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arXiv 1102.0301math.PR
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加权随机和的渐近性

Asymptotics for Weighted Random Sums

Mariana Olvera-Cravioto

摘要:

设$\{X_i\}$是具有中间正则变化(IR)右尾$\bar{F}$的独立同分布随机变量序列。设$(N, C_1, ..., C_N)$是一个与具有$N \in \mathbb{N} \cup \{\infty\}$的$\{X_i\}$无关的非负随机向量。研究了加权随机和$S_N = \sum_{i=1}^N C_i X_i$及其最大值$M_N = \sup_{1 \leq k < N+1} \sum_{i=1}^k C_i X_i$ .这些类型的和出现在随机递归的分析中,包括加权分支过程和自回归过程。特别是,我们推导出条件下,$$P(M_N > x) \sim P(S_N > x) \sim E[\sum_{i=1}^N \bar{F}(x/C_i)],$$作为$x \to \infty$。当$E[X_1] > 0$和$Z_N = \sum_{i=1}^N C_i$的分布也是IR时,我们得到了渐近关系$$P(M_N > x) \sim P(S_N > x) \sim E[\sum_{i=1}^N \bar{F}(x/C_i)] + P(Z_N > x/E[X_1]).$$。为了完整,当$Z_N$的分布是IR并且比$\bar{F}$重时,我们还得到了渐近关系$$P(M_N > x) \sim P(S_N > x) \sim P(Z_N > x/E[X_1])$$成立的条件。

英文摘要:

Let $\{X_i\}$ be a sequence of independent identically distributed random variables with an intermediate regularly varying (IR) right tail $\bar{F}$. Let $(N, C_1, ..., C_N)$ be a nonnegative random vector independent of the $\{X_i\}$ with $N \in \mathbb{N} \cup \{\infty\}$. We study the weighted random sum $S_N = \sum_{i=1}^N C_i X_i$, and its maximum, $M_N = \sup_{1 \leq k < N+1} \sum_{i=1}^k C_i X_i$. These type of sums appear in the analysis of stochastic recursions, including weighted branching processes and autoregressive processes. In particular, we derive conditions under which $$P(M_N > x) \sim P(S_N > x) \sim E[\sum_{i=1}^N \bar{F}(x/C_i)],$$ as $x \to \infty$. When $E[X_1] > 0$ and the distribution of $Z_N = \sum_{i=1}^N C_i$ is also IR, we obtain the asymptotics $$P(M_N > x) \sim P(S_N > x) \sim E[\sum_{i=1}^N \bar{F}(x/C_i)] + P(Z_N > x/E[X_1]).$$ For completeness, when the distribution of $Z_N$ is IR and heavier than $\bar{F}$, we also obtain conditions under which the asymptotic relations $$P(M_N > x) \sim P(S_N > x) \sim P(Z_N > x/E[X_1])$$ hold.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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