STRICT LOCAL MARTINGALES VIA FILTRATION ENLARGEMENT
Aditi Dandapani, Philip Protter
Abstract
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Aditi Dandapani, Philip Protter
Abstract
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A strict local martingale is a local martingale that is not a martingale. We investigate how such a process might arise from a true martingale as a result of an enlargement of the filtration and a change of measure. We study and implement a particular type of enlargement, initial expansion of filtration, for stochastic volatility models with and without jumps and provide sufficient conditions in each of these cases such that initial expansion can create a strict local martingale. We provide examples of initial enlargement that effect this change.
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A strict local martingale is a local martingale that is not a martingale. We investigate how such a process might arise from a true martingale as a result of an enlargement of the filtration and a change of measure. We study and implement a particular type of enlargement, initial expansion of filtration, for stochastic volatility models with and without jumps and provide sufficient conditions in each of these cases such that initial expansion can create a strict local martingale. We provide examples of initial enlargement that effect this change.
Key concepts: Local martingale, Martingale (probability theory), Doob's martingale inequality, Mathematics, Martingale difference sequence, Martingale pricing, Filtration (mathematics), Stochastic differential equation