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تسجيل مستخدم جديدNear optimal thresholding estimation of a Poisson intensity on the real line
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The purpose of this paper is to estimate the intensity of a Poisson process $N$ by using thresholding rules. In this paper, the intensity, defined as the derivative of the mean measure of $N$ with respect to $ndx$ where $n$ is a fixed parameter, is assumed to be non-compactly supported. The estimator $tilde{f}_{n,gamma}$ based on random thresholds is proved to achieve the same performance as the oracle estimator up to a possible logarithmic term. Then, minimax properties of $tilde{f}_{n,gamma}$ on Besov spaces ${cal B}^{ensuremath alpha}_{p,q}$ are established. Under mild assumptions, we prove that $$sup_{fin B^{ensuremath alpha}_{p,q}cap ensuremath mathbb {L}_{infty}} ensuremath mathbb {E}(ensuremath | | tilde{f}_{n,gamma}-f| |_2^2)leq C(frac{log n}{n})^{frac{ensuremath alpha}{ensuremath alpha+{1/2}+({1/2}-frac{1}{p})_+}}$$ and the lower bound of the minimax risk for ${cal B}^{ensuremath alpha}_{p,q}cap ensuremath mathbb {L}_{infty}$ coincides with the previous upper bound up to the logarithmic term. This new result has two consequences. First, it establishes that the minimax rate of Besov spaces ${cal B}^{ensuremath alpha}_{p,q}$ with $pleq 2$ when non compactly supported functions are considered is the same as for compactly supported functions up to a logarithmic term. When $p>2$, the rate exponent, which depends on $p$, deteriorates when $p$ increases, which means that the support plays a harmful role in this case. Furthermore, $tilde{f}_{n,gamma}$ is adaptive minimax up to a logarithmic term.
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