ABSTRACT

Ultralight bosons (ULBs) can form macroscopic superradiant clouds around spinning black holes. For scalar ULB mass μ ～ 10^(?21) eV, its cloud-induced dynamical friction significantly impacts supermassive black hole (SMBH) binary dynamics. Considering orbital-decay power of the century-monitored OJ287 system, we place novel bounds restricting ULB mass range μ ? (8.5?22)×10^(?22) eV independent of any dark matter assumptions and show ULB drag can also efficiently reconcile any future confirmations of the debated orbital decay excess. Meanwhile, we show that for scalar ULB masses μ ～ 10^(?22) ? 10^(?21) eV boson cloud dynamical friction drives SMBH final-parsec evolution in ? 1 Gyr and suppresses the nanohertz gravitational wave background with turnover. Forthcoming pulsar timing array data and precise SMBH orbital timings will decisively test this scenario.

BIOGRAPHY

Dr. Qianhang Ding is currently a postdoctoral researcher in the Center for Theoretical Physics of the Universe (CGA Group) in the Institute for Basic Science (South Korea). He obtained his PhD in Physics from the Hong Kong University of Science and Technology in 2023. Dr. Qianhang Ding mainly works on gravitational wave cosmology, and uses gravitational wave as a probe to understand the fundamental physics in cosmology, such as cosmic tensions in Lambda-CDM model, the property of dark universe.