Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2018/iii/paper-141/3/d/solution

Star the adjacent regions . Choose the Kauffman state of a knot diagram putting the marker at in region , at in region , at in region , and at in region . Every unstarred region is used exactly once, and every crossing has exactly one marker.
Figure 1.
The figure-eight graph, regions and Heegaard state
. Details.
In the full Alexander matrix, circle the entries , namely
In the reduced Alexander matrix , these are the diagonal entries in column order . The associated permutation is the identity, with sign of a permutation , so this Kauffman state of a knot diagram contributes
to . The other four nonzero permutation terms are . The drawing circles the same four entries literally; the boxes above identify them in the typeset matrix. Different row or generator conventions multiply the Alexander polynomial of a knot and its state weights by the corresponding overall unit.

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