000065242 001__ 65242 000065242 005__ 20200117211559.0 000065242 0247_ $$2doi$$a10.1016/j.physletb.2017.12.010 000065242 0248_ $$2sideral$$a104152 000065242 037__ $$aART-2018-104152 000065242 041__ $$aeng 000065242 100__ $$aVisinelli, L. 000065242 245__ $$aDilute and dense axion stars 000065242 260__ $$c2018 000065242 5060_ $$aAccess copy available to the general public$$fUnrestricted 000065242 5203_ $$aAxion stars are hypothetical objects formed of axions, obtained as localized and coherently oscillating solutions to their classical equation of motion. Depending on the value of the field amplitude at the core |¿0|=|¿(r=0)|, the equilibrium of the system arises from the balance of the kinetic pressure and either self-gravity or axion self-interactions. Starting from a general relativistic framework, we obtain the set of equations describing the configuration of the axion star, which we solve as a function of |¿0|. For small |¿0|¿1, we reproduce results previously obtained in the literature, and we provide arguments for the stability of such configurations in terms of first principles. We compare qualitative analytical results with a numerical calculation. For large amplitudes |¿0|¿1, the axion field probes the full non-harmonic QCD chiral potential and the axion star enters the dense branch. Our numerical solutions show that in this latter regime the axions are relativistic, and that one should not use a single frequency approximation, as previously applied in the literature. We employ a multi-harmonic expansion to solve the relativistic equation for the axion field in the star, and demonstrate that higher modes cannot be neglected in the dense regime. We interpret the solutions in the dense regime as pseudo-breathers, and show that the life-time of such configurations is much smaller than any cosmological time scale. 000065242 536__ $$9info:eu-repo/grantAgreement/ES/MINECO/RYC-2012-10597$$9info:eu-repo/grantAgreement/ES/MINECO/FPA2015-65745-P$$9This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 674896-ELUSIVES$$9info:eu-repo/grantAgreement/EC/H2020/674896/EU/The Elusives Enterprise: Asymmetries of the Invisible Universe/ELUSIVES 000065242 540__ $$9info:eu-repo/semantics/openAccess$$aby$$uhttp://creativecommons.org/licenses/by/3.0/es/ 000065242 590__ $$a4.162$$b2018 000065242 591__ $$aASTRONOMY & ASTROPHYSICS$$b18 / 69 = 0.261$$c2018$$dQ2$$eT1 000065242 591__ $$aPHYSICS, PARTICLES & FIELDS$$b8 / 29 = 0.276$$c2018$$dQ2$$eT1 000065242 591__ $$aPHYSICS, NUCLEAR$$b6 / 19 = 0.316$$c2018$$dQ2$$eT1 000065242 592__ $$a1.806$$b2018 000065242 593__ $$aNuclear and High Energy Physics$$c2018$$dQ1 000065242 655_4 $$ainfo:eu-repo/semantics/article$$vinfo:eu-repo/semantics/publishedVersion 000065242 700__ $$aBaum, S. 000065242 700__ $$0(orcid)0000-0002-1044-8197$$aRedondo, J.$$uUniversidad de Zaragoza 000065242 700__ $$aFreese, K. 000065242 700__ $$aWilczek, F. 000065242 7102_ $$12004$$2405$$aUniversidad de Zaragoza$$bDpto. Física Teórica$$cÁrea Física Teórica 000065242 773__ $$g777 (2018), 64-72$$pPhys. lett., Sect. B$$tPHYSICS LETTERS B$$x0370-2693 000065242 8564_ $$s499391$$uhttps://zaguan.unizar.es/record/65242/files/texto_completo.pdf$$yVersión publicada 000065242 8564_ $$s103816$$uhttps://zaguan.unizar.es/record/65242/files/texto_completo.jpg?subformat=icon$$xicon$$yVersión publicada 000065242 909CO $$ooai:zaguan.unizar.es:65242$$particulos$$pdriver 000065242 951__ $$a2020-01-17-21:10:24 000065242 980__ $$aARTICLE