A Unified Origin of Primordial Black Hole Dark Matter and Nanohertz Gravitational Waves

TL;DR

This paper proposes a unified primordial origin for planet-mass primordial black holes and nanohertz gravitational waves, linking microlensing observations and PTA signals through a broad enhancement of the early universe's curvature spectrum.

Contribution

It introduces a single primordial curvature spectrum feature that explains both PBH dark matter and PTA gravitational wave signals, consistent with current constraints.

Findings

PBH mass function spans planet to solar mass range

Unified model predicts testable signals in future experiments

Consistent with all current observational constraints

Abstract

Recent high-cadence observations by Subaru-HSC have identified a population of ultrashort-timescale microlensing events, providing a compelling window for planet-mass primordial black holes (PBHs) to constitute the entirety of dark matter. In this Letter, we demonstrate that this PBH population and the nanohertz stochastic gravitational-wave (GW) background reported by pulsar timing arrays (PTAs) can be naturally unified by a single primordial origin: a broad, nearly-flat enhancement of the curvature power spectrum with an amplitude of $O(10^{-2})$. The resulting PBH mass function spans the planet-to-solar mass range, while remaining consistent with all current observational constraints. This unified PBH--induced-GW framework makes concrete multi-messenger predictions, which can be decisively scrutinized by forthcoming microlensing surveys, next-generation PTAs, space-borne interferometers, precision astrometry, and laser ranging experiments.