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A reduced alternating link diagram is an alternating link diagram with no nugatory crossing. Its Tait graph and dual have no loops, so it is an adequate link diagram. If connected, its Jones polynomial breadth equals its crossing count.

// Target: module-theory.bigb

A split diagram has two nonempty parts separated by a simple closed curve disjoint from the diagram. For a two-component link, this is equivalent to disconnectedness of its projection graph. An alternating link diagram representing a split link cannot have a connected projection graph, as its Jones value at minus one detects a nonzero spanning-tree count.

Choose a checkerboard coloring of the complementary regions of a link diagram. The Tait graph has one vertex for each black region and one edge through each crossing joining its adjacent black regions. The other coloring gives its planar dual. For a connected alternating link diagram, all-A and all-B smoothing circles correspond to the regions of its two checkerboard colors; one-circle smoothing states correspond to spanning trees.