K-Bounce

By demanding that a bounce is nonsingular and that perturbations are well-behaved at all times, we narrow the scope of possible models with one degree of freedom that can describe a bounce in the absence of spatial curvature. We compute the general properties of the transfer matrix of perturbations through the bounce, and show that spectral distortions of the Bardeen potential $\mathrm{\Phi }$ are generically produced only for the small wavelengths, although the spectrum of long wavelength curvature perturbations produced in a contracting phase gets propagated unaffected through such a bounce.