title: Reheating the universe once more: the dissipation of acoustic waves as a novel probe of primordial inhomogeneities on even smaller scales.
abstract: We provide a simple but robust bound on the primordial curvature perturbation in the range 10(4)  Mpc(-1)<k<10(5)  Mpc(-1), which has not been constrained so far unlike low-wave-number modes. Perturbations on these scales dissipate the energy of their acoustic oscillations by the Silk damping after primordial nucleosynthesis but before the redshift z∼2×10(6) and reheat the photon bath without invoking cosmic microwave background distortions. This acoustic reheating results in the decrease of the baryon-photon ratio. By combining independent measurements probing the nucleosynthesis era and around the recombination epoch, we find an upper bound on the amplitude of the curvature perturbation over the above wave number range as P(ζ)<0.06. Implications for supermassive black holes are also discussed.
authors.affiliation: Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan and Research Center for the Early Universe (RESCEU), Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Nakama
authors.affiliation: Research Center for the Early Universe (RESCEU), Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Teruaki
authors.initials: T
authors.lastname: Suyama
authors.affiliation: Research Center for the Early Universe (RESCEU), Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan and Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), WPI, TODIAS, The University of Tokyo, Kashiwa, Chiba 277-8568, Japan.
authors.forename: Jun'ichi
authors.initials: J
authors.lastname: Yokoyama