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Description
Table-top-size ultra-stable Fabry-Perot optical cavities are one of the most precise measuring instruments and, together with optical atomic clocks, play a vital role in state-of-the-art metrology and fundamental physics tests. Here we present two applications for the cavity itself: detecting gravitational waves [1] and testing the hypothesis of space-time fluctuations [2].
The first gravitational-wave detection attempts were based on mechanical resonances in large aluminum bars triggered by a passing gravitational wave [3]. To date, none of the proposed resonant-mass bar detectors have provided evidence of gravitational-wave events through acoustic resonance, despite their extremely stable operation and excellent noise reduction. We propose a resonant detector based on existing and rapidly developing Fabry-Perot cavities. This "bar-like" detector can observe frequencies from a few kHz to tens of kHz, depending on its length and material, surpassing the range covered by previous resonant detectors. Ultra-stable optical cavities allow detection not only of predicted gravitational-wave signals such as binary neutron star mergers, post-mergers, subsolar-mass primordial black hole mergers, and collapsing stellar cores, but also of new physics beyond the Standard Model, including searches for ultralight bosons such as QCD axions and axion-like particles formed through black hole superradiance.
Beyond their potential as gravitational-wave detectors, ultra-stable optical cavities may offer a way to test fundamental limits of spacetime itself. Many unifying theories predict quantum fluctuations of spacetime at extremely small distances [4]. This fundamental fuzziness, often called space-time foam, may limit the precision of length measurements to the Planck length [5]. As a result, quantum-gravity-induced fluctuations may set the ultimate limit for distance measurements and as a result frequency stability of ultra-stable Fabry-Perot optical cavities [6]. Therefore, the noise budget of a set of independent ultra-stable cavities can be used to constrain the amplitude of such fluctuations.
[1] M. Narożnik, M. Bober, and M. Zawada, Phys. Lett. B 846, 138260 (2023).
[2] M. Narożnik, et al. in preparation.
[3] J. Weber, Phys. Rev. 117, 306 (1960).
[4] G. Amelino-Camelia, Living Reviews in Relativity 16, 5 (2013).
[5] G. Calcagni, M. Ronco, Nuclear Physics B 923, 144 (2017).
[6] G. Amelino-Camelia, Nature 398, 216 (1999).
| Parallel session | New Physics Searches: Dark Matter and High-Frequency Gravitational Waves |
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