Our paper offers an analysis of how Dante describes the tre giri (three rings) of the Holy Trinity in Paradiso 33 of the Divine Comedy. We point to the myriad possibilities Dante may have been envisioning when he describes his vision of God at this f
inal stage in his journey. Saiber focuses on the features of shape, motion, size, color, and orientation that Dante details in describing the Trinity. Mbirika uses mathematical tools from topology (specifically, knot theory) and combinatorics to analyze all the possible configurations that have a specific layout of three intertwining circles which we find particularly compelling given Dantes description of the Trinity: the round figures arranged in a triangular format with rotational and reflective symmetry. Of the many possible link patterns, we isolate two particularly suggestive arrangements for the giri: the Brunnian link and the (3,3)-torus link. These two patterns lend themselves readily to a Trinitarian model.
The Springer variety is the set of flags stabilized by a nilpotent operator. In 1976, T.A. Springer observed that this varietys cohomology ring carries a symmetric group action, and he offered a deep geometric construction of this action. Sixteen yea
rs later, Garsia and Procesi made Springers work more transparent and accessible by presenting the cohomology ring as a graded quotient of a polynomial ring. They combinatorially describe an explicit basis for this quotient. The goal of this paper is to generalize their work. Our main result deepens their analysis of Springer varieties and extends it to a family of varieties called Hessenberg varieties, a two-parameter generalization of Springer varieties. Little is known about their cohomology. For the class of regular nilpotent Hessenberg varieties, we conjecture a quotient presentation for the cohomology ring and exhibit an explicit basis. Tantalizing new evidence supports our conjecture for a subclass of regular nilpotent varieties called Peterson varieties.
