A, B, α, β, λ1, λ2
The inter-arrival times of the topics follow a Poisson point process with a mean of λ1
The times of activity of each user follow a Poisson point process with density λ2
All topics in the global list are adopted with an equal weight A
The weight decays exponentially with time with a decay parameter of α
Likewise, B and β are the corresponding parameters for local weights (weights of topic instances created by any user)

Variation with A
Variation with A (after truncating initial topics)

Variation with alpha for super-viral regime