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arXiv 1209.5909math.MGmath.FA
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Wasserstein空间中测地线的分解及其整体化性质

Decomposition of geodesics in the Wasserstein space and the globalization property

Fabio Cavalletti

摘要:

我们将证明Wasserstein测地线在以下意义下的分解:设$(X,d,m)$是一个验证$\mathsf{CD}_{loc}(K,N)$或等价于$\mathsf{CD}^{*}(K,N)$的无分支度量测度空间。我们证明了$L^{2}$-Wasserstein空间中的每个测地线$μ_{t}$(带有$μ_{t} \ll m$)都可以分解为两个密度的乘积,一个对应于具有余维支持的测地线,一个验证了$\mathsf{CD}^{*}(K,N-1)$,另一个与精确的一维测量相关联,只要长度映射具有局部Lipschitz正则性。我们进行分解的动机是使用像全球化问题中的$\mathsf{CD}^{*}$那样不断演化的组件。对于一个特定的类的最佳运输,我们证明了其他组件的线性时间,因此获得全球$\mathsf{CD}(K,N)$为$μ_{t}$。因此,这个结果可以解释为$\mathsf{CD}(K,N)$在这类最优运输中的一个全球化定理,或者解释为$\mathsf{CD}^{*}(K,N)$的一个"自我改进性质"。假设更多的规则性,即在无限小严格凸度量测度空间的设置中,一维密度是两个微分的乘积,从而对密度分解有更多的了解。

英文摘要:

We will prove a decomposition for Wasserstein geodesics in the following sense: let $(X,d,m)$ be a non-branching metric measure space verifying $\mathsf{CD}_{loc}(K,N)$ or equivalently $\mathsf{CD}^{*}(K,N)$. We prove that every geodesic $μ_{t}$ in the $L^{2}$-Wasserstein space, with $μ_{t} \ll m$, is decomposable as the product of two densities, one corresponding to a geodesic with support of codimension one verifying $\mathsf{CD}^{*}(K,N-1)$, and the other associated with a precise one dimensional measure, provided the length map enjoys local Lipschitz regularity. The motivation for our decomposition is in the use of the component evolving like $\mathsf{CD}^{*}$ in the globalization problem. For a particular class of optimal transportation we prove the linearity in time of the other component, obtaining therefore the global $\mathsf{CD}(K,N)$ for $μ_{t}$. The result can be therefore interpret as a globalization theorem for $\mathsf{CD}(K,N)$ for this class of optimal transportation, or as a ``self-improving property'' for $\mathsf{CD}^{*}(K,N)$. Assuming more regularity, namely in the setting of infinitesimally strictly convex metric measure space, the one dimensional density is the product of two differentials giving more insight on the density decomposition.

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