Inferring the linear power spectrum from the Lyα forest

We discuss the determination of the linear power spectrum of dark matter fluctuations from measurements of the transmitted flux Lyalpha forest power spectrum. We show that on most scales probed by current measurements, the flux power spectrum is significantly affected by nonlinear corrections to the linear dark matter power spectrum due to gravitational clustering. Inferring the linear dark matter power spectrum shape is therefore difficult due to nonlinear corrections driving the nonlinear power spectrum to a k(-1.4) shape nearly independent of initial conditions. We argue that some methods used in previous estimates underestimate the uncertainties in the shape of the linear dark matter power spectrum.