Speaker
Description
Admitting the inflationary scenario in the primordial universe, the cosmological structure today originated from quantum fluctuations during cosmic inflation. Since the dynamics of curvature perturbations after inflation is well described by classical equations of motion, there should have been a quantum-to-classical transition in the history of the universe. This classicalization process has been mainly discussed through decoherence of the cosmological perturbations due to the limitation in observable degrees of freedom. However, the decoherence may not be sufficient to completely explain the classicalization. We would like to sharpen the discussion based on quantum Darwinism. This formulation demonstrates the "measurement" process of the cosmological perturbations by radiations and matters, resulting in branch structure of the universe and an effective coherent state of cosmological perturbations.