Welcome to CMBverse
Explore the fascinating world of cosmological parameters and their impact on the Cosmic Microwave Background (CMB)! On this website, you can interact with the 6 different parameters of \( \Lambda\rm{CDM} \) and explore their effects on the CMB. \( \Lambda\rm{CDM} \) is the standard cosmological model that describes the large-scale structure and evolution of the universe, integrating the cosmological constant \( \Lambda\) and cold dark matter (CDM) while assuming a flat universe that is isotropic and homogenous on large scales.
Specifically, \( \Lambda\rm{CDM} \) includes six key cosmological parameters. Two of these parameters provide information on the initial conditions of the universe: the scalar amplitude (\(10^{9}A_{s}\)) and the scalar spectral index (\(n_{s}\)). Three of these parameters describe the physical content of the universe: the physical baryon density (\(100\omega_{b}\)), the physical matter density (\(100\omega_{m}\)), and the dark energy density (\(\Omega_{\Lambda}\)). Finally, the last parameter, optical depth (\(\tau\)), informs us on the opacity of the universe after recombination, providing information on a later period called reionization.
With these 6 parameters, we can numerically solve for the evolution of cosmological perturbations, and hence determine the corresponding CMB power spectrum. By comparing this output with observational data, we can find the best fit for the six parameters, whose values are provided below. This observational data is provided by the Planck Satellite, Atacama Cosmology Telescope, and South Pole Telescope.
\[ \begin{array}{|c|c|c|} \hline \text{Parameter} & \text{Definition} & \text{Value} \\ \hline 10^{9}A_{s} & \text{scalar amplitude} & 3.047 \pm 0.014 \\ n_{s} & \text{scalar spectral index} & 0.9665 \pm 0.0038 \\ 100\omega_{b} & \text{physical baryon density} & 2.242 \pm 0.014 \\ 100\omega_{m} & \text{physical matter density} & 14.24 \pm 0.087 \\ \Omega_{\Lambda} & \text{dark energy density} & 0.6889 \pm 0.0056 \\ \tau & \text{optical depth} & 0.0561 \pm 0.0071 \\ \hline \end{array} \]
