FirstPeriodProjectB4 - TransRegio

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Exploring the dark universe with the cosmic microwave background

Different models for the Dark Energy influence the CMB in several ways. All of them change the angular-diameter distance to the CMB and thus shift its angular power spectrum. Dynamical dark energy enhances the integrated Sachs-Wolfe effect and thus the CMB fluctuations on large angular scales.

Current constraints on Dark Energy from CMB fluctuations yield an equation-of-state parameter w_0\lesssim-0.75 today, and an upper bound on the abundance of dark energy at the time of recombination of \Omega_\mathrm{early}\sim8\%. More importantly, however, models in which the Dark Energy has a non-negligible density at early times strongly affect the non-linear structure growth and predict several substantial effects on CMB observations. If normalised to the observed CMB power spectrum, such models have of order ten times more galaxy clusters at redshift \sim1 which will be detectable for CMB experiments through their thermal Sunyaev-Zel'dovich effect. Similarly, they predict earlier formation of ionising sources such as massive stars and active galactic nuclei, thus earlier cosmic reionisation and potentially measurable effects on the cosmic polarisation. Finally, galaxies form earlier and produce a point-source signal different from that expected in the standard, low-density, spatially-flat CDM model with cosmological constant.

Within this Teilprojekt, the impact of Early Dark Energy on the appearance of the CMB will be investigated, focusing on the CMB power spectrum, thermal-SZ cluster counts, their redshift distribution and auto-correlation, the the onset, history, and spatial morphology of reionisation and its impact on CMB polarisation, and, time permitting, the expected counts and correlation properties of high-redshift galaxies.
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