Quantum to classical transition from the cosmic background radiation

We have revisited the Ghirardi-Rimini-Weber-Pearle (GRWP) approach for continuous dynamical evolution of the state vector for a macroscopic object. Our main concern is to recover the decoupling of the state vector dynamics for the center-of-mass (CM) and internal motion, as in the GRWP model, but within the framework of the standard cosmology. In this connection we have taken the opposite direction of the GRWP argument that the cosmic background radiation (CBR) has originated from a fundamental stochastic hitting process. We assume the CBR to be a clue of the Big Bang, playing a main role in the decoupling of the state vector dynamics of the CM and internal motion. In our model, instead of describing a continuous spontaneous localization (CSL) of a system of massive particles as proposed by Ghirardi, Pearle, and Rimini [Phys. Rev. A 42, 78 (1990)] the Ito stochastic equation accounts for the intervention of the CBR on the system of particles. Essentially, this approach leads to a precursor of the master equation for both the CBR and particle degrees of freedom. The violation of the principle of energy conservation characteristic of the CSL model is avoided as well as the additional assumption on the size of the GRWP’s localization width necessary to reach the decoupling between the collective and internal motions. Moreover, realistic estimation for the decoherence time, exhibiting an interesting dependence on the CBR temperature, is obtained. From the formula for the decoherence time it is possible to analyze the transition from micro- to macrodynamics in both the early hot universe and the nowadays cold one. The entropy of the system under decoherence is analyzed and the emergent “pointer basis” is discussed. In spite of not having imposed a privileged basis, in our model the position still emerges as the preferred observable as in the CSL model.