Cox processes model overdispersed point process data via a latent stochastic intensity, but both nonparametric estimation of the intensity model and posterior inference over intensity paths are typically intractable, relying on expensive MCMC methods. We introduce Neural Diffusion Intensity Models, a variational framework for Cox processes driven by neural SDEs. Our key theoretical result, based on enlargement of filtrations, shows that conditioning on point process observations preserves the diffusion structure of the latent intensity with an explicit drift correction. This guarantees the variational family contains the true posterior, so that ELBO maximization coincides with maximum likelihood estimation under sufficient model capacity. We design an amortized encoder architecture that maps variable-length event sequences to posterior intensity paths by simulating the drift-corrected SDE, replacing repeated MCMC runs with a single forward pass. Experiments on synthetic and real-world data demonstrate accurate recovery of latent intensity dynamics and posterior paths, with orders-of-magnitude speedups over MCMC-based methods.
Figures & tables
Figure 1: The variance curve exceeds the mean curve, indicating strong overdispersion of the arrival point process, in the US Bank data from ( SEE Lab, Technion, 2024 ) .
Figure 2: Comparing learned prior drift bθ(Zt,t) (purple) to the ground truth drift b~(Zt,t)=0.3(80−Zt) (yellow).
Figure 3: The learned data samples (red) compared to the true data samples (blue).
Figure 4: The learned posterior sample paths (red) are generated using the learned (bθ,uβ) pair, and the baseline “true” posterior sample paths are generated using extensive MCMC simulations (blue).
Figure 5: Train vs. test Wasserstein distance between amortized posterior samples and high-fidelity MCMC posterior samples as a function of the training sample size n . A train-test gap indicates overfitting of the amortized correction uβ(⋯,X) , which vanishes as n goes beyond 16 .
True drift b~
EM ( ℓ2 loss)
VI ( ℓ2 loss)
0.3(80−Zt)
6.159
5.792
0.3(80−Zt)−5t
6.721
4.989
Table 1: Comparison of the learned prior quality in terms of ℓ2 deviation of the intensity paths.
Figure 6: The learned data samples (red) compared to the true data samples (blue).
Faculty of Informatics, Università della Svizzera italiana, Lugano, Switzerland · Department of Mathematics and Statistics, University of Cyprus, Nicosia, Cyprus