Intermittency in large scale structures in the universe

Abstract

I study the weak nonlinear regime of structure formation using high resolution and high signal-to-noise ratio (S/N) samples of Quasi Stellar Objects' (QSOs) Lyα transmission spectra. Using a space-scale decomposition, the Discrete Wavelet Transform (DWT), I show that the field traced by Lyα transmission flux is intermittent on scales less than 2000 km/s. The distribution of the local power of fluctuations is spiky with almost no power between the spikes. This spike-gap-spike feature gets more pronounced on smaller scales (128-16 km/s). This feature contradicts the predictions of the correlation hierarchy model on small scales ( < 64 km/s). Intermittency renders lower order statistics, like the power spectrum of fluctuations, ineffective in describing an intermittent field and discriminating between various structure formation models. I show that the structure functions and the intermittent exponent are not only able to quantitatively differentiate between different dark matter models but also qualitatively describe the nature of non-Gaussianity. The structure functions and the intermittent exponent are powerful tools for describing an intermittent field. Intermittency opens a new window in the study of the nonlinear evolution of structure in the universe.