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 ...
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Conclusions and perspectives<br />
In the first part of this thesis we have solved, using <strong>en</strong>tropic regularization, the ill-posed problem<br />
of calibrating an expon<strong>en</strong>tial Lévy mo<strong>de</strong>l to options data and proposed a stable numerical<br />
m<strong>et</strong>hod for computing this solution. Applying our m<strong>et</strong>hod to prices of in<strong>de</strong>x options allowed us<br />
to estimate the risk-neutral Lévy measures, implied by mark<strong>et</strong> prices. This object is the analog,<br />
for expon<strong>en</strong>tial Lévy mo<strong>de</strong>ls, of implied volatility, used in the Black-Scholes framework. Our<br />
empirical results allow to make a number of important conclusions. First, using an expon<strong>en</strong>tial<br />
Lévy mo<strong>de</strong>l one can calibrate with high precision the prices of a s<strong>et</strong> of options with common<br />
maturity. Moreover, high quality of calibration is achieved already by using finite-int<strong>en</strong>sity Lévy<br />
processes. Therefore, from the point of view of option pricing the imperative for using more<br />
complex infinite-int<strong>en</strong>sity mo<strong>de</strong>ls is not clear. The third conclusion is that ev<strong>en</strong> in the nonparam<strong>et</strong>ric<br />
s<strong>et</strong>ting it is impossible, using an expon<strong>en</strong>tial Lévy mo<strong>de</strong>l, to calibrate accurately<br />
the prices of stock in<strong>de</strong>x options of several maturities at the same time: options of differ<strong>en</strong>t<br />
maturities produce differ<strong>en</strong>t implied Lévy measures. This confirms the observation already ma<strong>de</strong><br />
by several authors [13, 68] that the framework of expon<strong>en</strong>tial Lévy mo<strong>de</strong>ls is not suffici<strong>en</strong>tly<br />
flexible to reproduce the term structure of implied volatilities correctly.<br />
In view of the above conclusions, we plan to continue the line of research initiated by this<br />
thesis, by ext<strong>en</strong>ding its results to mo<strong>de</strong>ls of stock price behavior that do allow to <strong>de</strong>scribe the<br />
<strong>en</strong>tire term structure of implied volatilities, e.g. mo<strong>de</strong>ls based on additive processes (processes<br />
with in<strong>de</strong>p<strong>en</strong><strong>de</strong>nt but not stationary increm<strong>en</strong>ts) and hybrid mo<strong>de</strong>ls including both jumps and<br />
stochastic volatility. The second important direction of future research is to investigate the<br />
impact of our calibration m<strong>et</strong>hodology on the m<strong>et</strong>hods of hedging in pres<strong>en</strong>ce of jumps in stock<br />
prices.<br />
In the second part of this thesis we introduced the notion of Lévy copula, providing a<br />
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