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Published online by Cambridge University Press: 25 March 2025
Let X be the sum of a diffusion process and a Lévy jump process, and for any integer $n\ge 1$ let
$\phi_n$ be a function defined on
$\mathbb{R}^2$ and taking values in
$\mathbb{R}$, with adequate properties. We study the convergence of functionals of the type
\begin{align*} \Delta_n\sum_{i=1}^{[t/\Delta_n]} \phi_n\!\left(\alpha_n\left[\frac{X_{(i-1)\Delta_n}}{\alpha_n}\right], \:\frac{\alpha_n}{\sqrt{\Delta_n}}\left(\left[\frac{X_{i\Delta_n}}{\alpha_n}\right]-\left[\frac{X_{(i-1)\Delta_n}}{\alpha_n}\right]\right)\right),\end{align*}
$(\Delta_n)$ and
$(\alpha_n)$ tend to 0 as
$n\to +\infty$. We then prove the law of large numbers and establish, in the case where
$\frac{\alpha_n}{\sqrt{\Delta_n}}$ converges to a real number in
$[0,+\infty)$], a new central limit theorem which generalizes that in the case where X is a continuous Itô’s semimartingale.