Asymptotically massless towers of species are ubiquitous in the string landscape when infinite-distance limits are approached. Due to the remarkable properties of string dualities, they always comprise Kaluza-Klein states or higher-spin excitations of weakly coupled, asymptotically tensionless critical strings. The connection between towers of light species and small black holes warrants...
Three distinct infinite distance limits appear in the conformal manifolds of four-dimensional superconformal field theories admitting large N limit. They are distinguished by the CFT Distance Conjecture parameter, controlling the exponential behavior with the distance of the anomalous dimension of higher-spin currents. Borrowing lessons from the moduli spaces of flat space vacua in string...
Metastable de Sitter vacua are widely explored in the classical corner of string theory and notoriously difficult to realise. In addition, metastable de Sitter vacua in the parametrically controlled region have been conjectured to be in the Swampland. In this talk we explore a non-supersymmetric corner of string theory given by type II Scherk-Schwarz toroidal orbifolds, where supersymmetry is...
We begin by studying configurations of particles at equilibrium at a temperature T inside a box in the presence of towers of species. By playing with the control parameters, we can obtain configurations that avoid gravitational collapse and fulfill the Covariant Entropy Bound (CEB). These interpolate between the usual dependence of the entropy with the volume (when T is low enough and the...
I will discuss the computation of correlators and observable quantities, in particular OPE coefficients, in Argyres-Douglas theories, that are 4-dimensional N = 2 superconformal field theories, intrinsically strongly coupled and without a Lagrangian description. I will recall some results for extremal correlators and OPE coefficients derived through localization on the 4-sphere, showing their...
Scale-separated AdS compactifications of string theory can be constructed at the two-derivative supergravity level in the presence of smeared orientifold planes. The "unsmearing" corrections are known to leading order in the large volume, weak coupling limit. However, first-order perturbative approximations of non-linear problems can often produce spurious solutions, which are only weeded out...
We aim to derive the species thermodynamics from a bottom up perspective, namely from purely thermodynamic considerations of towers of species at finite temperature. As we will show, in a certain high temperature limit and invoking the concept of UV/IR mixing, the entropy of certain towers will change its behaviour from extensive volume scaling to an area low and in this way will end up with...
New methods have emerged in the context of black hole perturbation theory, which are based on the correspondence between the equations describing the propagation of waves in these geometries and the Seiberg-Witten curves for an N=2 SYM theory with SU(2) gauge group in the non-commutative Nekrasov-Shatashvili background. These techniques are employed to compute observables such as quasi-normal...
The Festina Lente (FL) swampland bound follows from demanding that charged black holes of cosmological size in quasi-de Sitter space evaporate in a consistent, non-singular way. The FL bound demands that all charged particles are heavier than a lower bound determined by the gauge coupling and vacuum energy. If one applies the FL bound to nonabelian gauge theories in de Sitter space, one finds...
We investigate the high-energy fixed-angle scattering of pions and rho mesons in a holographic QCD model, following the Polchinski--Strassler proposal. In agreement with earlier findings of Polchinski, Strassler and other authors, we observe partonic behaviour coming from string amplitudes in AdS spacetime. In our holographic approach, 2-to-n pion scattering amplitudes display agreement with...
For the anti-D3-brane uplift one places $p$ anti-D3-branes at the tip of a Klebanov-Strassler (KS) throat. This setup can only contribute positively to the vacuum energy if it is stable against the so called KPV decay where the anti-branes puff up into an NS5-brane which subsequently annihilates against flux and forms a supersymmetric state at zero vacuum energy. In this talk, I will discuss...
We propose a scenario that might result in a transient phase of cosmological acceleration on asymptotic corners of string theory moduli space. In a cosmological version of the chameleon mechanism, a steep potential is stabilized by a non-zero density of heavy states. This can also be realized by balancing effects of light and heavy towers. We show that in both cases, which end once states are...
Utilizing freely acting asymmetric orbifolds in type IIB string theory, we construct a class of theories in 5D and 4D with 8 supercharges, where the moduli spaces for both vector multiplets and hypermultiplets can be determined without quantum corrections. By tuning the duality twist, all fields from the R-R sector can be rendered massive. This talk highlights two minimal examples: one with...
I will review how black holes can be used to probe infinite distance points in moduli space and the phenomenological opportunities that lie there. Then I will discuss how the picture drastically changes when one considers a vacuum where the scalars are stabilized.
We present a new technique to derive the quiver and the superpotential of a D2-brane probe at the singularity of a specific class of Calabi-Yau Threefolds. These spaces are constructed as non trivial fibrations of deformed ADE singularities on a complex plane and can be conceived as non toric generalizations of the conifold geometry. We establish a correspondence between monopole operator...
Dynamical Cobordism is an implementation of the Cobordism Conjecture in the framework of Effective Field Theory, with End-of-the-World (ETW) Branes realized as codimension-1 solutions of the EFT becoming singular at infinite field distance and finite spacetime distance. In this talk, I will describe how codimension-2 ETW branes can be realized as intersecting solutions, providing both a...
First, we generalize the construction of scale-separated vacua in massless Type IIA compactified on an SU(3)-structure manifold with geometric fluxes beyond the double T-dualization of a DGKT toroidal orbifold. We propose new infinite families of vacua based on elliptic fibrations with metric fluxes. They display parametric scale separation, achieved by an asymmetric flux rescaling.
Controlled de Sitter vacua, if they exist, seem to be hiding in difficult regions of the string Landscape -- they seem to require such an intricate interplay of ingredients, that many things can go wrong and invalidate the solutions. In fact, checking their validity with explicit computations is itself a difficult task. With this in mind, we explore a combination of ingredients that are both...
In the presence of massless scalar fields, mediating long-range forces, the Weak Gravity Conjecture (WGC) must be modified to take such interactions into account. This suggested the possibility that a relation analogous to the WGC could hold for scalar fields only, dubbed Scalar Weak Gravity Conjecture (SWGC). In this talk we discuss the SWGC in the case where the scalar fields are...
The lack of experimental evidence for supersymmetry has recently fueled a resurgence of interest in non-supersymmetric strings, where supersymmetry is absent at the string scale. In particular, new theories have been found recently with a very rich and interesting spectra.
A great deal of effort has been put in understanding the structure underlying the supersymmetric landscape. Much of it...
In our research, we studied the decay of the Kaluza-Klein vacuum via an instanton solution, which has a singularity. For the Kaluza-Klein vacuum, there is a non-perturbative decay channel where literally a "bubble of nothing" expands and overwhelms the spacetime. The instanton solution that mediates this decay is the Euclidean 5D Schwarzshild solution, and, in general discussion, we fix the...
In six dimensions, there is an exotic N=(4,0) supermultiplet that contains only fields of spin ≤2, but no graviton, and that on a circle reduces to 5D N=4 supergravity. It has been proposed that, if suitable interactions exist, the (4,0) theory might provide a consistent alternative UV completion for N=4 5D supergravity, realizing a supersymmetric version of asymptotic safety. We argue that...
The landscape of low-energy effective field theories stemming from string theory is too vast for a systematic exploration. However, the meadows of the string landscape may be fertile ground for the application of machine learning techniques. In this talk, I will illustrate that Quantum Gravity effective field theories are endowed with key statistical learnability properties due to their...
The gravitational backreaction of the absence of spacetime supersymmetry in string theory has dramatic effects, forbidding the tree-level flat Minkowski and requiring new vacuum solutions. A similar fate is expected for localized sources: brane solutions must change drastically.
In this talk, I will discuss ongoing work on the gravity description of branes in non-supersymmetric tachyon-free...
The cobordism conjecture predicts end-of-the-world (ETW) branes to generally exist. As a consequence, universes can decay to nothing and be created from nothing in various ways. We discuss how the existence of ETW branes changes predictions cosmological predictions.
Higher-curvature corrections appear naturally as stringy corrections in the different effective actions of String Theory. In recent years this has motivated an intensive research on higher-curvature terms by themselves, beyond their fundamental origin. In this contribution, I will focus first on showing how a very special class of higher-curvature theories may be used to study \alpha’...
Cobordism offers an unique perspective into the non-perturbative sector of string theory by demanding quantum gravitational consistency.
The AdS Distance conjecture proposes a notion of distance between AdS vacua in quantum gravity. Although the need for such a notion is evident, defining and computing this distance is challenging, both conceptually and technically. In my talk, I will address this challenge by proposing a consistent framework for defining and computing the metric over AdS vacua, establishing a well-defined...
Brane Supersymmetry Breaking (BSB) is a phenomenon occurring in lower dimensional orientifold vacua in which supersymmetry is broken without admitting tachyonic instabilities. Such vacua are characterised by the simultaneous presence of a tree-level supersymmetric closed string sector coupled with a non-supersymmetric open string one, which underlies a non-linear realisation of supersymmetry....
We revisit the Green-Schwarz (GS) mechanism in the 10d Sugimoto model and explicitly show the consistency with anomaly-inflow onto the branes involved in the GS-mechanism. The branes’ degrees of freedom establishes Sp(16) as the global gauge group of the 10d non-supersymmetric theory. We then interpret and generalize the computation with a bottom-up perspective, to study the consistency of...
The dynamical realization of the cobordism conjecture in type IIB in AdS5xS5 will be presented, using the existing gravity duals of 4d N = 4 SYM with Gaiotto-Witten superconformal boundary conditions (near-horizon limits of D3-branes ending on NS5- and D5-branes). These configurations are, from the 5d perspective, dynamical cobordism solutions which start from an asymptotic AdS5 vacuum and...
Flux compactifications that give three- or four-dimensional Anti-de-Sitter vacua with a parametrically-small negative cosmological constant are supposed to be ubiquitous in String Theory. However, the 1+1 and 2+1 dimensional CFT duals to such vacua should have a very large central charges and rather unusual spectra. Furthermore, there are various swampland conjectures that such vacua should...
Does string theory predict extra dimensions? It is common folklore that consistency dictates ten or eleven in total. However, the structures appearing in string theory generalize the classical notion of geometry to something more abstract, which may not always reduce to the familiar idea of compact extra dimensions. I will present some recent results to the effect that classical geometry does...
We study the phenomenological usefulness of including geometric and non-geometric fluxes to the flux-induced scalar potential for type IIA orientifolds. The resulting potential presents a bilinear structure, which we use to explore two topics: scale separation and the search of dS vacua. First, we generalize the construction of scale-separated vacua in massless Type IIA compactified on an...
We perform a detailed study of stringy moduli-driven cosmologies between the end of inflation and the commencement of the Hot Big Bang, including both the background and cosmological perturbations: a period that can cover half the lifetime of the universe on a logarithmic scale. Compared to the standard cosmology, stringy cosmologies motivate extended kination, tracker and moduli-dominated...
In its original formulation, the Emergence Proposal postulates that terms in the low-energy effective action are emerging by integrating out towers of states becoming exponentially light in asymptotic regions of the moduli space, in agreement with the Swampland Distance Conjecture. In this talk, I will motivate an M-theoretic refinement of the Emergence Proposal by revisiting the computation...
6d supergravity with minimal supersymmetry is highly constrained by various low-energy consistency conditions, including anomaly cancellation. In this talk I will discuss the use of ideas from graph theory to exhaustively enumerate all consistent models with few tensor multiplets (modulo some minimal assumptions). Testing this complete list of models against several Swampland bounds reduces...
I will discuss stringy, moduli-driven cosmologies between the end of inflation and the commencement of the Hot Big Bang,a period that can cover half the lifetime of the universe on a logarithmic scale. Compared to the standard cosmology, stringy cosmologies motivate extended kination, tracker and moduli-dominated epochs involving significantly trans-Planckian field excursions. The...
Among various predictions of string compactifications, axions hold a pivotal role, as they provide a unique avenue to tie UV physics to experiments.
Most experimental setups aim to detect a signal using the direct coupling between the axion and the Standard Model. However, string axions do not necessarily need to couple to the Standard Model directly. In this talk I will describe how...
Based on 2401.00549
The dualization of the scalar fields of a theory into (d-2)-form potentials preserving all the global symmetries is one of the main problems in the construction of democratic pseudoactions containing simultaneously all the original fields and their duals. We study this problem starting with the simplest cases and we show how it can be solved for scalars parametrizing...
We study limits of vanishing Yukawa couplings in Quantum Gravity, using type IIA orientifolds as a laboratory. We show that in the limit Y → 0 there are some towers (called gonions) which become asymptotically massless, while at the same time, the kinetic term of some chiral fields becomes singular. In addition, we study how tiny masses of Dirac neutrinos can arise consistent with experimental...
In the context of the Swampland program, the Distance Conjecture predicts an infinite tower of states becoming massless at infinite distance in moduli spaces of string compactifications. This is widely believed to be a general feature of quantum gravity, but it is difficult to prove in full generality. On the other hand, the moduli spaces of maximally and half-maximally supersymmetric theory...
The topic of this talk will be a new inflationary model called ‘Loop Blow-Up Inflation’, first presented in 2403.04831. This model is based on string loop corrections to the scalar potential of ‘Kähler moduli inflation’, which originally featured only non-perturbative contributions. The perturbative effects become dominant over the non-perturbative ones as soon as the inflaton is displaced...
A classification proposal exists for string vacua with 16 supercharges in six dimensions. It predicts in particular a family of type II strings without moduli apart from the dilaton, including the only known example given by Dabholkar and Harvey some time ago. It is also predicted that some of these theories admit nontrivial discrete theta angles. Here I will show how such theories can be...
We use branes to generalize the Distance Conjecture. We conjecture that, in any asymptotic distance phi in the moduli space of string vacua of a d-dimensional theory, among the set of particle towers or branes with at most p spacetime dimensions, at least one particle tower or brane becomes exponentially low tension by the formula T~exp(-alpha phi) where alpha is at least 1/sqrt(d-p-1). Since...
I will discuss supersymmetric AdS_3 flux vacua of massive type IIA supergravity on G2 orientifolds, focusing on (non) scale separated configurations at large volume and weak coupling, even highly anisotropic. I will also present the realization of the Swampland Distance Conjecture within such setups via the inclusion of appropriate D4-branes.
In addition, inspired by the desire of finding all...
We study in detail and generalise a recent formulation of brane-antibrane inflation in which the problems of the original formulations are addressed: separation between branes larger than the size of the extra dimension, lack of modulus stabilisation, the eta problem, and the reduction of the set-up to the unrealistic inflection point inflation. We explicitly compute the effect of brane...
Dynamical Cobordism provides a powerful method to probe infinite distance limits in moduli/field spaces parameterized by scalars constrained by generic potentials, employing configurations of codimension-1 end of the world (ETW) branes. These branes, characterized in terms of critical exponents, mark codimension-1 boundaries in the spacetime in correspondence of finite spacetime distance...
Using flat space string amplitudes and recently computed equilibration rates for a gas of highly excited strings, we argue that a Hagedorn phase could have occured in the early Universe with a bath of open strings dominating the energy density. These strings would predominantly decay in Standard Model fields, providing a successful reheating, and would release a gravitational wave spectrum...
Scale separation is the important phenomenological property for a given vacuum to have an internal compact space much "smaller" than the extended spacetime, so that a lower-dimensional effective description indeed makes sense. At a practical level, this is measured by the decoupling or not of the magnitude of the cosmological constant from the Kaluza-Klein scale. The status of scale separation...
The landscape of Type-II Little String Theories (LSTs) is very sparse compared to its Heterotic counterpart. We show that this difference can be explained by analysing the bounds imposed on their flavor symmetries when demanding unitarity of the worldsheet theory. We then study Type-II LSTs from the bottom up through the associated Superconformal Field Theories, enabling us to identify T-dual...
We investigate the dynamics of a multifield dark energy model, which arises from certain rapid-turning and inspiraling trajectories in field space. We find the speed of sound of the dark energy perturbations around the background and show that this speed is monotonically decreasing with time. Furthermore, it has a positive-definite lower bound that implies a certain clustering scale. We also...
We examine the minimal constraints imposed by the Weak Gravity Conjecture (WGC) on the particle spectrum of quantum gravity theories. Recently, we argued for the existence of a minimal radius in circle reductions of generic quantum gravity theories. Consequently, whenever a minimal radius exists and the WGC is satisfied at the particle level below the black hole threshold by some states, these...
FTheoryTools (https://docs.oscar-system.org/stable/Experimental/FTheoryTools/introduction/) is an in-development component of the OSCAR computer algebra system (https://www.oscar-system.org/).
The goal is to automate tedious computations in the field of F-theory.
Among others, a large database of existing models from the literature is included (in compliance with the established MARDI...
In its original version, the Emergence Proposal states that the kinetic terms of all fields in the low-energy effective action arise from integrating out towers of states becoming light in asymptotic corners of the moduli space. In my talk I want to motivate why the natural home of the Emergence Proposal should be M-theory. I will discuss this idea in the context of a well-known setup, namely...
It is known that single-field models of accelerated expansion with nearly flat potentials, despite being able to provide observationally viable explanations for the early-time cosmic inflation and the late-time cosmic acceleration, are in strong tension with the conjectured de Sitter swampland constraints. It has recently been argued that in an open universe, where the spatial curvature is...
Any scalar FLRW-cosmology with multi-field multi-exponential potentials exhibits a universal bound on late-time cosmic acceleration. We discuss the conditions under which scaling solutions are inevitable late-time attractors for this class of theories. Without the need to find explicit solutions to the cosmological equations, we are also able to identify bounds on the late-time expansion rate...
In this work, we explore the realization of the Convex Hull version of the Swampland Distance Conjecture in various 4D N=1 effective theories. In these setups, we identify the infinite towers of states that become light in the infinite distance limits and we compute the corresponding scalar charge-to-mass ratio vectors in order to construct their convex hull. We consider the possible EFT...
Higgsing on symmetric matter in an SU(N) gauge theory breaks to a special SO(N) subgroup with exotic matter representations. We discuss the explicit realization of such Higgsings in F-theory models and analyze the resulting models via dualities with heterotic and type IIB. The SO(N) gauge factors are supported on Kodaira type I_N singularities with nontrivial Tate monodromy. These models have...
In this talk, I discuss how a charged Nariai black hole arises in the dark bubble scenario, as a brane embedding in an AdS5 black string background. The construction allows us to identify the U(1) gauge coupling, arising from the D3-worldvolume gauge theory, in terms of the string coupling and gives the same relation as was found previously for microscopic black holes.
We present a numerical computation, based on neural network techniques, of the physical Yukawa couplings in a heterotic string theory model obtained by compactifying on a smooth Calabi-Yau threefold. We consider one of a large class of heterotic line bundle models which give precisely the MSSM low-energy spectrum plus fields uncharged under the standard-model group. The relevant quantities,...
We analyse the scalar curvature of the vector multiplet moduli space of type IIA string theory compactified on a Calabi–Yau manifold. While the volume of this moduli space is known to be finite, cases have been found where the scalar curvature diverges positively along trajectories of infinite distance. We classify the asymptotic behaviour of the scalar curvature for all large volume limits...
We present some recent progress about the study of the moduli space curvature along infinite distance limits. We consider the vector multiplet sector of type IIA string theory compactified on a Calabi-Yau three-fold, where such limits can be roughly classified as M-theory limits, F-theory limits or emergent string limits. We discuss the relation between divergences of the scalar curvature,...
This presentation delves into recent developments in string cosmology, specifically focusing on the refinement of the Hohm-Zwiebach approach through an Hamiltonian reformulation. A general criterion is established to have $\mathcal{O}(d,d)$
invariant actions to all orders in $\alpha'$
connecting
$T$-duality related perturbative solutions of string cosmology equations. Assuming a timely...
Vector bundles made from sums of line bundles have proven to be a particularly fruitful region of the heterotic string landscape, with tens of thousands of models having the exact particle spectrum of the MSSM. A salient feature of these models is their unique and highly constraining S(U(1)^N) flavour symmetry, which strongly affects low-energy physics. In this talk, we apply genetic...
We analyse theories that do not have a de Sitter vacuum and cannot lead to slow-roll quintessence, but which nevertheless support a transient era of accelerated cosmological expansion due to interactions between a scalar and either a hidden sector thermal bath, which evolves as Dark Radiation, or an extremely-light component of Dark Matter. We show that simple models can explain the...
One of the challenges of heterotic compactification on a Calabi-Yau threefold is to determine the physical (27)3 Yukawa couplings of the resulting four-dimensional N=1 theory. In general, the calculation necessitates knowledge of the Ricci-flat metric. However, in the standard embedding, which references the tangent bundle, we can compute normalized Yukawa couplings from the Weil-Petersson...
The distance conjecture diagnoses viable low-energy effective realisations of consistent theories of quantum gravity by examining
their breakdown at infinite distance in their parameter space. At the
same time, infinite distance points in parameter space are naturally intertwined with string dualities. We explore the implications of the distance conjecture when T-duality is applied to curved...
