无参数粗糙路径空间拓扑学

Thomas Cass, William F. Turner
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引用次数: 0

摘要

一条 $p$ 弱几何粗糙路径的签名概括了一条路径的广义重参数化概念。对无参数化路径空间拓扑的研究始于 [CT24b] 对有界变化路径的研究,对基于签名的方法在各种应用中的使用具有实际意义。本注释将 [CT24b] 中的大部分结果扩展到无参数弱几何粗糙路径空间。我们研究了三类拓扑:商映射连续的可元拓扑;从底层路径空间导出的商拓扑;以及每个等价类的树还原代表之间的显式度量。我们证明了第一类拓扑(在附加假设下)是可分离的、Lusin 的,但不是局部紧凑的或完全可度量的。商拓扑是 Hausdorff 的,但不是可元的,而生成第三种拓扑的度量不是完全的,其拓扑也不是局部紧凑的。我们还证明,当$p=1$时,第三拓扑是波兰拓扑。
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Topologies on unparameterised rough path space
The signature of a $p$-weakly geometric rough path summarises a path up to a generalised notion of reparameterisation. The quotient space of equivalence classes on which the signature is constant yields unparameterised path space. The study of topologies on unparameterised path space, initiated in [CT24b] for paths of bounded variation, has practical bearing on the use of signature based methods in a variety applications. This note extends the majority of results from [CT24b] to unparameterised weakly geometric rough path space. We study three classes of topologies: metrisable topologies for which the quotient map is continuous; the quotient topology derived from the underlying path space; and an explicit metric between the tree-reduced representatives of each equivalence class. We prove that topologies of the first type (under an additional assumption) are separable and Lusin, but not locally compact or completely metrisable. The quotient topology is Hausdorff but not metrisable, while the metric generating the third topology is not complete and its topology is not locally compact. We also show that the third topology is Polish when $p=1$.
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