We derive a closed-form solution for the price of an average price as well as
an average strike geometric Asian option, by making use of the path integral
formulation. Our results are compared to a numerical Monte Carlo simulation. We
also develop a pricing formula for an Asian option with a barrier on a control
process, combining the method of images with a partitioning of the set of paths
according to the average along the path. This formula is exact when the
correlation is zero, and is approximate when the correlation increases.
In this paper, a time substitution as used by Duru and Kleinert in their
treatment of the hydrogen atom with path integrals is performed to price timer
options under stochastic volatility models. We present general pricing formulas
for both the perpetual timer call options and the finite time-horizon timer
call options. These general results allow us to find closed-form pricing
formulas for both the perpetual and the finite time-horizon timer options under
the 3/2 stochastic volatility model as well as under the Heston stochastic
volatility model.