Anatomy of Einstein Manifolds

TL;DR

This paper explores the geometric and gauge-theoretic structure of four-dimensional Einstein manifolds, their stability, and how these properties might extend to five dimensions through group embeddings, revealing a substructure akin to particle physics models.

Contribution

It introduces a gauge-theoretic perspective on Einstein manifolds, demonstrating their substructure via $SU(2)$ instantons and proposing a higher-dimensional embedding analogous to grand unification.

Findings

Four-dimensional Einstein manifolds relate to $SU(2)_ ext{+}$ and $SU(2)_ ext{-}$ instantons.

Higher-dimensional embedding involves group $SO(5)$, extending stability considerations.

Manifold substructure resembles quark model with instantons as fundamental components.

Abstract

An Einstein manifold in four dimensions has some configuration of $SU(2)_+$ Yang-Mills instantons and $SU(2)_-$ anti-instantons associated with it. This fact is based on the fundamental theorems that the four-dimensional Lorentz group $Spin(4)$ is a direct product of two groups $SU(2)_\pm$ and the vector space of two-forms decomposes into the space of self-dual and anti-self-dual two-forms. It explains why the four-dimensional spacetime is special for the stability of Einstein manifolds. We now consider whether such a stability of four-dimensional Einstein manifolds can be lifted to a five-dimensional Einstein manifold. The higher-dimensional embedding of four-manifolds from the viewpoint of gauge theory is similar to the grand unification of Standard Model since the group $SO(4) \cong Spin(4)/\mathbb{Z}_2 = SU(2)_+ \otimes SU(2)_-/\mathbb{Z}_2$ must be embedded into the simple group $SO(5) = Sp(2)/\mathbb{Z}_2$. Our group-theoretic approach reveals the anatomy of Riemannian manifolds quite similar to the quark model of hadrons in which two independent Yang-Mills instantons represent a substructure of Einstein manifolds.