论文标题
著名的风扇I:刻有锥形和虚拟的多面体
Inscribable fans I: Inscribed cones and virtual polytopes
论文作者
论文摘要
我们调查刻在一个通常等效(或非常同构)与给定多层$ p $的球体中的多面体。我们表明,在Minkowski添加的下,$ P $的铭文圆锥的相关空间(称为铭文的圆锥体)。铭文锥被解释为理想双曲线多型的类型锥,也是Delaunay细分的变形空间。特别是,测试是否存在通常相当于$ p $的铭文的多元式时间是多项式时间。 正常的等效性是在普通风扇的水平上确定的,我们研究了各种多种类和风扇的铭文锥体的结构,包括简单,简单,甚至。我们将(实际上)可划分的粉丝分类为$ 2 $,以及可铭文的Permutahedra和Nestohedra。 该论文的第二个目标是引入刻有虚拟的多面有。具有固定普通风扇$ \ MATHCAL {n} $相对于Minkowski添加而形成的单体和相关的Grothendieck组形成单体的polytopes称为$ \ Mathcal {n} $的类型空间。类型空间的元素对应于正式的Minkowski差异,并且自然配备了顶点,因此具有可划界性的概念。我们表明,即使$ \ Mathcal {n} $没有实际的刻有脑电图,铭刻的虚拟多面体形成一个子组,即使$ \ Mathcal {n} $也可能是非平凡的。 我们将铭刻的虚拟多面体与路由粒子轨迹相关联,即在有限制方向的球中的粒子的分段线性轨迹。状态空间产生由反射产生的连接的类固定,称为反射类固醇。反射类固醇的内态群体可以被认为是轨迹的离散全能组,我们确定它们何时是反射组。
We investigate polytopes inscribed into a sphere that are normally equivalent (or strongly isomorphic) to a given polytope $P$. We show that the associated space of polytopes, called the inscribed cone of $P$, is closed under Minkowski addition. Inscribed cones are interpreted as type cones of ideal hyperbolic polytopes and as deformation spaces of Delaunay subdivisions. In particular, testing if there is an inscribed polytope normally equivalent to $P$ is polynomial time solvable. Normal equivalence is decided on the level of normal fans and we study the structure of inscribed cones for various classes of polytopes and fans, including simple, simplicial, and even. We classify (virtually) inscribable fans in dimension $2$ as well as inscribable permutahedra and nestohedra. A second goal of the paper is to introduce inscribed virtual polytopes. Polytopes with a fixed normal fan $\mathcal{N}$ form a monoid with respect to Minkowski addition and the associated Grothendieck group is called the type space of $\mathcal{N}$. Elements of the type space correspond to formal Minkowski differences and are naturally equipped with vertices and hence with a notion of inscribability. We show that inscribed virtual polytopes form a subgroup, which can be non-trivial even if $\mathcal{N}$ does not have actual inscribed polytopes. We relate inscribed virtual polytopes to routed particle trajectories, that is, piecewise-linear trajectories of particles in a ball with restricted directions. The state spaces gives rise to connected groupoids generated by reflections, called reflection groupoids. The endomorphism groups of reflection groupoids can be thought of as discrete holonomy groups of the trajectories and we determine when they are reflection groups.