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math.GT2026
How natural of a geometric operation is Murasugi sum?
Thomas Kindred
Gabai proved that any Murasugi sum of -essential Seifert surfaces is also -essential, and Ozawa extended this result to unoriented spanning surfaces. We show, however, th…
math.GT2026
Spanning solids and Murasugi sum in dimension four
Homayun Karimi, Seungwon Kim, Thomas Kindred +2
We study various constructions of spanning solids for knotted surfaces in the 4-sphere. In particular, we consider a 4-dimensional analogue of Murasugi sum, which we use to define…