分类： 天文学 >> 星系和宇宙学 提交时间： 2023-02-21
摘要： In this paper we consider the effects of adding curvature in extended cosmologies involving a free-to-vary neutrino sector and different parametrizations of Dark Energy (DE). We make use of the Planck 2018 cosmic microwave background temperature and polarization data, Baryon Acoustic Oscillations and Pantheon type Ia Supernovae data. Our main result is that a non-flat Universe cannot be discarded in light of the current astronomical data, because we find an indication for a closed Universe in most of the DE cosmologies explored in this work. On the other hand, forcing the Universe to be flat can significantly bias the constraints on the equation of state of the DE component and its dynamical nature.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We study the global agreement between the most recent observations of the Cosmic Microwave Background temperature and polarization anisotropies angular power spectra released by the Atacama Cosmology Telescope and the Planck satellite in various cosmological models that differ by the inclusion of different combinations of additional parameters. By using the Suspiciousness statistic, we show that the global "CMB tension" between the two experiments, quantified at the Gaussian equivalent level of $\sim 2.5\,\sigma$ within the baseline $\Lambda$CDM, is reduced at the level of $1.8\sigma$ when the effective number of relativistic particles ($N_{\rm eff}$) is significantly less than the standard value, while it ranges between $2.3\,\sigma$ and $3.5\,\sigma$ in all the other extended models.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present an updated data-analysis comparison of the most recent observations of the Cosmic Microwave Background temperature anisotropies and polarization angular power spectra released by four different experiments: the Planck satellite on one side, and the Atacama Cosmology Telescope (ACTPol) and the South Pole Telescope (SPT-3G), combined with the WMAP satellite 9-years observation data in order to be "Planck-independent" on the other side. We investigate in a systematic way 8 extended cosmological models that differ from the baseline $\Lambda$CDM case by the inclusion of many different combinations of additional degrees of freedom, with the aim of finding a viable minimal extended model that can bring all the CMB experiments in agreement. Our analysis provides several hints for anomalies in the CMB angular power spectra in tension with the standard cosmological model that persist even in these multi-parameter spaces. This indicates that either significant unaccounted-for systematics in the CMB data are producing biased results or that $\Lambda$CDM is an incorrect/incomplete description of Nature. We conclude that only future independent high-precision CMB temperature and polarization measurements could provide a definitive answer.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present strong model-marginalized limits on mixed hot dark matter scenarios, which consider both thermal neutrinos and thermal QCD axions. A novel aspect of our analyses is the inclusion of small-scale Cosmic Microwave Background (CMB) observations from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT), together with those from the Planck satellite and Baryon Acoustic Oscillation (BAO) data. After marginalizing over a number of well-motivated non-minimal background cosmologies, the tightest $95\%$ CL upper bound we obtain is $0.21$ eV, both for $\sum m_\nu$ and $m_{\rm a}$, from the combination of ACT, Planck and BAO measurements. Restricting the analyses to the standard $\Lambda$CDM picture, we find $\sum m_\nu<0.16$ eV and $m_{\rm a}<0.18$ eV, both at $95\%$ CL. Interestingly, the best background cosmology is never found within the minimal $\Lambda$CDM plus hot relics, regardless of the data sets exploited in the analyses. The combination of Planck with either BAO, SPT or ACT prefers a universe with a non-zero value of the running in the primordial power spectrum with strong evidence. Small-scale CMB probes, both alone and combined with BAO, either prefer, with substantial evidence, non-flat universes (as in the case of SPT) or a model with a time varying dark energy component (as in the case of ACT).
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Inflationary gravitational waves, behaving as additional radiation in the Early Universe, can increase the effective number of relativistic species ($N_{\rm eff}$) by a further correction that depends on the integrated energy-density in gravitational waves over all scales. This effect is typically used to constrain (blue-tilted) models of inflation in light of the bounds resulting from the Big Bang Nucleosynthesis. In this paper, we recompute this contribution, discussing some caveats of the state-of-the-art analyses. Through a parametric investigation, we first demonstrate that the calculation is dominated by the ultraviolet frequencies of the integral and therefore by the behavior of the tensor spectrum on scales corresponding to modes that cross the horizon very close to the end of inflation, when the slow-roll dynamics breaks down and the production of gravitational waves becomes strongly model dependent. Motivated by these results, we realize a theoretical Monte Carlo and, working within the framework of the Effective Field Theory of inflation, we investigate the observable predictions of a very broad class of models. For each model, we solve a system of coupled differential equations whose solution completely specifies the evolution of the spectrum up to the end of inflation. We prove the calculation of $\Delta N_{\rm eff}^{\rm GW}$ to be remarkably model-dependent and therefore conclude that accurate analyses are needed to infer reliable information on the inflationary Universe.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Up-to-date cosmological data analyses have shown that \textit{(a)} a closed universe is preferred by the Planck data at more than $99\%$ CL, and \textit{(b)} interacting scenarios offer a very compelling solution to the Hubble constant tension. In light of these two recent appealing scenarios, we consider here an interacting dark matter-dark energy model with a non-zero spatial curvature component and a freely varying dark energy equation of state in both the quintessential and phantom regimes. When considering Cosmic Microwave Background data only, a phantom and closed universe can perfectly alleviate the Hubble tension, without the necessity of a coupling among the dark sectors. Accounting for other possible cosmological observations compromises the viability of this very attractive scenario as a global solution to current cosmological tensions, either by spoiling its effectiveness concerning the $H_0$ problem, as in the case of Supernovae Ia data, or by introducing a strong disagreement in the preferred value of the spatial curvature, as in the case of Baryon Acoustic Oscillations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Data Release 4 of the Atacama Cosmology Telescope (ACT) shows an agreement with an Harrison-Zel'dovich primordial spectrum ($n_s=1.009 \pm 0.015$), introducing a tension with a significance of $99.3\%$ CL with the results from the Planck satellite. The discrepancy on the value of the scalar spectral index is neither alleviated with the addition of large scale structure information nor with the low multipole polarization data. We discuss possible avenues to alleviate the tension relying on either neglecting polarization measurements from ACT or in extending the inflationary sector of the theory.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In this paper we consider the effects of adding curvature in extended cosmologies involving a free-to-vary neutrino sector and different parametrizations of Dark Energy (DE). We make use of the Planck 2018 cosmic microwave background temperature and polarization data, Baryon Acoustic Oscillations and Pantheon type Ia Supernovae data. Our main result is that a non-flat Universe cannot be discarded in light of the current astronomical data, because we find an indication for a closed Universe in most of the DE cosmologies explored in this work. On the other hand, forcing the Universe to be flat can significantly bias the constraints on the equation of state of the DE component and its dynamical nature.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In this paper we consider the effects of adding curvature in extended cosmologies involving a free-to-vary neutrino sector and different parametrizations of Dark Energy (DE). We make use of the Planck 2018 cosmic microwave background temperature and polarization data, Baryon Acoustic Oscillations and Pantheon type Ia Supernovae data. Our main result is that a non-flat Universe cannot be discarded in light of the current astronomical data, because we find an indication for a closed Universe in most of the DE cosmologies explored in this work. On the other hand, forcing the Universe to be flat can significantly bias the constraints on the equation of state of the DE component and its dynamical nature.
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