Welcome Room: ISEC

The geometric II, III, IV of complex structure degenerations

• Timo Weigand

Room: ISEC Complex structure degenerations of Calabi-Yau threefolds at infinite distance have played an important role in testing various quantum gravity conjectures. At the same time, their geometric properties are relatively less intuitive compared to their counterparts in Kähler moduli space. In particular, new geometric insights are needed to establish the existence of the leading towers of light states, including in particular those of asymptotically light critical strings in emergent string limits. We will explain the geometric origin of these key quantum gravitational ingredients. At a technical level, the new input is a geometric interpretation of the three-cycles with asymptotically vanishing volume. Among other things, we will explain how Type IIB string theory on Calabi-Yau threefolds can be seen to be dual to heterotic string theory without invoking mirror symmetry, and develop new predictions for the counting of asymptotically vanishing three-cycles and for the types of complex structure limits that can be geometrically realized on Calabi-Yau threefolds.

String Phenomenology and Gravitational Waves

• Fernando Quevedo

Room: ISEC An overview will be given about the importance of gravitational waves to search for future ways of comparing string theory to observations. In particular the spectrum of gravitational waves produced in the Hagedorn phase will be highlighted as well as the recent progress on the search for high frequency gravitational waves.

Complexity bounds in the String Landscape

• Thomas Grimm

Room: ISEC

Quantum tunneling in the geometric landscape

• Yinan Wang

Room: ISEC

Quantum stress-energy at timelike boundaries: testing a new beyond-ΛCDM parameter with cosmological data

• Eva Silverstein

Room: ISEC We analyze the basic cosmological effects of a population of timelike boundaries – a form of nontrivial spacetime topology – containing a boundary layer of quantum stress energy. This accumulation of vacuum fluctuations of quantum fields can be consistently negative and UV sensitive, providing an additional source of cosmic energy density strong enough to compete with matter and dark energy. For boundary conditions enabling a solution with fixed comoving boundary size, this effect contributes a qualitatively new term to the Friedmann equation determining the expansion history, scaling like −1/a for scale factor a. It naturally dominates at relatively late times (a ≈ 1/2), while leaving intact well-measured early universe physics such as big bang nucleosynthesis and recombination. For a wide window of parameters, the boundaries can be larger than the Planck length throughout their history, back through the start of inflation at any viable scale. We analyze CMB and BAO data sets (Planck, ACT, and DESI) allowing for this component, finding a slight preference (∼ 2σ) and a relaxation of current tensions in the data (including the neutrino mass) in a physical manner. This novel parameter fits into a larger space of physical parameters beyond-ΛCDM that may serve this role, including negative spatial curvature, which may also be motivated by topological considerations and chaotic dynamics. Finally, we comment on additional phenomenological prospects for testing for this form of topology in the universe.

Building the Axiverse

• Liam McAllister

Room: ISEC

Axion Couplings in Heterotic String Theory

• Michael Nee

Room: ISEC

QCD Axion Dark Matter and Hierarchies in the Axiverse

• Naomi Gendler

Room: ISEC

¡The R7-Brane is Stable!

• Jonathan Heckman

Room: ISEC The Swampland Cobordism Conjecture predicts the existence of several novel non-supersymmetric objects. These include the existence of a domain wall between IIA and IIB string theories, as well as R7-branes in F-theory in which the F-theory torus undergoes a reflection in winding around the R7-brane. In this talk we argue that the long string probe characterization of the IIA/IIB wall is an interface between different GSO projections. Moreover, wrapping this GSO wall on a bubble-like configuration with IIB on the outside leads to a collapsing configuration with stable endpoint an R7-brane; a GSO vortex. We also sketch some potential applications in string compactification and model building. Based on joint work with McNamara, Parra-Martinez, and Torres.

Symmetries and M-theory-like Vacua in Four Dimensions

• Damian van de Heisteeg

Room: ISEC Non-geometric flux vacua have recently been revisited, leading to the remarkable discovery of isolated 4D N=1N=1 supersymmetric Minkowski vacua. These constructions rely on the non-renormalization of the superpotential, which is supported by heuristic arguments. Given the significance of verifying the existence of these isolated M-theory-like vacua, we present alternative symmetry-based arguments that arrive at the same conclusion. Additionally, we leverage these symmetries to argue for the existence of unstable dS solutions as well as supersymmetric AdS solutions.

Building a Calabi-Yau Factory

• Gary Shiu

Room: ISEC

Stasis, Stasis, Stasis: The Universe on Pause

• Keith Dienes

Room: ISEC

Precision String Phenomenology

• Vishnu Jejjala

Room: ISEC Calabi-Yau compactifications of string theory lead to quantum field theories in four dimensions with chiral matter. Calculating parameters of the low-energy effective theory in general compactifications requires the Ricci-flat metric on the Calabi-Yau manifold. Such metrics are not known analytically. In this talk, we discuss how to approximate the Ricci-flat metric using neural networks. The accuracy of the numerical metrics is assessed for K3 and the quintic threefold. In the standard embedding, we calculate Yukawa couplings for compactifications on various Calabi-Yau geometries and show the existence of hierarchies. This is an initial step toward a first principles calculation of particle masses from string theory.

Classical and quantum aspects of N=1 heterotic G2 compactifications

• Magdalena Larfors

Room: ISEC Supersymmetric flux compactifications of string theory are coupled system of gauge theory and gravity. In all such systems, the interplay between gauge fields, flux and geometry makes it non-trivial to determine the deformation theory that governs the compactification moduli. In this talk, we explore this question in N=1 compactifications of the heterotic string on 7D G2 structure manifolds. We will present a classical deformation theory for these systems, that rely on an elliptic double complex, that we will explicitly construct. This will allow us to compute infinitesimal moduli and their obstructions. Our analysis is governed by a real superpotential, which we determine by dimensional reduction. Finally, we will outline the computation of the one-loop partition function of the heterotic G2 system, and how it decomposes into a product of one-loop partition functions of Abelian and non-Abelian instanton gauge theories.

AI for the String Landscape: Targeted Discovery in Type IIB Flux Vacua

• Sven Krippendorf

Room: ISEC Understanding the vast landscape of string theory vacua is a central challenge in connecting fundamental theory to low-energy phenomenology. In this talk, I present recent advances in using machine learning — specifically conditional generative models — as tools for automated discovery in the string landscape. Focusing on the inverse problem in Type IIB flux compactifications, I demonstrate how Conditional Variational Autoencoders (CVAEs) can efficiently generate flux vacua with targeted properties, such as specified values of the superpotential or satisfying strict tadpole constraints. These models enable controllable sampling in regions of moduli space that are computationally inaccessible via traditional methods like MCMC, achieving speedups of several orders of magnitude while discovering physically novel vacua beyond the training data. Complementing this, I will also present a framework for systematic enumeration of flux vacua in compact regions of moduli space using a tailored algorithm, applied to a two-modulus Calabi-Yau orientifold. This analysis reveals detailed structure in the vacuum distribution, including hierarchical mass scales and rare vacua with very small superpotentials, offering a complementary, data-driven view of the landscape. Together, these results illustrate how AI methods can augment theoretical tools to enable both exploratory and targeted investigation of the string landscape — with potential implications for bottom-up model building and upcoming agent-based scientific discovery.

Invariants of 2d N=(0,1) supersymmetric field theories

• Kazuya Yonekura

Room: ISEC Two-dimensional N=(0,1) supersymmetric field theories have subtle invariants beyond the standard elliptic genus. They have applications to heterotic strings and cobordism conjecture. In the talk, I will discuss these invariants.

Non-linear sigma model in string field theory

• Manki Kim

Room: ISEC I will describe how to construct data of the worldsheet CFT of the strings probing a curved background with a non-trivial topology in string field theory. As a simple application, I will describe how to use this result to compute the D-instanton superpotential and loop corrections to the Kahler potential in Calabi-Yau orientifold compactifications in the large volume limit. This talk is based on my upcoming work.

Echo-Sounding Axiverses

• Alexander Westphal

Room: ISEC The axiverse comes in different varieties (‘axiverses’) depending on their origin. Taking a closer look at the heterotic axiverse, we find the instanton-induced axion mass spectrum, as well as their matter sector couplings to be quite different from type IIB. We then look how leftover axiverse ‘echoes’ such as the presence of fuzzy DM, high-frequency GW production from axion inflation, or a dark radiation signal from axionic preheating, can be used toward ‘sounding’ out the type of axiverse.

Cosmic Superstrings in the Early Universe

• Joe Conlon

Room: ISEC Very few constraints exist on the universe between inflation and Big Bang Nucleosynthesis. String cosmology motivates non-standard behaviour in this epoch, in particular extended kination and tracker epochs associated to rolling moduli. Particularly interesting is the behaviour of cosmic (super)strings in such epoch: small loops of cosmic string can grow, and there exists an attractor solution in which three-quarter of the energy density of the universe lies in fundamental strings. Work based on 2401.04064, 2406.12637 and 2505.14187.

End-of-the-World Branes and the Beginning of the Universe

• Arthur Hebecker

Room: ISEC I will start by explaining in which precise sense the Measure Problem remains important even though our picture of the Landscape may have changed. I will then argue for a fundamental, quantum mechanical approach, which suggests that conditions on the initial state of the universe are, in fact, decisive. Thus, arguably, Cosmological Initial Condition Problem is a more fitting term. I will discuss the Hartle-Hawking and Linde-Vilenkin proposals explaining that there are good reasons to take the latter seriously. This implies that End-of-the-World branes are absolutely crucial for inflationary and other predictions, leading to well-defined challenges for future research.

Computing Yukawa couplings from string theory

• Andre Lukas

Room: ISEC I will discuss how to compute Yukawa couplings in realistic heterotic string models, using machine learning techniques. More specifically, I will explain how training of neural networks can be used to find the main geometrical ingredients of string theory Yukawa couplings, namely approximate Ricci-flat metrics on Calabi-Yau manifolds, Hermitian Yang-Mill connections and harmonic bundle-valued forms. The techniques are illustrated for a specific string model with a low-energy standard model spectrum.

How will we use AI in theoretical physics?

• Michael Douglas

Room: ISEC TBA

Dark dimension boundary or shiny bulk? - Modular Quintessence

• Dieter Lüst

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

Mapping Moduli Spaces Across Geometric Transitions

• Lara Anderson

Room: ISEC I will highlight recent progress in studying new (potential) dualities in 4-dimensional N=1 theories and how moduli spaces in heterotic theories can extend across multiple background geometries connected by geometric transitions.

Riemann-flat manifolds + Casimir energies + flux = dS maximum in M-theory

• Miguel Montero

Room: ISEC TBD

Exploring U-topia

• Markus Dierigl

Room: ISEC In this talk we will explore different topological charges of supergravity theories supported by a non-trivial U-duality bundle. In case these charges would be conserved, they would lead to global symmetries, which we believe to be absent in any consistent theory of quantum gravity. With the UV completions of string and M-theory at hand, we explore which kind of UV objects are necessary to break all global symmetries in the IR supergravity theory. This leads to interesting string backgrounds including higher-dimensional superconformal field theories, twisted compactifications, and non-geometric defects.

Anomaly Coefficients and Eta Invariants for Quantum Field Theories in Geometric Engineering

• Mirjam Cvetič

Room: ISEC In recent years, much progress has been made in understanding the extra-dimensional origin of higher symmetry structures of many quantum field theories (QFTs) obtained via geometric engineering. Among others, our understanding of anomaly structures in QFTs has been significantly improved. Key in these considerations is the asymptotic boundary of the internal dimensions which geometrizes many topological QFT features. Within this context we present explicit results for anomaly coefficients in 5D supersymmetric QFTs that are engineered in M-theory on Calabi-Yau three-folds, and show that eta-invariants of the asymptotic boundary of the engineered geometry determine 1-form self-anomaly coefficients. For isolated orbifold singularities this leads to closed form expressions which in toric cases are checked against intersection computations of resolved geometry. For non-isolated singularities these contributions receive corrections which we make explicit in families of examples.

A novel quantum computing approach to non-perturbative physics

• Steven Abel

Room: ISEC TBD

Holography with Null Boundaries

• Savdeep Sethi

Room: ISEC TBD

The dark dimension and its interplay with recent cosmological data

• Georges Obied

Room: ISEC TBD

Non-supersymmetric vacua in string theory and their stability

• Alessandro Tomasiello

Room: ISEC I will show how to quickly check stability under many non-perturbative decay channels for several old and new non-supersymmetric AdS vacua in type II string theory, on coset spaces, sphere fibrations, and Kähler–Einstein manifolds. I will do so using calibrations, which are more commonly used for supersymmetric vacua. I will also mention how some of the same spaces can be used to produce new AdS solutions for the heterotic SO(16)xSO(16) theory

Constraints on 4d N=1 theories using EFT strings

• Irene Valenzuela

Room: ISEC TBA

Spectral Bounds in 6d N=(1,0) Supergravity

• Seung-Joo Lee

Room: ISEC TBA

Exploring distant corners of Calabi-Yau moduli spaces

• Johanna Knapp

Room: ISEC The notion of a string compactification on a smooth Calabi-Yau manifold is only valid in certain "large volume" regions in the moduli space. In this talk we will discuss what can happen in other asymptotic regions of the moduli space where a simple geometric picture does not apply and how one can use physics technology such as gauged linear sigma models (GLSMs) to study those regions.

An index for flux vacua

• Severin Lüst

Room: ISEC TBD

A Quantum Cobordism Category

• Jacob McNamara

Room: ISEC TBD

6D Anomaly cancellation for discrete gauge symmetries and their UV completion

• Paul-Konstantin Oehlmann

Room: ISEC In this talk, we discuss 6D discrete gauge symmetries and their anomaly cancellation from several perspectives. First, we approach the problem from a field theory viewpoint by lifting fermions and B-fields to the 7D anomaly theory, which allows us to extract non-trivial consistency conditions, refined up to a choice of quadratic refinement. Second, we demonstrate how these conditions can be matched to a Higgsed remnant of a U(1) gauge theory, for a specific fixed choice of quadratic refinement—one that we also show to be realized in the F-theory geometry. By exploiting anomaly inflow on the 2D non-critical strings that couple to the 6D B-fields, along with the modularity of the Type IIA topological string partition function, we extract the corresponding Green-Schwarz-Sagnotti-West couplings from the geometry of torus-fibered Calabi-Yau threefolds. We conclude by highlighting several applications of these discrete anomaly cancellation conditions for both field theory and geometry.

Finite Landscape of 6d N=(1,0) Supergravity

• Hee-Cheol Kim

Room: ISEC TBD

Classifying Elliptically Fibered Toric Hypersurface CY3s

• Richard Nally

Room: ISEC The largest known set of Calabi-Yau threefolds originates from triangulations of the 473,800,776 four-dimensional reflexive polytopes constructed by Kreuzer and Skarke. Earlier work by Huang and Taylor showed that all but 29,223 of these polytopes admit at least one elliptic fibration. In this talk, we enumerate all such fibrations, finding a total of 2.25 billion fibrations, and classify their fiber and base types. We comment on generic and exotic features of these fibrations, such 6D SCFTs and gauge groups hosted on nontoric divisors. We conclude by discussing elliptic fibrations in the actual Calabi-Yaus built out of these polytopes.