Conceptual

Ribbonness of Surface-Bounding Classical Links in the Upper Half 4-Space

A result and its proof in geometric topology showing that if a classical link in 3-space bounds a compact oriented proper surface (with no closed components) in the upper half of 4-space, then it also bounds a ribbon surface there, realized as a boundary-relative renewal embedding of that surface. The proof is built from banded loop systems and surgery on trivial sphere-links along handle systems, and the construction is shown invariant under isotopies respecting its arcs and loops.