Limit Theorems for Sums of Heavy-tailed Variables with Random Dependent Weights

摘要

Let $U_{j} ,;j in mathbb{N}$ be independent and identically distributed random variables with heavy-tailed distributions. Consider a sequence of random weights ${left{ {W_{j} } right}}_{{j in mathbb{N}}}$ , independent of ${left{ {U_{j} } right}}_{{j in mathbb{N}}}$ and focus on the weighted sums ${sumnolimits_{j = 1}^{{left[ {nt} right]}} {W_{j} {left( {U_{j} - mu } right)}} }$ , where μ involves a suitable centering. We establish sufficient conditions for these weighted sums to converge to non-trivial limit processes, as n→∞, when appropriately normalized. The convergence holds, for example, if ${left{ {W_{j} } right}}_{{j in mathbb{N}}}$ is strictly stationary, dependent, and W 1 has lighter tails than U 1. In particular, the weights W j s can be strongly dependent. The limit processes are scale mixtures of stable Lévy motions. We establish weak convergence in the Skorohod J 1-topology. We also consider multivariate weights and show that they converge weakly in the strong Skorohod M 1-topology. The M 1-topology, while weaker than the J 1-topology, is strong enough for the supremum and infimum functionals to be continuous.