2 papers
math.GT1999
Quandle Cohomology and State-sum Invariants of Knotted Curves and Surfaces
J. Scott Carter, Daniel Jelsovsky, Seiichi Kamada +2
The 2-twist spun trefoil is an example of a sphere that is knotted in 4-dimensional space. Here this example is shown to be distinct from the same sphere with the reversed orientat…
math.QA1998
Higher-Dimensional Algebra IV: 2-Tangles
John C. Baez, Laurel Langford
Just as knots and links can be algebraically described as certain morphisms in the category of tangles in 3 dimensions, compact surfaces smoothly embedded in R^4 can be described a…