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I am looking for good references (survey, monograph, or paper with a solid background section) on the Banach space / functional analytic structure of spaces of finite signed measures $\mathcal{M}(X)$, primarily for $X = \mathbb{R}$, $\mathbb{R}^2$, or more generally $\mathbb{R}^d$ (and possibly Polish spaces).

I am interested in understanding these spaces as Banach spaces in their own right—particularly the geometry and topology relevant to studying operators acting on them. The following topics are of particular interest:

  • The tensor product structure, e.g. the canonical identification $M(\mathbb{R}) \widehat{\otimes}_\pi M(\mathbb{R}) \cong M(\mathbb{R}^2)$, and its generalizations to higher dimensions.
  • Weak and weak* topologies on $\mathcal{M}(X)$, including compactness and tightness criteria.
  • Properties of linear operators on these spaces and their continuity under the relevant topologies.
  • Structural questions such as whether the subset of measures of the form $\sum_{i=1}^k \prod_{j=1}^d \mu_{i,j}$ (finite “rank” measures) is closed in suitable norms or topologies.

I am also interested, more secondarily, in the behavior of probability measures on $\mathcal{M}(X)$, particularly differences of probability measures and how these behave under linear transformations, as well as transform methods (Fourier, Laplace) on these spaces.

For background, I am currently using:

  • Folland, Real Analysis
  • Kallenberg, Foundations of Modern Probability
  • Fabian et al., Functional Analysis and Infinite-Dimensional Geometry

I have also looked at Ryan's Introduction to Tensor Products of Banach Spaces, though it seems to address a somewhat different setting.

I understand this is a bit vague, but I am mainly trying to get a sense of what functional-analytic or Banach space tools are available for studying $\mathcal{M}(X)$ in this way.

Edit: I am also interested in settings where $X$ is a compact subset of $\mathbb{R}$ or $\mathbb{R}^d$, we could just assume that set is the unit interval or cube.

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    $\begingroup$ Not an answer to the question, but one useful functional analytic property of $\mathcal{M}(X)$ that you have not mentioned in the post is its order structure: the space $\mathcal{M}(X)$ is a Banach lattice. For properties related to the order structure I find the chapters on charges and measures in "Infinite-dimensional analysis: a hitchhiker's guide" by Aliprantis and Borde quite useful. $\endgroup$ Commented Oct 14 at 10:39
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    $\begingroup$ Even more explicit, $\mathcal{M}(X)$ with the variation norm is an AL-space, a special kind of Banach lattice. By a result of Kakutani (which can be found in the same book but without proof), it is just a monstrous $L_1$-space for suitable measure. $\endgroup$ Commented Oct 14 at 13:13
  • $\begingroup$ The Euclidian examples in the question are abelian topological groups. For those, $\mathcal{M}(X)$ is a Banach algebra (with convolution). This is the measure algebra of the group, studied extensively in (abstract) harmonic analysis. $\endgroup$ Commented Nov 25 at 1:30

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