An important purpose of derivatives modelling is to provide practitioners with actionable measures of risk. The Black and Scholes volatility remains a favourite on trading floors in spite of well-known biases. One popular extension is to make volatility a function of time and the underlying...

In derivatives modelling, it has often been necessary to make assumptions about the volatility of the underlying variable over the life of the contract. This can involve specifying an exact trajectory, as in the Black and Scholes (1973), Merton (1973) or Black (1976) models; one that depends on...

In this addendum to Carey (2005), we draw several more analogies with the Black-Scholes model. We derive the characteristic function of the underlying log process as a function of the volatilities of all orders. Option prices are shown to satisfy an infinite-order version of the Black-Scholes...