Figures 10-12

Figure 10

Baryon drag in the inflationary model. Baryon drag enhances the compressional, here odd, acoustic peaks. (a) Although diffusion damping at small scales coupled with the intrinsically small baryon drag effect in low $\Omega_b h^2$ models hides the effect, the third peak is clearly anomalously high in all but the most extreme case $\Omega_b h^2 =0.0025$ which is in clear violation of BBN constraints. (b) Lowering $\Omega_0 h^2$ also reduces the effect by reducing the potential fluctuation $\Psi$.{Baryon drag in the inflationary model. Baryon drag enhances the compressional, here odd, acoustic peaks. (a) Although diffusion damping at small scales coupled with the intrinsically small baryon drag effect in low $\Omega_b h^2$ models hides the effect, the third peak is clearly anomalously high in all but the most extreme case $\Omega_b h^2 =0.0025$ which is in clear violation of BBN constraints. (b) Lowering $\Omega_0 h^2$ also reduces the effect by reducing the potential fluctuation $\Psi$.

Figure 11

Standard rulers and the angular diameter distance. Acoustic features in the CMB, in particular the peak locations and the damping tail, act as standard rulers with which a measurement of the curvature can be made. Thin solid lines represent the $\Omega_0=1$, $\Lambda=0$ calculation scaled in $\ell$ to account for the projection in the $\Omega_0=0.1$ open and $\Lambda$ models.

Figure 12

Peak spacing and damping scale as a function of $\Omega_0$. Even allowing for uncertainties in the baryon content (solid shading, $h=0.5$) and Hubble constant (dashed shading, $\Omega_bh^2 = 0.0125$), open models with $\Omega_0 \simlt 0.5$ can be distinguished from flat ($\Omega_0 + \Omega_\Lambda = 1$) $\Lambda$ models through either scale. The damping scale is entirely independent of the model for the fluctuations but may be more difficult to measure than the peak spacing.