New Horizons in Primordial Black Hole Physics

NEHOP 2026 brought together physicists working on primordial black holes, early-Universe cosmology and their observational probes. I was glad to contribute a plenary on connecting these signals across experiments.

Primordial black holes (PBHs) offer a particularly rich window onto the early Universe: the same large primordial curvature perturbations that collapse to form PBHs also generate a stochastic background of scalar-induced gravitational waves (SIGWs), while the PBHs themselves can later form binaries and merge, producing gravitational-wave signals in complementary frequency bands. In this talk, I explore how these signals can be connected across different experiments to probe PBHs over a vast range of masses. I begin with planetary-mass PBHs, whose formation is associated with micro-Hz SIGWs that could be targeted by future Lunar and Satellite Laser Ranging measurements. I then turn to sub-solar PBHs, discussing how mergers in ground-based interferometers and a nano-Hz SIGW background observed by pulsar timing arrays (PTAs) can arise from a common primordial origin. Finally, I switch gears to supermassive PBHs, whose binaries can produce chirping signals in PTAs, but whose abundance is strongly constrained by an effective field theory description of the high-redshift Lyman-alpha forest.

More information is available on the NEHOP 2026 event page, and the slides are available here.