Processus de Lévy en Finance - Laboratoire de Probabilités et ...
Processus de Lévy en Finance - Laboratoire de Probabilités et ...
Processus de Lévy en Finance - Laboratoire de Probabilités et ...
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Abstract<br />
This thesis <strong>de</strong>als with the mo<strong>de</strong>lling of stock prices by the expon<strong>en</strong>tials of Lévy processes.<br />
In the first part we <strong>de</strong>velop a non-param<strong>et</strong>ric m<strong>et</strong>hod allowing to calibrate expon<strong>en</strong>tial Lévy<br />
mo<strong>de</strong>ls, that is, to reconstruct such mo<strong>de</strong>ls from the prices of mark<strong>et</strong>-quoted options. We<br />
study the stability and converg<strong>en</strong>ce properties of this calibration m<strong>et</strong>hod, <strong>de</strong>scribe its numerical<br />
implem<strong>en</strong>tation and give examples of its use. Our approach is first to reformulate the calibration<br />
problem as that of finding a risk-neutral expon<strong>en</strong>tial Lévy mo<strong>de</strong>l that reproduces the option<br />
prices with the best possible precision and has the smallest relative <strong>en</strong>tropy with respect to a<br />
giv<strong>en</strong> prior process, and th<strong>en</strong> to solve this problem via the regularization m<strong>et</strong>hodology, used in<br />
the theory of ill-posed inverse problems. Applying this calibration m<strong>et</strong>hod to the empirical data<br />
s<strong>et</strong>s of in<strong>de</strong>x options allows us to study some properties of Lévy measures, implied by mark<strong>et</strong><br />
prices.<br />
The second part of this thesis proposes a m<strong>et</strong>hod allowing to characterize the <strong>de</strong>p<strong>en</strong><strong>de</strong>nce<br />
structures among the compon<strong>en</strong>ts of a multidim<strong>en</strong>sional Lévy process and to construct multidim<strong>en</strong>sional<br />
expon<strong>en</strong>tial Lévy mo<strong>de</strong>ls. This is done by introducing the notion of Lévy copula,<br />
which can be se<strong>en</strong> as an analog for Lévy processes of the notion of copula, used in statistics<br />
to mo<strong>de</strong>l <strong>de</strong>p<strong>en</strong><strong>de</strong>nce b<strong>et</strong>we<strong>en</strong> real-valued random variables. We give examples of param<strong>et</strong>ric<br />
families of Lévy copulas and <strong>de</strong>velop a m<strong>et</strong>hod for simulating multidim<strong>en</strong>sional Lévy processes<br />
with <strong>de</strong>p<strong>en</strong><strong>de</strong>nce giv<strong>en</strong> by a Lévy copula.<br />
Key words: Lévy processes, option pricing, calibration, inverse problems, regularization,<br />
ill-posed problems, relative <strong>en</strong>tropy, copulas, <strong>de</strong>p<strong>en</strong><strong>de</strong>nce