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Mariana Graña

Publications and source records attributed to Mariana Graña.

At least 19 recordsLinked to original sources
arXiv2026

The landscape and the swampland of O(3,3) gauged supergravities

Compactifications of string theory on group manifolds with fluxes, performed via the Scherk-Schwarz mechanism, give rise to gauged supergravities. Using double field theory, this procedure can be made T-duality covariant, yielding a set of geometric and non-geometric fluxes whose string theory origin is often unclear. In this paper, we systematically analyze the complete catalog of half-maximal gauged supergravities in seven dimensions. By constructing a dictionary between orbifold twists and generalized fluxes, we identify which gaugings admit a realization as (a)symmetric orbifolds, and which do not, establishing the latter as candidates for the gauged supergravity swampland.

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arXiv2026

Lost in Translation: Moduli Stabilization from EFT to Eleven Dimensions

We explicitly show how moduli stabilization is realized geometrically in M-theory compactified on $T^4/\mathbb{Z}_2\, \times\, $K3, by using the Gibbons-Hawking approximation of the K3 metric. By relating this compactification to certain microstate geometries, we present the explicit solutions in which fully backreacted fluxes on certain four-cycles stabilize three of the $T^4/\mathbb{Z}_2$ compactification moduli. The minimal tadpole contribution of these fluxes is linear in the number of stabilized moduli, and we argue that this linear relation holds for more general fluxes. We also construct a one-parameter family of supersymmetric eleven-dimensional solutions that break Lorentz invariance and the warped-product structure of the compactification. These solutions are a continuous deformation of the warped-product Lorentz-invariant compactification, to which they reduce when the moduli reach their stabilized values. Away from the Lorentz-invariant locus, the fluxes are no longer self-dual in the internal space, and include fields that do not exist in the corresponding EFT. Remarkably, although these fluxes still stabilize a modulus, it is not the $T^4/\mathbb{Z}_2$ modulus that appears stabilized in the Lorentz-invariant solution, but rather a nontrivial combination of the $T^4$ volume and K3 shape moduli. The existence of these solutions suggests that the EFT description of moduli stabilization can be misleading and does not reflect the moduli-stabilization dynamics of the full eleven-dimensional theory. Our results extend straightforwardly to Type IIB String Theory compactified on orientifolds of $T^2 \times K3$.

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arXiv2026

EFTs with Symmetric Moduli Spaces: the Landscape and the Swampland

The Swampland Distance Conjecture (SDC) states that, for any infinite-distance limit in the moduli space of a quantum gravity effective field theory (EFT), there should exist an infinite tower of states that become exponentially light. According to the Emergent String Conjecture, such a tower should consist either of tensionless strings or of Kaluza-Klein modes, each with a mass-decay rate that depends in a precise way on the dimension of the effective field theory. In this paper, we use the results obtained in arXiv:2508.18401 on the SDC for symmetric moduli spaces and how these rates are encoded in the weight polytope of the corresponding particle-state representations to determine the symmetric space EFTs and representations that have these decay rates. Remarkably, assuming that the particle states transform in an irreducible representation, the list of possible polytopes and moduli spaces is finite. Different EFTs are related by embedding one moduli space in another or by taking a decompactification limit. Requiring compatibility of the particle representations under such branching, we find that, while most of the theories can be obtained from an EFT based on $E_{8(8)}$, there remain three in our list that appear to be impossible to get from M- or string-theory compactifications. Using the same embedding procedure, we also identify the string and brane representations that should be present in the spectrum.

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arXiv2025

The Boundary of Symmetric Moduli Spaces and the Swampland Distance Conjecture

For non-compact, locally symmetric moduli spaces M, the set of geodesics and the geometry of the boundary can be completely characterised using group theory. In particular, geodesics that asymptote to a given infinite distance boundary point are characterised by a choice of rational parabolic subgroup P(Q) of the local isometry group G and an element of the Cartan subalgebra of P(Q). Under the assumption that M satisfies the "compactifiability" constraint of arXiv:2412.03640 and some mild conditions on the spectrum of states, we use this formalism to prove the Swampland Distance Conjecture for essentially all locally symmetric spaces M. We show that the states necessarily transform in some representation of G, and further that the convex hull encoding the exponential rate at which the leading tower of states becomes light is simply the convex hull of the weights of the representation. In a companion paper, we then use the formalism to classify all locally symmetric spaces and irreducible representations that are consistent with the Emergent String Conjecture.

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arXiv2025

Tadpole conjecture in non-geometric backgrounds

Calabi-Yau compactifications have typically a large number of complex structure and/or Kähler moduli that have to be stabilised in phenomenologically-relevant vacua. The former can in principle be done by fluxes in type IIB solutions. However, the tadpole conjecture proposes that the number of stabilised moduli can at most grow linearly with the tadpole charge of the fluxes required for stabilisation. We scrutinise this conjecture in the $2^6$ Gepner model: a non-geometric background mirror dual to a rigid Calabi-Yau manifold, in the deep interior of moduli space. By constructing an extensive set of supersymmetric Minkowski flux solutions, we spectacularly confirm the linear growth, while achieving a slightly higher ratio of stabilised moduli to flux charge than the conjectured upper bound. As a byproduct, we obtain for the first time a set of solutions within the tadpole bound where all complex structure moduli are massive. Since the $2^6$ model has no Kähler moduli, these show that the massless Minkowski conjecture does not hold beyond supergravity.

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arXiv2024

Non-Supersymmetric Heterotic Strings on a Circle

Motivated by a recent construction of non-supersymmetric $\text{AdS}_3$, we revisit the $O(16)\times O(16)$ heterotic string compactified on a torus. The string one-loop potential energy has interesting dependence on the classical moduli; extrema of this potential include loci where the gauge symmetry is maximally enhanced. Focusing on the case of a circle, we use lattice embeddings to find the maximal enhancement points together with their spectra of massless and tachyonic modes. We find an extended Dynkin diagram that encodes the global structure of the moduli space, as well as all symmetry enhancements and the loci where they occur. We find $107$ points of maximal enhancement with $8$ that are free of tachyons. The tachyon-free points each have positive cosmological constant. We determine the profile of the potential energy near each of these points and find that one is a maximum while three are saddle points. The remaining four live at the boundary of a tachyonic region in field space. In this way, we show that every point of maximal symmetry enhancement is unstable. We further find that the curvature of this stringy potential satisfies the de Sitter swampland conjecture. Finally, we discuss the implications for constructions of $\text{AdS}_3$.

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arXiv2023

Tadpoles and Gauge Symmetries

The tadpole conjecture proposes that complex structure moduli stabilisation by fluxes that have low tadpole charge can be realised only at special points in moduli space, leading generically to (large) gauge symmetries. Here we provide an exhaustive survey of the gauge symmetries arising in F-theory flux compactifications on products of attractive $\mbox{K3}$ surfaces, with complex structure moduli fully stabilised. We compute the minimal rank of the left-over non-abelian gauge group for all flux configurations within the tadpole bound, finding that it is always non-zero. It decreases in a roughly linear fashion with the tadpole charge, reaching zero at charge 30. By working out possible gauge algebras for different values of the tadpole, we find that all simple ADE Lie algebras of rank $\le 18$ appear.

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arXiv2022

Smearing and Unsmearing KKLT AdS Vacua

Gaugino condensation on D-branes wrapping internal cycles gives a mechanism to stabilize the associated moduli. According to the effective field theory, this gives rise, when combined with fluxes, to supersymmetric AdS$_4$ solutions. In this paper we provide a ten-dimensional description of these vacua. We first find the supersymmetry equations for type II AdS$_4$ vacua with gaugino condensates on D-branes, in the framework of generalized complex geometry. We then solve them for type IIB compactifications with gaugino condensates on smeared D7-branes. We show that supersymmetry requires a (conformal) Calabi-Yau manifold and imaginary self-dual three-form fluxes with an additional (0,3) component. The latter is proportional to the cosmological constant, whose magnitude is determined by the expectation value of the gaugino condensate and the stabilized volume of the cycle wrapped by the branes. This confirms, qualitatively and quantitatively, the results obtained using effective field theory. We find that exponential separation between the AdS and the KK scales seems possible as long as the three-form fluxes are such that their (0,3) component is exponentially suppressed. As for the localized solution, it requires going beyond SU(3)-structure internal manifolds. Nevertheless, we show that the action can be evaluated on-shell without relying on the details of such complicated configuration. We find that no "perfect square" structure occurs, and the result is divergent. We compute the four-fermion contributions, including a counterterm, needed to cancel these divergencies.

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arXiv2022

Anti D3-branes and gaugino condensation

Anti-D3 branes at the bottom of warped throats, commonly used to uplift the cosmological constant in String-Theory de Sitter proposals, source a plaethora of supersymmetry-breaking fluxes, that can interact nontrivially with other ingredients of the flux compactification. In this paper we perform a complex-structure decomposition of these fluxes, and compute the effect of the (0,3) flux component on the stabilization of Kähler moduli via D7-branes gaugino condensation. This allows us to obtain a new constraint on the validity of this stabilization mechanism. This effect does not appear hard to satisfy in de Sitter construction proposals that use long warped throats, but may be problematic in proposals where the warping is small.

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arXiv2022

Affine Algebras at Infinite Distance Limits in the Heterotic String

We analyze the boundaries of the moduli spaces of compactifications of the heterotic string on $T^d$, making particular emphasis on $d=2$ and its F-theory dual. We compute the OPE algebras as we approach all the infinite distance limits that correspond to (possibly partial) decompactification limits in some dual frame. When decompactifying $k$ directions, we find infinite towers of states becoming light that enhance the algebra arising at a given point in the moduli space of the $T^{d-k}$ compactification to its $k$-loop version, where the central extensions are given by the $k$ KK vectors. For $T^2$ compactifications, we reproduce all the affine algebras that arise in the F-theory dual, and show all the towers explicitly, including some that are not manifest in the F-theory counterparts. Furthermore, we construct the affine $SO(32)$ algebra arising in the full decompactification limit, both in the heterotic and in the F-theory sides, showing that not only affine algebras of exceptional type arise in the latter.

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arXiv2022

The Tadpole Conjecture in Asymptotic Limits

The tadpole conjecture suggests that the complete stabilization of complex structure deformations in Type IIB and F-theory flux compactifications is severely obstructed by the tadpole bound on the fluxes. More precisely, it states that the stabilization of a large number of moduli requires a flux background with a tadpole that scales linearly in the number of stabilized fields. Restricting to the asymptotic regions of the complex structure moduli space, we give the first conceptual argument that explains this linear scaling setting and clarifies why it sets in only for a large number of stabilized moduli. Our approach relies on the use of asymptotic Hodge theory. In particular, we use the fact that in each asymptotic regime an orthogonal sl(2)-block structure emerges that allows us to group fluxes into sl(2)-representations and decouple complex structure directions. We show that the number of stabilized moduli scales with the number of sl(2)-representations supported by fluxes, and that each representation fixes a single modulus. Furthermore, we find that for Calabi-Yau four-folds all but one representation can be identified with representations occurring on two-folds. This allows us to discuss moduli stabilization explicitly and establish the relevant scaling constraints for the tadpole.

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arXiv2022

Bare-Bones de Sitter

We compute the supersymmetry-breaking three-form fluxes generated by the addition of anti-D3 branes at the tip of a Klebanov-Strassler throat. These fluxes give rise to nontrivial terms in the superpotential when the throat is embedded in a flux compactification. We describe these terms both from a ten-dimensional and from a four-dimensional perspective and show that, upon including Kähler-moduli stabilization, the resulting potential admits de Sitter minima. Our proposed de Sitter construction does not require additional supersymmetry-breaking (0,3) fluxes, and hence is more minimalist than the KKLT proposal.

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arXiv2022

$E_9$ symmetry in the Heterotic String on $S^1$ and the Weak Gravity Conjecture

We show that compactifications of the heterotic string on a circle exhibit at the boundary of moduli space ($R\to 0$, or equivalently the decompactification limit $R \to \infty$) a tower of winding or momentum modes that enhance the $E_8 \times E_8$ or $SO(32)$ gauge symmetry to the affine algebras $(E_9 \oplus E_9)/\sim$ (the identification means that the two copies of $E_9$ share the same central extension) and $\hat{D}_{16}$, respectively. We also prove that these towers of modes satisfy the lattice Weak Gravity and Repulsive Force Conjectures.

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arXiv2021

D7 Moduli Stabilization: The Tadpole Menace

D7-brane moduli are stabilized by worldvolume fluxes, which contribute to the D3-brane tadpole. We calculate this contribution in the Type IIB limit of F-theory compactifications on Calabi-Yau four-folds with a weak Fano base, and are able to prove a no-go theorem for vast swathes of the landscape of compactifications. When the genus of the curve dual to the D7 worldvolume fluxes is fixed and the number of moduli grows, we find that the D3 charge sourced by the fluxes grows faster than 7/16 of the number of moduli, which supports the Tadpole Conjecture of Ref.~\cite{Bena:2020xrh}. Our lower bound for the induced D3 charge decreases when the genus of the curves dual to the stabilizing fluxes increase, and does not allow to rule out a sliver of flux configurations dual to high-genus high-degree curves. However, we argue that most of these fluxes have very high curvature, which is likely to be above the string scale except on extremely large (and experimentally ruled out) compactification manifolds.

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arXiv2021

The Swampland Conjectures: A bridge from Quantum Gravity to Particle Physics

The swampland is the set of seemingly consistent low-energy effective field theories that cannot be consistently coupled to quantum gravity. In this review we cover some of the conjectural properties that effective theories should possess in order not to fall in the swampland, and we give an overview of their main applications to particle physics. The latter include predictions on neutrino masses, bounds on the cosmological constant, the electroweak and QCD scales, the photon mass, the Higgs potential and some insights about supersymmetry.

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arXiv2021

Exploring the landscape of CHL strings on T^d

Compactifications of the heterotic string on special T^d/Z_2 orbifolds realize a landscape of string models with 16 supercharges and a gauge group on the left-moving sector of reduced rank d+8. The momenta of untwisted and twisted states span a lattice known as the Mikhailov lattice II_{(d)}, which is not self-dual for d > 1. By using computer algorithms which exploit the properties of lattice embeddings, we perform a systematic exploration of the moduli space for d=1 and 2, and give a list of maximally enhanced points where the U(1)^{d+8} enhances to a rank d+8 non-Abelian gauge group. For d = 1, these groups are simply-laced and simply-connected, and in fact can be obtained from the Dynkin diagram of E_{10}. For d = 2 there are also symplectic and doubly-connected groups. For the latter we find the precise form of their fundamental groups from embeddings ofof lattices into the dual of II_{(2)}. Our results easily generalize to d > 2.

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arXiv2021

Algorithmically solving the Tadpole Problem

The extensive computer-aided search applied in [arXiv:2010.10519] to find the minimal charge sourced by the fluxes that stabilize all the (flux-stabilizable) moduli of a smooth K3xK3 compactification uses differential evolutionary algorithms supplemented by local searches. We present these algorithms in detail and show that they can also solve our minimization problem for other lattices. Our results support the Tadpole Conjecture: The minimal charge grows linearly with the dimension of the lattice and, for K3xK3, this charge is larger than allowed by tadpole cancelation. Even if we are faced with an NP-hard lattice-reduction problem at every step in the minimization process, we find that differential evolution is a good technique for identifying the regions of the landscape where the fluxes with the lowest tadpole can be found. We then design a "Spider Algorithm," which is very efficient at exploring these regions and producing large numbers of minimal-tadpole configurations.

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