String Phenomenology 2024

24 Jun 2024, 08:30 → 28 Jun 2024, 18:00 Europe/Rome

Auditorium (Centro Culturale Altinate - San Gaetano - Padova (Italy))

String Phenomenology 2024

 

The 23rd String Phenomenology conference is jointly organized by the Department of Physics and Astronomy "G. Galilei" of the University of Padua and the INFN - National Institute for Nuclear Physics. The event will take place at the Centro Culturale Altinate - San Gaetano of Padova, Italy.        

This annual conference discusses recent progress in string theory, with a particular emphasis on aspects relevant to the theory of fundamental interactions and its phenomenological implications for particle physics and cosmology. 

Plenary and parallel sessions cover the most impactful results recently presented by the community, which have unveiled new ideas and opened previously unexplored research lines. The main topics include:

Swampland and Quantum Gravity Criteria String Model Building in Particle Physics and Cosmology Physical and Geometrical Aspects of String Compactifications Perturbative (Super)String and Non-Geometric Models Machine Learning Techniques in the String Landscape Generalized Symmetries in QFT and String Theory

Participation to this event is by registration only. The link to the registration page will become available on March 4, 2024 on the menu on the left. The registration page will include the possibility to propose a title and abstract for a parallel session talk, or a poster. 

 

Invited Speakers 

Steven Abel Lara Anderson Ralph Blumenhagen Andreas P. Braun Joseph Conlon Clay Cordova Niccolò Cribiori Mirjam Cvetič Giuseppe Dibitetto Emilian Dudas Anamaria Font Marian Graña Thomas Grimm James Halverson Arthur Hebecker Jonathan J. Heckman Manki Kim Magdalena Larfors Seung-Joo Lee Jacob M. Leedom Dieter Lüst

Anshuman Maharana Fernando Marchesano Liam McAllister Jacob McNamara Miguel Montero Jakob Moritz Susha Parameswaran Francisco G. Pedro Erik Plauschinn Fernando Quevedo Matthew Reece Augusto Sagnotti Andreas Schachner Gary Shiu Washington Taylor Alessandro Tomasiello Cumrun Vafa Irene Valenzuela Timo Weigand Alexander Westphal

 

Equity, Diversity and Inclusion Talk

Marika Taylor

 

Scientific Committee   

Michele Cicoli (University of Bologna)     
Luca Martucci (University of Padua)       
Raffaele Savelli (University of Rome Tor Vergata)       
Roberto Valandro (University of Trieste)

Local Organizing Committee  

Fabio Apruzzi (University of Padua)       
Davide Cassani (INFN-Padova)        
Alessandra Gnecchi (INFN-Padova)       
Gianluca Inverso (INFN-Padova)       
Luca Martucci (University of Padua)       
Stefano Massai (University of Padua)

Secretariat  

Pina Salente (INFN-Padova)       
Silvana Schiavo (University of Padua)        
Paola Zenere (University of Padua)

Conference Poster  

 

 

 

 

         

 

       

 

           

Mappa Padova.jpg

Mappa Padova.pdf

Monday, 24 June

08:30 Welcome & registration

08:45 Opening Remarks

1 Swampland and Dark Relations

Speaker: Dieter Lüst

Dieter_Luest.pdf

Dieter Luest Video

2 Open Strings and Heterotic Instantons

Speaker: Jacob Leedom

Jacob_Leedom.pdf

Jacob Leedom Video

3 Percolating Cosmic String Networks from Kination

Speaker: Joseph Conlon

Joseph_Conlon.pdf

Joseph Conlon Video

10:30 Coffee Break

4 The Structure of the Flux Landscape – Unlimited Edition

Speaker: Thomas Grimm

Thomas-Grimm.pdf

Thomas Grimm Video

5 Stop at Nothing

Speaker: Jakob Moritz

Jakob_Moritz.pdf

Jakob Moritz Video

6 Fluxes, Tadpoles and Singularities

Speaker: Andreas Braun

Andreas_Braun.pdf

Andreas Braun Video

12:30 Lunch

7 Inference, Towers, and Stasis

Speaker: Jim Halverson

James_Halverson

Jim Halverson Video

8 New nonrenormalisation theorems in string theory

Speaker: Steven Abel

Steven_Abel.pdf

Steven Abel Video

9 Candidate de Sitter vacua: Construction

Speaker: Andreas Schachner

Andreas_Schachner.pdf

Andreas Schachner Video

16:00 Coffee Break

10 Euclidean wormholes and String Phenomenology

Speaker: Gary Shiu

Gary-Shiu.pdf

Gary Shiu Video

11 Massive IIA vacua with dynamical open strings

Speaker: Giuseppe Dibitetto

Giuseppe_Dibitetto.pdf

Giuseppe Dibitetto Video

12 Quintessence, the cosmological constant, and the weak gravity conjecture

Speaker: Francisco Gil Pedro

Francisco_Gil_Pedro.pdf

Francisco Gil Pedro Video

18:15 Reception

Tuesday, 25 June

13 Reflections on the Dark Dimension

Speaker: Cumrun Vafa

Cumrun-Vafa.pdf

Cumrun Vafa Video

14 A Minimal Weak Gravity Conjecture

Speaker: Timo Weigand

Timo-Weigand.pdf

Timo Weigand Video

15 A Bumpy Ride: Distances Beyond Minkowski Space

Speaker: Irene Valenzuela

Irene-Valenzuela.pdf

Irene Valenzuela Video

10:30 Coffee Break

16 On 4D dS Solutions of 6D Supergravity and String Theory

Speaker: Fernando Quevedo

Fernando-Quevedo.pdf

Fernando Quevedo Video

17 Candidate de Sitter Vacua: Corrections

Speaker: Liam McAllister

Liam-McAllister.pptx

Liam McAllister Video

18 Higher Symmetry in Particle Physics

Speaker: Clay Cordova

Clay-Cordova.pdf

Clay Cordova Video

12:30 Lunch

Parallel session: A1

19 Black hole thermodynamics, tower of states, and the emergent string conjecture

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 seeking a bottom-up rationale for this dichotomoy, dubbed emergent string conjecture. We will explore bottom-up constraints on towers of light species motivated purely from the consistency of the corresponding thermodynamic picture for small black holes. These constraints shed light on the allowed towers in quantum gravity providing evidence for the emergent string scenario with no reference to a specific ultraviolet completion.

Speaker: Carmine Montella

1 Montella.pdf

20 A black hole-tower correspondence and the origin of species thermodynamics

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 momentum modes available to massless particles dominate) and a dependence on the number of species that are “active” at a temperature T (when the T is high enough to “see" the towers of species). In the latter case, we recover the species entropy (and thus the area scaling of the entropy) in the limit in which the temperature approaches the maximum one, namely the species scale, which is also the point at which gravitational collapse and saturation of the CEB would occur for the smallest possible box. We then put this in the bigger picture of the black hole-tower correspondence, a generalization of the black hole-string correspondence that allows to qualitatively account for the scaling of the entropy of black holes with their area by adiabatically following them towards weak gravitational coupling regimes, up to the point where a transition to a system whose entropy is dominated by the towers of species should occur.

Speaker: Alvaro Herraez

2 A_Herraez_StringPheno2024.pdf

21 On the Origin of Species Thermodynamics

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 the same thermodynamics laws for the species particles, as obtained from the minimal black hole perspective. This will also restrict their possible mass spectra, proving another bottom up support for the emergent string conjecture.

Speaker: Joaquin Masias

3 slides_joaquin_masias_stringpheno.pdf

22 Cosmological phase transitions and the swampland

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 that all nonabelian gauge theories must be either Higgsed or confined, with a characteristic scale above the Hubble scale. I will discuss an extension of these results to include finite-temperature effects. I will argue that accounting for a thermal background can significantly strengthen the constraints coming from FL. I argue that the confinement scale should be higher than a scale proportional to the vacuum energy, while Festina Lente without thermal effects only bounds the confinement scale to be above the Hubble scale. For Higgsing, I find that the magnitude of the Higgs mass should be heavier than a bound proportional the scale set by the Higgs VEV. A way to avoid the bound being violated during inflation is to have a large number of species becoming light. If one wants the inflationary scale to lie below the species scale in this case, this bounds the inflationary scale to be ≪10^5 GeV.

Speaker: Gerben Venken

4 GerbenVenkenStringPheno24.pdf

23 Cosmological Chameleons, String Theory and the Swampland

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 diluted by the cosmological expansion, it is not possible to obtain more than O(1) e-folds without transplankian values for the fields. We propose possible string embeddings and discuss the issues they might have.

Speaker: Ignacio Ruiz

5 StringPheno2024 - Ignacio Ruiz(1).pdf

24 Black Hole Probes of Moduli Space and Stabilization

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.

Speaker: Matilda Delgado

6 String Pheno 24_ Black Holes and Moduli Stabilization-1.pdf

Parallel session: B1

25 Non-perturbative production of axions in string inflation

The standard reheating process after inflation can be anticipated by a phase of preheating, where the oscillations of the inflaton field at the bottom of its potential give rise to an explosive production of particles via parametric resonance, which can potentially alter the history of the universe. In this talk, I consider an inflating modulus coupled to an axion via a typical potential coming from type IIB string theory on Calabi-Yau orientifolds. First, I will show that parametric resonance in string inflation has distinctive outcomes which depart from the usual EFT results. Then, I will study specific models and show how the production of axions via parametric resonance imposes interesting constraints to model building.

Speaker: Nicole Righi

1_Righi_StringPheno24.pdf

26 (A)dS solutions from type II Scherk-Schwarz toroidal orbifold

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 broken at the compactification scale and the 1-loop vacuum energy can be computed. We provide no-go theorems for (quantum) de Sitter solutions in d=8,9. We also show that any de Sitter solution in d=4 or bigger is unavoidably perturbatively unstable. Finally, we comment on the difficulty of realising such de Sitter solutions in the weakly coupled/large volume regime as in accordance with de Sitter Swampland conjectures. In contrast, AdS solutions under parametric control can be easily realised.

Speaker: Marco Serra

2_Serra_SP2024.pdf

27 Conditions for O-plane unsmearing from second-order perturbation theory

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 by additional consistency conditions imposed by higher-order terms. In this talk, we revisit the "unsmearing" procedure and present consistency conditions obtained at second order, which can be written as integral constraints on various non-linear combinations of the first order corrections. We will then describe when and how these constraints can be satisfied and discuss the implications for the consistency of scale-separated AdS compactifications.

Speaker: Maxim Emelin

3_MaximEmelin-StringPheno2024.pdf

28 News on the anti-D3-brane uplift

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 this setup of $p$ anti-D3 branes at the tip of the KS throat at higher orders in $\alpha'$ from the perspective of a nonabelian stack of D3-branes and recap some earlier results from the puffed up NS5-brane perspective. I will point out advantages of both pictures and discuss implications for phenomenology.

Speaker: Simon Schreyer

4_Schreyer_session_B1.pdf

29 Moduli Stabilization in Landau-Ginzburg Orientifold Models.

Speaker: Muthusamy Rajaguru

5_Muthu_StringPheno24.pdf

30 Flux Landscape with Enhanced Symmetry Not on SL(2,ℤ) Elliptic Points

We study structures of solutions for SUSY Minkowski F-term equations on two toroidal orientifolds with h2,1=1. Following our previous study (2011.09154), with fixed upper bounds of a flux D3-brane charge Nflux, we obtain a whole Landscape and a distribution of degeneracies of physically-distinct solutions for each case. In contrast to our previous study, we consider a non-factorizable toroidal orientifold and its Landscape on which SL(2,ℤ) is violated into a certain congruence subgroup, as it had been known in past studies. We find that it is not the entire duality group that a complex-structure modulus U enjoys but its outer semi-direct product with a "scaling" outer automorphism group. The fundamental region is enlarged to include the |U|<1 region. In addition, we find that high degeneracy is observed at an elliptic point, not of SL(2,Z) but of the outer automorphism group. Furthermore, ℤ2-enhanced symmetry is realized on the elliptic point. The outer automorphism group is exceptional in the sense that it is consistent with a symplectic basis transformation of background three-cycles, as opposed to the outer automorphism group of SL(2,ℤ). We also compare this result with Landscape of another factorizable toroidal orientifold. This work is based on arXiv:2311.12425 [hep-th].

Speaker: Takafumi Kai

6_Presentation_Takafumi_Kai_3.pdf

Parallel session: C1

31 Tensionless Strings Limits in 4d Conformal Manifolds

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 theory, we argue that these three limits correspond to three different strings becoming tensionless in AdS. To support this claim, we show that the large N Hagedorn temperature of the CFT in these limits only depends on the CFT Distance Conjecture parameter. Thus, these three limits are physically distinguished by the density of states at high energies. Along the way, we build the first Distance Conjecture convex hull for a CFT and find a remarkable connection to no separation of scales in AdS.

Speaker: José Calderón Infante

CalderonInfante.pdf

32 Extremal Correlators and OPE coefficients in Argyres-Douglas Theories

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 almost compatibility with the conformal boostrap method. Then I will pass to discuss the large R-charge limit for the localization results, in order to compare them with the ones obtained through the EFT technique, and in this scenario I will present some new coefficients coming inside the perturbative expansion, showing also consistency with what already known in literature. Finally, I will show some results about the goodness of a particular ansatz that produces a match with the results from the EFT method much better.

Speaker: Andrea Cipriani

Cipriani.pdf

33 Perturbations in horizonless geometries, Quasi Normal modes, Echoes and Tidal deformations

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 modes, tidal deformations, and amplification factors, aiming to distinguish black holes from other compact geometries.

Speaker: Giorgio Di Russo

DiRusso.pdf

34 High-Energy Fixed-Angle Meson Scattering and Holographic QCD Strings

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 known constituent counting rules found in QCD and other asymptotically free confining gauge theories. However, in naïve disagreement with these rules, we further report that 2-to-n scattering amplitudes that involve rho mesons, and where all the other scattered states can be pions, are suppressed in Mandelstam-s relative to the 2-to-n pion scattering amplitudes. Finally, several plots of differential cross-sections for 2-to-2 pion scattering as a function of s and the scattering angle are obtained at fixed values of s and separately at fixed scattering angles, some of the predictions are compared to experimental data and phenomenological aspects are discussed.

Speaker: Bartosz Pyszkowski

Pyszkowski.pdf

35 Minimalism in N = 2 moduli spaces from orbifold constructions

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 only two moduli in 5 dimensions, and another with only three moduli in 4 dimensions. All examples receive no perturbative nor non-perturbative corrections.

Speaker: Guoen Nian

Nian.pdf

36 Calabi-Yau Threefold Flops as Quiver Varieties from Monopole Deformations

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 deformations of the 3d superpotential and resolution patterns of the probed geometry.

Speaker: Marina Moleti

Moleti.pdf

16:00 Coffee Break

Parallel session: A2

37 Dynamical Cobordism and Codimension-2 End-of-the-world Branes

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 general framework and specific examples for this description. From the cobordism perspective, the intersections can be regarded as describing the end of the world for end-of-the-world branes, or as boundary domain walls interpolating between different ETW brane boundary conditions for the same bulk theory.

Speaker: Andriana Makridou

1_Makridou_StringPheno24_final.pdf

38 The Scalar Weak Gravity Conjecture, moduli fields and gauged supergravity

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 compactification moduli, a setup which allows to probe the conjecture and test its validity. More specifically, we'll discuss under which conditions the SWGC can be satisfied, its relation to the WGC, its stability under dimensional reduction and its potential connection with identities in supergravity.

Speaker: Gabriele Casagrande

2_Casagrande_Gabriele.pdf

39 Exotic supergravities and the Swampland

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 any Lorentz-invariant (4,0) theory (interacting or not) carries an exact global symmetry when compactified on S1, and is therefore incompatible with the Swampland no global symmetries conjecture. Another example of exotic supergravity, the 6D (3,1) theory, does not have this problem. We study the general case and find that the only exotic spin-2 field that reduces to Einsteinian gravity and has no global symmetries when compactified on a high-dimensional torus is that of the (3,1) theory. All other possibilities either yield several gravitons or have global symmetries.

Speaker: Michelangelo Tartaglia

3_StringPheno24_Tartagliav4.pdf

40 Cobordism and cosmology

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.

Speaker: Bjoern Friedrich

4_Bjoern_Friedrich_Stringpheno_2024.pdf

41 Cobordism and the half-spin group

Cobordism offers an unique perspective into the non-perturbative sector of string theory by demanding quantum gravitational consistency.

Speaker: Christian Kneißl

5_String_Pheno_2024_CK.pdf

42 Dynamical Cobordism in AdS/CFT

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 evolve until they hit an end of the world (ETW) brane with AdS4 worldvolume. The latter displays localization of gravity, and provides a completion of the Karch-Randall (KR) AdS branes, in which the backreaction of running scalars replace the KR cusp in the warp factor with a smooth bump.

Speaker: Jesús Huertas

6_Huertas_talk.pdf

Parallel session: B2

43 Massive spin-2 particles and the swampland

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.

Speaker: Joan Quirant

1_quirant_joan_slides.pdf

44 Flat manifolds, fluxes & Casimir energies -- a recipe for deSitter?

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 common and simple enough to be computed explicitly -- flat manifolds, fluxes and Casimir energies -- and could in principle provide de Sitter vacua in 3d and 4d.

Speaker: Bruno Bento

2_bbento.pdf

45 Decay of Kaluza-Klein Vacuum via Singular Instanton

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 periodicity of the imaginary time to an appropriate value to avoid a singularity at the location of the event horizon. We relax this smoothness condition and evaluate the contribution of the singularity based on the conical deficit regularization. This contribution is always negative and finite and works to reduce the Euclidean action. If this argument is correct, decay via singular instantons may be a more dominant process in higher-dimensional theories. Moreover, we also reproduce the bounce action using thermodynamic functions and attempt a thermodynamic interpretation of the aforementioned catalytic effects.

Speaker: Sohei Tsukahara

3_240625stPheno_Tsukahara.pdf

46 Higher-curvature gravities, EFTs and the Swampland

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’ corrections in String Theory, illustrating this feature with an explicit example. Secondly, I will present how the Weak Gravity Conjecture may be used to constrain low-energy effective actions which are consistent with Quantum Gravity.

Speaker: Ángel Jesús Murcia Gil

4_Talk-AngelMurcia.pdf

47 Exploring the AdS conjecture: a positive metric over DGKT vacua

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 distance. The key idea involves considering the off-shell quadratic variation of the string theory action and evaluating it over the space of on-shell solutions. I will particularly focus on DGKT vacua. Given the ongoing debate regarding whether these vacua exist as fully localized solutions, it is particularly intriguing to test our proposed metric over AdS vacua within this framework. I will show that DGKT vacua exhibit a positive metric, yielding a well-defined AdS distance. In conclusion, I will introduce a potential new Swampland criterion, suggesting that the metric over the space of vacua in quantum gravity, as defined by our proposed procedure, is positive definite.

Talk from the paper https://arxiv.org/pdf/2405.01084 in collaboration with Eran Palti (Ben-Gurion U.)

Speaker: Nicolò Petri

48 Holography for KKLT: Anatomy of a Flow

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 not exist. In this talk, I will explain how we construct brane configurations that source the would-be AdS vacua coming out of these flux compactifications, and identify certain UV AdS geometries that these systems of branes source. These place upper bounds on the possible values of the cosmological constants of the scale-separated AdS vacua.

Speaker: Yixuan Li

6_Yixuan Li.pdf

Parallel session: C2

49 New Non-SUSY Tachyon-Free Rigid Strings

In the past four decades of string theory research, the O(16) × O(16) heterotic string in 10d has
stood alone as the only non-supersymmetric, tachyon-free string model with one scalar. We introduce new non-supersymmetric and tachyon-free string theories that serve as the lower-dimensional
counterparts to the O(16) × O(16) string in 4d, 6d, and 8d, each featuring only one neutral scalar.

Speaker: Houri Christina Tarazi

Tarazi.pdf

50 Uncovering the Non-supersymmetric Heterotic String Landscape

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 is retained for some classes of non-supersymmetric theories, allowing for a precise description of their moduli spaces, predicting new ones, finding dualities between them and relating their spectra with their supersymmetric counterparts. 
Moreover, an analysis of geodesics and their infinite distance limits reveals a complex web interrelating both known and previously unknown theories, while the asymptotic behavior of the states becoming massless suggests that some constraints imposed by the swampland program seem to hold when going out of the supersymmetric lamppost.

Speaker: Bernardo Fraiman

Fraiman.pdf

51 Neural Network Learning and Quantum Gravity

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 underlying tame structures. Consequently, several problems therein formulated can be concretely addressed with machine learning techniques, delivering results with sufficiently high accuracy.

Speaker: Stefano Lanza

Lanza.pdf

52 Brane solutions in non-supersymmetric strings

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 ten-dimensional strings, emphasizing the emergence of universal asymptotic behavior.
I will also describe an alternative viewpoint in which branes are embedded in the shifted vacuum.

Speaker: Salvatore Raucci

Raucci.pdf

53 Rigid Orientifold Vacua in 6d with Broken SUSY

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. After reviewing the original construction in six dimensions built on the T^4/Z_2 orbifold, I will present an almost rigid variation that can only be deformed via an overall D-branes recombination. Afterwards, I will describe the BSB orientifold built upon the T^4/Z_4 orbifold in which, in contrast to the previous case, the presence of fractional orientifold planes forbids any further continuous deformation. Finally, I will briefly comment on the structure of the gauge kinetic functions entering the low-energy effective action and the unitarity constraints arising from the presence of 2d defects coupled to the R-R 2-forms required by the Green-Schwarz-Sagnotti mechanism.

Speaker: Giorgio Leone

Leone.pdf

54 Chiral anomalies and their implications in 10d non-supersymmetric sp(16) gauge theories.

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 non-supersymmetric sp(16) gauge theories with different chiral spectra coupled to gravity. Our findings suggest that it is surprisingly challenging to have a consistent theory with Sp(16)/Z2 gauge group.

Speaker: Vittorio Larotonda

Larotonda.pdf

Wednesday, 26 June

55 Generalized Global Symmetries and Nested Symmetry Theories

Speaker: Mirjam Cvetič

Mirjam_Cvetic.pdf

Mirjam Cvetič Video

56 Natural Standard Model-like theories from E_7 flux breaking in F-theory: features and challenges

Speaker: Washington Taylor

Washington Taylor Video

Washngton-Taylor.pdf

57 Machine-learning in Calabi-Yau geometry

Speaker: Magdalena Larfors

Magdalena-Larfors.pdf

Magdalena Larfors Video

10:30 Coffee Break

58 A new SUSY breaking orientifold of type IIB string

Speaker: Emilian Dudas

Emilian-Dudas.pptx

Emilian Dudas Video

59 Loop Blow-up Inflation

Speaker: Arthur Hebecker

Arthur-Hebecker.pdf

Arthur Hebecker Video

60 An axion cosmology scenario

Speaker: Matthew Reece

Matthew_Reece.pdf

Matthew Reece Video

12:30 Lunch

61 Celestial Topology, Symmetry Theories, and Non-SUSY D3-Brane CFTs

Speaker: Jonathan Heckman

Jonathan-Heckman.pptx

Jonathan Heckman Video

62 Cosmological & topological aspects of nonsupersymmetric strings

Speaker: Miguel Montero

Miguel-Montero.pdf

Miguel Montero Video

Diversity and inclusion in physics

Convener: Marika Taylor

Marika-Taylor.pdf

Marika Taylor Video

16:00 Free afternoon

20:00 Social Dinner

Thursday, 27 June

63 Reflections on the Emergence Proposal

Speaker: Ralph Blumenhagen

Ralph-Blumenhagen.pdf

Ralph Blumenhagen Video

64 Yukawas and neutrinos at infinite distance

Speaker: Fernando Marchesano

Fernando-Marchesano.pdf

Fernando Marchesano Video

65 Can you hear the Planck mass?

Speaker: Alessandro Tomasiello

Alessandro-Tomasiello.pdf

Alessandro Tomasiello Video

10:30 Coffee Break

66 The Tadpole Conjecture beyond geometry

Speaker: Mariana Graña

Mariana-Grana.pdf

Mariana Grana Video

67 Strings In and Out of Equilibrium & Cosmology

Speaker: Anshuman Maharana

Anshuman-Maharana.pdf

Anshuman Maharana Video

68 On Gauge Sector of F-theory: Bounds and Limits

Speaker: Seung-Joo Lee

Seung-Joo-Lee.pdf

Seung-Joo Lee Video

12:30 Lunch

Parallel session: A3

69 Emergent geometry in string theory

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 emerge toward the boundary of moduli space in perturbative string vacua.

Speaker: Ivano Basile

1 basile_stringpheno2024_v2.pdf

70 Emergence of R^4 terms in M-theory

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 of a particular higher derivative coupling in toroidal compactifications of M-theory. On a technical level, these calculations rely on employing an appropriate regularization method and demonstrate that integrating out the full infinite towers of light states is crucial for reproducing the known results completely.

Speaker: Antonia Paraskevopoulou

2 String_Pheno_Paraskevopoulou.pdf

71 Swampland Constraints on small Dirac Neutrino Yukawa Couplings

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 constraints on SM-type vacua in string theory. We find that two large hidden dimensions arise only perceived by the ν_R sector, while the string scale is around Ms≃gνMP≃10-700 TeV. As a byproduct, independently of the neutrino issue, we argue that a single large dimension in the context of SM-like type IIA Calabi--Yau orientifolds leads to too small Yukawa couplings for quarks and charged leptons.

Speaker: Gonzalo F. Casas

3 GonzaloStringpheno.pdf

72 Boundaries and geodesics in moduli spaces

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 are coset spaces of the globally symmetric type, which are mathematically fairly well understood. In this work, we provide a framework to study systematically the infinite distance limits in these simple cases, and use this knowledge to argue for the Distance Conjecture in this subset of theories.

Speaker: Veronica Collazuol

4 collazuol Presentationsp24.pdf

73 A Distance Conjecture for Branes

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 p can vary, this is multiple conjectures in one, and the Sharpened Distance Conjecture is the p=1 case. This conjecture is a necessary condition imposed on higher-dimensional theories in order for the Sharpened Distance Conjecture to hold in lower-dimensional theories. We test this proposal in multiple 32 and 16 supercharge examples in diverse dimensions, and see that our conjecture is satisfied and often saturated.

(Based on work with Ben Heidenreich and Tom Rudelius).

Speaker: Muldrow Etheredge

5 etheredge 24-6-27-String_Pheno_Talk_v4.pdf

74 End of The World brane networks for infinite distance limits in CY moduli space

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 singularities at which the scalars diverge. Using these tools, I will explore the network of infinite distance singularities in the complex structure moduli space of Calabi-Yau fourfolds compactifications in M-theory with a four-form flux turned on, which is described in terms of normal intersecting divisors classified by asymptotic Hodge theory. I will provide spacetime realizations for these loci in terms of networks of intersecting codimension-1 ETW branes classified by specific critical exponents which encapsulate the relevant information of the asymptotic Hodge structure characterizing the corresponding divisors.

Speaker: Roberta Angius

6 Angius_CY_moduli_StringPheno24.pdf

Parallel session: B3

75 String Theory and the First Half of the Universe

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 epochs involving significantly trans-Planckian field excursions. Conventional effective field theory is unable to control Planck-suppressed operators and so such epochs require a stringy completion for a consistent analysis. Perturbation growth in these stringy cosmologies is substantially enhanced compared to conventional cosmological histories. The transPlanckian field evolution results in radical changes to Standard Model couplings during this history and we outline potential applications to baryogenesis, dark matter and gravitational wave production.

Speaker: Fien Apers

1_Apers_SP24.pdf

76 String Theory (and Gravitational Waves) from the First Half of the Universe

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 transPlanckian field evolution may result in radical changes to Standard Model couplings during this history, such as a time-dependent string scale. We will highlight how this can naturally explain a population of cosmic superstrings compatible with existing bounds, and provide predictions for their gravitational wave signatures.

Speaker: Filippo Revello

2_Revello_SP24.pdf

77 Gravitational Axiverse Spectroscopy

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 inflationary models with multiple “spectator" axions coupled dark gauge sectors via Chern-Simons coupling could source observable gravitational waves.
If string axions coupled to Abelian gauge fields undergo slow-roll during inflation, they produce a multi-peak GW signal whose magnitude depends on the details of the compactification. I will discuss how to embed spectator axions into type IIB orientifold compactifications and the restrictions imposed on such models from consistency and control requirements, thereby motivating models that may live in the landscape as opposed to the swampland.

Speaker: Margherita Putti

3_stringpheno24_MargheritaPutti.pdf

78 Loop Blow-Up Inflation: a novel way to inflate with the Kähler moduli

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 from its post-inflationary minimum. This gives rise to a new form of inflationary potential with an inverse-power law behaviour. Slow-roll inflation can happen with control over the effective theory. This talk will focus mostly on the post-inflationary history predicted for different brane set-ups that realize the Standard Model. The predictions for the spectral index, the tensor-to-scalar ratio, and dark radiation are in good agreement with CMB data.

Speaker: Luca Brunelli

4_Loop Blow-up Inflation_Brunelli.pdf

79 Realistic Brane-Antibrane Inflation

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 antibrane attraction in a supersymmetric way in terms of general nilpotent superfield interactions and include perturbative moduli stabilisation. We determine the region of parameter space in which realistic slow-roll inflation is allowed as well as late-time modulus stabilisation with the volume hierarchically larger than its value during inflation. The inflationary region corresponds to the standard Coulomb attraction potential with a realistic value of the spectral index and a very small tensor-to-scalar ratio. The parameter space determined by imposing a series of consistency conditions to have control on the approximations and experimental constraints is large enough indicating that inflation happens naturally in this scenario.

Speaker: Mario Ramos Hamud

5_StringPheno2024.pdf

80 Measuring the string scale with gravitational waves

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 whose amplitude peaks at a frequency similar to the Cosmic Gravitational Wave Background predicted by the Standard Model, but with a generically larger amplitude, which depends linearly with the local string scale.

Speaker: Gonzalo Villa

6_GV-SPHENO24-Hagedorn-GWs.pdf

Parallel session: C3

81 Geometry of Type IIA compactifications with (non-)geometric fluxes

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 SU(3)-structure manifold with geometric fluxes. 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. Second, we perform an analytical exploration of de Sitter conditions in type IIA compactifications with (non-)geometric fluxes. We find four conditions that the scalar fields and fluxes must satisfy to achieve dS vacua, extending previous results in the literature. We then impose an Ansatz in which the F-terms are proportional to the respective Kähler derivatives. In this set-up we are able to derive additional constraints and to classify the possible dS no-go scenarios.

Speaker: David Prieto

1Prieto.pdf

82 On the landscape of 6d supergravities

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 their number by ~50%.

Speaker: Gregory Loges

2Loges.pdf

83 On a new democratic formulation of type 2B superstring theory

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 Riemannian symmetric sigma-models as in maximal and half-maximal supergravities. Then, we use this result to write democratic pseudoactions for theories in which the scalars are non-minimally coupled to (p+1)-form potentials in any dimension. These results include a proposal of democratic pseudoaction for the generic bosonic sector of 4-dimensional maximal and half-maximal ungauged supergravities. Furthermore, we propose a democratic pseudoaction for the bosonic sector of N=2B,d=10 supergravity (the effective action of the type IIB superstring theory) containing two 0-, two 2-, one 4-, two 6- and three 8-forms which is manifestly invariant under global SL(2,R) transformations.

Speaker: Matteo Zatti

3Zatti.pdf

84 String islands and discrete theta angles

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 constructed as asymmetric orbifolds.

Speaker: Hector Parra De Freitas

4ParradeFreitas.pdf

85 On M-theory and string flux vacua in three dimensions

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 possible flux choices which give rise to the aforementioned AdS_3 scale-separated configurations, I will discuss some recent developments concerning a systematic study of M-theory and type-II flux vacua in three dimensions, including gauge and metric fluxes, O-planes and D-branes, and admitting a description in terms of three-dimensional gauged supergravitites with half-maximal supersymmetry.

Speaker: Matteo Morittu

5Morittu.pdf

86 New families of scale separated vacua

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 in AdS vacua obtained from string theory is under debate. On the one hand bottom-up constructions in type IIA string theory seem to achieve this hierarchy of scales parametrically. However on the other hand some Swampland arguments as well as holographic considerations cast a pessimistic shadow on scale separation and about its presence in the Landscape. After a brief overview of the evolution of scale separation in string theory over the last twenty years, I will present new families of scale separated vacua obtained via a 4d EFT analysis in massless type IIA flux compactifications on elliptic fibrations with metric fluxes. Parametric scale separation is achieved by an asymmetric flux rescaling which, however, in general is not a simple symmetry of the 4d equations of motion. At this level of approximation the vacua are stable but, unlike in the Calabi-Yau case, they display a non-universal mass spectrum of light fields.

Speaker: Thibaut Coudarchet

6Coudardchet.pdf

16:00 Coffee Break

Parallel session: A4

87 The Minimal Weak Gravity Conjecture

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 states are sufficient for consistency under dimensional reduction, even without a tower of super-extremal particles. Conversely, the absence of a minimal radius always coincides with the presence of a weakly coupled super-extremal tower of particle states. This observation motivates the Minimal Weak Gravity Conjecture, which posits that towers of super-extremal particles appear only when required for consistency of the WGC under dimensional reduction. The talk is based on [2312.04619].

Speaker: Alessandro Mininno

1 Mininno.pdf

88 M-theoretic Emergence

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 the vector multiplet moduli space of type IIA N=2 vacua in four dimensions. For the M-theory limit, one can setup an emergence computation for certain topological quantities thanks to the seminal work of Gopakumar and Vafa. I will demonstrate the computation of the genus-one free energy for the (non-compact) resolved conifold.

Speaker: Aleksandar Gligovic

2 slides-gligovic-parallel.pdf

89 EFT strings and the Convex Hull Distance Conjecture

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 string limits and their associated charge-to-mass vectors and explore their relation with the convex hull of light towers.

Speaker: Alessandra Grieco

3 AlessandraGrieco.pdf

90 On the moduli space curvature at infinity

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 within the moduli space, for any choice of Calabi-Yau, and provide the source of the divergence both in geometric and physical terms. Geometrically, there are effective divisors whose volumes do not vary along the limit. Physically, the EFT subsector associated to such divisors is decoupled from gravity along the limit, and defines a rigid N = 2 field theory with a non-vanishing moduli space curvature. We propose that the relation between scalar curvature divergences and field theories decoupled from gravity is a common trait of moduli spaces compatible with quantum gravity.

Speaker: Lorenzo Paoloni

4 String Pheno 2024 Lorenzo Paoloni.pdf

91 Asymptotic curvature, SCFTs and LSTs

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, that arise both at the classical level and including quantum corrections, and properties of gauge theory sectors that decouple from gravity. In particular, we focus our attention on the imprint of LSTs and SCFTs on the moduli space curvature.

Speaker: Luca Melotti

5 Melotti String Pheno 2024.pdf

92 Topology change and non-geometry at infinite distance

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 compact manifolds and in presence of (non-)geometric fluxes. We provide evidence of how divergent potentials signal pathological infinite distance points in the scalar field space where towers of light states cannot be sustained by the curved background. This leads us to suggest an extension to the current statement of the Swampland distance conjecture in curved spaces or in presence of non-trivial fluxes supporting the background.

Speaker: Thomas Raml

6 Raml.pdf

Parallel session: B4

93 Dynamics of Inspiraling Dark Energy

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 extend the previously known background solution for dark energy to an exact solution that includes matter. This allows us to address the implications of our model for the Hubble and $\sigma_8$ tensions. The latter are important observational puzzles that motivate the study of cosmological models beyond $\Lambda$ CDM.

Speaker: Lilia Anguelova

L_Anguelova.pdf

94 To curve, or not to curve: Observational unviability of curvature-assisted accelerated expansion

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 negative (i.e., with $\Omega_K>0$), a new stable fixed point arises, which may lead to viable single-field-based accelerated expansion with an arbitrarily steep potential. In this talk, I will show, through a dynamical systems analysis and a Bayesian statistical inference of cosmological parameters, that the additional cosmological solutions based on the new fixed point do not render steep-potential, single-field, accelerated expansion observationally viable. I will mainly focus on quintessence models of dark energy, but I will also argue that a similar conclusion can be drawn for cosmic inflation.

Speaker: Yashar Akrami

2_String-Phenomenology-June-27-2024-YAkrami.pdf

95 Analytic bounds on asymptotic cosmologies

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 of the universe in the additional presence of fluids with constant equation of state and of scalars with exponential kinetic couplings. We can further see how the contraction rate of cosmologies with negative potentials can be bounded by similar methods as those for cosmic acceleration.

Speaker: Flavio Tonioni

3_ftonioni_analytic_bounds_on_asymptotic_cosmologies_stringphenomenology_2024.pdf

96 Charged Nariai black holes on the dark bubble

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.

Speaker: Vincent Van Hemelryck

4_VanHemelryck_SP24.pdf

97 Cosmological Bouncing solutions in non perturbative String Theory

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 approach to the perturbative string vacuum with zero curvature and string coupling, our solutions demonstrate dilaton stabilization at later times. The result converges dynamically towards a matter-dominated FLRW cosmology or a De-Sitter-like inflationary phase, dependent on the initial conditions and the characteristics of the dilation potential. As a remarkable feature, for the same class of initial conditions, this scenario also provides a mechanism to wash out (arbitrarly large) anisotropic initial conditions.
This work explores Hamiltonian reformulations, non-perturbative effects, and the emergence of late time attractors in string cosmology.
The presentation will be based on arXiv:2308.16076

Speaker: Eliseo Pavone

5_Eliseo_Padua.pdf

98 Dark Energy with a Little Help from its Friends

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 present-day Dark Energy of the Universe consistently with current observations. This is possible both when the scalar's potential has a hilltop form and when it has a steep exponential run-away, as might naturally arise from string theory. We also discuss a related theory of multi-field quintessence, in which the scalar is coupled to a sector that sources a subdominant component of Dark Energy, which overcomes many of the challenges of slow-roll quintessence.

Speaker: Joaquim M. Gomes

6_12_min_StringPheno2024.pdf

Parallel session: C4

99 Bounds and Dualities of Type-II Little String Theories

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 pairs via certain duality-invariant quantities. Finally, we confirm the duality explicitely by giving a top-down geometric construction via F-theory.

Speaker: Florent Baume

1Baume.pdf

100 Efficiency in F-Theory: FTheoryTools

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 standard: https://www.mardi4nfdi.de/about/mission). Thereby, complicated geometries underlying constructions from the literature can be created with the click of a button.

Recall also that non-trivial F-theory vacua are defined by singular geometries, which are currently best understood by crepantly resolving the singularities. Among its many features, FTheoryTools allows executing such resolutions.

I will provide an overview of FTheoryTools and how it can be used to facilitate and simplify future F-theory research.

Speaker: Martin Bies

2Bies.pdf

101 Higgsing on Symmetric Matter in F-theory

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 nontrivial global gauge group quotients with no apparent Mordell–Weil torsion or additional U(1) factors, and our results suggest that one can similarly obtain a locally supported U(1) gauge factor without additional Mordell–Weil sections.

Speaker: Andrew Turner

3Turner.pdf

102 Computation of Quark Masses in String Theory

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, that is, the Ricci-flat Calabi-Yau metric, the Hermitian Yang-Mills bundle metrics and the harmonic bundle-valued forms, are all computed by training suitable neural networks. The calculation is carried out at several points along a one-parameter family in complex structure moduli space, and each complete calculation takes about half a day on a laptop. The methods presented here generalise to other string models and constructions, including to F-theory models.

Speaker: Cristofero Fraser-Taliente

4Fraser-Taliente.pdf

103 Exploring the flavour symmetries of heterotic line bundle sum models

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 algorithms to explore the flavour symmetries of these models, focussing on the quark sector of the MSSM.

Speaker: Lucas Tsun Yin Leung

5Leung.pdf

104 Physical Yukawa Couplings in Heterotic String Compactifications

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 metric on the moduli space of complex structure deformations of the Calabi-Yau manifold. In various examples (the Fermat quintic, the intersection of two cubics in ℙ5, and the Tian-Yau manifold), we calculate the normalized Yukawa couplings for (2,1)-forms using the Weil-Petersson metric obtained from the Kodaira-Spencer map. In cases where h1,1=1, this is compared to a complementary calculation based on performing period integrals. A third expression for the normalized Yukawa couplings is obtained from a machine learned approximate Ricci-flat metric making use of explicit harmonic representatives. The excellent agreement between the different approaches opens the door to precision string phenomenology.

Speaker: Justin Tan

6Tan.pdf

Friday, 28 June

105 Surprises from non-supersymmetric strings

Speaker: Augusto Sagnotti

Augusto-Sagnotti.pdf

Augusto Sagnotti Video

106 Heterotic asymmetric orbifolds revisited

Speaker: Anamaria Font

Anamaria-Font.pdf

Anamaria Font Video

107 Asymptotic Acceleration in Light of the Landscape and the Stars

Speaker: Susha Parameswaran

Susha-Parameswaran.pdf

Susha Parameswaran Video

10:30 Coffee Break

108 Towards string perturbation theory in Ramond backgrounds

Speaker: Manki Kim

Manki-Kim.pdf

Manki Kim Video

109 Conifold Transitions and New N=1 Dualities

Speaker: Lara Anderson

Lara_Anderson_v2.pdf

Lara Anderson Video

110 Flux vacua of the mirror octic

Speaker: Erik Plauschinn

Erik-Plauschinn.pdf

Erik Plauschinn Video

12:30 Lunch

111 Non-Invertible Symmetries on the Worldsheet

Speaker: Jacob McNamara

Jacob-McNamara.pdf

Jacob McNamara Video

112 The scale of many devices

Speaker: Niccolò Cribiori

Niccolo-Cribiori.pdf

Niccolò Cribiori Video

113 Spectator-Verse Echoes

Speaker: Alexander Westphal

Alexander-Westphal.pdf

Alexander Westphal Video