Seminario

Il giorno 6 marzo alle ore 11 presso la stanza C412, Yuki Inoue (National Central University, Taiwan) terra' un seminario dal titolo

CHRONOS: A Cryogenic Sub-Hz Torsion-Bar Speed-Meter for Stochastic Gravitational-Wave Background Searches

Abstract

Abstract: The sub-Hz frequency band represents one of the last unexplored frontiers in gravitational-wave (GW) astronomy. Access to this regime opens a unique observational window onto cosmological stochastic gravitational-wave backgrounds (SGWB), early-Universe phase transitions, cosmic strings, and low-frequency compact binaries beyond the reach of current ground-based interferometers.
In this talk, I will present CHRONOS (Cryogenic sub-Hz cROss torsion-bar detector with quantum NOn-demolition Speed meter), a novel interferometric concept designed to probe the 0.1–10 Hz band from the ground. CHRONOS combines a cross torsion-bar topology with a Sagnac speed-meter configuration, implementing quantum non-demolition (QND) measurement principles to suppress radiation-pressure noise at low frequencies. In contrast to conventional position-meter Michelson interferometers, the rotational speed-meter observable intrinsically modifies the quantum noise coupling, enabling stable low-frequency performance. By operating cryogenic sapphire test masses, the detector further reduces thermal noise and aims to achieve quantum-noise-limited sensitivity in the sub-Hz regime. I will first outline the interferometer topology and the associated quantum-noise behavior that distinguish rotational speed-meter measurements from traditional configurations. I will then present the projected sensitivity and noise budget of CHRONOS, highlighting the achievable performance in the sub-Hz band.
Finally, I will discuss the prospects for stochastic gravitational-wave background searches, including sensitivity projections to cosmological models. CHRONOS provides a complementary path toward extending terrestrial gravitational-wave detection into the sub-Hz domain, bridging the frequency gap between existing ground-based detectors and future space missions, and opening new opportunities for probing fundamental physics and cosmology.