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Precise Asymptotics in the Law of the Iterated Logarithm of Moving-Average Processes
Authors:Yun Xia Li  Li Xin Zhang
Institution:(1) Zhejiang University of Finance and Economics, Hangzhou 310012, P. R. China;(2) Department of Mathematics, Zhejiang University, Hangzhou 310028, P. R. China
Abstract:Abstract   In this paper, we discuss the moving-average process $$
X_{k}  = {\sum\nolimits_{i =  - \infty }^\infty  {\alpha _{{i + k}} \varepsilon _{i} } }
$$ , where {α i ;-∞ < i < ∞} is a doubly infinite sequence of identically distributed φ-mixing or negatively associated random variables with mean zeros and finite variances, {α i ;-∞ < i < ∞} is an absolutely summable sequence of real numbers. Set $$
S_{n}  = {\sum\nolimits_{k = 1}^n {X_{k} ,n \geqslant 1} }
$$ . Suppose that $$
\sigma ^{2}  = E\varepsilon ^{2}_{1}  + 2{\sum\nolimits_{k = 2}^\infty  {E\varepsilon _{1} \varepsilon _{k} } } > 0
$$ . We prove that for any $$
\delta  \geqslant 0,{\text{if}}E{\left {\varepsilon ^{2}_{1} {\left( {\log \log {\left| {\varepsilon _{1} } \right|}} \right)}^{{\delta  - 1}} } \right]} < \infty 
$$ ,
$$
{\mathop {\lim }\limits_{ \in  \searrow o} } \in ^{{2\delta  + 2}} {\sum\limits_{n = 1}^\infty  {\frac{{{\left( {\log \log n} \right)}^{\delta } }}
{{n\log n}}} }P{\left\{ {{\left| {S_{n} } \right|} \geqslant \varepsilon \tau {\sqrt {2n\log \log n} }} \right\}} = \frac{1}
{{{\left( {\delta  + 1} \right)}{\sqrt \pi  }}}\Gamma {\left( {\delta  + 3/2} \right)},
$$
, and if $$
E{\left {\varepsilon ^{2}_{1} {\left( {\log {\left| {\varepsilon _{1} } \right|}} \right)}^{{\delta  - 1}} } \right]} < \infty 
$$ ,
$$
{\mathop {\lim }\limits_{ \in  \searrow o} } \in ^{{2\delta  + 2}} {\sum\limits_{n = 1}^\infty  {\frac{{{\left( {\log n} \right)}\delta }}
{n}} }P{\left\{ {{\left| {S_{n} } \right|} \geqslant \varepsilon \tau {\sqrt {n\log n} }} \right\}} = \frac{{\mu ^{{{\left( {2\delta  + 2} \right)}}} }}
{{\delta  + 1}}\tau ^{{2\delta  + 2}} ,
$$
where $$
\tau  = \sigma  \cdot {\sum\nolimits_{i =  - \infty }^\infty  {\alpha _{i} ,\Gamma {\left(  \cdot  \right)}} }
$$ is a Gamma function and μ(2δ+2) stands for the (2δ + 2)-th absolute moment of the standard normal distribution. Research supported by National Natural Science Foundation of China
Keywords:" target="_blank">                          Moving-average process  φ  -mixing  Negative association  The law of the iterated logarithm
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