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JOURNALS // Zapiski Nauchnykh Seminarov POMI // Archive

Zap. Nauchn. Sem. POMI, 2011 Volume 396, Pages 144–154 (Mi znsl4656)

This article is cited in 1 paper

Beneš condition for discontinuous exponential martingale

R. Liptser

Department of Electrical Engineering Systems, Tel Aviv University, Tel Aviv, Israel

Abstract: It is known that the Girsanov exponent $\mathfrak z_t$, being solution of Doléans-Dade equation $\mathfrak z_t=1+\int_0^t\mathfrak z_s\alpha(s)\,dB_s$ generated by Brownian motion $B_t$ and a random process $\alpha(t)$ with $\int_0^t\alpha^2(s)\,ds<\infty$ a.s., is the martingale provided that the Beneš condition
$$ |\alpha(t)|^2\le\mathrm{const.}\big[1+\sup_{s\in[0,t]}B^2_s\big],\quad\forall\ t>0, $$
holds true. In this paper, we show that $\int_0^t\alpha(s)\,dB_s$ can be replaced by a purely discontinuous square integrable martingale $M_t$ paths from the Skorokhod space $ \mathbb D_{[0,\infty)}$ having jumps $\alpha(s)\triangle M_t>-1$. The method of proof differs from the original Beneš proof.

Key words and phrases: Girsanov's exponential martingale, uniform integrability.

UDC: 519.1+519.2

Received: 29.08.2011

Language: English


 English version:
Journal of Mathematical Sciences (New York), 2013, 188:6, 717–723

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