- The paper demonstrates that a near-inflection point in the single-field inflaton potential produces a spike in the curvature power spectrum.
- The enhanced perturbations lead to the formation of a broad PBH mass spectrum, with some evaporating and others potentially accounting for dark matter.
- The model complies with CMB and LSS observations and offers promising signatures for gravitational wave detectors like AdvLIGO and LISA.
Primordial Black Holes from Single Field Models of Inflation
The paper "Primordial black holes from single field models of inflation" explores the intriguing possibility of forming primordial black holes (PBHs) as candidate constituents for dark matter, employing single-field inflationary models. The authors propose that a pronounced peak in the power spectrum of curvature perturbations, resulting from a near-inflection point in the potential of a single-field inflation model, could give rise to PBH formation. These PBHs, upon gravitational collapse during the radiation-dominated era, could potentially account for all dark matter observed today.
Summary of the Model
The primary aim of the paper is to demonstrate that single-field inflationary models can naturally generate a significant peak in the primordial power spectrum. The proposed mechanism involves an inflection point in the inflaton's potential, which induces a temporary slowdown—a so-called "ultra-slow-roll" phase—enhancing curvature perturbations at specific scales. The paper employs a toy model characterized by a simple polynomial potential featuring a near-inflection point, which satisfies constraints from Cosmic Microwave Background (CMB) and Large Scale Structure (LSS) observations while predicting a broad mass spectrum for PBHs.
Key Findings
- Curvature Power Spectrum: The mechanics of the inflaton during inflation can produce a pronounced spike in the curvature power spectrum when there is a near-inflection point in the potential. This spike occurs at scales beyond those typically observable via CMB and LSS.
- Mass and Abundance of PBHs: Upon re-entry into the horizon during the radiation era, these enhanced perturbations could lead to the formation of PBHs. The derived distribution of PBH masses covers a wide range, and some masses are low enough that evaporation would occur before the commencement of structure formation.
- Compatibility with Observations: The model satisfies existing observational constraints from CMB anisotropies and structure formation, and the resulting PBHs could make up the totality of dark matter. The spectrum's broad mass distribution implies that current bounds from microlensing and other observational phenomena do not exclude these PBHs.
- Outlook for Future Detection: The paper notes that gravitational wave detectors like Advanced LIGO (AdvLIGO) and LISA could play a pivotal role in testing this model by providing signals or stochastic backgrounds from merging PBHs, further probing the proposed mass distribution.
Implications and Future Developments
The theoretical implications of PBHs forming the entirety of dark matter are profound. It shifts the focus from particle dark matter candidates to gravitationally collapsed objects resulting from early universe phenomena. Additionally, it suggests that early universe conditions, specifically the details of inflationary dynamics, could dictate significant aspects of the current universe.
For future research, the intersection of cosmology and observational astrophysics presents numerous opportunities. Gravitational wave astronomy offers a novel window into primordial universe conditions, possibly yielding insights into PBH formation and their role as dark matter. The ability to detect PBH mergers and associated gravitational radiation could either substantiate this model or constrain it, depending on empirical results.
Overall, the exploration of single-field models for generating PBHs as dark matter is a compelling direction, promising to interlink theories of inflation with observable consequences in the universe's dark matter composition.