2014/01/27 by V. Balek, Balek, Vladimír, Matej Škovran +1 · 1 citation
Physics and Astronomy · Earth and Planetary Sciences · #Cosmology and Gravitation Theories #Geophysics and Gravity Measurements #Solar and Space Plasma Dynamics
paper · pdf · doi:10.48550/arxiv.1401.7004
Evolution of scalar perturbations in a universe containing solid matter with\npositive pressure is studied. Solution for pure solid is found and matched with\nsolution for ideal fluid, including the case when the pressure to energy\ndensity ratio w has a jump. Two classes of solutions are explored in detail,\nsolutions with radiation-like solid (w = 1/3) and solutions with stiff solid\n(w > 1/3) appearing in a universe filled with radiation. For radiation-like\nsolid, an almost flat spectrum of large-scale perturbations is obtained only if\nthe shear stress to energy density ratio \ξ is close to zero, |\ξ|\n lesssim 10-5. For a solid with stiff equation of state, large-scale\nperturbations are enhanced for \ξ negative and suppressed for \ξ\npositive. If the solid dominated the dynamics of the universe long enough,\nperturbations could end up suppressed as much as by several orders of\nmagnitude, and in order that the inclination of the large-scale spectrum is\nconsistent with observations, radiation must have prevailed over the solid long\nenough before recombination. In Newtonian gauge, corrections to metric and\nenergy density are typically much greater than 1 in the first period after the\nshear stress appears, but the linearized theory is still applicable because the\ncorrections stay small when one uses the proper-time comoving gauge.\n