Minimal Euler Characteristics of 4-manifolds with 3-manifold groups

TL;DR

This paper investigates the minimal Euler characteristic of 4-manifolds with fundamental groups of 3-manifolds, determining exact values for specific classes and addressing key equalities among invariants.

Contribution

It provides explicit calculations of the invariant  for certain 3-manifold groups and clarifies conditions under which it equals other known invariants.

Findings

Determined  for all 3-manifold groups not containing two-sided RP^2.

Established when  equals p() and q^*().

Answered a question posed by Hillman regarding these invariants.

Abstract

Let $\pi=\pi_1(M)$ for a compact 3-manifold $M$, and let $\chi_4$, $p$ and $q^*$ be the invariants of Hausmann-Weinberger, Kotschick and Hillman respectively. For certain class of compact 3-manifolds $M$, including all those not containing two-sided $RP^2$, we determine $\chi_4(\pi)$. We address when does $\chi_4(\pi)=p(\pi)$, when does $\chi_4(\pi)=q^*(\pi)$, and answer a question raised by Hillman.