Probing ALP-photon couplings in Neutron Stars: Scalar versus pseudoscalar cases

Fuente: arXiv
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Autores principales: Suárez-Fontanella, D., Albertus, C., Pérez-García, M. Ángeles
Formato: Preprint
Publicado: 2025
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author Suárez-Fontanella, D.
Albertus, C.
Pérez-García, M. Ángeles
author_facet Suárez-Fontanella, D.
Albertus, C.
Pérez-García, M. Ángeles
contents We investigate the distribution of an interacting axion-like massive field within a magnetized Neutron Star. For this we consider the effect of an intense density-dependent axially symmetric stellar magnetic field ${\bf B}(r,θ)$ adding another much weaker, but non-vanishing, electric field. We particularize the latter for the case when a finite chiral charge density is present. The axion field is thus coupled to a generic function $Q(F_0,G_0)$ depending on Lorentz invariants $F_0, G_0$ which can be constructed from these electromagnetic fields. From this, the static axion field equations are solved as function of stellar radial coordinate and angular direction, $a(r,θ)$, using a prescribed linear form for $Q$. In addition, we use a semi-analytical approach to calculate the stellar structure in this hybrid system where pressure components are treated under a perturbative scheme, provided induced deformations with respect to spherical symmetry are tiny. Our results show that the axion couplings to magnetic and electric fields along with its mass, critically determine the axion spatial distribution. Furthermore, we focus on the possibility that the axion field might accumulate in specific outer regions of the star, particularly within the crust, where it could form a condensate. We explore the possible presence of magnetic flux tubes from superconductor phases in this outer layers and qualitatively show they may enhance local conversion into photons. We explore prospects of detectability through indirect methods.
format Preprint
id arxiv_https___arxiv_org_abs_2508_09141
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Probing ALP-photon couplings in Neutron Stars: Scalar versus pseudoscalar cases
Suárez-Fontanella, D.
Albertus, C.
Pérez-García, M. Ángeles
High Energy Astrophysical Phenomena
Cosmology and Nongalactic Astrophysics
Solar and Stellar Astrophysics
High Energy Physics - Phenomenology
We investigate the distribution of an interacting axion-like massive field within a magnetized Neutron Star. For this we consider the effect of an intense density-dependent axially symmetric stellar magnetic field ${\bf B}(r,θ)$ adding another much weaker, but non-vanishing, electric field. We particularize the latter for the case when a finite chiral charge density is present. The axion field is thus coupled to a generic function $Q(F_0,G_0)$ depending on Lorentz invariants $F_0, G_0$ which can be constructed from these electromagnetic fields. From this, the static axion field equations are solved as function of stellar radial coordinate and angular direction, $a(r,θ)$, using a prescribed linear form for $Q$. In addition, we use a semi-analytical approach to calculate the stellar structure in this hybrid system where pressure components are treated under a perturbative scheme, provided induced deformations with respect to spherical symmetry are tiny. Our results show that the axion couplings to magnetic and electric fields along with its mass, critically determine the axion spatial distribution. Furthermore, we focus on the possibility that the axion field might accumulate in specific outer regions of the star, particularly within the crust, where it could form a condensate. We explore the possible presence of magnetic flux tubes from superconductor phases in this outer layers and qualitatively show they may enhance local conversion into photons. We explore prospects of detectability through indirect methods.
title Probing ALP-photon couplings in Neutron Stars: Scalar versus pseudoscalar cases
topic High Energy Astrophysical Phenomena
Cosmology and Nongalactic Astrophysics
Solar and Stellar Astrophysics
High Energy Physics - Phenomenology
url https://arxiv.org/abs/2508.09141