Quantum discord of cosmic inflation: Can we show that CMB anisotropies are of quantummechanical origin?
Abstract
We investigate the quantumness of primordial cosmological fluctuations and its detectability. The quantum discord of inflationary perturbations is calculated for an arbitrary splitting of the system, and shown to be very large on superHubble scales. This entails the presence of large quantum correlations, due to the entangled production of particles with opposite momentums during inflation. To determine how this is reflected at the observational level, we study whether quantum correlators can be reproduced by a nondiscordant state, i.e. a state with vanishing discord that contains classical correlations only. We demonstrate that this can be done for the power spectrum, the price to pay being twofold: first, large errors in other twopoint correlation functions that cannot however be detected since they are hidden in the decaying mode; second, the presence of intrinsic nonGaussianity, the detectability of which remains to be determined but which could possibly rule out a nondiscordant description of the cosmic microwave background. If one abandons the idea that perturbations should be modeled by quantum mechanics and wants to use a classical stochastic formalism instead, we show that any twopoint correlators on superHubble scales can be exactly reproduced regardless of the squeezing of the system. The latter becomes important only for higher order correlation functions that can be accurately reproduced only in the strong squeezing regime.
 Publication:

Physical Review D
 Pub Date:
 January 2016
 DOI:
 10.1103/PhysRevD.93.023505
 arXiv:
 arXiv:1510.04038
 Bibcode:
 2016PhRvD..93b3505M
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology;
 High Energy Physics  Theory;
 Quantum Physics
 EPrint:
 typos in section II fixed