Figures 4-6


Figure 4

Baryon fluctuation time evolution. The baryon density fluctuation $\delta_b$ follows the photons before the drag epoch $a_d$ yielding a simple oscillatory form for $a_H \ll a \ll a_d$. The Silk damping length is given by the diffusion length at the drag epoch. The portion of the baryon fluctuations that enter the growing mode is dominated by the velocity perturbation at the drag epoch $a_d$ due to the velocity overshoot effect (see also \Figno\velov). Since a flat $\Lambda$ model is chosen here, the growth rate is slowed by the rapid expansion for $a \simgt a_\Lambda = (\Omega_0/\Omega_\Lambda)^{1/3}$.

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Figure 5

Matter transfer function. The analytic estimates of the intrinsic acoustic amplitude is a good approximation for $k \gg k_{eq}$. The Silk damping scale is adequately approximated although its value is underestimated by $\sim 10\%$. For isocurvature BDM and adiabatic CDM, the acoustic contributions do not dominate the small scale fluctuations. We have added in the contributions from the initial entropy fluctuations and the cold dark matter potentials according to the analytic treatment of Appendix E.

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Figure 6
CDM and matter fluctuation time evolution. The cold dark matter fluctuations are constant outside the horizon scale and experience a boost into a logarithmically growing mode at horizon crossing in the radiation dominated epoch. Between equality and the drag epoch, the presence of baryons suppress the growth rate of CDM fluctuations [see eqn.~(7)]. By lowering $\Omega_0 h^2$, this region of suppression can be reduced for fixed $\Omega_b/\Omega_0$, {\it cf.} (a) and (b). After the drag epoch, we plot $\delta_m = (\delta_b\rho_b + \delta_c\rho_c)/(\rho_b+\rho_c)$ rather than $\delta_c$ since the two components thereafter contribute similarly to the total growth. Baryons also lower the contribution of $\delta_c$ to $\delta_m$ at the drag epoch.

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