A new toric ALF gravitational instanton

Abstract

We construct a new explicit toric ALF gravitational instanton. The instanton has Euler characteristic $χ= 4$ and Hirzebruch signature $τ= 1$. The topology at infinity is a lens space $L(3,1)$. The solution depends on one parameter and is constructed from the Belinski--Zakharov four-soliton solution. We prove that the instanton is smooth and positive definite on and away from the axis. This is the first example of a non-Hermitian ALF (not AF) gravitational instanton.