Orientation signs on bordism currents [04HH]
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Orientation signs on bordism currents
In section 3.1, 3.1.2 we encountered the -dimensional moduli spaces such as and . The special case of holmorphic strips was already mentioned in Example 6.2.
We now consider the moduli of polygons with at least 3 corners , all regarded as inputs, arranged in clockwise order on , each carrying the local system factors and the orientation factors . The clockwise composition of the local system hom factors and the parallel transport along , produces a holonomy factor around , which is a number in depending on the coefficient ring choice. Using (69) and Remark 6.9, as well as the clockwise orientation convention on the Stasheff associahedron, we acquire a (naïve) orientation on . To assign orientation and weighting factors to , we take the product of the holonomy factor, the naïve orientation on , and another universal sign factor
The appearance of this universal sign adjustment is a familiar convention in the open-closed map, cf. [2, eqn 5.24]. The notation is a shorthand for the weighted sum of all the -dimensional moduli spaces involved in the construction of the bordism current.
We equip the domain with the complex orientation, and together with an extra minus sign, the orientation on induces the orientation on . This minus sign arises for the same reason as in Example 6.2, namely the discrepancy between our clockwise convention on , with the standard complex orientation on .