Accurate Calculations of CMB Anistropies in Cold and Mixed Dark Matter Models

Details Accurate Calculations of CMB Anistropies in Cold and Mixed Dark Matter Models Accurate Calculations of CMB Anistropies in Cold and Mixed Dark Matter Models

May 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995aas...186.0805b&link_type=abstract

American Astronomical Society, 186th AAS Meeting, #08.05; Bulletin of the American Astronomical Society, Vol. 27, p.823

Physics

Scientific paper

The LINGER (Linear General Relativity) code integrates the coupled, linearized, Einstein, Boltzmann, and fluid equations governing the evolution of metric perturbations and the density fluctuations to compute both the CMB anisotropy and the linear power spectrum of matter fluctuations. A portable, parallel implementation (PLINGER) which achieves Gflop rates on current parallel supercomputers is also available. Scalar mode fluctuations only in a flat Robertson-Walker background are assumed; either synchronous or Newtonian gauge can be used. Massive neutrinos and photon polarization are included. We have completed 30 models with a variety of constituents (varying Omega_ {CDM}, Omega_ ν, and Omega_ Λ), H_0, and initial perturbation spectrum (isentropic, isocurvature CDM, or isocurvature baryon). We present the coefficients C_l of the angular power spectrum with errors <0.1% for angular degree l<3000. We believe this is the most accurate treatment to date of both the physics and the numerical integration. This accuracy requires the inclusion of up to 10,000 moments l, and the integration of up to 5000 points in k. A full integration to z=0 is done without using any free-streaming approximation. The inclusion of massive neutrinos leads to larger anisotropies since the potential decays as they steam away from density peaks. The first doppler peak changes less (relative to standard CDM) than later peaks. As Omega_ ν is increased, the second and third peaks become more pronounced (for Omega_ ν=0.3 they are 5--10% higher than for CDM) and move to slightly smaller l. The first peak behaves differently; while for Omega_ ν=0.1 the first peak is higher (by ~ 2%) than in CDM, for Omega_ ν=0.3 it is slightly lower than the first CDM peak. LINGER and PLINGER will be made available through the GC3 (Grand Challenge Cosmology Consortium) Software Archive (http:zeus.ncsa.uiuc.edu:8080/GC3_software_archive.html).

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