1989/05/01 by Craig J. Hogan · 1 citation
Physics and Astronomy · Earth and Planetary Sciences · #Cosmology and Gravitation Theories #Solar and Space Plasma Dynamics #Geophysics and Gravity Measurements #Physics #Instability #Gravitational instability #Structure formation #Astrophysics #Opacity #Cosmic ray #Computational physics #Mechanics #Galaxy #Optics
paper · doi:10.1086/167371
openalex publication_date 1989/05/01 · openalex created_date 2025/10/10 · openalex updated_date 2025/11/06
The process of generating large-scale cosmic structure from the radiation-pressure or "mock gravity" instability is studied with particular emphasis on the implications of the Berkeley-Nagoya rocket data for the sub-millimeter background (SMB). The linear theory of perturbations in an absorbing medium embedded in an expanding universe of radiation sources is presented, including the effect of an inhomogeneous luminosity density or opacity. The instability sets up collapse velocities in linear perturbation theory which far exceed those from gravitational instability, so growth continues even after the instability switches off. Perturbation growth due to this "coasting effect" is analyzed and related to the growth of large-scale cosmic structures at recent times; large-scale structure is shown to evolve very little from 1 + z ~ 5 to the present. Nonlinear small-scale effects of the instability are analyzed; it is shown that radiation pressure would compress gas into small, dense pressure-confined clouds with τ >> 1, which leads to a substantial atomic continuum opacity and consequently a stronger linear instability. However, the range of the instability is limited by optical depth; it only operates on large scales (2π/k1_ ~ 40h-1^50_ Mpc) if the gas density is low (OMEGAg_ <~ 10-2^). A nonlinear self-similar bubble "attractor" solution is described which grows to a comoving diameter of more than 40hs-1^50_ Mpc for a wide range of initial conditions and can in principle reach a maximum diameter of 180h-1^50_ Mpc by the present epoch. Linear theory is used to estimate anisotropy in background radiation. Doppler scattering typically produces anisotropy comparable to current 1.5 cm limits on arcminute scales. A search for subarcminute fluctuations in the SMB at short wavelengths (~ 1 mm) should reveal fluctuations of much larger amplitude, δT/T ~ 10-3^, due to dust optical depth fluctuations.