RT Journal Article T1 Constraints on anharmonic corrections of fuzzy dark matter A1 Ruiz Cembranos, José Alberto A1 López Maroto, Antonio A1 Núñez Jareño, S.J. A1 Villarrubia-Rojo, H. AB 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. PB Springer SN 1029-8479 YR 2018 FD 2018-08-14 LK https://hdl.handle.net/20.500.14352/12980 UL https://hdl.handle.net/20.500.14352/12980 LA eng NO © 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. NO Ministerio de Economía y Competitividad (MINECO)/FEDER NO Consolider-Ingenio MULTIDARK DS Docta Complutense RD 1 may 2024