COBE has provided us with a whole-sky map of the CBR anisotropies. However, even if the noise level is negligible when the four year COBE data are available, the cosmic variance will prevent us from obtaining information about the Gaussian nature of the primordial fluctuations. This important issue is addressed here by studying the angular bispectrum of the cosmic microwave background anisotrop...

We extend a previous bispectrum analysis of the COBE-DMR 4 year maps, allowing for the presence of correlations between all possible angular scales. We find that the non-Gaussian signal found earlier for bispectrum components including adjacent modes does not extend to triplets of modes with larger separations. Indeed for all separations ∆l > 1 we find that the COBE-DMR data is very Gaussian. T...

Using the gradient expansion method of Rigopoulos, Shellard and van Tent which treats cosmological perturbations as gradients on top of a homogeneous and isotropic FRW background, we study the production of nongaussianities in the roulette model of inflation. Investigating a number of trajectories within this two-field model of inflation, we find that while the superhorizon influence of the iso...

This paper considers the classification of radar target using Backscatter Doppler signature of moving object. Classification performance evaluated by the integrated Bispectrum based technique of feature extraction and compared it with Cepstrum based feature extraction technique. Classifier performance is tested by GMM (Gaussian Mixture Model) and ML (Maximal Likelihood) decision making method. ...

Fault Diagnosis for Crankshaft Bearing in Diesel Engine Based on Bispectrum Analysis Fuzhou Feng, Aiwei Si* b , Pengcheng Jiang Department of Mechanical Engineering, Academy of Armored Force Engineering, No.21, Dujiakan District, Fentai area, Beijing 100072, China Military Transportation Department, Military Transportation University, No. 1, Dongjuzi District, Hedong area, Tianjin 300161, China...

We compute the leading order contribution to the four-point function of the primordial curvature perturbation in a class of single field models where the inflationary Lagrangian is a general function of the inflaton and its first derivative. This class of models includes string motivated inflationary models such as DBI inflation. We find that the trispectrum for some range of parameters could p...

Abstract: The purpose of this paper is to join two different threads of the recent literature on random fields on the sphere, namely the statistical analysis of higher order angular power spectra on one hand, and the construction of second-generation wavelets on the sphere on the other. To this aim, we introduce the needlets bispectrum and we derive a number of convergence results. Here, the li...

Abstract The dependence of the bispectrum on size and shape triangle contains a wealth cosmological information. Here we consider parameterization which allows us to separate dependence. We have implemented an FFT based fast estimator for three dimensional (3D) bin averaged bispectrum, demonstrate that it study variation across triangles all possible shapes (and also sizes). computational requi...