Stock market variance-return or price relations are sometimes negative and sometimes positive. We explain these puzzling findings using a model with two ("bad" and "good") variances. In the model, conditional equity premium depends positively on bad variance and negatively on good variance....

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...