Year: 2026
Type: preprint
Abstract: In General Relativity, axial and polar black-hole perturbations share identical quasinormal-mode spectra, a property known as isospectrality. New physics can break this degeneracy, producing a spectral splitting analogous to atomic fine structure. We perform a theory-agnostic search for such splitting in gravitational-wave observations. We find no evidence for isospectrality breaking and place a combined $90\%$ upper limit of $<28.5\%$ on the relative frequency splitting. We map these constraints onto several modified-gravity theories, constraining the coupling-lengths to be $\lesssim 28\,\mathrm{km}$.
Source: arXiv (Cornell University)
Institution: University of Cambridge
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, National Centre for Supercomputing Applications, National Research Foundation, Ministry of Education, Culture, Sports, Science and Technology, Academia Sinica, Centre National de la Recherche Scientifique, Istituto Nazionale di Fisica Nucleare, Ministry of Science and ICT, South Korea, National Science and Technology Council, Science and Technology Facilities Council, Japan Society for the Promotion of Science
OpenAlex ID: W7222294619