Omega Syndrome

Starring: Doug McClure, spatial curvature

Spatial curvature was completely irrelevant at z>1000, when the acoustic oscillations were created. Omega_k therefore doesn't change the shape of the peaks at all - it merely shifts them sideways, since the conversion from the physical scale of the wiggles (in meters) into the angular scale (in degrees, or multipole l) depends on whether space is curved. If space has negative curvature (positive Omega_k), like a Pringles potato chip or a saddle, then the angle subtended on the sky decreases, shifting the peaks to the right. If space has positive curvature, like a balloon, then the peaks shift to the left.
Meanwhile, you'll see that the galaxy power spectrum shifts both horizontally (in the opposite direction) and vertically. Let's start with the vertical part. Curvature slows the growth of fluctuations and therefore lowers the curve. The horizontal shift wouldn't occur if the horizontal axis had physical distance units on it (meters or Mpc, say). But it uses astronomical distance units (Mpc/h), so changing the Hubble parameter h shifts the curve.
Did somebody say h? Weren't we just changing the curvature? No! Of the 12 parameters shown, only 11 are independent. So when we change the curvature with Lambda and all the matter densities fixed, then the Hubble constant automatically changes too.
Finally,if you've patiently read this far, let's return to the CMB (top) panel. In addition to shifting the peaks sideways, curvature also causes fluctuations in the gravitational field to decrease over time. This means that if a photon flies though a potential well on the way to us, its blueshift from falling in will exceed its redshift from climbing out. Since these extra fluctuations in the photon temperature (known as the late ISW effect) happen at late times, they show up on large scales (to the left in the power spectrum).