“…As already mentioned, experiments with ultra-cold atoms in which the interaction strength and other parameters are controlled provide the main motivation for these studies [ 61 , 62 , 63 , 64 , 65 , 80 ]. There is now a series of theoretical investigations by a Kolkata group (references [ 25 , 26 , 27 , 28 , 29 , 81 , 82 , 83 ]), and the results of these studies are briefly described in this section. These include (i) an analysis of level fluctuations using GOE and related ensembles in trapped interacting boson systems, diffuse van der Walls clusters and molecular resonances in erbium isotopes; and (ii) statistical relaxation in interaction quench dynamics of ultra-cold bosons and thermalization in isolated quantum systems.…”