11D supergravity on Calabi-Yau orbifolds naturally induces exceptional symmetries in that can be realized as U-duality symmetries of M-theory upon -discretization and without Betti-truncations. Hence, exceptional field theory based on the modular group uses a dimensionally extended spacetime to 12-D that fully covariantizes supergravity under the U-duality symmetry group of M-theory. Taking full advantage of the M/F-theory duality, and the Kovalev’s twisted connected sum constructed manifolds via gluing pairs of asymptotically cylindrical Calabi–Yau threefolds, M-theory is hence up to isomorphism the unique UV completion of the Standard Model of physics coupled to gravity. Moreover, by mirror symmetry, there exists an internal symmetry induced between M-theory and F-theory upon KK-reduction to Type-IIB SUGRA. Here I shall discuss the crucial step in this process involving M-theory on Calabi-Yau manifolds that arise in the Kovalev construction specifically involving an action with half-maximal gauged supergravity:
where we have:
with the scalar potential. In the formalism taking the Klebanov-Witten limit, the theory is given by the action:
where we have:
and:
and where the Chern-Simons-topological Lagrangian has covariant variational form:
with:
and the Yang-Mills field equation for the covariant field strength form is:
Thus, we can derive the Chern-Simons-type topological action:
with:
and:
and the covariant curvature form and holomorphic curvature form are, respectively:
and:
where the Ramond-Ramond gauge-coupling sector is given by the action:
and the Ramond-Ramond term being:
thus giving us the Type-IIB Calabi-Yau three-fold superpotential:
Before we can see the duality relations between M-theory and F-theory elliptically fibered Calabi-Yau Standard-Model constructions, note that the topologically mixed Yang-Mills action:
where the corresponding Chern-Simons action is:
with the Ramond-Ramond coupling-term:
has the following variational action:
with:
Since 11-D SUGRA on a torus is equivalent to Type-IIB string-theory on a circle, the action of the modular group on the Type-IIB axio-dilaton allows us to take the zero limit of:
and by mirror symmetry, we get a Type-IIA dimensional uplift to M-theory, given that in the Einstein frame, the Type-IIB bosonic SUGRA action is:
with:
This is one angle from which to appreciate, via the exceptional field theory modular group action, the F-theory/M-theory duality. The essence of EFT is thus a deeper double duality relating M-theory/Type-IIA and F-theory/Type-IIB. The key is the role of U-duality in the modular holomorphic action on the Neveu-Schwarz sector of Type-IIB. Our generalized diffeomorphisms, generated by a vector , act fully locally on yielding the Lie derivative that differs from the classic Lie derivative by a Calabi-Yau induced -tensor and is implicitly defined by the transformation rules for a generalized vector:
The associated diffeomorphism algebra has an exceptional field bracket:
with closure condition:
The action diffeomorphism symmetries are parametrized by vector bundles over the metaplectic space and take the form:
with:
where the gauge vector transforms as:
The corresponding generalized exceptional scalar metric hence has the following property:
which decomposes in light of the orbifold blow-up:
as such:
thus allowing us to define the crucial exceptional metric:
Since the full Type-IIB Calabi-Yau superpotential is given by:
where the Kähler Type-IIB orientifold moduli is:
with:
and the volume of the divisor, , is:
with:
we now hence have the ingredients to write the modular exceptional field theory action as:
with the exceptional Ricci scalar:
the kinetic part:
and the gauge term:
and the 10+3-D Chern-Simons topological term:
where the potential has the form:
This is a theory dynamically equivalent to 11-D SUGRA and Type-IIB under the covariantized U-duality group-action. However, the gauged kinetic terms corresponding to the gauge form appears only topologically in:
Hence, the EoM for the field is given by:
Since exceptional field theory based on the modular group uses a dimensionally extended spacetime to 12-D that fully covariantizes supergravity under the U-duality symmetry groups of M-theory, homological mirror symmetry entails the existence of an internal symmetry induced between M-theory and F-theory upon dimensional-reduction to Type-IIB SUGRA which, in the formalism, taking the 6/8 Klebanov-Witten limit, is defined by the action:
It is straightforward now to derive the dimensional reduction of M-theory on ACCY threefolds that are building blocks of twisted connected sum G2 manifolds. We begin with the two-derivative action for 11d supergravity, unique up to isomorphism, with a pure bosonic action given as such:
admitting a quantum gauge-gravitational correction:
where we have:
We then expand the 11D fields in a dimensional reduction on a Calabi-Yau threefold on a basis of zero-modes of the Dirac-Dolbeault differential operator on the ACCY internal threefold with metric:
whose external part describes a maximally symmetric spacetime. Note that the fluctuations of the internal metric are zero-modes of the Lichnerowicz operator satisfying the relations:
parameterized by the complex structure moduli and the Kähler moduli defined implicitly by the Kähler expansion:
with the following cohomological Laplacian Calabi-Yau expansion:
and where all our fields are naturally embeddable in 5d N=2 SUSY multiplets. To see that, recall that the following identity holds:
since the total volume of our Calabi-Yau threefold is given as such:
with being the threefold Cartan-Weyl intersection numbers. Furthermore, we recall the decomposition of the third CY-cohomology into complex cohomologies:
Now since we have:
the scalar fields satisfy the following relation:
leading to the natural interpretation of as 5-D holomorphic coordinates inducing a potential of the form:
yielding the dimensionally reduced bosonic action:
with the following being a logical consequence:
In light of the threefold Cartan-Weyl intersection numbers , the elliptically fibered Calabi-Yau geometry satisfies the following relation:
To allow the 5D/6D lift, one defines T-shifted fields:
as required by supersymmetry, which yield the following correction to our cubic potential:
Hence, our Chern-Simons term reduces to:
with:
Hence, for M-theory on G2 TCS Kovalev manifolds with ACCY building blocks, the 4D action takes the following form:
thus effectively establishing a proof from first principles that M-theory is—up to isomorphism—the unique UV completion of the Standard Model of physics coupled to gravity.