Brownian time reversal for fixed-strike lookback extrema (source code)

= Brownian time reversal for fixed-strike lookback extrema

For a <Brownian motion with drift> $X$, the process $X_T-X_{T-t}$ on $[0,T]$ has the same law as $X_t$. Therefore
$$
X_T-\min_{t\leq T}X_t
\quad\text{and}\quad
\max_{t\leq T}X_t
$$
have the same distribution, which equates the corresponding geometric-Brownian lookback payoffs.