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Problem 326 of 333MediumStochastic CalculusP326
Volatility of volatility and the square root
Under the pricing measure, a stock's instantaneous variance follows a driftless geometric Brownian motion,
so volatility starts at 20%. The volatility of variance is , with time in years.
(a) Use Itô's lemma to find the SDE for the volatility . What are its drift and its volatility?
(b) Find and compare it with .
(c) Find the median of . A trader argues that variance is a fair game here, so volatility must be one too. What is wrong with the argument?
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