PT  - JOURNAL ARTICLE
AU  - Hideharu Funahashi
TI  - An Approximate Swaption Formula in Heath-Jarrow-Morton Models
AID  - 10.3905/jod.2020.1.101
DP  - 2020 Mar 27
TA  - The Journal of Derivatives
PG  - jod.2020.1.101
4099  - https://pm-research.com/content/early/2020/03/27/jod.2020.1.101.short
4100  - https://pm-research.com/content/early/2020/03/27/jod.2020.1.101.full
AB  - This article provides an analytical approximation formula for a swaption price when the instantaneous forward rate follows a Heath-Jarrow-Morton (HJM) model. Our approximation strategy, based on the chaos expansion approximation, is to replicate the probability density function of the complex quasi-Gaussian process from a simpler one, which has a semi-closed form solution. It is not restricted to the liner approximation, as is the technique proposed by the existing literature, but can be extended to higher order approximations. Moreover, computation of our approximation is fast; hence, it is suitable for calibration purposes. We illustrate our results through numerical implementation and calibration done using market data.TOPICS: Options, interest-rate and currency swaps, derivativesKey Findings• Our approximation strategy, based on the chaos expansion approximation, is to replicate the probability density function of the complex quasi-Gaussian process from a simpler one, which has a semi-closed form solution.• It is not restricted to the liner approximation, as is the technique proposed by the existing literature, but can be extended to higher order approximations.• Computation of our approximation is fast; hence, it is suitable for calibration purposes.