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XIV: 25, 220-222, LNM 784 (1980)

**YAN, Jia-An**

Caractérisation d'ensembles convexes de $L^1$ ou $H^1$ (Stochastic calculus, Functional analysis)

This is a new and simpler approach to the crucial functional analytic lemma in 1354 (the proof that semimartingales are the stochastic integrators in $L^0$). That is, given a convex set $K\subset L^1$ containing $0$, find a condition for the existence of $Z>0$ in $L^\infty$ such that $\sup_{X\in K}E[ZX]<\infty$. A similar result is discussed for $H^1$ instead of $L^1$

Comment: This lemma, instead of the original one, has proved very useful in mathematical finance

Keywords: Semimartingales, Stochastic integrals, Convex functions

Nature: Original

Retrieve article from Numdam

Caractérisation d'ensembles convexes de $L^1$ ou $H^1$ (Stochastic calculus, Functional analysis)

This is a new and simpler approach to the crucial functional analytic lemma in 1354 (the proof that semimartingales are the stochastic integrators in $L^0$). That is, given a convex set $K\subset L^1$ containing $0$, find a condition for the existence of $Z>0$ in $L^\infty$ such that $\sup_{X\in K}E[ZX]<\infty$. A similar result is discussed for $H^1$ instead of $L^1$

Comment: This lemma, instead of the original one, has proved very useful in mathematical finance

Keywords: Semimartingales, Stochastic integrals, Convex functions

Nature: Original

Retrieve article from Numdam