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A recent paper by Kumar (2012) (hereafter K12) claimed that in a contractingmodel, described by perturbations around a collapsing Friedmann modelcontaining dust or radiation, the perturbations can grow in such a way that thelinearity conditions would become invalid. This conclusion is not correct dueto the following facts: first, it is claimed that the linearity conditions arenot satisfied, but nowhere in K12 the amplitudes of the perturbations were infact estimated. Therefore, without such estimates, the only possible conclusionfrom this work is the well known fact that the perturbations indeed grow duringcontraction, which, per se, does not imply that the linearity conditions becomeinvalid. Second, some evaluations of the linearity conditions are incorrectbecause third other terms, instead of the appropriate second order ones, aremistakenly compared with first order terms, yielding artificially fast growingconditions. Finally, it is claimed that the results of K12 are in sharpcontrast with the results of the paper by Vitenti and Pinto-Neto (2012)(hereafter VPN12), because the former was obtained in a gauge invariant way.However, the author of K12 did not realized that the evolution of theperturbations were also calculated in a gauge invariant way in VPN12, but someof the linearity conditions which are necessary to be checked cannot beexpressed in terms of gauge invariant quantities. In the present work, theincorrect or incomplete statements of K12 are clarified and completed, and itis shown that all other correct results of K12 were already present in VPN12,whose conclusions remain untouched, namely, that cosmological perturbations ofquantum mechanical origin in a bouncing model can remain in the linear regimeall along the contracting phase and at the bounce itself for a wide interval ofenergy scales of the bounce. (Abstract abridged)

Comments on "Growth of Covariant Perturbations in the Contracting Phase of a Bouncing Universe" by A. Kumar