I am having trouble understanding the QE scheme of Andersen.
Leif Andersen: Efficient Simulation of the Heston Stochastic Volatility Model, 2006
Is it possible for the variance process to become zero? There is a switching rule. If $v=a(b+Z)^2$, then the probability is zero I think. (Only if b=Z since a>0). But for the other process, I don't know what will happen.