arXiv:2403.00021v1 Announce Type: new
Abstract: Here, we investigate the formation of primordial black holes (PBHs) in non-minimal coupling Gauss-Bonnet inflationary model in the presence of power-law potentials. We employ a two part coupling function to enhance primordial curvatures at small scales as well as satisfy Planck measurements at the CMB scale. Moreover, our model satisfies the swampland criteria. We find PBHs with different mass scales and demonstrate that PBHs with masses around $mathcal{O}(10^{-14})M_{odot}$ can account for almost all of the dark matter in the universe. In addition, we investigate the implications of the reheating stage and show that the PBHs in our model are generated during the radiation-dominated era. Furthermore, we investigate the production of scalar-induced gravitational waves (GWs). More interestingly enough, is that for the specific cases $D_{rm n}$ in our model, the GWs can be considered as a source of NANOGrav signal. %evaluate the idea that the induced GWs propagating concurrently with the PBH production are the source of NANOGrav signal. Also, we conclude that the GWs energy density parameter at the nano-Hz regime can be parameterized as $Omega_{rm GW_0} (f) sim f^{5-gamma}$, where the obtained $gamma$ is consistent with the NANOGrav 15 years data.
Formation of Primordial Black Holes in Non-Minimal Coupling Gauss-Bonnet Inflationary Model
In this study, we investigate the formation of primordial black holes (PBHs) in a non-minimal coupling Gauss-Bonnet inflationary model with power-law potentials. We propose a two-part coupling function that enhances primordial curvatures at small scales and is consistent with Planck measurements at the Cosmic Microwave Background (CMB) scale. Importantly, our model also satisfies the swampland criteria.
PBHs as Dark Matter Candidates
We find that PBHs with different mass scales can be formed in our model. Particularly, PBHs with masses around $mathcal{O}(10^{-14})M_{odot}$ are capable of explaining a significant portion of the dark matter in the universe. This discovery opens up new possibilities for understanding the nature of dark matter.
Implications of Reheating Stage
In addition to PBH formation, we also investigate the implications of the reheating stage in our model. Our findings suggest that the PBHs are generated during the radiation-dominated era. This insight provides valuable information about the early universe and the dynamics of inflation.
Scalar-Induced Gravitational Waves
We further delve into the production of scalar-induced gravitational waves (GWs). Interestingly, we identify special cases in our model where the GWs can be considered as a source of the NANOGrav signal. This connection between PBHs and GWs presents an exciting avenue for future research.
Note: NANOGrav refers to the North American Nanohertz Observatory for Gravitational Waves, which is a collaboration striving to detect low-frequency gravitational waves.
Predicting GWs Energy Density
Additionally, our study allows us to predict the energy density parameter of GWs in the nano-Hertz regime. We propose a parameterization of $Omega_{rm GW_0} (f) sim f^{5-gamma}$, where the value of $gamma$ obtained from our model is consistent with the NANOGrav 15 years data. This alignment with observational data strengthens the validity of our theoretical framework.
Future Roadmap
- Further investigate the non-minimal coupling Gauss-Bonnet inflationary model to analyze its implications on primordial black hole formation and other cosmological phenomena.
- Conduct observational studies to validate the presence and properties of primordial black holes with masses around $mathcal{O}(10^{-14})M_{odot}$, potentially shedding light on the nature of dark matter.
- Explore the connection between scalar-induced gravitational waves and the NANOGrav signal, considering different scenarios and refining the predictions for future experiments.
- Refine the parameterization of the energy density parameter for gravitational waves in the nano-Hertz regime, potentially contributing to a better understanding of the universe’s gravitational wave background.
- Continuously compare and validate theoretical predictions with new observational data, such as future NANOGrav measurements, to further validate and refine the proposed model.
Overall, the findings from this study open up exciting opportunities for research in the field of primordial black holes, dark matter, gravitational waves, and early universe cosmology. By addressing the challenges and building upon the conclusions of this work, future studies can provide a more comprehensive understanding of the universe’s fundamental properties.