Ruiz Cembranos, José AlbertoLópez Maroto, AntonioNúñez Jareño, S.J.Villarrubia-Rojo, H.2023-06-172023-06-172018-08-141029-847910.1007/JHEP08(2018)073https://hdl.handle.net/20.500.14352/12980© The Authors (2018). This work has been supported by the MINECO (Spain) projects FIS2014-52837-P, FIS2016- 78859-P(AEI/FEDER, UE), and Consolider-Ingenio MULTIDARK CSD2009-00064.he cold dark matter (CDM) scenario has proved successful in cosmology. However, we lack a fundamental understanding of its microscopic nature. Moreover, the apparent disagreement between CDM predictions and subgalactic-structure observations has prompted the debate about its behaviour at small scales. These problems could be alleviated if the dark matter is composed of ultralight fields m ∼ 10^(−22) eV, usually known as fuzzy dark matter (FDM). Some specific models, with axion-like potentials, have been thoroughly studied and are collectively referred to as ultralight axions (ULAs) or axion-like particles (ALPs). In this work we consider anharmonic corrections to the mass term coming from a repulsive quartic self-interaction. Whenever this anharmonic term dominates, the field behaves as radiation instead of cold matter, modifying the time of matter-radiation equality. Additionally, even for high masses, i.e. masses that reproduce the cold matter behaviour, the presence of anharmonic terms introduce a cut-off in the matter power spectrum through its contribution to the sound speed. We analyze the model and derive constraints using a modified version of class and comparing with CMB and large-scale structure data.engAtribución 3.0 Españahttps://creativecommons.org/licenses/by/3.0/es/journal articlehttps://doi.org/10.1007/JHEP08(2018)073https://link.springer.comopen access53Cosmological perturbationsParticlesProbeLightPowerAxionWaveBigFísica-Modelos matemáticos