arXiv subjects

Giovanni Cabass

Publications and source records attributed to Giovanni Cabass.

41 records · Page 3Linked to original sources

arXiv2016

Running the running

We use the recent observations of Cosmic Microwave Background temperature and polarization anisotropies provided by the Planck satellite experiment to place constraints on the running $α_\mathrm{s} = \mathrm{d}n_{\mathrm{s}} / \mathrm{d}\log k$ and the running of the running $β_{\mathrm{s}} = \mathrm{d}α_{\mathrm{s}} / \mathrm{d}\log k$ of the spectral index $n_{\mathrm{s}}$ of primordial scalar fluctuations. We find $α_\mathrm{s}=0.011\pm0.010$ and $β_\mathrm{s}=0.027\pm0.013$ at $68\%\,\mathrm{CL}$, suggesting the presence of a running of the running at the level of two standard deviations. We find no significant correlation between $β_{\mathrm{s}}$ and foregrounds parameters, with the exception of the point sources amplitude at $143\,\mathrm{GHz}$, $A^{PS}_{143}$, which shifts by half sigma when the running of the running is considered. We further study the cosmological implications of such preference for $α_\mathrm{s},β_\mathrm{s}\sim0.01$ by including in the analysis the lensing amplitude $A_L$, the curvature parameter $Ω_k$, and the sum of neutrino masses $\sum m_ν$. We find that when the running of the running is considered, Planck data are more compatible with the standard expectations of $A_L = 1$ and $Ω_k = 0$ but still hint at possible deviations. The indication for $β_\mathrm{s} > 0$ survives at two standard deviations when external datasets such as BAO and CFHTLenS are included in the analysis, and persists at $\sim 1.7$ standard deviations when CMB lensing is considered. We discuss the possibility of constraining $β_\mathrm{s}$ with current and future measurements of CMB spectral distortions, showing that an experiment like PIXIE could provide strong constraints on $α_\mathrm{s}$ and $β_\mathrm{s}$.

astro-ph.CO↗

arXiv2016

$μ$-Distortions or Running: A Guaranteed Discovery from CMB Spectrometry

We discuss the implications of a PIXIE-like experiment, which would measure $μ$-type spectral distortions of the CMB at a level of $σ_μ=(1/n)\times 10^{-8}$, with $n\geq1$ representing an improved sensitivity (e.g. $n=10$ corresponds to PRISM). Using Planck data and considering the six-parameter $Λ$CDM model, we compute the posterior for $μ_8\equivμ\times 10^{8}$ and find $μ_8=1.57^{+0.11}_{-0.13}$ ($68\%\,\mathrm{CL}$). This becomes $μ_{8} = 1.28^{+0.30}_{-0.52}$ ($68\%\,\mathrm{CL}$) when the running $α_\mathrm{s}$ of the spectral index is included. We point out that a sensitivity of about $3\times$ PIXIE implies a guaranteed discovery: $μ$-distortion is detected or $α_\mathrm{s}\geq 0$ is excluded (both at $95\%\,\mathrm{CL}$ or higher). This threshold sensitivity sets a clear benchmark for CMB spectrometry. For a combined analysis of PIXIE and current Planck data, we discuss the improvement on measurements of the tilt $n_\mathrm{s}$ and the running $α_\mathrm{s}$ and the dependence on the choice of the pivot. A fiducial running of $α_\mathrm{s}=-0.01$ (close to the Planck best-fit) leads to a detection of negative running at $2σ$ for $5\times$ PIXIE. A fiducial running of $α_\mathrm{s}=-0.02$, still compatible with Planck, requires $3\times$ PIXIE to rule out $α_\mathrm{s} = 0$ (at $95\%\,\mathrm{CL}$). We propose a convenient and compact visualization of the improving constraints on the tilt, running and tensor-to-scalar ratio.

astro-ph.CO↗

arXiv2016

Recent results and perspectives on cosmology and fundamental physics from microwave surveys

Recent cosmic microwave background data in temperature and polarization have reached high precision in estimating all the parameters that describe the current so-called standard cosmological model. Recent results about the integrated Sachs-Wolfe effect from cosmic microwave background anisotropies, galaxy surveys, and their cross-correlations are presented. Looking at fine signatures in the cosmic microwave background, such as the lack of power at low multipoles, the primordial power spectrum and the bounds on non-Gaussianities, complemented by galaxy surveys, we discuss inflationary physics and the generation of primordial perturbations in the early Universe. Three important topics in particle physics, the bounds on neutrinos masses and parameters, on thermal axion mass and on the neutron lifetime derived from cosmological data are reviewed, with attention to the comparison with laboratory experiment results. Recent results from cosmic polarization rotation analyses aimed at testing the Einstein equivalence principle are presented. Finally, we discuss the perspectives of next radio facilities for the improvement of the analysis of future cosmic microwave background spectral distortion experiments.

astro-ph.CO↗

arXiv2016

Constraints on the Early and Late Integrated Sachs-Wolfe effects from Planck 2015 Cosmic Microwave Background Anisotropies angular power spectra

The Integrated Sachs-Wolfe (ISW) effect predicts additional anisotropies in the Cosmic Microwave Background due to time variation of the gravitational potential when the expansion of the universe is not matter dominated. The ISW effect is therefore expected in the early universe, due to the presence of relativistic particles at recombination, and in the late universe, when dark energy starts to dominate the expansion. Deviations from the standard picture can be parameterized by $A_{e\text{ISW}}$ and $A_{l\text{ISW}}$, which rescale the overall amplitude of the early and late ISW effects. Analyzing the most recent CMB temperature spectra from the Planck 2015 release, we detect the presence of the early ISW at high significance with $A_{e\mathrm{ISW}} = 1.06\pm0.04$ at 68% CL and an upper limit for the late ISW of $A_{l\mathrm{ISW}} < 1.1$ at 95% CL. The inclusion of the recent polarization data from the Planck experiment results in $A_{e\mathrm{ISW}} = 0.999\pm0.028$ at 68% CL, in better agreement with the value $A_{e\mathrm{ISW}} = 1$ of a standard cosmology. When considering the recent detections of the late ISW coming from correlations between CMB temperature anisotropies and weak lensing, a value of $A_{l\mathrm{ISW}}=0.85\pm0.21$ is predicted at 68% CL, showing a $4σ$ evidence. We discuss the stability of our result in the case of an extra relativistic energy component parametrized by the effective neutrino number $N_\mathrm{eff}$ and of a CMB lensing amplitude $A_\mathrm{L}$.

astro-ph.CO↗

arXiv2016

Updated Constraints and Forecasts on Primordial Tensor Modes

We present new, tight, constraints on the cosmological background of gravitational waves (GWs) using the latest measurements of CMB temperature and polarization anisotropies provided by the Planck, BICEP2 and Keck Array experiments. These constraints are further improved when the GW contribution $N^{\rm GW}_{\rm eff}$ to the effective number of relativistic degrees of freedom $N_{\rm eff}$ is also considered. Parametrizing the tensor spectrum as a power law with tensor-to-scalar ratio $r$, tilt $n_\mathrm{t}$ and pivot $0.01\,\mathrm{Mpc}^{-1}$, and assuming a minimum value of $r=0.001$, we find $r < 0.089$, $n_\mathrm{t} = 1.7^{+2.1}_{-2.0}$ ($95\%\,\mathrm{CL}$, no $N^{\rm GW}_{\rm eff}$) and $r < 0.082$, $n_\mathrm{t} = -0.05^{+0.58}_{-0.87}$ ($95\%\,\mathrm{CL}$, with $N^{\rm GW}_{\rm eff}$). When the recently released $95\,\mathrm{GHz}$ data from Keck Array are added to the analysis, the constraints on $r$ are improved to $r < 0.067$ ($95\%\,\mathrm{CL}$, no $N^{\rm GW}_{\rm eff}$), $r < 0.061$ ($95\%\,\mathrm{CL}$, with $N^{\rm GW}_{\rm eff}$). We discuss the limits coming from direct detection experiments such as LIGO-Virgo, pulsar timing (European Pulsar Timing Array) and CMB spectral distortions (FIRAS). Finally, we show future constraints achievable from a COrE-like mission: if the tensor-to-scalar ratio is of order $10^{-2}$ and the inflationary consistency relation $n_\mathrm{t} = -r/8$ holds, COrE will be able to constrain $n_\mathrm{t}$ with an error of $0.16$ at $95\%\,\mathrm{CL}$. In the case that lensing $B$-modes can be subtracted to $10\%$ of their power, a feasible goal for COrE, these limits will be improved to $0.11$ at $95\%\,\mathrm{CL}$.

astro-ph.CO↗