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arXiv · 1704.08787

Real sets

George Janelidze·Ross Street
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Abstract

After reviewing a universal characterization of the extended positive real numbers published by Denis Higgs in 1978, we define a category which provides an answer to the questions: \begin{itemize} \item what is a set with half an element? \item what is a set with $\pi$ elements? \end{itemize} The category of these extended positive real sets is equipped with a countable tensor product. We develop somewhat the theory of categories with countable tensors; we call the commutative such categories {\em series monoidal} and conclude by only briefly mentioning the non-commutative possibility called {\em $\omega$-monoidal}. We include some remarks on sets having cardinalities in $[-\infty,\infty]$.

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George Janelidze, Ross Street. 2017-04-28. Real sets. https://doi.org/10.1515/tmj-2017-0101

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