Scale-dependent rigidity of polymer-ornamented membranes

We study the fluctuation spectrum of fluid membranes carrying grafted polymers. Contrary to usual descriptions, we find that the modifications induced by the polymers cannot be reduced to the renormalization of the membrane bending rigidity. Instead we show that the ornamented membrane exhibits a scale-dependent elastic modulus that we evaluate. In ornamented lamellar stacks, we further show that this leads to a modification of the Caille parameter characterizing the power-law singularities of the Bragg peaks.