Axionic defects in the CMB : birefringence and gravitational waves
Ferreira, Ricardo Zambujal (University of Coimbra. Department of Physics)
Gasparotto, Silvia (Universitat Autònoma de Barcelona. Departament de Física)
Hiramatsu, Takashi (Rikkyo University. Department of Physics)
Obata, Ippei (University of Tokyo. Kavli Institute for the Physics and Mathematics of the Universe)
Pujolàs Boix, Oriol (Institut de Física d'Altes Energies)

Fecha:	2024
Resumen:	The evidence for a non-vanishing isotropic cosmic birefringence in recent analyses of the CMB data provides a tantalizing hint for new physics. Domain wall (DW) networks have recently been shown to generate an isotropic birefringence signal in the ballpark of the measured value when coupled to photons. In this work, we explore the axionic defects hypothesis in more detail and extending previous results to annihilating and late-forming networks, and by pointing out other smoking-gun signatures of the network in the CMB spectrum such as the anisotropic birefringent spectrum and B-modes. We also argue that the presence of cosmic strings in the network does not hinder a large isotropic birefringence signal because of an intrinsic environmental contribution coming from low redshifts thus leaving open the possibility that axionic defects can explain the signal. Regarding the remaining CMB signatures, with the help of dedicated 3D numerical simulations of DW networks, that we took as a proxy for the axionic defects, we show how the anisotropic birefringence spectrum combined with a tomographic approach can be used to infer the formation and annihilation time of the network. From the numerical simulations, we also computed the spectrum of gravitational waves (GWs) generated by the network in the post-recombination epoch and use previous searches for stochastic GW backgrounds in the CMB to derive for the first time a bound on the tension and abundance of networks with DWs that annihilate after recombination. Our bounds extend to the case where the network survives until the present time and improve over previous bounds by roughly one order of magnitude. Finally, we show the interesting prospects for detecting B-modes of DW origin with future CMB experiments.
Ayudas:	European Commission 801370 Agencia Estatal de Investigación PID2020-115845GB-I00 Agència de Gestió d'Ajuts Universitaris i de Recerca 2021/SGR-00649
Nota:	Altres ajuts: SG has the support of the predoctoral program AGAUR FI SDUR 2022 from the Departament de Recerca i Universitats from Generalitat de Catalunya and the European Social Plus Fund.
Derechos:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, i la comunicació pública de l'obra, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original. No es permet la creació d'obres derivades.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió acceptada per publicar
Publicado en:	Journal of Cosmology and Astroparticle Physics, Vol. 2024, issue 5 (May 2024) , art. 66, ISSN 1475-7516

DOI: 10.1088/1475-7516/2024/05/066

Postprint 32 p, 3.5 MB

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