Geometric resonances for high-frequency gravitational-wave detection

by Jan Heisig

Thursday Mar 5, 2026, 12:00 PM → 1:30 PM Europe/Madrid

IFAE Seminar Room (In-Person)

Gravitational waves at kilohertz and higher frequencies provide a unique window onto the early Universe at energy scales far beyond those accessible through the cosmic microwave background, potentially probing physics well above the electroweak scale. Yet existing detector concepts fall many orders of magnitude short of the big-bang nucleosynthesis bound on a stochastic gravitational-wave background in this regime. In this talk, I will present a new interferometric concept that exploits geometric resonances arising from directional changes of light inside high-Q optical cavities. For suitable folded or looped geometries, gravitational-wave–induced phase shifts can accumulate coherently over many traversals, leading to narrowband resonances with a characteristic comb-like structure. This distinctive spectral signature provides a powerful handle to discriminate a stochastic background from instrumental noise, without relying on cross-correlation between detectors. I will explain the underlying physical mechanism, discuss possible realizations compatible with planned tunnel layouts such as the Einstein Telescope, and comment on projected sensitivities, open challenges, and connections to established interferometer designs.