I am recently studying about chemical reaction networks. And I have problem about application of Kolmogorov system to actual examples.
So, here's a chemical reaction
$S_1 + S_2 \rightarrow S_3$ with $k_1$.
$S_3 \rightarrow S_1 + S_2$ with $k_2$.
So, I know that propensity functions are $k_1 N_1 N_2$ and $k_2 N_3$. But how can I get the mean and variance of $S_1$ from Kolmogorov system? I studied the concept of Kolmogorov system, but I still have no idea how to get it.
And here's the paper : https://aip.scitation.org/doi/10.1063/1.3103264