nLab F-theory on Spin(7)-manifolds




The KK-compactification of F-theory on Spin(7)-manifolds to 4d. Differs subtly from F-theory on CY4.

Related by T-duality to 3d M-theory on Spin(7)-manifolds


(Non-)Supersymmetry and (vanishing) cosmological constant

What has been called Witten's dark fantasy in Heckmann-Lawrie-Lin-Zoccarato 19, Section 8 is an argument, going back to Witten 95a, Witten 95b, Sec. 3, Witten 00, p. 7 for the existence of non-perturbative non-supersymmetric 4d string vacua/string phenomenology with fundamentally vanishing cosmological constant (“dark energy”).

The original idea was formulated in terms of 3d M-theory on 8-manifolds decompactified at strong coupling to 4d via duality between M-theory and type IIA string theory (recall the super 2-brane in 4d).

Based on the observation of Vafa 96, Section 4.3 that the argument should have a natural realization in 4d F-theory on Spin(7)-manifolds (T-dual to the previous perspective), a detailed construction was finally laid out in Bonetti-Grimm-Pugh 13, Heckmann-Lawrie-Lin-Zoccarato1 18, Heckman-Lawrie-Lin-Sakstein-Zoccarato 19.

The key technical point is the claim that a careful analysis of D=4 N=1 supergravity obtained after KK-compactification of F-theory on Spin(7)-manifolds T-dual to M-theory on Spin(7)-manifolds reveals a “1/2 supersymmetry” where

  1. the vacuum state is supersymmetric and hence has vanishing cosmological constant;

  2. but no finite-energy-excitation of the vacuum appears supersymmetrically,

    hence fermions and bosons in the model do not appear in supersymmetric spectra.

(Vafa 96, Sec. 4.3 BGP 13, HLLZ 18, Sec. 4)

Relation to J-twisted Cohomotopy

On a spin-manifold of dimension 8 a choice of topological Spin(7)-structure is equivalently a choice of cocycle in J-twisted Cohomotopy cohomology theory. This follows (FSS 19, 3.4) from

  1. the standard coset space-structures on the 7-sphere (see here)

  2. the fact that coset spaces G/HG/H are the homotopy fibers of the maps BHBGB H \to B G of the corresponding classifying spaces (see here)

F-theory KK-compactified on elliptically fibered complex analytic fiber Σ\Sigma

dim (Σ)dim_{\mathbb{C}}(\Sigma)12345
F-theoryF-theory on CY2F-theory on CY3F-theory on CY4F-theory on CY5



The concept goes back to

See also:

Relating M-theory on Spin(7)-manifolds with F-theory on Spin(7)-manifolds via Higgs bundles:

Witten’s Dark Fantasy

Already Vafa 96, Section 4.3 mentions the relation to Witten's Dark Fantasy, then developed in

See also

Last revised on April 1, 2020 at 07:42:37. See the history of this page for a list of all contributions to it.