Abstract
We consider the problem of superhedging under volatility uncertainty for an
investor allowed to dynamically trade the underlying asset and statically trade
European call options for all possible strikes and finitely-many maturities. We
present a general duality result which converts this problem into a min-max
calculus of variations problem where the Lagrange multipliers correspond to the
static part of the hedge. Following Galichon, Henry-Labordére and Touzi
ght, we apply stochastic control methods to solve it explicitly for
Lookback options with a non-decreasing payoff function. The first step of our
solution recovers the extended optimal properties of the Azéma-Yor solution
of the Skorokhod embedding problem obtained by Hobson and Klimmek
hobson-klimmek (under slightly different conditions). The two marginal
case corresponds to the work of Brown, Hobson and Rogers
brownhobsonrogers. The robust superhedging cost is complemented by
(simple) dynamic trading and leads to a class of semi-static trading
strategies. The superhedging property then reduces to a functional inequality
which we verify independently. The optimality follows from existence of a model
which achieves equality which is obtained in Obłój and Spoida OblSp.
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