December 22nd, 2010, 10:38 am
perhaps nothing much: in a black-schole world the pnl due to difference in price vol and realized vol can be expressed as gamma profits integrated over the option maturity at realized vol minus the same at price vol (see the paper "which free lunch would you like today, sir?: delta hedging, volatility arbitrage and optimal portfolios" by Ahmad and Wilmott for the exact expressions). this is equivalent to vega in some sense (and without normalizing i.e. vega in this sense is not dV/dVol, rather only dV due to change in vol)