Hagan, Patrick; Woodward, Diana - In: Applied Mathematical Finance 6 (1999) 3, pp. 147-157
We consider European calls and puts on an asset whose forward price F(t) obeys dF(t)=α(t)A(F)dW(t,) under the forward measure. By using singular perturbation techniques, we obtain explicit algebraic formulas for the implied volatility σB in terms of today's forward price F0 ≡ F(0), the...