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On merge trees with a given homological sequence

Nicholas A. Scoville, Dylan Wen

Abstract

In this paper, we study the induced homological sequence and the induced merge tree of a discrete Morse function on a tree. A discrete Morse function on a tree gives rise to a sequence of Betti numbers that keep track of the number of components at each critical value. A discrete Morse function on a tree also gives rise to an induced merge tree which keeps track of component birth, death, and merging information. These topological indicators are similar but neither one contains the information of the other. We show that given a merge tree and a homological sequence along with some mild conditions on their relationship, there is a discrete Morse function on a tree that induces both the given merge tree and the given homological sequence.

On merge trees with a given homological sequence

Abstract

In this paper, we study the induced homological sequence and the induced merge tree of a discrete Morse function on a tree. A discrete Morse function on a tree gives rise to a sequence of Betti numbers that keep track of the number of components at each critical value. A discrete Morse function on a tree also gives rise to an induced merge tree which keeps track of component birth, death, and merging information. These topological indicators are similar but neither one contains the information of the other. We show that given a merge tree and a homological sequence along with some mild conditions on their relationship, there is a discrete Morse function on a tree that induces both the given merge tree and the given homological sequence.

Paper Structure

This paper contains 9 sections, 1 theorem, 10 equations, 2 algorithms.

Table of Contents

  1. Introduction
  2. Background
  3. Graphs and trees
  4. Discrete Morse theory
  5. Merge trees
  6. Basics of merge trees
  7. The realization problem
  8. Merge trees and homological sequences
  9. Open questions

Key Result

Theorem 4.1

Let $M$ be any chiral merge tree on $n=2k+1>0$ nodes. If $B_0=B$ is any homological sequence of length $n$ such that $J_0^M\leq B$, then there is a graph $G$ and discrete Morse function $f\colon G\to \Bbb{N}$ such that $M_f=M$ and $B^f=B$.

Theorems & Definitions (16)

  • Definition 2.1
  • Example 2.1
  • Definition 2.2
  • Definition 2.3
  • Example 2.2
  • Definition 3.1
  • Remark 3.1
  • Example 3.1
  • Example 3.2
  • Example 3.3
  • ...and 6 more