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Groupoids: Unifying Internal and External Symmetry

Alan Weinstein

Often the group of transformations of an object, such as a honeycomb or a herd of zebras, misses its essential symmetry. This article explains how groupoids are used to capture that symmetry.
(pp. 744)
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Model Theory and Exponentiation

David Marker

Tarski's theorem asserts that all sentences about the axiomatic real number system are decidable. Progress is reported on extending this theorem when exponentiation, or truncated analytic functions are added; with applications to real analytic geometry.
(pp. 753)
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