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arXiv 1411.0899math.MGmath.COmath.GR
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轨道多面体的仿射对称性

Affine Symmetries of Orbit Polytopes

Erik Friese, Frieder Ladisch

摘要:

轨道多面体是有限群$G \leq \operatorname{GL}(d,\mathbb{R})$下轨道的凸包。我们发展了一个一般的理论,可能的仿射对称群的轨道多面体。对于每个群,我们定义一个开的稠密的泛点集,使得泛点的轨道多面体具有共轭仿射对称群。我们证明了一般轨道多面体的对称群又是$G$,如果$G$本身是某个轨道多面体的仿射对称群,或者如果$G$是绝对不可约的。另一方面,我们描述了一些一般情况下,仿射对称群的增长。我们应用我们的理论表示多面体(有限矩阵群的凸包),并表明它们的仿射对称性可以有效地计算从一定的字符。我们用它来构造Baumeister等人的一个猜想的反例。[Advances in Math.222(2009),431- 452,Conjecture~5.4].

英文摘要:

An orbit polytope is the convex hull of an orbit under a finite group $G \leq \operatorname{GL}(d,\mathbb{R})$. We develop a general theory of possible affine symmetry groups of orbit polytopes. For every group, we define an open and dense set of generic points such that the orbit polytopes of generic points have conjugated affine symmetry groups. We prove that the symmetry group of a generic orbit polytope is again $G$ if $G$ is itself the affine symmetry group of some orbit polytope, or if $G$ is absolutely irreducible. On the other hand, we describe some general cases where the affine symmetry group grows. We apply our theory to representation polytopes (the convex hull of a finite matrix group) and show that their affine symmetries can be computed effectively from a certain character. We use this to construct counterexamples to a conjecture of Baumeister et~al.\ on permutation polytopes [Advances in Math. 222 (2009), 431--452, Conjecture~5.4].

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