Ultradense Dark Matter Halos with Poisson Noise from Stellar-mass Primordial Black Holes

Abstract In this work, we investigate the impact of Poisson noise from stellar-mass primordial black holes (PBHs) on the formation of ultradense dark matter halos (UDMHs). Our findings reveal that the discrete spatial distribution of PBHs significantly enhances small-scale density fluctuations, particularly for massive stellar-mass PBHs. Our results indicate that the modified power spectrum, incorporating both adiabatic and isocurvature contributions from PBH-induced Poisson noise, strongly depends on PBH mass and fraction. Specifically, increasing PBH mass shifts the differential mass function of UDMHs toward higher masses, while variations in the suppression parameter n modulate the efficiency of UDMH formation at small scales. For lower values of n , our findings show a significant boost in UDMH abundance, favoring multicomponent dark matter scenarios. Conversely, at higher values of n , the predicted UDMH distributions align more closely with single-component models dominated by stellar-mass PBHs. Furthermore, our analysis demonstrates that more realistic halo mass functions, which account for angular momentum and dynamical friction, consistently predict higher UDMH abundances compared to the traditional Press–Schechter formalism.