Logarithmic Tree-Numbers for Acyclic Complexes

  • Hyuk Kim
  • Woong Kook
Keywords: Acyclic Complexes, High-Dimensional Trees, Combinatorial Laplacians

Abstract

For a $d$-dimensional cell complex $\Gamma$ with $\tilde{H}_{i}(\Gamma)=0$ for $-1\leq i < d$, an $i$-dimensional tree is a non-empty collection $B$ of $i$-dimensional cells in $\Gamma$ such that $\tilde{H}_{i}(B\cup \Gamma^{(i-1)})=0$ and $w(B):= |\tilde{H}_{i-1}(B\cup \Gamma^{(i-1)})|$ is finite, where $\Gamma^{(i)}$ is the $i$-skeleton of $\Gamma$. The $i$-th tree-number is defined $k_{i}:=\sum_{B}w(B)^{2}$, where the sum is over all $i$-dimensional trees. In this paper, we will show that if $\Gamma$ is acyclic and $k_{i}>0$ for $-1\leq i \leq d$, then $k_{i}$ and the combinatorial Laplace operators $\Delta_{i}$  are related by  $\sum_{i=-1}^{d}\omega_{i}\,x^{i+1}=(1+x)^{2}\sum_{i=0}^{d-1}\kappa_{i} x^{i}$, where $\omega_{i}=\log \det \Delta_{i}$ and $\kappa_{i}=\log k_{i}$.  We will discuss various consequences and applications of this equation.

Author Biographies

Hyuk Kim, Seoul National University
Department of Mathematical Sciences
Woong Kook, Seoul National University
Department of Mathematical Sciences
Published
2014-03-10
Article Number
P1.50