The actual equation is probably in the journal article, which is pay-walled here:

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.204101

I really wish that paper wasn't paywalled because the linked article, as well as the one it in turn links, are not satisfactory at all. "An exact equation" could mean a lot of things.

EDIT: Oh, I see, what they did is to get an exact result for a previously perturbative one. Basically, the old formula was an approximation using certain assumptions which have now been dropped. - This does not mean, however, that quantum chaos now no longer "suffers" from a very strong sensitivity to initial conditions, as the two articles seem to imply.

No, if I use the link you provided it times out and doesn't finish loading at all, unfortunately.