Baryon 5

Starring: Captain John Sheridan, Commander Susan Ivanova, baryon density

This movie keeps the total matter density constant, but increases the fraction of ordinary matter, baryons (see the two dials shift in sync). Density oscillations caused by the competition between pressure and gravity in the early Universe give rise to wiggles "acoustic peaks") in both the CMB and galaxy power spectra - the more baryons, roughly speaking. Hower, it's actually mainly the odd-numbered peaks (1, 3, etc) that get boosted, which helps distinguish baryons from cold dark matter. Indeed, you can see that the 2nd peak actually shrinks for a while. This is why the Boomerang and Maxima measurements prefer lots of baryons - they don't see much of a 2nd peak. For more details on the baryon effect, see Wayne's CMB tutorial. Note that both the CMB and galaxy fluctuations are unaffected on the largest (leftmost) scales. Moreover, note that the galaxy power spectrum doesn't merely get wigglier, but gets suppressed as well.