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The recent detection of the primordial gravitational waves from the BICEP2observation seems to be in tension with the upper bound on the amplitude oftensor perturbations from the PLANCK data. We consider a phenomenological modelof inflation in which the microscopical properties of the inflationary fluidsuch as the equation of state $w$ or the sound speed $c_s$ jump in a sharpmanner. We show that the amplitude of the scalar perturbations is controlled bya non-trivial combination of $w$ and $c_s$ before and after the phasetransition while the tensor perturbations remains nearly intact. With anappropriate choice of the fluid parameters $w$ and $c_s$ one can suppress thescalar perturbation power spectrum on large scales to accommodate a largetensor amplitude with $r=0.2$ as observed by BICEP2 observation.

Jump in fluid properties of inflationary universe to reconcile scalar and tensor spectra