Constraining Fundamental Physics with Future CMB Experiments

TL;DR

The paper addresses how future CMB experiments can constrain beyond-ΛCDM physics by forecasting parameter sensitivities using synthetic Planck, ACTPol, and CMBPol data. It employs CAMB to compute spectra, includes lensing via the Hu–Okamoto estimator, and analyzes a nine-parameter model with extensions for $p_{ann}$, $\alpha/\alpha_0$, and $\lambda_G$, up to $\ell_{max}=2500$. Key findings show Planck+ACTPol improving Planck's constraints by about a factor of $1.5$ and CMBPol delivering roughly a $4\times$ improvement on core parameters, with the ability to probe $\sum m_\nu$ down to $<0.08$ eV (Planck+ACTPol) and $<0.05$ eV (CMBPol), tighten $N_{eff}$ to $\sigma(N_{eff})\approx0.044$ (CMBPol), and place strong bounds on $p_{ann}$, $Y_p$, $w$, and variations in $\alpha$ and $G$. These results highlight the complementary value of small-scale CMB data for testing particle physics and fundamental physics with cosmology. The work also underscores the importance of improved recombination modeling and foreground control for realizing these potential gains.

Abstract

The Planck experiment will soon provide a very accurate measurement of Cosmic Microwave Background anisotropies. This will let cosmologists determine most of the cosmological parameters with unprecedented accuracy. Future experiments will improve and complement the Planck data with better angular resolution and better polarization sensitivity. This unexplored region of the CMB power spectrum contains information on many parameters of interest, including neutrino mass, the number of relativistic particles at recombination, the primordial Helium abundance and the injection of additional ionizing photons by dark matter self-annihilation. We review the imprint of each parameter on the CMB and forecast the constraints achievable by future experiments by performing a Monte Carlo analysis on synthetic realizations of simulated data. We find that next generation satellite missions such as CMBPol could provide valuable constraints with a precision close to that expected in current and near future laboratory experiments. Finally, we discuss the implications of this intersection between cosmology and fundamental physics.

Figures (14)

• Figure 1: 68% and 95% likelihood contour plots on the $\sum m_\nu$ - $\omega_c$ plane for Planck (blue), Planck+ACTPol (red) and CMBPol (green).
• Figure 2: 68% and 95% likelihood contour plots on the $\sum m_\nu$ - $n_s$ plane for Planck (blue), Planck+ACTPol (red) and CMBPol (green).
• Figure 3: 68% and 95% likelihood contour plots on the $N_{eff}$ - $n_s$ plane for Planck (blue), Planck+ACTPol (red) and CMBPol (green).
• Figure 4: 68% and 95% likelihood contour plots on the $N_{eff}$ - $\omega_b$ plane for Planck (blue), Planck+ACTPol (red) and CMBPol (green).
• Figure 5: 68% and 95% likelihood contour plots on the $N_{eff}$ - $\omega_c$ plane for Planck (blue), Planck+ACTPol (red) and CMBPol (green).