Abstract

We describe off-shell $\mathcal{N}=1$ M-theory compactifications down to four dimensions in terms of eight-dimensional manifolds equipped with a topological $Spin(7)$-structure. Motivated by the exceptionally generalized geometry formulation of M-theory compactifications, we consider an eight-dimensional manifold $\mathcal{M}_{8}$ equipped with a particular set of tensors $\mathfrak{S}$ that allow to naturally embed in $\mathcal{M}_{8}$ a family of $G_{2}$-structure seven-dimensional manifolds as the leaves of a codimension-one foliation. Under a different set of assumptions, $\mathfrak{S}$ allows to make $\mathcal{M}_{8}$ into a principal $S^{1}$ bundle, which is equipped with a topological $Spin(7)$-structure if the base is equipped with a topological $G_{2}$-structure. We also show that $\mathfrak{S}$ can be naturally used to describe regular as well as a singular elliptic fibrations on $\mathcal{M}_{8}$, which may be relevant for F-theory applications, and prove several mathematical results concerning the relation between topological $G_{2}$-structures in seven dimensions and topological $Spin(7)$-structures in eight dimensions.

Highlights

  • We show that S can be naturally used to describe regular as well as a singular elliptic fibrations on M8, which may be relevant for F-theory applications, and prove several mathematical results concerning the relation between topological G2-structures in seven dimensions and topological Spin(7)-structures in eight dimensions

  • Since M8 contains in a natural way a family of seven-dimensional manifolds with G2 structure, which are the leaves of the foliation, we find a natural correspondence between the G2-structure manifolds and the corresponding Spin (7)-structure manifolds, which may have a physical meaning in terms of dualities in String/M/F-theory

  • In this paper we have studied N = 1 M-theory compactifications down to four dimensions in terms of an eight-dimensional manifold M8 endowed with an intermediate structure S, whose presence is motivated by the exceptionally generalized geometric description of such compactifications

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Summary

M-theory compactifications

We are interested in bosonic solutions to eleven-dimensional Supergravity, and we will give from the onset a zero vacuum expectation value to the Majorana gravitino Ψ. Where M denotes the eleven-dimensional space-time differentiable, orientable and spinnable manifold, dV is the canonical volume form induced by the metric g, and G is the closed four-form flux associated to C, i.e. locally we can write G = dC. Given the product structure (2.3) of the space-time manifold M, the tangent bundle splits as follows. Let us respectively denote by S1+,3 and S7R the corresponding spin bundles over M1,3 and M7. Given the decomposition (2.7), M7 is equipped with a globally defined no-where vanishing complex spinor η, that is a globally defined section of the complexified spin bundle S7R⊗C → M7. Its real components η1 and η2 can a priori vanish at points or become parallel, as long as they do not simultaneously vanish

The seven dimensional manifold M7
The underlying eight-dimensional manifold M8
Motivation for M8: the generalized geometric formulation
Connection to F-theory
Linear algebra of positive and admissible forms
Positive forms on seven-dimensional vector spaces
Relation between admissible and positive forms
Decrypting the 8-dimensional manifold
G2-intermediate structures
G2-structure seven-manifolds in M8
Structure of the foliation
M8 as a S1 principal bundle
General intermediate manifolds and elliptic fibrations
Regular elliptic fibrations
Possibility of singular points
Conclusions
A G2-manifolds

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