It is not within the universe that is visible but its surface, just like the Sun is the photosphere of the Sun as … The major topics will be: • Expansion history. This signal in the matter power spec-trum can be used as a “standard ruler” to map out the evolution of the Hubble parameter H(z) and the angular diameter distance DA(z) at redshift z. Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical … Following a series of attempts to explore non-standard recombination [21, 22, 31], Ref. [14] found that phenomenological modi cation to the timing and width of the recombination process can signi cantly reduce the Hubble … If vector type perturbations are present in the primordial plasma before recombination, the generation of magnetic fields is known to be inevitable through the Harrison mechanism. Its value may be determined using a variety of methods. Photons interact to a much lesser degree with neutral matter, and therefore at recombination the universe became transparent to photons, allowing them to decouple from the matter and free-stream through the universe. The first phase change of hydrogen in the universe was recombination, which occurred at a redshift z = 1089 (379,000 years after the Big Bang), due to the cooling of the universe to the point where the rate of recombination of electrons and protons to form neutral hydrogen was higher than the reionization rate. [14] found that phenomenological modi cation to the timing and width of the recombination process can signi cantly reduce the Hubble tension to … Anti-de Sitter (AdS) vacua, being theoretically important, might have an unexpected impact on the observable Universe. Following a series of attempts to explore non-standard recombination [21, 22, 31], Ref. Gen Ye 1and Yun-Song Piao;2y 1 School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China and 2 Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. The figure includes results from distance ladder determinations (labeled HST Key Project, Cepheids+SNIa, Distance Ladder, TRGB Dist Ladder), indirect CMB measurements (WMAP9++, Planck_PR3++, both of which combine CMB with other data), BAO in … Shortly after recombination, the photon mean free path became larger than the Hubble length, and photons traveled freely without interacting with matter. 1 Recombination - Overview This lecture will cover the subject of cosmological recombination. Recombination also marks the time when the universe became transparent as photons can travel long distances before being absorbed or diffused by matter. We compute the cosmic microwave background temperature bispectrum generated by nonlinearities at recombination on all scales. Is the Hubble tension a hint of AdS around recombination? If we define recombination as an ionization fraction X e = 0.1, we have that the temperature at recombination T R = 0.3 eV. Recombination happens quickly (i.e., in much less than a Hubble time t ~ H-1), but is not instantaneous. • Compton heating and the gas temperature. • Hydrogen recombination. Hubble tension for a broad class of models. The universe goes from a completely ionized state to a neutral state over a range of redshifts z ~ 200. The four free parameters include a fraction of a parent DM rest mass transferred to a daughter massless particle (ϵ), a life time of the parent DM (τ), a dark matter abundance today Ω DM and a reduced Hubble parameter h = H 0 /(100 km/sec/Mpc) which are used to infer the parent DM energy density at recombination via ρ DDM (a rec) = Ω DM ρ crit a rec − 3. Box 2735, Beijing 100190, China Anti-de Sitter (AdS) vacua, being theoretically important, might have unexpected impact on the