Before revision:  Carr with Itkin and Sun have discussed the pricing of variance swaps under this type of model. This paper studies a special case of this model and observes an explosion of prices for squared volatility and variance swaps . It argues that such a price explosion may have deeper economic reasons, which should be taken into account when designing volatility derivativesraire portfolio.
After revision:  Carr with Itkin and Sun have discussed the pricing of variance swaps are obtained under the benchmark approach, which only requires the existence of the num\'{eraire portfolio.