The group of Prof. R. Walter focuses on three directions, driven by the study of the physics surrounding SMBHs at the centre of galaxies.

• The Cherenkov Telescope Array Observatory is the next generation of gamma-ray astronomy research infrastructure with a leading role in multi-wavelength and multi-messenger studies of the Universe. Its construction has started under the umbrella of an ERIC founded in January 2025, which Switzerland has joined. Ultra-relativistic jets powered by SMBH are the most impressive particle accelerators in the Universe. The trigger of their formation and the details of particle acceleration are not yet understood. As most of the jet power can be emitted in the gamma-ray band, CTAO will provide key information to answer these questions.
• The accretion power of the Universe is measured by the Cosmic X-ray Background (CXB), formed by the cumulative spectra emitted by accretion under various conditions, absorption geometry and the X-ray luminosity evolution of SMBH across the Universe. The CXB is measured with large systematic uncertainties. The group is leading the design and construction of the CXB Explorer, an instrument to be placed on the Chinese space station in 2029 to measure the CXB with an accuracy of 1%.
• Finally, the group is building a new optical spectral interferometer “QUASAR” for QUantum Astrophysics for Super Angular Resolution, aiming at obtaining optical images of accretion discs in quasars at a resolution of 10 micro-arcseconds, five times better than that obtained in the radio by the Event Horizon Telescope, and 1000 times the current observational capabilities in the optical.