Fine structure constant and the CMB damping scale

Menegoni, Eloisa, Archidiacono, Maria, Calabrese, Erminia ORCID: https://orcid.org/0000-0003-0837-0068, Galli, Silvia, Martins, C. J. A. P. and Melchiorri, Alessandro 2012. Fine structure constant and the CMB damping scale. Physical Review D 85 (10) , 107301. 10.1103/PhysRevD.85.107301

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Abstract

The recent measurements of the Cosmic Microwave Background anisotropies at arc minute angular scales performed by the ACT and SPT experiments are probing the damping regime of CMB fluctuations. The analysis of these data sets unexpectedly suggests that the effective number of relativistic degrees of freedom is larger than the standard value of Neff ¼ 3:04, and inconsistent with it at more than two standard deviations. In this paper we study the role of a mechanism that could affect the shape of the CMB angular fluctuations at those scales, namely, a change in the recombination process through variations in the fine structure constant. We show that the new CMB data significantly improve the previous constraints on variations of �, with �=�0 ¼ 0:984 � 0:005, i.e. hinting also at a more than two standard deviation from the current, local, value �0. A significant degeneracy is present between � and Neff, and when variations in the latter are allowed the constraints on � are relaxed and again consistent with the standard value. Deviations of either parameter from their standard values would imply the presence of new, currently unknown physics

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Subjects:	Q Science > QB Astronomy
Publisher:	American Physical Society
ISSN:	2470-0010
Date of First Compliant Deposit:	9 October 2017
Date of Acceptance:	8 February 2012
Last Modified:	07 May 2023 15:18
URI:	https://orca.cardiff.ac.uk/id/eprint/105336

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