## Brazilian Journal of Probability and Statistics

- Braz. J. Probab. Stat.
- Volume 29, Number 4 (2015), 833-865.

### Angular spectra for non-Gaussian isotropic fields

#### Abstract

Cosmic microwave background (CMB) Anisotropies is a subject of intensive research in recent years, and therefore it is necessary to develop suitable theory and methods for the analysis of isotropic fields on spheres. The main object of our paper is to show that the polyspectra can be given as the coefficients of the orthogonal expansion of cumulants of the field in terms of irreducible tensor products of spherical harmonics. We obtain necessary and sufficient conditions for isotropy of a non-Gaussian field and the conditions are stated in terms of higher order spectra (polyspectra). The relation between cumulants and spectra gives a new method of estimating spectra.

#### Article information

**Source**

Braz. J. Probab. Stat., Volume 29, Number 4 (2015), 833-865.

**Dates**

Received: December 2013

Accepted: May 2014

First available in Project Euclid: 17 September 2015

**Permanent link to this document**

https://projecteuclid.org/euclid.bjps/1442513449

**Digital Object Identifier**

doi:10.1214/14-BJPS249

**Mathematical Reviews number (MathSciNet)**

MR3397396

**Zentralblatt MATH identifier**

1328.83219

**Keywords**

Bispectrum trispectrum angular polyspectra CMB non-Gaussianity spherical random fields isotropy

#### Citation

Terdik, György. Angular spectra for non-Gaussian isotropic fields. Braz. J. Probab. Stat. 29 (2015), no. 4, 833--865. doi:10.1214/14-BJPS249. https://projecteuclid.org/euclid.bjps/1442513449