Time evolution of the simulation with Σ₀ = 30 M_⊙ pc⁻² and speed of sound c_s = 10 km s⁻¹, as an example of weak accretion with central shocks. Top: simulation showing a steady accretion rate of 10^−3⋯−2 M_⊙ yr⁻¹. Bottom: firstfragmentation occurring around 100 pc and inside the nuclear ring at 800 pc. Later onthe inner fragmentation fades and a rather eccentric ring and inner shocks form at 80 pc.