The objective of this article is to derive a general martingale characterization of G-Brownian motion, which generalizes the results obtained in Xu [17]. For this end, we first study some extensions of stochastic calculus with respect to G-martingales under the sublinear expectation spaces

It is shown how to construct an arbitrage-free short rate model under uncertainty about the drift and the volatility. The uncertainty is represented by a set of priors, which naturally leads to a G-Brownian motion. Within this framework, it is shown how to characterize the whole term structure...