In this article we prove the positive invariance of a closed subset by the semiflow generated by a semi-linear non densely Cauchy problem. The condition impose to obtain such a property is a so called sub-tangential condition. We apply our results to a class of age structured population models.

中文翻译：

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非密集定义柯西问题的正不变子集

在本文中，我们通过半线性非密集柯西问题生成的半流证明了封闭子集的正不变性。获得这种特性所施加的条件是所谓的次切线条件。我们将我们的结果应用于一类年龄结构化的人口模型。