Alleviating CMB-BAO tension with a large cosmic birefringence angle during reionization induced by energy injection to axion-like particles

arXiv:2610.29764 · astro-ph.CO · Submitted 2026-10-21 · Read on arXiv

astro-ph.CO

Submitted: 2026-10-21

Updated: 2026-10-21

Comments: 14 pages, 7 figures

License: http://creativecommons.org/licenses/by/4.0/

The gist: The recent measurement of baryon acoustic oscillations by the Dark Energy Spectroscopic Instrument reveals a mild tension with observations of the cosmic microwave background (CMB) within the

Abstract

The recent measurement of baryon acoustic oscillations by the Dark Energy Spectroscopic Instrument reveals a mild tension with observations of the cosmic microwave background (CMB) within the standard Λ CDM cosmological model. Another interesting hint beyond standard cosmology arises from recent analyses of Planck polarization data which has been interpreted as cosmic birefringence. One possible solution to explain both observations is to introduce cosmic birefringence induced by axion-like particles (ALPs) that has a much larger rotation angle during the reionization epoch than that during the recombination: the large rotation suppresses the EE reionization signal, allowing an elevated value of the CMB optical depth τ that alleviates the CMB-BAO tension. In this paper, we explore a scenario where the energy transfers from matter to ALPs before the reionization. Using Planck low- EE, BB, and EB data, we show that, for energy injection at 10 z 100, there exist parameter regions where τ 0.08-0.10 is compatible with the data.

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