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Super-hedging American options with semi-static trading strategies under model uncertainty. (English) Zbl 1396.91716

Summary: We consider the super-hedging price of an American option in a discrete-time market in which stocks are available for dynamic trading and European options are available for static trading. We show that the super-hedging price \(\pi\) is given by the supremum over the prices of the American option under randomized models. That is, \(\pi =\sup_{(c_i,Q_i)_i}\sum_ic_i\phi^{ Q_i}\), where \(c_i \in \mathbb{R}_+\) and the martingale measure \(Q^i\) are chosen such that \(\sum_ic_i=1\) and \(\sum_ic_iQ_i\) prices the European options correctly, and \(\phi^{Q_i}\) is the price of the American option under the model \(Q_i\). Our result generalizes the example given in [D. Hobson and A. Neuberger, “More on hedging American options under model uncertainty”, Preprint, arXiv:1604.0227] that the highest model-based price can be considered as a randomization over models.

MSC:

91G20 Derivative securities (option pricing, hedging, etc.)
60G40 Stopping times; optimal stopping problems; gambling theory
60G42 Martingales with discrete parameter

References:

[1] Bayraktar, E., Huang, Y.-J. & Zhou, Z. (2015) On hedging American options under model uncertainty, SIAM Journal on Financial Mathematics6 (1), 425-447, http://dx.doi.org/10.1137/140961869. · Zbl 1315.91060
[2] Bayraktar, E. & Zhou, Z. (2016a) Arbitrage, hedging and utility maximization using semi-static trading strategies with American options, Annals of Applied Probability26 (6), 3531-3558, http://dx.doi.org/10.1214/16-AAP1184. · Zbl 1357.91046
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[7] D. Hobson & A. Neuberger (2016) More on hedging American options under model uncertainty, arXiv:1604.0227v1.
[8] Hobson, D. & Neuberger, A. (2017) Model uncertainty and the pricing of American options, Finance and Stochastics21 (1), 285-329, http://dx.doi.org/10.1007/s00780-016-0314-2. · Zbl 1380.91131
[9] A. Neuberger (2007) Bounds on the American option, http://ssrn.com/abstract=966333.
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