A comprehensive study of modulation effects on CMB polarization
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Date
2022
Authors
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Journal ISSN
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Publisher
Springer
Abstract
The Cosmic Microwave Background is characterized by temperature and linear polar ization fields. Dipole modulation in the temperature field has been extensively studied
in the context of hemispherical power asymmetry. In this article, we show that a
dipole modulation, and in general, any kind of modulation isn’t allowed in the E and
B modes. This is the main result of this paper. This result explains why no evidence
of modulation in E mode has been found in the literature. On the contrary, the linear
polarization fields Q and U have no such restrictions. We show that modulation under
certain situations can be thought of as local U(1) gauge transformations on the surface
of a sphere. As far as the modulation function is concerned, we show that physical
considerations enforce it to be (i) a spin 0 field and (ii) a scalar under parity. As mask ing is a specific type of modulation, our study suggests that a direct masking of E
mode isn’t also possible. Masking in E map can only be applied through Q and U
fields. This means that in principle, leaking of E and B mode powers into each other
is unavoidable
Description
Keywords
Cosmic microwave background, Polarization, Modulation
Citation
Kothari, Rahul. “A Comprehensive Study of Modulation Effects on CMB Polarization.” General relativity and gravitation 54.4 (2022): n. pag. Web.