A remark on Gatheral's 'most-likely path approximation' of implied volatility

Abstract

We give a new proof of the representation of implied volatility as a time-average of weighted expectations of local or stochastic volatility. With this proof we clarify the question of existence of 'forward implied variance' in the original derivation of Gatheral, who introduced this representation in his book 'The Volatility Surface'.

arXiv comment6 pages