Tropical Poincar\'e duality spaces

Abstract

The tropical fundamental class of a rational balanced polyhedral fan induces cap products between tropical cohomology and tropical Borel-Moore homology. When all these cap products are isomorphisms, the fan is said to be a tropical Poincar\'e duality space. If all the stars of faces also are such spaces, such as for fans of matroids, the fan is called a local tropical Poincar\'e duality space. In this article, we first give some necessary conditions for fans to be tropical Poincar\'e duality spaces and a classification in dimension one. Next, we prove that tropical Poincar\'e duality for the stars of all faces of dimension greater than zero and a vanishing condition implies tropical Poincar\'e duality of the fan. This leads to necessary and sufficient conditions for a fan to be a local tropical Poincar\'e duality space. Finally, we use such fans to show that certain abstract balanced polyhedral spaces satisfy tropical Poincar\'e duality.