Title:	Capturing Statistical Isotropy Violation with Generalized Isotropic Angular Correlation Functions of Cosmic Microwave Background Anisotropy
Authors:	Dipanshu Souradeep, Tarun Hirve, Shriya
Keywords:	Two-point correlation function Cosmic microwave background radiation
Issue Date:	6-Sep-2023
Publisher:	IOP Publishing Ltd
Citation:	The Astrophysical Journal, 2023, Vol. 954, p181
Abstract:	The exquisitely measured maps of fluctuations in the cosmic microwave background (CMB) present the possibility of systematically testing the principle of statistical isotropy of the Universe. A systematic approach based on strong mathematical formulation allows any nonstatistical isotropic (nSI) feature to be traced to the nature of physical effects or observational artifacts. Bipolar spherical harmonics (BipoSH) representation has emerged as an overarching general formalism for quantifying the departures from statistical isotropy for a field on a 2D sphere. We adopt a little-known reduction of the BipoSH functions, dubbed minimal harmonics in the original paper by Manakov et al. We demonstrate that this reduction technique of BipoSH leads to a new generalized set of isotropic angular correlation functions referred to here as minimal BipoSH functions that are observable quantifications of nSI features in a sky map. This paper presents a novel observable quantification of deviation from statistical isotropy in terms of generalized angular correlation functions that are compact and complementary to the BipoSH spectra that generalize the angular power spectrum of CMB fluctuations.
Description:	Open Access
URI:	http://hdl.handle.net/2289/8148
Alternative Location:	https://ui.adsabs.harvard.edu/abs/2023arXiv230104539D/abstract https://arxiv.org/abs/2301.04539 http://dx.doi.org/10.3847/1538-4357/ace895
Copyright:	2023 The Author(s)
Appears in Collections:	Research Papers (A&A)

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