Cannibal domination and the matter power spectrum

• Published in: Physical review. D 2021-05, Vol.103 (10), p.1, Article 103508
• Main Authors: Erickcek, Adrienne L., Ralegankar, Pranjal, Shelton, Jessie
• Format: Article
• Language: English
• Subjects: Astronomical models; Big bang cosmology; Cosmology; Couplings; Dark matter; Equations of state; Nuclear fusion; Nuclei (nuclear physics); Thermal energy
• ISSN: 2470-0010; 2470-0029
• DOI: 10.1103/PhysRevD.103.103508

Decoupled hidden sectors can easily and generically result in a period of cannibal domination, during which the dominant component of the Universe has an equation of state intermediate between radiation and matter due to self-heating by number-changing interactions. We present for the first time the consequences of a cannibal-dominated era prior to big bang nucleosynthesis for structure formation on small scales. We find that an early cannibal-dominated era imprints a characteristic peak on the dark matter power spectrum, with scale and amplitude directly determined by the mass, lifetime, and number-changing interaction strength of the cannibal field. This enhancement to the small-scale matter power spectrum will generate early-forming dark matter microhalos, and we provide a detailed and transparent map between the properties of the cannibal species and the characteristic mass and formation time of these structures. These relations demonstrate how the internal workings of a hidden sector leave a potentially observable imprint on the matter power spectrum even if dark matter has no direct couplings to the Standard Model.