Searches for Axionlike Particles Using Gamma-Ray Observations

Axionlike particles (ALPs) are a common prediction of theories beyond the Standard Model of particle physics that could explain the entirety of the cold dark matter. These particles could be detected through their mixing with photons in external electromagnetic fields. Here, we provide a short review over ALP searches that utilize astrophysical $\gamma$-ray observations. We summarize current bounds as well as future sensitivities and discuss the possibility that ALPs alter the $\gamma$-ray opacity of the Universe.