  We analyze minimally coupled massless scalar field in a Friedmann (FRW)
universe in conformal co-ordinates to model the evolution of tensor
perturbations and study the structure of the Wightman function therein. Using a
duality map from a power law FRW universe to the de Sitter universe for such
fields we obtain unequal time commutation relations between quantum field
variables. We demonstrate that the commutation relations are invariant under
state change and/or vacuum state selection. Using such commutators it is then
possible to construct out of time ordered commutators (OTOC) in the FRW
universes. The OTOCs are supposed to suggest the onset of chaotic behavior
during the quantum evolution, we see that in case of Friedmann universes,
unlike the scalar perturbations, the causal structure arrests the growth of
quantum tensor perturbations for all the relevant epochs of the universe e.g.
the de Sitter phase, the radiation dominated and the matter dominated era.
Therefore the semi classical results of having a large backreaction and
omnipresent noise in certain branches of the Friedmann universes with massless
fields such as the tensor perturbations remain robust and stable.
