Bond pricing under Knightian uncertainty: A short rate model with drift and volatility uncertainty

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 without admitting arbitrage. The pricing of zero-coupon bonds in such a setting differs substantially from the traditional models, since the prices need to be chosen in a different way in order to exclude arbitrage.