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Tensor Minkowski Functionals: first application to the CMB

Ganesan, Vidhya and Chingangbam, Pravabati (2017) Tensor Minkowski Functionals: first application to the CMB. In: JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS (6).

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Abstract

Tensor Minkowski Functionals (TMFs) are tensor generalizations of the usual Minkowski Functionals which are scalar quantities. We introduce them here for use in cosmological analysis, in particular to analyze the Cosmic Microwave Background (CMB) radiation. They encapsulate information about the shapes of structures and the orientation of distributions of structures. We focus on one of the TMFs, namely W-2(1,1), which is the (1, 1) rank tensor generalization of the genus. The ratio of the eigenvalues of the average of W-2(1,1) over all structures, a, encodes the net orientation of the structures; and the average of the ratios of the eigenvalues of W-2(1,1) for each structure, 13, encodes the net intrinsic anisotropy of the structures. We have developed a code that computes W-2(1,1), and from it alpha and beta, for a set of structures on the 2-dimensional Euclidean plane. We use it to compute alpha and beta as functions of chosen threshold levels for simulated Gaussian and isotropic CMB temperature and E mode fields. We obtain the value of a to be one for both temperature and E mode, which means that we recover the statistical isotropy of density fluctuations that we input in the simulations. We find that the standard ACDM model predicts a charateristic shape of beta for temperature and E mode as a function of the threshold, and the average over thresholds is beta similar to 0.62 for temperature and beta similar to 0.63 for E mode. Accurate measurements of a and beta can be used to test the standard model of cosmology and to search for deviations from it. For this purpose we compute alpha and beta for temperature and E mode data of various data sets from PLANCK mission.(1) We compare the values measured from observed data with those obtained from simulations to which instrument beam and noise characteristics of the 44GHz frequency channel have been added (which are provided as part of the PLANCK data release). We find very good agreement of beta and alpha between all PLANCK temperature data sets with ACDM expectations. E mode data show good agreement for 13 but a for all data sets deviate from ACDM predictions higher than 3 - sigma. It is most likely that the deviations are probing the anisotropy of the noise field and beam characteristics of the detector rather than the true E mode signal since for 44GHz the signal-to-noise ratio is well below one. This will be further investigated after the full PLANCK data becomes publicly available.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to the IOP PUBLISHING LTD, TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND
Department/Centre: Division of Physical & Mathematical Sciences > Mathematics
Depositing User: Id for Latest eprints
Date Deposited: 07 Jul 2017 10:25
Last Modified: 04 Feb 2019 06:32
URI: http://eprints.iisc.ac.in/id/eprint/57323

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