arXiv subjects

Niccolò Cribiori

Publications and source records attributed to Niccolò Cribiori.

At least 19 recordsLinked to original sources

arXiv2026

Type IIA on Spin(7) manifolds with fluxes

We initiate a systematic study of compactifications of type II string theory to two dimensions on Ricci-flat spaces with fluxes and sources. We derive universal constraints on such compactifications, and then develop type IIA compactifications on $\mathrm{Spin}(7)$-holonomy spaces with bulk fluxes whose tadpole is cancelled by $\mathrm{OF1}$-planes. We derive the resulting two-dimensional $\mathcal N=(1,1)$ supergravity for a toroidal $\mathrm{Spin}(7)$ orbifold, and we extend the metric and universal sectors geometrically to general compact $\mathrm{Spin}(7)$ manifolds. In candidate supersymmetric Minkowski vacua, all untwisted shape modes appear in the flux scalar potential and can in principle be classically stabilised. However, in an explicit toroidal orbifold example flux quantisation together with the tadpole bound may obstruct the existence of candidate vacua supported entirely within the untwisted sector. The string-frame volume in string units is bounded by $7χ/192$, so suppressing $α'$ corrections requires $\mathrm{Spin}(7)$ manifolds with large Euler characteristic.

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arXiv2026

A domain wall bound on anti-de Sitter vacua

We consider anti-de Sitter flux vacua interpolated by flux-changing domain walls. Demanding that the tension of such a domain wall be above the ultraviolet cutoff of the effective description, we derive an upper bound on the anti-de Sitter radius, which we term domain wall bound. It translates into a lower bound on the gravitino mass, thus realizing the gravitino conjecture and the anti-de Sitter distance conjecture of the swampland program. We test the domain wall bound on several examples with a candidate hierarchy of scales: classical flux vacua, racetrack models, LVS and KKLT-like anti-de Sitter vacua. The classical flux vacua and LVS are found to be compatible with the bound. For racetrack and KKLT-like anti-de Sitter vacua, the bound poses a non-trivial constraint on achieving large hierarchies of scales.

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arXiv2026

Scale-separated vacua with extended supersymmetry

We propose the first examples of scale-separated vacua with extended supersymmetry. They arise as circle compactifications of four-dimensional vacua of massive type IIA supergravity with scale separation, upon introducing additional fluxes and sources. We provide both the ten-dimensional solutions and the three-dimensional effective descriptions in terms of Kähler potential and superpotential. The conformal dimensions of the putative dual two-dimensional field theory appear not to be integers. The superpotential for the additional fluxes of one of our models was guessed by ChatGPT and, to the best of our knowledge, it does not appear in existing literature. Should these vacua be solutions of string theory, they would allow to address the open problem of scale separation from the vantage point of extended supersymmetry.

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arXiv2026

Cosmological constraints from UV/IR mixing

Holography and entropy bounds suggest that the ultraviolet (UV) and infrared (IR) cutoffs of gravitational effective theories are related to one another as a form of UV/IR mixing. Motivated by this, we derive a bound on the allowed scalar field range in theories with cosmic horizons. We show how this bound challenges several inflationary scenarios, such as $α$-attractors and modular-invariant inflation. Besides, we find a relation between the number of extra spatial dimensions and the tensor-to-scalar ratio.

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arXiv2025

Scale separation, rolling solutions and entropy bounds

We revisit scale separation for compactifications of ten- and eleven-dimensional supergravity. For cosmological solutions rolling down flux-generated potentials, we observe that scale separation is achieved as time flows, and is fairly generic. This is realized without the need of orientifolds nor corrections to the classical supergravity approximation. We then confront scale separation with the Covariant Entropy Bound (CEB) and the CKN bound. We show that a naive application of these bounds to vacua hints at the existence of at least two extra dimensions. For rolling solutions, we observe that the CEB is not always respected, but since these examples lack a cosmic horizon, the application of entropy bounds remains delicate.

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arXiv2025

Bulk/boundary Modular Quintessence and DESI

The latest DESI DR2 results, when combined with other independent cosmological data on the Cosmic Microwave Background and supernovas, suggest a preference for dynamical dark energy. We propose a novel cosmological scenario, which features two distinct scalar fields. One governs the magnitude of the present-day dark energy density and is related to the size of extra-dimensions. Accounting for the observed smallness of this energy density requires the scalar to reside near the boundary of field space. The second field, responsible for the time evolution of dark energy and associated with the string coupling, must instead lie in the bulk to remain consistent with the non-observation of light string states. We show that a natural candidate for such dark energy dynamics is a quintessence modular-invariant potential, in which the second scalar field rolls down a negatively curved slope, starting from a self-dual critical point. We find that this scenario is in good agreement with the latest findings by DESI.

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arXiv2024

String dualities and modular symmetries in supergravity: a review

We review the remarkable interplay between modular symmetries and supergravity, which has led to major advances in both physics and mathematics in recent decades. Our focus will be on four-dimensional models with $\mathcal{N}=1$ and $\mathcal{N}=2$ local supersymmetry. We will look at the early articles on the topic, but also touch on recent developments. These results testify to how supergravity, when supplemented with the appropriate assumptions, can be turned into a unique window into quantum gravity.

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arXiv2024

Emergence of $R^4$-terms in M-theory

It has been recently suggested that the strong Emergence Proposal is realized in M-theory limits by integrating out all light towers of states with a typical mass scale not larger than the species scale, i.e. the eleventh dimensional Planck mass. Within the BPS sector, these are transverse $M2$- and $M5$-branes, that can be wrapped and particle-like, carrying Kaluza-Klein momentum along the compact directions. We provide additional evidence for this picture by revisiting and investigating further the computation of $R^4$-interactions in M-theory à la Green-Gutperle-Vanhove. A central aspect is a novel UV-regularization of Schwinger-like integrals, whose actual meaning and power we clarify by first applying it to string perturbation theory. We consider then toroidal compactifications of M-theory and provide evidence that integrating out all light towers of states via Schwinger-like integrals thus regularized yields the complete result for $R^4$-interactions. In particular, this includes terms that are tree-level, one-loop and space-time instanton corrections from the weakly coupled point of view. Finally, we comment on the conceptual difference of our approach to earlier closely related work by Kiritsis-Pioline and Obers-Pioline, leading to a correspondence between two types of constrained Eisenstein series.

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arXiv2024

Minimal Black Holes and Species Thermodynamics

The species scale provides a lower bound on the shortest possible length that can be probed in gravitational effective theories. It may be defined by the size of the minimal black hole in the theory and, as such, it has recently been given an interpretation along the lines of the celebrated black hole thermodynamics. In this work, we extend this interpretation to the case of charged species. We provide working definitions of minimal black holes for the case of uncharged and charged species constituents. Then, examining the modifications in the thermodynamic properties of near-extremal charged species compared to the uncharged case, we uncover interesting implications for the cosmology of an expanding universe, particularly within the context of the Dark Dimensions Scenario. Finally, we explore possible microscopic constructions in non-supersymmetric string theories in which towers of charged near-extremal species may arise.

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arXiv2024

Reflections on an M-theoretic Emergence Proposal

In a pedagogical manner, we review recent developments in the investigation of the Emergence Proposal. Although it is fair to say that this idea is still at an exploratory level and a fully coherent picture has yet to be developed, we put it into perspective to previous work on the swampland program and on emergence in QG. In view of the emergent string conjecture, we argue and provide evidence that it is not the emergent string but rather the decompactification limit which is a natural candidate for the potential realization of the Emergence Proposal. This resonates in a compelling way with old ideas of emergence in M(-atrix) theory and gives rise to a number of further speculations.

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arXiv2024

Demystifying the Emergence Proposal

We revisit the Emergence Proposal in the vector multiplet moduli space of type IIA N=2 supersymmetric string vacua in four dimensions, for which the string tree-level prepotential and the string one-loop correction are exactly known via mirror symmetry. We argue that there exists an exact notion of emergence, according to which these four-dimensional couplings can be computed exactly in any asymptotic limit in field space. In such limits, a perturbative quantum gravity theory emerges, whose fundamental degrees of freedom include all complete infinite towers of states with typical mass scale not larger than the species scale. For a decompactification limit, this picture is closely related to and in fact motivated by the computation of Gopakumar-Vafa invariants. In addition, in the same limit our results suggest that the emergent theory will also contain asymptotically tensionless wrapped NS5-branes.

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arXiv2023

Species Entropy and Thermodynamics

We analyse particle species and the species scale in quantum gravity from a thermodynamic perspective. In close analogy to black hole thermodynamics, we propose that particle species own an entropy and a temperature, which is determined by the species scale. This is identical to the Bekenstein-Hawking entropy of a corresponding minimal black hole and agrees with the number of species in a given tower of states. Through the species entropy, we find that certain entropy bounds are connected to recent swampland constraints. Moreover, the concept of species entropy and temperature allow us to formulate the laws of species thermodynamics, which are argued to govern the variations of moduli in string theory. They can be viewed as general rules that imply certain swampland conjectures, and vice versa.

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arXiv2023

Black hole entropy and moduli-dependent species scale

We provide a moduli-dependent definition of species scale in quantum gravity based on black hole arguments. Concretely, it is derived from of a lower bound on the entropy of extremal black holes with higher curvature corrections, which ensures that the black hole can be reliably described within the effective theory. By demanding that our definition coincides with a recent proposal for a moduli-dependent species scale motivated from the topological string, we conclude that the conjecture $\mathcal{Z}_{BH} = |\mathcal{Z}_{\rm top}|^2$ relating the black hole to the topological string partition functions should hold, at least within the regime of validity of our analysis.

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arXiv2023

Supergravity EFTs and swampland constraints

In these proceedings, we review recent progress in analyzing the behavior of lower-dimensional supergravity theories when combined with swampland conjectures. We show that within supergravity the effectiveness and usefulness of swampland conjectures gets amplified, existing criteria can be intertwined and also new ones can be uncovered. Furthermore, we elaborate on some previously unpublished work. This includes evidence for the possible existence of a novel conjecture on Yukawa couplings and an argument to constrain large classes of D-term inflationary models using known conjectures.

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arXiv2023

The Emergent M-theory Limit

It has been recently proposed that at each infinite distance limit in the moduli space of quantum gravity a perturbative description emerges with fundamental degrees of freedom given by those infinite towers of states whose typical mass scale is parametrically not larger than the ultraviolet cutoff, identified with the species scale. This proposal is applied to the familiar ten-dimensional type IIA and IIB superstring theories, when considering the limit of infinite string coupling. For type IIB, the light towers of states are given by excitations of the D1-brane, as expected from self-duality. Instead, for type IIA at strong coupling, which is dual to M-theory on $S^1$, we make the observation that the emergent degrees of freedom are bound states of transversal M2- and M5-branes with Kaluza-Klein momentum along the circle. We speculate on the interpretation of the necessity of including all these states for a putative quantum formulation of M-theory.

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arXiv2023

A note on modular invariant species scale and potentials

The species scale provides an upper bound for the ultraviolet cutoff of effective theories of gravity coupled to a number of light particle species. We point out that modular invariant (super-)potentials provide a simple and computable expression of the species scale as a function of the moduli in toroidal orbifold compactifications of type II and heterotic string. Due to modular symmetry, these functions are valid over all moduli space and not only in asymptotic regions. We observe that additive logarithmic corrections to the species scale arise from the requirement that the latter be modular invariant. We recast the moduli-dependent expression of the species scale in terms of the gravitino mass or the scalar potential of these models and we connect it to swampland conjectures such as the anti-de Sitter distance conjecture and the gravitino conjecture.

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arXiv2023

Quantum gravity constraints on scale separation and de Sitter in five dimensions

We give evidence that supersymmetric anti-de Sitter vacua of five-dimensional supergravity cannot be scale separated as a consequence of quantum gravity constraints, such as the weak gravity conjecture or the species scale. We show this in a model-independent way for the minimal and the maximal theory and we believe that the argument can be extended to any amount of preserved supercharges in the between. If combined with previous works stating that non-supersymmetric anti-de Sitter vacua must be unstable, our results suggest that no genuinely five-dimensional effective theory in anti-de Sitter exists. At the cost of introducing an additional assumption on the gravitino mass, we can extend our analysis to de Sitter vacua as well. However, the few known stable de Sitter vacua of minimal five-dimensional supergravity do not satisfy such an assumption and thus evade our constraints. This suggest that they are on a somehow different footing than their four-dimensional counterparts and therefore deserve further investigation.

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arXiv2023

The Scale of Supersymmetry Breaking and the Dark Dimension

We argue for a relation between the supersymmetry breaking scale and the measured value of the dark energy density $Λ$. We derive it by combining two quantum gravity consistency swampland constraints, which tie the dark energy density $Λ$ and the gravitino mass $M_{3/2}$, respectively, to the mass scale of a light Kaluza-Klein tower and, therefore, to the UV cut-off of the effective theory. Whereas the constraint on $Λ$ has recently led to the Dark Dimension scenario, with a prediction of a single mesoscopic extra dimension of the micron size, we use the constraint on $M_{3/2}$ to infer the implications of such a scenario for the scale of supersymmetry breaking. We find that a natural scale for supersymmetry signatures is $M={\cal O}\left(Λ^{1/8}\right)={\cal O}({\rm TeV})$. This mass scale is within reach of LHC and of the next generation of hadron colliders. Finally, we discuss possible string theory and effective supergravity realizations of the Dark Dimension scenario with broken supersymmetry.

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