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

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Session 8 -- Surveys and Cosmology
Display presentation, Monday, June 12, 1995, 9:20am - 6:30pm

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

Paul W. Bode (MIT), Edmund Bertschinger (MIT)

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 $\Omega_{CDM}$, $\Omega_{\nu}$, and $\Omega_{\Lambda}$), $H_0$, 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 $\Omega_{\nu}$ is increased, the second and third peaks become more pronounced (for $\Omega_{\nu}=0.3$ they are 5--10\% higher than for CDM) and move to slightly smaller $l$. The first peak behaves differently; while for $\Omega_{\nu}=0.1$ the first peak is higher (by $\sim2\%$) than in CDM, for $\Omega_{\nu}=0.3$ 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:\/\/\_software\_archive.html).

Monday program listing