A Brownian sheet martingale with the same marginals as the arithmetic average of geometric Brownian motion.
Let (Ω, , ()t≥0, ) be a filtered probability space satisfying the usual assumptions: it is usually not possible to extend to (theσ-algebra generated by ()t≥0) a coherent family of probability measures () indexed byt≥0, each of them being defined on . It is known that for instance, on the Wiener space, this extension problem has a positive answer if one takes the filtration generated by the coordinate process, made right-continuous, but can have a negative answer if one takes its usual augmentation....
Let (Ω, , ()t≥0, ) be a filtered probability space satisfying the usual assumptions: it is usually not possible to extend to (the σ-algebra generated by ()t≥0) a coherent family of probability measures () indexed by t≥0, each of them being defined on . It is known that for instance, on the Wiener space, this extension problem has a positive answer if one takes the filtration generated by the coordinate process, made right-continuous, but can have a negative answer if one takes its usual...