Approximating the Minimum $k$-Section Width in Bounded-Degree Trees with Linear Diameter

TL;DR

This paper presents a polynomial-time approximation method for the minimum $k$-section problem in trees with linear diameter, improving understanding of partitioning in bounded-degree trees and extending results to general graphs with tree decompositions.

Contribution

It introduces a new approximation bound for $k$-sections in trees with linear diameter and extends the approach to general graphs using tree decompositions.

Findings

Provides a polynomial-time constant-factor approximation for trees with linear diameter.

Shows the approximation bound depends on tree diameter and maximum degree.

Extends the approximation approach to arbitrary graphs via tree decompositions.

Abstract

Minimum $k$-Section denotes the NP-hard problem to partition the vertex set of a graph into $k$ sets of sizes as equal as possible while minimizing the cut width, which is the number of edges between these sets. When $k$ is an input parameter and $n$ denotes the number of vertices, it is NP-hard to approximate the width of a minimum $k$-section within a factor of $n^c$ for any $c<1$, even when restricted to trees with constant diameter. Here, we show that every tree $T$ allows a $k$-section of width at most $(k-1) (2 + 16n / diam(T) ) \Delta(T)$. This implies a polynomial-time constant-factor approximation for the Minimum $k$-Section Problem when restricted to trees with linear diameter and constant maximum degree. Moreover, we extend our results from trees to arbitrary graphs with a given tree decomposition.