Quantum-to-classical transition and imprints of continuous spontaneous
  localization in classical bouncing universes
  The perturbations in the early universe are generated as a result of the
interplay between quantum field theory and gravitation. Since these primordial
perturbations lead to the anisotropies in the cosmic microwave background and
eventually to the inhomogeneities in the Large Scale Structure (LSS), they
provide a unique opportunity to probe issues which are fundamental to our
understanding of quantum physics and gravitation. One such fundamental issue
that remains to be satisfactorily addressed is the transition of the primordial
perturbations from their quantum origins to the LSS which can be characterized
completely in terms of classical quantities. Classical bouncing universes
provide an alternative to the more conventional inflationary paradigm as they
can help overcome the horizon problem in a fashion very similar to inflation.
While the problem of the quantum-to-classical transition of the primordial
perturbations has been investigated extensively in the context of inflation, we
find that there has been a rather limited effort towards studying the issue in
classical bouncing universes. In this work, we analyze certain aspects of this
problem with the example of tensor perturbations produced in classical matter
and near-matter bouncing universes. We investigate the issue mainly from two
perspectives. Firstly, we approach the problem by examining the extent of
squeezing of a quantum state associated with the tensor perturbations with the
help of the Wigner function. Secondly, we analyze the issue from the
perspective of the quantum measurement problem. In particular, we study the
effects of wave function collapse, using a phenomenological model known as
continuous spontaneous localization, on the tensor power spectra. We conclude
with a discussion of results.
