Author Archives: Fabrice Baudoin

MA694 Rough paths theory

During the Spring 2013 semester I will teach a class on rough paths theory and post the lectures on this blog. The rough paths theory was discovered by Terry Lyons in the 1990’s. The theory allows to solve differential equations … Continue reading

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Lecture 35. Weak differentiability for solutions of stochastic differential equations and the existence of a smooth density

As usual, we consider a filtered probability space which satisfies the usual conditions and on which is defined a -dimensional Brownian motion . Our purpose here, is to prove that solutions of stochastic differential equations are differentiable in the sense … Continue reading

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Lecture 34. The Wiener chaos expansion

As in the previous Lectures, we consider a filtered probability space on which is defined a Brownian motion , and we assume that is the usual completion of the natural filtration of . Our goal is here to write an … Continue reading

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Some advices to young mathematicians

Being a mathematician constantly ranks among the best jobs. The research in mathematics certainly offers an exciting intellectual adventure. For the young mathematicians and graduate students who wish to pursue a career in this domain, this article by Gian-Carlo Rota … Continue reading

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Lecture 33. The Malliavin matrix and existence of densities

More generally, by using the same methods as in the previous Lecture, we can introduce iterated derivatives. If , we set . We may then consider as a square integrable random process indexed by and valued in . By using … Continue reading

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Lecture 32. The Malliavin derivative

The next Lectures will be devoted to the study of the problem of the existence of a density for solutions of stochastic differential equations. The basic tool to study such questions is the so-called Malliavin calculus. Let us consider a … Continue reading

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Lecture 31. Then, a miracle occurs

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Lecture 30. Stratonovitch stochastic differential equations

As usual, let be a filtered probability space which satisfies the usual conditions. It is often useful to use the language of Stratonovitch ‘s integration to study stochastic differential equations because the Itō’s formula takes a much nicer form. If … Continue reading

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Lecture 29. The strong Markov property for solutions of stochastic differential equations

In the previous section, we have seen that if is the solution of a stochastic differential equation then is a Markov process, that is for every , where . It is remarkable that this property still holds when is now … Continue reading

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Lecture 28. The Feynman-Kac formula

It is now time to give some applications of the theory of stochastic differential equations to parabolic second order partial differential equations. In particular we are going to prove that solutions of such equations can represented by using solutions of … Continue reading

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