark matter is fed by dark energy, the reconstructed values of H 0 and σ 8 nicely agree with their local determinations, with a full reconciliation between high-and low-redshift observations. A non-zero coupling between dark energy and dark matter, with an energy flow from the former to the latter, appears therefore to be in better agreement with cosmological data.
The simplest inflationary models predict a primordial power spectrum (PPS) of the curvature fluct... more The simplest inflationary models predict a primordial power spectrum (PPS) of the curvature fluctuations that can be described by a power-law function that is nearly scale-invariant. It has been shown, however, that the low-multipole spectrum of the CMB anisotropies may hint the presence of some features in the shape of the scalar PPS, which could deviate from its canonical power-law form. We study the possible degeneracies of this non-standard PPS with the neutrino anisotropies, the neutrino masses, the effective number of relativistic species and a sterile neutrino or a thermal axion mass. The limits on these additional parameters are less constraining in a model with a non-standard PPS when only including the temperature auto-correlation spectrum measurements in the data analyses. The inclusion of the polarization spectra noticeably helps in reducing the degeneracies, leading to results that typically show no deviation from the ΛCDM model with a standard power-law PPS. CONTENTS
The recent discovery of B-modes in the polarization pattern of the Cosmic Microwave Background by... more The recent discovery of B-modes in the polarization pattern of the Cosmic Microwave Background by the BICEP2 experiment has important implications for neutrino physics. We revisit cosmological bounds on light sterile neutrinos and show that they are compatible with all current cosmological data provided that the mass is relatively low. Using CMB data, including BICEP-2, we find an upper bound of m s < 0.85 eV (2σ Confidence Level). This bound is strengthened to 0.48 eV when HST measurements of H 0 are included. However, the inclusion of SZ cluster data from the Planck mission and weak gravi-tational measurements from the CFHTLenS project favours a non-zero sterile neutrino mass of 0.44 +0.11 −0.16 eV. Short baseline neutrino oscillations, on the other hand, indicate a new mass state around 1.2 eV. This mass is highly incompatible with cosmological data if the sterile neutrino is fully thermalised (∆χ 2 > 10). However, if the sterile neutrino only partly thermalises it can be compatible with all current data, both cosmological and terrestrial.
We introduce a cosmological invisible decay of the sterile neutrino with the eV-scale mass indica... more We introduce a cosmological invisible decay of the sterile neutrino with the eV-scale mass indicated by short-baseline neutrino oscillation experiments in order to allow its full thermalization in the early Universe. We show that the fit of the cosmological data is practically as good as the fit obtained with a stable sterile neutrino without mass constraints, which has been recently considered by several authors for the explanation of the observed suppression of small-scale matter density fluctuations and for a solution of the tension between the Planck and BICEP2 measurements of the tensor to scalar ratio of large-scale fluctuations. Moreover, the extra relativistic degree of freedom corresponding to a fully thermalized sterile neutrino is correlated with a larger value of the Hubble constant, which is in agreement with local measurements.
We present cosmological bounds on the thermal axion mass in an extended cosmological scenario in ... more We present cosmological bounds on the thermal axion mass in an extended cosmological scenario in which the primordial power spectrum of scalar perturbations differs from the usual power-law shape predicted by the simplest inflationary models. The power spectrum is instead modeled by means of a "piecewise cubic Hermite interpolating polynomial" (PCHIP). When using Cosmic Microwave Background measurements combined with other cosmological data sets, the thermal axion mass constraints are degraded only slightly. The addition of the measurements of $\sigma_8$ and $\Omega_m$ from the 2013 Planck cluster catalogue on galaxy number counts relaxes the bounds on the thermal axion mass, mildly favouring a $\sim 1$~eV axion mass, regardless of the model adopted for the primordial power spectrum.However, in general, such a preference disappears if the sum of the three active neutrino masses is also considered as a free parameter in our numerical analyses, due to the strong correlation between the masses of these two hot thermal relics.
The recent discovery of B-modes in the polarization pattern of the Cosmic Microwave Background by... more The recent discovery of B-modes in the polarization pattern of the Cosmic Microwave Background by the BICEP2 experiment has important implications for neutrino physics. We revisit cosmological bounds on light sterile neutrinos and show that they are compatible with all current cosmological data provided that the mass is relatively low. Using CMB data, including BICEP-2, we find an upper bound of m s < 0.85 eV (2σ Confidence Level). This bound is strengthened to 0.48 eV when HST measurements of H 0 are included. However, the inclusion of SZ cluster data from the Planck mission and weak gravi-tational measurements from the CFHTLenS project favours a non-zero sterile neutrino mass of 0.44 +0.11 −0.16 eV. Short baseline neutrino oscillations, on the other hand, indicate a new mass state around 1.2 eV. This mass is highly incompatible with cosmological data if the sterile neutrino is fully thermalised (∆χ 2 > 10). However, if the sterile neutrino only partly thermalises it can be compatible with all current data, both cosmological and terrestrial.
We investigate a phenomenological non-gravitational coupling between dark energy and dark matter,... more We investigate a phenomenological non-gravitational coupling between dark energy and dark matter, where the interaction in the dark sector is parameterized as an energy transfer either from dark matter to dark energy or the opposite. The models are constrained by a whole host of updated cosmological data: cosmic microwave background temperature anisotropies and polarization, high-redshift supernovae, baryon acoustic oscillations, redshift space distortions and gravitational lensing. Both models are found to be compatible with all cosmological observables, but in the case where dark matter decays into dark energy, the tension with the independent determinations of H 0 and σ 8 , already present for standard cosmology, increases: this model in fact predicts lower H 0 and higher σ 8 , mostly as a consequence of the higher amount of dark matter at early times, leading to a stronger clustering during the evolution. Instead, when dark matter is fed by dark energy, the reconstructed values of H 0 and σ 8 nicely agree with their local determinations, with a full reconciliation between high-and low-redshift observations. A non-zero coupling between dark energy and dark matter, with an energy flow from the former to the latter, appears therefore to be in better agreement with cosmological data.
The simplest inflationary models predict a primordial power spectrum (PPS) of the curvature fluct... more The simplest inflationary models predict a primordial power spectrum (PPS) of the curvature fluctuations that can be described by a power-law function that is nearly scale-invariant. It has been shown, however, that the low-multipole spectrum of the CMB anisotropies may hint the presence of some features in the shape of the scalar PPS, which could deviate from its canonical power-law form. We study the possible degeneracies of this non-standard PPS with the neutrino anisotropies, the neutrino masses, the effective number of relativistic species and a sterile neutrino or a thermal axion mass. The limits on these additional parameters are less constraining in a model with a non-standard PPS when only including the temperature auto-correlation spectrum measurements in the data analyses. The inclusion of the polarization spectra noticeably helps in reducing the degeneracies, leading to results that typically show no deviation from the ΛCDM model with a standard power-law PPS. CONTENTS
The recent discovery of B-modes in the polarization pattern of the Cosmic Microwave Background by... more The recent discovery of B-modes in the polarization pattern of the Cosmic Microwave Background by the BICEP2 experiment has important implications for neutrino physics. We revisit cosmological bounds on light sterile neutrinos and show that they are compatible with all current cosmological data provided that the mass is relatively low. Using CMB data, including BICEP-2, we find an upper bound of m s < 0.85 eV (2σ Confidence Level). This bound is strengthened to 0.48 eV when HST measurements of H 0 are included. However, the inclusion of SZ cluster data from the Planck mission and weak gravi-tational measurements from the CFHTLenS project favours a non-zero sterile neutrino mass of 0.44 +0.11 −0.16 eV. Short baseline neutrino oscillations, on the other hand, indicate a new mass state around 1.2 eV. This mass is highly incompatible with cosmological data if the sterile neutrino is fully thermalised (∆χ 2 > 10). However, if the sterile neutrino only partly thermalises it can be compatible with all current data, both cosmological and terrestrial.
We introduce a cosmological invisible decay of the sterile neutrino with the eV-scale mass indica... more We introduce a cosmological invisible decay of the sterile neutrino with the eV-scale mass indicated by short-baseline neutrino oscillation experiments in order to allow its full thermalization in the early Universe. We show that the fit of the cosmological data is practically as good as the fit obtained with a stable sterile neutrino without mass constraints, which has been recently considered by several authors for the explanation of the observed suppression of small-scale matter density fluctuations and for a solution of the tension between the Planck and BICEP2 measurements of the tensor to scalar ratio of large-scale fluctuations. Moreover, the extra relativistic degree of freedom corresponding to a fully thermalized sterile neutrino is correlated with a larger value of the Hubble constant, which is in agreement with local measurements.
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