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Axion-like particles (ALPs) are hypothetical particles and compelling candidates for cold dark matter. Their existence could be probed through their conversions into photons in the presence of magnetic fields. In this work, we explore the…

Very high energy (VHE, energy >~ 100 GeV) {\gamma}-rays originating from extragalactic sources interact with low energy photons of background radiation fields and produce electron-positron pairs. Alternatively, in the presence of ambient…

High Energy Astrophysical Phenomena · Physics 2012-11-28 Manuel Meyer , Dieter Horns , Luca Maccione , Alessandro Mirizzi , Daniele Montanino , Marco Roncadelli

Axion-like particles (ALPs) are attracting increasing interest since, among other things, they are a prediction of many extensions of the standard model of elementary particles physics and in particular of superstrings and superbranes.…

High Energy Astrophysical Phenomena · Physics 2019-07-23 Giorgio Galanti , Marco Roncadelli

Extensions of the Standard Model of particles commonly predict the existence of axion(-like) particles (ALPs) that could be detected through their coupling to photons in external magnetic fields. This coupling could lead to modifications of…

High Energy Astrophysical Phenomena · Physics 2014-12-11 M. Meyer , J. Conrad

We perform a linear mode analysis of a uniformly distributed cloud of axion-like particles (ALPs) embedded in a magnetized intergalactic medium, in order to investigate the stability of axion stars under realistic astrophysical conditions.…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-14 Kuldeep J. Purohit , Jitesh R. Bhatt , Subhendra Mohanty , Prashant K. Mehta

One interpretation of the unexplained signature observed in the PVLAS experiment invokes a new axion-like particle (ALP) with a two-photon vertex, allowing for photon-ALP oscillations in the presence of magnetic fields. In the range of…

Astrophysics · Physics 2008-11-26 Alessandro Mirizzi , Georg G. Raffelt , Pasquale D. Serpico

We study magnetic conversion of ultra-relativistic axion-like particles (ALPs) into photons in compact-star environments, focusing on the hot, transient conditions of core-collapse supernova (SN) remnants and neutron-star mergers (NSMs). We…

High Energy Physics - Phenomenology · Physics 2026-05-06 Damiano F. G. Fiorillo , Ángel Gil Muyor , Hans-Thomas Janka , Georg G. Raffelt , Edoardo Vitagliano

Many extensions of the Standard Model predict the existence of ALPs, which are very light spin-zero bosons with a two-photon coupling. Photon-ALP oscillations occur in the presence of an external magnetic field, and ALPs can lead to…

High Energy Astrophysical Phenomena · Physics 2015-03-19 Alessandro De Angelis , Giorgio Galanti , Marco Roncadelli

Many extensions of the Standard Model include axions or axion-like particles (ALPs). Here we study ALP to photon conversion in the magnetic field of the Milky Way and starburst galaxies. By modelling the effects of the coherent and random…

High Energy Physics - Phenomenology · Physics 2016-01-26 Francesca V. Day

Axion like particles (ALPs) are fundamental pseudo scalar particles with properties similar to Axions which are a well-known extension of the standard model to solve the strong CP problem in Quantum Chromodynamics. ALPs can oscillate into…

High Energy Astrophysical Phenomena · Physics 2017-10-30 Jhilik Majumdar , Francesca Calore , Dieter Horns

Axion-like particles (ALPs), hypothetical extensions of the Standard Model, can convert into photons in an external magnetic field. Two recent studies~\cite{Todarello:2023ptf, Ruz:2024gkl} explored the phenomenology of ALP-photon conversion…

High Energy Physics - Phenomenology · Physics 2025-01-28 Elisa Todarello

Recently it has been pointed out that a cosmic background of relativistic axion-like particles (ALPs) would be produced by the primordial decays of heavy fields in the post-inflation epoch, contributing to the extra-radiation content in the…

Cosmology and Nongalactic Astrophysics · Physics 2016-05-25 Carmelo Evoli , Matteo Leo , Alessandro Mirizzi , Daniele Montanino

We study photon-ALP conversion by resonance effects in the magnetized plasma of galaxy clusters and compare the predicted distortion of the cosmic microwave background spectrum in the direction of such objects to measurements of the thermal…

High Energy Physics - Phenomenology · Physics 2016-02-05 Martin Schlederer , Günter Sigl

Very high energy gamma-ray observations of distant active galactic nuclei (AGN) generally result in higher fluxes and harder spectra than expected, resulting in some tension with the level of the extragalactic background light (EBL). If…

High Energy Astrophysical Phenomena · Physics 2015-06-19 Jonathan Harris , Paula M. Chadwick

Axion-Like Particles (ALPs) are the focus of intense current research. We analyze photon-ALP conversion in the context of relativistic jet models of Active Galactic Nuclei (AGN) for more than 100 sources. Contrary to previous claims, we…

High Energy Astrophysical Phenomena · Physics 2009-05-26 Nicola Bassan , Marco Roncadelli

Decaying axion-like particles (ALP) with masses in the eV range which might occupy dark matter halos of the Milky Way and other galaxies produce a characteristic "bump" feature in the spectrum of extragalactic background light (EBL). This…

High Energy Physics - Phenomenology · Physics 2020-04-20 A. Korochkin , A. Neronov , D. Semikoz

Axion Like Particles (ALPs) are predicted to couple with photons in the presence of magnetic fields. This effect may lead to a significant change in the observed spectra of gamma-ray sources such as AGNs. Here we carry out a detailed study…

Cosmology and Nongalactic Astrophysics · Physics 2009-08-31 M. A. Sanchez-Conde , D. Paneque , E. Bloom , F. Prada , A. Dominguez

Axion-like particles (ALPs) are light, neutral, pseudo-scalar bosons predicted by several extensions of the Standard Model of particle physics -- such as the String Theory -- and are supposed to interact primarily only with two photons. In…

High Energy Astrophysical Phenomena · Physics 2019-11-22 Giorgio Galanti

Axions and axion-like-particles (ALPs) are characterised by their two-photon coupling, which entails so-called photon-ALP oscillations as photons propagate through a magnetic field. These oscillations lead to distinctive signatures in the…

High Energy Physics - Phenomenology · Physics 2023-12-11 M. Kachelriess , J. Tjemsland

If axion-like particles (ALPs) exist, photons can convert to ALPs on passage through regions containing magnetic fields. The magnetised intracluster medium of large galaxy clusters provides a region that is highly efficient at ALP-photon…

High Energy Astrophysical Phenomena · Physics 2018-06-27 Linhan Chen , Joseph P. Conlon