Ghomi proved that every convex polyhedron could be stretched via an affine transformation so that it has an edge-unfolding to a net [Gho14]. A net is a simple planar polygon; in particular, it does not self-overlap. One can view his result as establishing that every combinatorial polyhedron has a metric realization that allows unfolding to a net. Joseph Malkevitch asked if the reverse holds (in some sense of ``reverse"): Is there a combinatorial polyhedron such that, for every metric realization P in R^3, and for every spanning cut-tree T, P cut by T unfolds to a net? In this note we prove the answer is NO: every combinatorial polyhedron has a realization and a cut-tree that unfolds the polyhedron with overlap.
翻译:Ghomi证明了每个凸多面体可通过仿射变换拉伸,使得其能沿边展开为一个网格图(net)[Gho14]。网格图是一个简单平面多边形,尤其不会自重叠。可将该结果理解为:每个组合多面体都存在一个度量实现,该实现允许展开为网格图。Joseph Malkevitch 提问反向结论是否成立(在某种"反向"意义上):是否存在一个组合多面体,使得对该多面体的每个度量实现 P ⊂ R³ 及每个生成割树(spanning cut-tree)T,经 T 切割后的 P 总能展开为网格图?本文证明答案为否:每个组合多面体均存在一个实现及一个割树,使得该多面体展开时产生重叠。