New strategies for seismic attenuation at low frequency for third generation gravitational waves detectors

Gravitational waves have revolutionised the way we study the Universe. The second-generation interferometers, LIGO, Virgo and KAGRA, are preparing for the next observational campaigns, while the future third-generation interferometers, Einstein Telescope and Cosmic Explorer, are expected to increase the sensitivity by an order of magnitude. In particular, improved low-frequency sensitivity is essential for detecting high-mass systems that allow to explore the Universe at high redshift, i.e., before the formation of the first stars. Furthermore, good low-frequency sensitivity allows for better source localisation, effective pre-alerts for electromagnetic follow-up campaigns, and the detection of expected (but yet to be observed) gravitational waves emitted by sources such as rotating pulsars. In this proceeding, we will present ongoing experimental studies on new mechanical prototypes to address the low-frequency seismic noise attenuation.