Root-mean-square (rms) fluctuations as a function of the smoothing mass M. The RMS σ_L of the linear power spectrum (calculated by CAMB) are dotted lines. The RMS σ_NL of the nonlinear power spectrum (calculated from z = 0 snapshots of DEUS simulations) are in solid lines. σ_NL(M) behaves essentially as a power law whose slope and intercept depend on the cosmology. The inner panel contains the corresponding linear and nonlinear power spectra, P_L and P_NL. At high mass (or low k), the linear and nonlinear rms fluctuations (as well as the power spectra) are superimposed, as expected.