Speaker: Dr. Joseph Samuel, International Centre for Theoretical Sciences (ICTS)

Abstract: Radio imaging of distant black holes by the Event Horizon Telescope involves Very-Long-Baseline-Interferometry (VLBI) observations, with intercontinental baselines. Polarisation information is also important as this can reveal the magnetic fields present in these sources. Such observations are often corrupted by local conditions at each telescope, with  ionospheric fluctuations and amplifier gains playing a role.  
This talk describes the use of the mathematics of non-abelian gauge theory, Group theory and Graph theory to find closure invariants: quantities robust against local fluctuations that reveal true information about the astronomical source.