In this study, we derived analytic expressions for the elliptical truncated moment generating function (MGF), the zeroth-, first-, and second-order moments of quadratic forms of the multivariate normal, Student's t, and generalised hyperbolic distributions. The resulting formulae were tested in a numerical application to calculate an analytic expression of the expected shortfall of quadratic portfolios with the benefit that moment based sensitivity measures can be derived from the analytic expression. The convergence rate of the analytic expression is fast -one iteration -for small closed integration domains, and slower for open integration domains when compared to the Monte Carlo integration method. The analytic formulae provide a theoretical framework for calculations in robust estimation, robust regression, outlier detection, design of experiments, and stochastic extensions of deterministic elliptical curves results.
Keywords: Multivariate truncated moments, Quadratic forms, Elliptical Truncation, Tail moments, Parametric distributions, Elliptical functionsThe first results on truncated moments were concerned with the linear truncated multivariate normal (MVN) distribution, and were provided by Tallis (1961). Tallis (1963) extended the results of linear truncations to the case of elliptical and radial truncation, and Tallis (1965) built on previous results to calculate the moments of a normal distribution with a plane truncation. Mantegna and Stanley (1994) used a truncated Lévy distribution to create a distribution where the sums have slow convergence towards the normal, providing first-and second-order moments. Masoom and Nadarajah (2007) calculated the truncated moments of a generalised Pareto distribution. Arismendi (2013) generalised the results of Tallis (1961) for higher-order moments, and for other elliptical distributions such as the Student's t and the lognormal distributions, and for a finite mixture of multivariate normal distributions.
1In this study, we derived analytical formulae for the calculation of the elliptical truncated moments of the multivariate normal distribution. We calculated an analytical expansion of the elliptical truncated moment generating function (MGF), and then derived this expression for the calculation of the elliptical truncated moments. Previous results on elliptical and radial truncated moments on multivarite normal distributions were provided by Tallis (1963). In this research we used the results of Ruben (1962) to derive the analytical expressions. We then applied the multivariate normal results to derive the multivariate Student's t (MST) and the multivariate generalised hyperbolic (MGH) elliptical truncated moments. Our results can be considered an extension of Ruben's (1962) results for the MST and MGH cases. The importance of elliptical truncated moments' expansions are evident in applications such as the design of experiments (Thompson, 1976;Cameron and Thompson, 1986), robust estimation (Cuesta-Albertos et al., 2008), outlier detection $ The author wish...