Rolling among G_2 vacua
H. Partouche, B. Pioline
TL;DR
The work develops a framework to study topology-changing transitions between $G_2$ manifolds constructed as quotients $(\mathcal{C}\times S^1)/\sigma$ of CICYs by antiholomorphic involutions, focusing on fixed-point-free cases to enable controlled analysis. By translating CY conifold transitions into the $G_2$ setting, the authors connect geometric transitions to low-energy ${\cal N}=1$ dynamics, illustrating Higgsing and branch changes in the effective theory, and they provide explicit examples with involutions on $\mathbb{C}P^7$ factors that yield different Betti-number patterns. The paper also builds a web of connected $G_2$ manifolds via determinantal contractions, showing how fixed-point data can alter the spectrum and exploring the possibility of mirror-like pairs with constant $b_2+b_3$. Finally, it discusses fixed-point cases at conifold points, highlighting new phenomena and signaling further work on Joyce-type fixed loci and their phase structure. The results advance understanding of the landscape of $G_2$ vacua and their non-perturbative transitions in M-theory.
Abstract
We consider topology-changing transitions between 7-manifolds of holonomy G_2 constructed as a quotient of CY x S^1 by an antiholomorphic involution. We classify involutions for Complete Intersection CY threefolds, focussing primarily on cases without fixed points. The ordinary conifold transition between CY threefolds descends to a transition between G_2 manifolds, corresponding in the N=1 effective theory incorporating the light black hole states either to a change of branch in the scalar potential or to a Higgs mechanism. A simple example of conifold transition with a fixed nodal point is also discussed. As a spin-off, we obtain examples of G_2 manifolds with the same value for the sum of Betti numbers b_2+b_3, and hence potential candidates for mirror manifolds.
