Uniformization
==============


* motivation for continuous model => BrowseRank

* d pi = pi Q dt 

* dpi/dt = pi Q

* e^A = sum A^n / n!  t^n

* pi(t) = e^{Qt}

* pi(t) = V diag(e^{lambda1}, e^{lambda2}, ..., e^{lambdan}) V^{-1}

-- one of the eigenvalues is 0, the others are positive

* example with 2 nodes

* P = I + Q/Lambda

* pi(t) = sum P^n P(N=n)