Search results for " Microwave"
showing 10 items of 253 documents
Improvement of cosmological neutrino mass bounds
2016
The most recent measurements of the temperature and low-multipole polarization anisotropies of the cosmic microwave background from the Planck satellite, when combined with galaxy clustering data f ...
A(4)-based neutrino masses with Majoron decaying dark matter
2010
We propose an A(4) flavor-symmetric SU(3) circle times SU(2) circle times U(1) seesaw model where lepton number is broken spontaneously. A consistent two-zero texture pattern of neutrino masses and mixing emerges from the interplay of type-I and type-II seesaw contributions, with important phenomenological predictions. We show that, if the Majoron becomes massive, such seesaw scenario provides a viable candidate for decaying dark matter, consistent with cosmic microwave background lifetime constraints that follow from current WMAP observations. We also calculate the subleading one-loop-induced decay into photons which leads to a monoenergetic emission line that may be observed in future x-r…
Do observations prove that cosmological neutrinos are thermally distributed?
2005
It is usually assumed that relic neutrinos possess a Fermi-Dirac distribution, acquired during thermal equilibrium in the Early Universe. However, various mechanisms could introduce strong distortions in this distribution. We perform a Bayesian likelihood analysis including the first moments of the three active neutrino distributions as free parameters, and show that current cosmological observations of light element abundances, Cosmic Microwave Background (CMB) anisotropies and Large Scale Structures (LSS) are compatible with very large deviations from the standard picture. We also calculate the bounds on non-thermal distortions which can be expected from future observations, and stress th…
Current cosmological bounds on neutrino masses and relativistic relics
2004
We combine the most recent observations of large-scale structure (2dF and SDSS galaxy surveys) and cosmic microwave anisotropies (WMAP and ACBAR) to put constraints on flat cosmological models where the number of massive neutrinos and of massless relativistic relics are both left arbitrary. We discuss the impact of each dataset and of various priors on our bounds. For the standard case of three thermalized neutrinos, we find an upper bound on the total neutrino mass sum m_nu < 1.0 (resp. 0.6) eV (at 2sigma), using only CMB and LSS data (resp. including priors from supernovae data and the HST Key Project), a bound that is quite insensitive to the splitting of the total mass between the th…
Measuring the cosmological background of relativistic with the Wilkinson Microwave Anisotropy Probe
2003
We show that the first year results of the Wilkinson Microwave Anisotropy Probe (WMAP) constrain very efficiently the energy density in relativistic particles in the Universe. We derive new bounds on additional relativistic degrees of freedom expressed in terms of an excess in the effective number of light neutrinos $\ensuremath{\Delta}{N}_{\mathrm{eff}}.$ Within the flat \ensuremath{\Lambda}CDM scenario, the allowed range is $\ensuremath{\Delta}{N}_{\mathrm{eff}}l6$ (95% confidence level) using WMAP data only, or $\ensuremath{-}2.6l\ensuremath{\Delta}{N}_{\mathrm{eff}}l4$ with the prior ${H}_{0}=72\ifmmode\pm\else\textpm\fi{}8\mathrm{km}{\mathrm{s}}^{\ensuremath{-}1}{\mathrm{Mpc}}^{\ensure…
Cosmic Microwave Background anisotropies from second order gravitational perturbations
1997
This paper presents a complete analysis of the effects of second order gravitational perturbations on Cosmic Microwave Background anisotropies, taking explicitly into account scalar, vector and tensor modes. We also consider the second order perturbations of the metric itself obtaining them, for a universe dominated by a collision-less fluid, in the Poisson gauge, by transforming the known results in the synchronous gauge. We discuss the resulting second order anisotropies in the Poisson gauge, and analyse the possible relevance of the different terms. We expect that, in the simplest scenarios for structure formation, the main effect comes from the gravitational lensing by scalar perturbati…
Most constraining cosmological neutrino mass bounds
2021
We present here up-to-date neutrino mass limits exploiting the most recent cosmological data sets. By making use of the cosmic microwave background temperature fluctuation and polarization measurements, supernovae Ia luminosity distances, baryon acoustic oscillation observations and determinations of the growth rate parameter, we are able to set the most constraining bound to date, $\ensuremath{\sum}{m}_{\ensuremath{\nu}}l0.09\text{ }\text{ }\mathrm{eV}$ at 95% C.L. This very tight limit is obtained without the assumption of any prior on the value of the Hubble constant and highly compromises the viability of the inverted mass ordering as the underlying neutrino mass pattern in nature. The …
Invisible neutrino decay in precision cosmology
2021
We revisit the topic of invisible neutrino decay in the precision cosmological context, via a first-principles approach to understanding the cosmic microwave background and large-scale structure phenomenology of such a non-standard physics scenario. Assuming an effective Lagrangian in which a heavier standard-model neutrino $\nu_H$ couples to a lighter one $\nu_l$ and a massless scalar particle $\phi$ via a Yukawa interaction, we derive from first principles the complete set of Boltzmann equations, at both the spatially homogeneous and the first-order inhomogeneous levels, for the phase space densities of $\nu_H$, $\nu_l$, and $\phi$ in the presence of the relevant decay and inverse decay p…
The present and future of the most favoured inflationary models after $Planck$ 2015
2015
The value of the tensor-to-scalar ratio $r$ in the region allowed by the latest $Planck$ 2015 measurements can be associated to a large variety of inflationary models. We discuss here the potential of future Cosmic Microwave Background cosmological observations in disentangling among the possible theoretical scenarios allowed by our analyses of current $Planck$ temperature and polarization data. Rather than focusing only on $r$, we focus as well on the running of the primordial power spectrum, $\alpha_s$ and the running of thereof, $\beta_s$. Our Fisher matrix method benefits from a detailed and realistic appraisal of the expected foregrounds. Future cosmological probes, as the COrE mission…
Can interacting dark energy solve the $H_0$ tension?
2017
The answer is Yes! We indeed find that interacting dark energy can alleviate the current tension on the value of the Hubble constant $H_0$ between the Cosmic Microwave Background anisotropies constraints obtained from the Planck satellite and the recent direct measurements reported by Riess et al. 2016. The combination of these two datasets points towards an evidence for a non-zero dark matter-dark energy coupling $\xi$ at more than two standard deviations, with $\xi=-0.26_{-0.12}^{+0.16}$ at $95\%$ CL. However the $H_0$ tension is better solved when the equation of state of the interacting dark energy component is allowed to freely vary, with a phantom-like equation of state $w=-1.184\pm0.…