CMB Constraints on a Stochastic Background of Primordial Magnetic Fields

We constrain a stochastic background of primordial magnetic field (PMF) by its contribution to the angular power spectrum of cosmic microwave background anisotropies. We parametrize such stochastic background by a power-law spectrum with index $n_B$ and by its Gaussian smoothed amplitude $B_\lambda$ on a comoving length $\lambda$. We give an approximation for the spectra of the relevant correlators of the energy-momentum of the stochastic background of PMF for any $n_B$. By using the WMAP 7 year data in combination with ACBAR, BICEP and QUAD we obtain the constraint $B_{1 {\rm Mpc}} < 5.0$ nG at 95% confidence level for a stochastic background of non-helical PMF. We discuss the relative importance of the scalar and vector contribution to CMB anisotropies in obtaining these constraints. We then forecast {\sc Planck} capabilities in constraining $B_{1 {\rm Mpc}}$.Comment: 13 pages, 7 figures, 3 tables. Revised version accepted for publication in Phys. Rev. D, conclusions unchange

Small Scale CMB Anisotropies with Planck: Constraints on Primordial Magnetic Fields and the Impact of Foreground/Secondary Anisotropy Residuals

The main subject of the thesis is the study of small sale Cosmic Microwave Background (CMB) radiation anisotropies. In particular two topics are investigated. The first concerns the study of the impact of a stochastic background of primordial magnetic felds (PMF) on CMB anisotropies intemperature and polarization and the derivation of the constraints on PMF with CMB data; the second topic concerns the study of the impact of small scale foreground and secondary anisotropy residuals on cosmological parameters extracted with CMB data in the contest of the Planck mission. The first part of the thesis is devoted to the investigation of all the types of perturbations induced by PMF: scalar, vector and tensor. We present the cosmological perturbation evolution equations with PMF contributions and the original results we obtained for magnetized initial conditions and for the analytical Fourier spectra of the PMF energy momentum tensor relevant components. In order to investigate the impact of magnetized perturbations on CMB anisotropies, it has been developed an extension of the public Einstein-Boltzmann code CAMB, which computes the angular power spectrum for CMB anisotropies, where all the PMF contributions have been included. The results show that the dominant PMF contribution is given by vector perturbations on small angular scales where primary CMB is suppressed by the Silk damping. In order to derive the constraints on PMF with CMB data we have developed an extension of the Markov Chain Monte Carlo public code CosmoMC, this extension is connected with the modified version of CAMB and includes PMF parameters together with the standard ones. We show the constraints we obtained with current CMB data and the forecasts we made for Planck and the satellite COrE proposal. The results show that with current data of WMAP7, ACBAR, QUaD and BICEP the PMF amplitude is constrained to less than few nGauss, with Planck the constraints are improved by a factor two and with a mission like COrE it would be possible to constrain PMF amplitude to less than nGauss. In the thesis it is investigated also the non-Gaussian contribution of PMF to CMB anisotropies. In particular, a stochastic background of PMF has a fully non-Gaussian contribution to CMB anisotropies and induce a non-zero bispectrum. We have derived the CMB magnetized bispectrum generated by scalar magnetized perturbations on large angular scales and we have derived the constraints on PMF with current non-Gaussianity data, we show that these constraints are comparable to the ones derived with CMB angular power spectrum data. The second part of the thesis is devoted to the investigation of the im¬pact of foreground and secondary anisotropy residuals on small scales on the cosmological parameters with Planck data. In particular the contributions which are relevant for Planck frequencies and capabilities are: the residual point source contributions and the residual Sunyaev Zeldovcih effect. For what concerns the point source contribution we have considered both the Poissonian term for all unresolved sources and the clustering term for the infrared galaxies. In order to marginalize over the residual contributions in cosmological parameters extraction, we have developed hybrid theoretical/empirical parametrizations for each residual considered. Together with the spectral shape of the sig¬nals it is parametrized also their frequency dependence, this allowed the reductio n of the number of parameters necessary to describe the residuals to the minimum of three, one for each contribution. We have developed an extension of the CAMB+CosmoMC code which includes the marginalization over the considered residual contributions with the approach we have presented. The code is used to investigate the impact of the foreground and secondary anisotropy residuals on the cosmological parameters and in particular, the results show the importance of the marginalization in order to not introduce biases. In the thesis it is addressed also the topic of the frequency channel combination. In particular, we have developed an original empirical method to combine the frequency channels. We show the comparison between the results obtained with this technique and the ones obtained with the standard inverse noise variance weighting method

CMB and BAO constraints for an induced gravity dark energy model with a quartic potential

We study the predictions for structure formation in an induced gravity dark energy model with a quartic potential. By developing a dedicated Einstein-Boltzmann code, we study self-consistently the dynamics of homogeneous cosmology and of linear perturbations without using any parametrization. By evolving linear perturbations with initial conditions in the radiation era, we accurately recover the quasi-static analytic approximation in the matter dominated era. We use Planck 2013 data and a compilation of baryonic acoustic oscillation (BAO) data to constrain the coupling $\gamma$ to the Ricci curvature and the other cosmological parameters. By connecting the gravitational constant in the Einstein equation to the one measured in a Cavendish-like experiment, we find $\gamma < 0.0012$ at 95% CL with Planck 2013 and BAO data. This is the tightest cosmological constraint on $\gamma$ and on the corresponding derived post-Newtonian parameters. Because of a degeneracy between $\gamma$ and the Hubble constant $H_0$, we show how larger values for $\gamma$ are allowed, but not preferred at a significant statistical level, when local measurements of $H_0$ are combined in the analysis with Planck 2013 data.Comment: 13 pages, 7 figure

Cosmological constraints on induced gravity dark energy models

We study induced gravity dark energy models coupled with a simple monomial potential $\propto \sigma^n$ and a positive exponent $n$. These simple potentials lead to viable dark energy models with a weak dependence on the exponent, which characterizes the accelerated expansion of the cosmological model in the asymptotic attractor, when ordinary matter becomes negligible. We use recent cosmological data to constrain the coupling $\gamma$ to the Ricci curvature, under the assumptions that the scalar field starts at rest deep in the radiation era and that the gravitational constant in the Einstein equations is compatible with the one measured in a Cavendish-like experiment. By using $Planck$ 2015 data only, we obtain the 95 % CL bound $\gamma < 0.0017$ for $n=4$, which is further tightened to $\gamma < 0.00075$ by adding Baryonic Acoustic Oscillations (BAO) data. This latter bound improves by $\sim 30$ % the limit obtained with the $Planck$ 2013 data and the same compilation of BAO data. We discuss the dependence of the $\gamma$ and $\dot G_N/G_N (z=0)$ on $n$.Comment: 16 pages, 10 figure

Constraints on primordial magnetic fields from magnetically-induced perturbations: current status and future perspectives with LiteBIRD and future ground based experiments

We present the constraints on the amplitude of magnetic fields generated prior to the recombination using CMB temperature and polarization anisotropy data from Planck 2018 release, alone and in combination with those from BICEP2/Keck array and the South Pole Telescope. We model the fields with a generic parametrization and we make no assumptions on their origin in order to provide general constraints on their characteristics. The analysis updates the former corresponding Planck 2015 results both on data and numerical implementation. We then perform forecasts for the next generation of CMB experiments such as LiteBIRD satellite alone and in combination with future ground based experiments.Comment: 26 pages, 9 figure

On the ISW-cluster cross-correlation in future surveys

We investigate the cosmological information contained in the cross-correlation between the Integrated Sachs-Wolfe (ISW) of the Cosmic Microwave Background (CMB) anisotropy pattern and galaxy clusters from future wide surveys. Future surveys will provide cluster catalogues with a number of objects comparable with galaxy catalogues currently used for the detection of the ISW signal by cross-correlation with the CMB anisotropy pattern. By computing the angular power spectra of clusters and the corresponding cross-correlation with CMB, we perform a signal-to-noise ratio (SNR) analysis for the ISW detection as expected from the eROSITA and the Euclid space missions. We discuss the dependence of the SNR of the ISW-cluster cross-correlation on the specifications of the catalogues and on the reference cosmology. We forecast that the SNRs for ISW-cluster cross-correlation are alightly smaller compared to those which can be obtained from future galaxy surveys but the signal is expected to be detected at high significance, i.e. more than $> 3\,\sigma$. We also forecast the joint constraints on parameters of model extensions of the concordance $\Lambda$CDM cosmology by combining CMB and the ISW-cluster cross-correlation.Comment: 12 pages, 10 figures. Matches version accepted in MNRA

CMB anisotropies generated by a stochastic background of primordial magnetic fields with non-zero helicity

We consider the impact of a stochastic background of primordial magnetic fields with non-vanishing helicity on CMB anisotropies in temperature and polarization. We compute the exact expressions for the scalar, vector and tensor part of the energy-momentum tensor including the helical contribution, by assuming a power-law dependence for the spectra and a comoving cutoff which mimics the damping due to viscosity. We also compute the parity-odd correlator between the helical and non-helical contribution which generate the TB and EB cross-correlation in the CMB pattern. We finally show the impact of including the helical term on the power spectra of CMB anisotropies up to multipoles with ell ~ O(10^3)$.Comment: 25 pages, 30 figure