Dynamic network models and graphon estimation

In the present paper we consider a dynamic stochastic network model. The objective is estimation of the tensor of connection probabilities $\Lambda$ when it is generated by a Dynamic Stochastic Block Model (DSBM) or a dynamic graphon. In particular, in the context of DSBM, we derive penalized least squares estimator $\widehat{\Lambda}$ of $\Lambda$ and show that $\widehat{\Lambda}$ satisfies an oracle inequality and also attains minimax lower bounds for the risk. We extend those results to estimation of $\Lambda$ when it is generated by a dynamic graphon function. The estimators constructed in the paper are adaptive to the unknown number of blocks in the context of DSBM or of the smoothness of the graphon function. The technique relies on the vectorization of the model and leads to to much simpler mathematical arguments than the ones used previously in the stationary set up. In addition, all our results are non-asymptotic and allow a variety of extensions.