Search Results (2 total)

We perform a discrete wavelet analysis of the Cosmic Background Explorer differential microwave radiometer (DMR) 4-yr sky maps and find a significant scale-scale correlation on angular scales from about 11° to 22°, only in the DMR face centered on the north galactic pole. This non-Gaussian signature does not arise either from the known foregrounds or the correlated noise maps, nor is it consistent with upper limits on the residual systematic errors in the DMR maps. Either the scale-scale correlations are caused by an unknown foreground contaminate or systematic errors on angular scales as large as 22°, or the standard inflation plus cold dark matter paradigm is ruled out at the >99% confidence level.

A method for measuring the spectrum of a density field by the discrete wavelet transform (DWT) is studied. We show how the Fourier power spectrum can be detected by using the wavelet function coefficients (WFC) of the DWT. This method can successfully measure the power spectrum in samples for which traditional methods often fail because the samples are finite sized, have a complex geometry, or are varyingly sampled. We demonstrate that the spectrum features, such as the power law index, the magnitude, and the typical scales can be determined by the DWT reconstructed spectrum. We apply this method to analyze the power spectrum of the spatial distribution of the Ly-α clouds. The two popular data sets used for the spectrum detection have quite different geometries and samplings, yet the one-dimensional (1D) power spectra and their 3D reconstruction given by the DWT estimator show the same features. The analysis makes clear that the DWT estimator is a sensitive tool in revealing common and physical properties from diverse data sets.