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The space of tropically collinear points is shellable
Collectanea Mathematica ( IF 0.7 ) Pub Date : 2007 , DOI: 10.1007/bf03191216
Hannah Markwig , Josephine Yu

The spaceT d;n ofn tropically collinear points in a fixed tropical projective space\(\mathbb{T}\mathbb{P}^{d - 1} \) is equivalent to the tropicalization of the determinantal variety of matrices of rank at most 2, which consists of reald×n matrices of tropical or Kapranov rank at most 2, modulo projective equivalence of columns. We show that it is equal to the image of the moduli space\(\mathcal{M}_{0,n} (\mathbb{T}\mathbb{P}^{d - 1} , 1)\) ofn-marked tropical lines in\(\mathbb{T}\mathbb{P}^{d - 1} \) under the evaluation map. Thus we derive a natural simplicial fan structure forT d;n using a simplicial fan structure of\(\mathcal{M}_{0,n} (\mathbb{T}\mathbb{P}^{d - 1} , 1)\) which coincides with that of the space of phylogenetic trees ond +n taxa. The space of phylogenetic trees has been shown to be shellable by Trappmann and Ziegler. Using a similar method, we show thatT d;n is shellable with our simplicial fan structure and compute the homology of the link of the origin. The shellability ofT d;n has been conjectured by Develin in [1].

中文翻译:

热带共线点的空间是可贝壳的

空间T d ; ÑÑ在固定热带射影空间热带共线点\(\ mathbb【T} \ mathbb {P} ^ {d - 1} \)相当于的行列式各种等级的矩阵的热带化至多2,其由最多为2的热带或Kapranov等级的实d × n矩阵组成,列的模射等价。我们表明,它等于模空间的图像\(\ mathcal {M} _ {0,N}(\ mathbb【T} \ mathbb {P} ^ {d - 1},1)\)Ñ评估图下\(\ mathbb {T} \ mathbb {P} ^ {d-1} \)中标记的热带线。因此,我们得出了T的自然简单扇形结构 d ; n使用\(\ mathcal {M} _ {0,n}(\ mathbb {T} \ mathbb {P} ^ {d-1},1)\)的简单扇形结构,该结构与d + n分类群上的系统发育树。系统发育树的空间已被Trappmann和Ziegler证明是可剥壳的。使用类似的方法,我们表明T dn具有简单的扇形结构,可以计算出起点链接的同源性。T d ; n的可壳性已由Develin在[1]中推测。
更新日期:2020-09-21
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