Constraints on primordial black holes as dark matter candidates from capture by neutron stars

Abstract: We investigate constraints on primordial black holes (PBHs) as dark matter candidates that arise from their capture by neutron stars (NSs). If a PBH is captured by a NS, the star is accreted onto the PBH and gets destroyed in a very short time. Thus, mere observations of NSs put limits on the abundance of PBHs. High DM densities and low velocities are required to constrain the fraction of PBHs in DM. Such conditions may be realized in the cores of globular clusters if the latter are of a primordial origin. Assuming that cores of globular clusters possess the DM densities exceeding several hundred GeV/cm$^3$ would imply that PBHs are excluded as comprising all of the dark matter in the mass range $3\times 10^{18} \text{g} \lesssim m_\text{BH}\lesssim 10^{24} \text{g}$. At the DM density of $2\times 10^3$ GeV/cm$^3$ that has been found in simulations in the corresponding models, less than 5% of the DM may consist of PBH for these PBH masses.

• The paper demonstrates that PBHs captured by neutron stars lead to rapid stellar destruction, setting strict limits on their dark matter contribution.
• It employs dynamical simulations and DM density calculations in globular clusters, showing that at 2x10³ GeV/cm³, PBHs can account for less than 5% of DM.
• The findings refine the viable dark matter candidate space and inform future research on astrophysical simulations and DM detection strategies.

Constraints on Primordial Black Holes as Dark Matter Candidates from Neutron Star Capture

The paper presents a rigorous analysis of constraints on the hypothesis that primordial black holes (PBHs) could constitute a significant portion of dark matter (DM), specifically through their interaction and potential capture by neutron stars (NSs). The authors, Fabio Capela, Maxim Pshirkov, and Peter Tinyakov, explore how the presence of PBHs within NSs could lead to observable destruction of these stars, thereby providing an upper bound on the abundance of PBHs as dark matter candidates.

Summary of Findings

In the context of DM, PBHs present an intriguing possibility due to their formation from density fluctuations in the early universe. The authors focus on the mass range $$3 \times 10^{18} \text{g} \lesssim m_\text{BH} \lesssim 10^{24} \text{g}$$, analyzing scenarios wherein PBHs might be captured by NSs. This scenario causes the NS material to accrete onto the PBH, leading to rapid star destruction. Consequently, merely observing NSs offers indirect constraints on the abundance of PBHs.

Through their calculations, the authors propose significant constraints based on assumptions of high DM densities and low velocity dispersions, particularly in the cores of globular clusters (GCs). GCs that might have originated from low-mass DM halos are hypothesized to meet these conditions. Assuming a DM density in the GC cores exceeding several hundred GeV/cm$^3$, the findings suggest that PBHs cannot comprise all dark matter in the specified mass range. More explicitly, at $\rho_\text{DM} = 2 \times 10^3$ GeV/cm$^3$, PBHs could make up less than 5% of DM for masses within this range.

Implications and Future Work

The work offers crucial implications for theoretical physics and cosmology. By excluding PBHs as dominant DM candidates in certain mass ranges, the research narrows the search space for viable DM constituents, aiding both theoretical modeling and experimental searches. The precise constraints detailed offer insights which could influence the direction of future astrophysical studies and DM detection strategies.

Furthermore, the paper highlights the potential of observational constraints in advancing our understanding of cosmic structures. Extensions of this work could involve more detailed simulations regarding DM distribution within various galactic environments or improved observational techniques to detect NSs in DM-rich regions.

In the broader scope of AI and simulation models, this analysis underscores the importance of incorporating physical constraints to refine theoretical hypotheses. Many of the methods employed here, such as dynamical simulations of NS interactions, could benefit from advanced computational models and AI-based optimization, potentially enhancing precision and expanding the yet unexplored avenues of research.

Conclusion

Capela, Pshirkov, and Tinyakov's study presents a coherent, detailed exploration of PBH interaction with NSs, proposing stringent constraints on their capacity to represent all DM. Through methodical analyses and simulations, the paper delivers significant contributions to the ongoing discourse on dark matter, offering a narrowed pathway for future research endeavors in both theoretical and observational astrophysics.