Strings and Geometry 2026

19 May 2026, 09:00 → 22 May 2026, 14:00 Europe/Stockholm

Hall X (Universitetshuset)

 

The Strings and Geometry conference is a continuation of the series of conferences "Physics and Geometry of F-theory", established in 2012. After it was renamed in 2019, it brings together leading international experts working more broadly at the interface of string theory and mathematics. Topics of the 2026 edition include: Mathematical aspects of string compactifications, geometric engineering of field theories, symmetries in their various incarnations, as well as geometrical aspects of the swampland program.

SPEAKERS

Acharya, Bobby (ICTP)

Apruzzi, Fabio (Padova U)

Castellano, Alberto (Chicago U)

Collinucci, Andrés (ULB)

Cvetič, Mirjam (UPenn)

Delgado, Matilda (Harvard U)

De Marco, Mario (ULB)

Dierigl, Markus (CERN)

García Etxebarria, Iñaki (Durham U)

Graña, Mariana (Saclay)

Grimminger, Julius (Oxford U)

Heckman, Jonathan (UPenn)

Kim, Hee-Cheol (POSTECH)

Lawrie, Craig (DESY)

Lin, Ling (Bologna U)

Lockhart, Guglielmo (Bonn U)

Lüst, Severin (LPTHE)

Marchesano, Fernando (Madrid U)

Montero, Miguel (Madrid U)

Moritz, Jacob (UW-Madison)

Parra de Freitas, Hector (Harvard U)

Prieto Rodríguez, David (Utrecht U)

Rudelius, Thomas (Durham U)

Shiu, Gary (UW-Madison)

Tarazi, Houri (Chicago U)

Tomasiello, Alessandro (Milan Bicocca)

Vafa, Cumrun (Harvard U)

Valandro, Roberto (Trieste U)

Valenzuela, Irene (Madrid U)

Wang, Yi-Nan (Peking U)

Weigand, Timo (Hamburg U)

Wiesner, Max (DESY)

 

 

 

Center For Geometry and Physics

Uppsala University

 

 

 

Tuesday, 19 May

09:00 → 09:25 Shiu

Uppsala_2026.pdf

09:30 → 09:55 Castellano: New Insights on Non-Perturbative BPS Black Hole Entropy

Black holes exhibit a non-vanishing entropy which, at leading order, is proportional to the horizon area in Planck units. A microscopic interpretation in quantum gravity requires this quantity to arise as the logarithm of an integer degeneracy, necessitating the inclusion of both perturbative and non-perturbative corrections. In this talk, we will review recent progress in understanding non-perturbative effects associated with massive, charged matter in four-dimensional N=2 theories and BPS black holes. These systems receive intricate higher-derivative corrections, and going beyond perturbation theory requires an exact treatment of quantum fluctuations. By computing exactly the functional determinants of BPS charged spin-0 and spin-1/2 fields, we uncover novel non-perturbative contributions and provide an interpretation in terms of complex semiclassical worldline saddles.

Strings&Geo2026.pdf

10:00 → 10:25 Rudelius: Swampland and Cone Conjectures in Calabi-Yau Moduli Spaces

Various swampland conjectures predict the existence of light particles and strings in infinite-distance limits of moduli space. In this talk, we will see that these swampland conjectures are intimately linked with the cone conjectures of Morrison in the context of M-theory compactifications on Calabi-Yau threefolds. In the process, we will clarify the subtle geometric distinction between asymptotic boundaries, which feature genuine infinite-distance limits, and periodic boundaries, which involve infinite-length geodesics that traverse the fundamental domain of moduli space an infinite number of times.

Cone Conjectures Uppsala.pdf

10:30 → 11:00 Coffee break

11:00 → 11:25 Tomasiello: New punctures for six-dimensional CFT compactifications

Compactifying 6D SCFTs with N=(1,0) supersymmetry on Riemann surfaces is expected to produce N=1 analogues of the famous Class S models. I will study holographic defects in massive IIA string theory AdS7 solutions, and use the results to obtain information about the punctures of these N=1 models, and their contribution to central charges.

punctures-uppsala-may26.pdf

11:30 → 11:55 Delgado: Constraints on Spacetime from Worldsheet Anomaly Cancellation

I will discuss recent progress in understanding non-supersymmetric string backgrounds through anomaly cancellation. Worldsheet anomaly cancellation imposes restrictions on the two-dimensional theory describing string propagation and, in turn, constrains the allowed target-space backgrounds. I will explain how these worldsheet anomaly-cancellation conditions can be used to identify and establish the viability of certain non-supersymmetric backgrounds in type II string theory. Based on upcoming work with L. Eberhardt and M. Tomasevic.

Strings and Geometry.pdf

12:00 → 14:00 Lunch break

Lunch is not provided, plenty of options for lunch can be found in the nearby city center -- see the practical info tab for some links

14:00 → 14:25 Lockhart: String probes and the supergravity landscape

String probes are a useful tool for studying the consistency conditions and properties of supergravity theories. I will present two novel applications along these lines. The first is a new link between the global form of gauge groups in the bulk and holomorphic simple current extensions of the worldsheet CFT of string probes, which gives a worldsheet explanation for the absence of global center one-form symmetries in variety of supergravity theories. The second application is a search for Gepner-like points in the landscape of 6d N=(1,0) supergravity models without tensor multiplets. This singles out five candidate supergravity models whose probe strings are governed by rational CFTs, making them amenable to detailed study despite the fact that they currently lack a known realization within string theory. This talk is based on works with Luca Novelli and Yann Proto.

Lockhart Strings and Geometry 2026.pdf

14:30 → 14:55 Heckman: On Physical Discretization and Arithmetic Geometry

We discuss a speculative formulation of quantum field theories and string theories with fields viewed as maps between mod p, p-adic geometries, and "smoother" analytifications. This provides a physical interpretation and refinement of discretization over lattice truncation schemes and motivates some natural generalizations of p-adic strings.

Sweden2026FINAL.pdf

15:00 → 15:30 Coffee break

15:30 → 15:55 Lawrie: Algebro-Geometric Bootstrapping from OPE Decoupling

In recent work, with M. J. Kang and J. Song, we conjecture that the Macdonald index (thus the Schur index) and the Higgs branch of a 4d N=2 SCFT can be obtained from an algebro-geometric object: a bifiltered affine scheme. This scheme, in practice a by-word for a collection of polynomial equations, is determined from nilpotency/decoupling relations in the operator product expansion of the SCFT. We propose such a scheme for a variety of theories, with particular focus on Argyres--Douglas theories where the Higgs branch is a point, and demonstrate how to recover the physical data. Although the associated scheme typically admits continuous deformations, we find that a geometric extremization principle uniquely fixes these moduli, thereby providing a possible geometric route toward a classification of 4d N=2 SCFTs.

2026-05-StringsAndGeometry.pdf

16:00 → 16:25 Dierigl: A missing link

In this talk we will explore how symmetry-breaking defects, predicted by the Cobordism Conjecture, can appear in brane networks. We will focus on theories with discrete symmetry groups, which naturally come with codimension-two branes defined by the gauge monodromy around them. Their second bordism group generically encodes generators described by discrete gauge bundles on genus g Riemann surfaces. The associated defects are given by brane networks involving their linking and junctions.

Dierigl_SG.pdf

16:30 → 16:45 Short break

16:45 → 17:10 Acharya: Spacetime Geometry in Geometric Engineering

17:15 → 17:40 Lin: SymTFTs with Interfaces in Geometric Engineering

I will show that torsion (co-)homology in the internal space of M-theory geometric engineering leads to topological interfaces in the Symmetry TFT (SymTFT) — a setup also known as the “club sandwich” in the literature. As a concrete example I will discuss geometries leading to 6d supersymmetric sp(n) gauge theories. By duality, I will further argue that also 7d and 8d frozen compactifications have such interfaces in the SymTFT for their electric/magnetic 1- and (d-3)-form symmetries. Finally I will use this symmetry structure to speculate about the IR limit upon SUSY breaking.

SG26_Lin.pdf

17:40 → 19:30 Reception and Poster Session

Wednesday, 20 May

09:00 → 09:25 Grimminger: 5d SCFTs on Brane Webs and CY3s -- non-toric

I will address some recent progress in the study of 5 dimensional SCFTs which can be engineered in M-theory on CY3s as well as fivebrane webs in Type IIB String Theory. Especially how the two approaches compare in the non-toric case.

Strings & Geometry 2026 Grimminger.pdf

09:30 → 09:55 Collinucci: 5d SCFT’s from Pagoda geometries

Geometric engineering constructs 5d SCFT from Calabi-Yau manifolds. The most studied case is the toric world, SCFT’s are defined implicitly as UV limits of standard Lagrangian theories like SYM with hypermultiplet matter.

In this talk I will introduce what I call Pagoda Theories. These are defined via M-theory on non-toric CY threefolds. They contain a SYM sector, and a non-conventional matter sector derived from the geometric properties of Reid’s Pagoda varieties.

One of the most intriguing features of these theories, is that this type of ‘Pagoda matter’, once Higgsed, triggers a mechanism that inextricably drives the theory to infinite coupling.

Uppsala 2026.pdf

10:00 → 10:25 Prieto: Complexity of Effective Field Theories in the Quantum Gravity Landscape

In this talk, I will present the recently developed mathematical framework of tameness as a candidate for a unifying finiteness principle underlying effective field theories. After introducing the central ideas of the formalism, I will show how it gives rise to a quantitative notion of complexity for EFTs, capturing the information required to specify a given theory. I will illustrate this perspective through explicit examples in which the complexity is finite, most notably in Seiberg-Witten theory. I will then formulate a conjecture according to which any EFT admitting a consistent ultraviolet completion in quantum gravity must exhibit finite complexity in this sense, and discuss the consequences of this idea for the swampland program.

Slides Strings and Geometry - David Prieto.pdf

10:30 → 11:00 Coffee break

11:00 → 11:25 Wiesner: Geometry and Physics of Degenerating Calabi-Yau three- and fourfolds

In this talk, I will discuss the physics of Type IIB and F-theory compactifications on Calabi–Yau 3- and 4-folds undergoing semi-stable degeneration. In the resulting 4d effective theory, these degenerations give rise to solitonic string solutions. I will describe how the worldsheet theory of these strings can be inferred from the degeneration geometry and how it encodes the effective physics in this regime of the 4d theory. For Type IIB compactifications on Calabi–Yau threefolds, the strings correspond to gravitational strings in a weakly coupled duality frame, in agreement with expectations from the classical low-energy effective action. In contrast, for F-theory compactifications on elliptic Calabi–Yau fourfolds, the strings arising from semi-stable degenerations do not admit an interpretation as gravitational strings in the weakly coupled dual frame predicted by the classical effective action. In the F-theory setting, these string solutions therefore provide evidence for perturbative and non-perturbative corrections to the classical effective action that become unsuppressed in the region of moduli space corresponding to the semi-stable degeneration.

Strings&Geometry_Wiesner-2.pdf

11:30 → 11:55 Montero

montero-SG26.pdf

12:00 → 14:00 Lunch break

14:00 → 14:25 Graña: Effective theories with symmetric moduli spaces: the landscape and the swampland

We will show that effective theories with symmetric moduli spaces satisfy the Swampland Distance Conjecture, namely for any infinite distance limit there is a tower of states becoming exponentially light. The mass decay rates of the states are entirely encoded in the Weyl polytope of the representation under which they transform. Imposing these rates to be those of either tensionless strings or Kaluza-Klein towers reduces the set of possible theories to a finite list. Many of these are in the string theory landscape, while a handful of them seem impossible to get from M or string theory.

Strings&geometry-05-26.pdf

14:30 → 14:55 Apruzzi: Gaillard-Zumino non-invertible symmetries

In this talk I will discuss an infinite class of novel zero-form non-invertible symmetries in a broad family of four-dimensional field theoretical models, studied years ago by Gaillard and Zumino (GZ). The GZ models consist of abelian gauge fields coupled to a neutral sector, typically including a set of scalars, whose equations of motion are classically invariant under a continuous group G acting on the electric and magnetic field strengths via symplectic transformations. The standard lore holds that, at the quantum level, these symmetries are broken to an integral subgroup. I will show how the subset of rational transformations survives, albeit through non-invertible topological defects. As illustrative example, I will first present the axion-dilaton-Maxwell model. Then I will illustrate the main aspects of the non-invertible GZ symmetries in the bosonic sector of certain supergravities, of the kind that appear in type II Calabi-Yau compactifications. Finally, I will comment on some implications of the gauging of the invertible integral subgroup.

Apruzzi-GZ-S&G-May26.pdf

16:00 → 17:30 OUTREACH EVENT - Cumrun Vafa - String Theory and The Dark Sector

The dark sector — comprising dark energy and dark matter — has remained a profound mystery for decades. In this talk, Cumrun Vafa will review this subject and show how string theory naturally leads to a predictive framework for a unified dark sector. He will also discuss how these string-theoretic predictions align with exciting recent cosmological observations.

https://www.uu.se/en/centre/geometry-and-physics/events-and-seminars/archive/2026-05-20-string-theory-and-the-dark-sector

Thursday, 21 May

09:00 → 09:25 Weigand: Infinity and Finiteness in Strings and Geometry

Two key properties of quantum gravity concern its universal behaviour linked to infinite towers of states that appear asymptotically in moduli space on the one hand, and the boundedness of its light degrees of freedom in the interior of moduli space on the other hand. We will report on recent results regarding these two hallmarks of quantum gravity: We will analyze the nature of towers of string states appearing in infinite distance limits in gravity in AdS, and present recent geometric proofs of bounds on the abelian part of the gauge group, which were inspired by methods in physics, but go beyond these.

Talk-Weigand.pdf

09:30 → 09:55 Valenzuela: Limits in Warpland and CFTs

talk-valenzuela-sg26.pdf

10:00 → 10:25 Marchesano: Six Lessons on Gravity Decoupling

MarchesanoS&G26.pdf

10:30 → 11:00 Coffee break

11:00 → 11:25 Vafa: Non-Supersymmetric Strings and Geometry

I discuss aspects of non-supersymmetric string vacua emphasizing both the geometry of target space as well as the moduli space of light fields. This will include the geometry of tachyon and dilaton fields in 0A and 0B strings.

11:30 → 11:55 Parra de Freitas: A Duality Web for Non-Supersymmetric Strings

I will describe a proposed duality web relating several non-supersymmetric string theories. Using recent M-theory and F-theory geometric descriptions of type 0 strings, I will show how suitable Z2​ quotients produce 0A/0B orientifolds. This perspective also gives new evidence for the Bergman–Gaberdiel and DMS duality conjectures relating type 0 orientifolds to bosonic string compactifications.

HPDF.pdf

12:00 → 14:00 Lunch break

14:00 → 14:25 Cvetic: Symmetry Theories, Anomalies and η Invariants (Geometric Engineering and Quiver Approaches)

Uppsala_2026_MC_F.pdf

14:30 → 14:55 García Etxebarria: Anomaly-induced vanishing of brane partition functions

In the presence of ’t Hooft anomalies, backgrounds for the
symmetries of a quantum field theory can lead to non-conservation of
Noether currents. When there is a net background charge, the partition
function evaluated on closed manifolds will vanish. For anomalous
symmetries, this statement can also be understood as the anomaly theory
giving rise to a non-trivial anomalous phase for the partition function
even for “rigid” transformations which leave all background fields
unchanged. I will explain how to use these ideas to give a new
derivation for the Freed-Witten anomaly-cancellation condition that can
be applied to non-perturbative backgrounds, and discuss some
implications to the study of non-invertible symmetries.

talk-4.pdf

15:00 → 15:30 Coffee break

15:30 → 15:55 Kim: 6d Supergravity Blocks

I will present a bottom-up framework for constructing 6d (1,0) supergravity theories from supergravity blocks. Each block is a basic unit built from a little string theory sector associated with the H-string, together with the external BPS generators attached to it, and is characterized by carrying intrinsic gravitational tensors. As a first application, I will give the classification of non-Higgsable gravity blocks and discuss candidate supergravity theories that arise in this framework but have no realization in ordinary F-theory geometry.

6d Supergravity Blocks.pdf

16:00 → 16:25 Moritz: Calabi-Yau Orientifold Hypersurfaces and Their F-theory Uplifts

I will describe a systematic combinatorial construction of O3/O7 orientifolds of Calabi-Yau hypersurfaces in toric varieties and of their corresponding F-theory uplifts. Starting from toric fourfolds associated to four-dimensional reflexive polytopes, the orientifold involutions can be classified combinatorially, while the F-theory uplifts arise as codimension-two complete intersections in toric sixfolds. A key ingredient is the use of normal fans to control the birational phases of the Calabi-Yau threefold, ensuring smoothness of the resulting Calabi-Yau fourfold away from loci associated with O3-planes. In many cases, these uplifts are moreover described by nef partitions of six-dimensional reflexive polytopes, allowing the computation of fourfold periods and the associated F-theory flux superpotential.

StringsGeometry_2026.pdf

Friday, 22 May

09:00 → 09:25 Tarazi: Toward a Universality Principle for Matter in String Theory

In this talk, I will discuss the classification of exotic matter representations arising in toroidal heterotic orbifolds that cannot be obtained through geometric engineering. We show that every such representation admits an interpretation as an embedding into the adjoint representation of a simple Lie algebra. Motivated by this, we argue more generally that consistent matter in string theory should arise through the Higgsing of an adjoint representation. Finally, we will discuss the relation to F-theory, where these constructions can be understood in terms of complex structure deformations or non-geometric T-brane configurations.

strings and geometry 2026-2.pdf

09:30 → 09:55 Valandro: D2-brane probes of non-toric cDV threefolds via monopole superpotentials

Abstract: D-branes probing singular Calabi–Yau threefolds give rise to supersymmetric quiver gauge theories whose moduli space reproduces the local geometry. While powerful techniques exist for toric singularities, no systematic method has been available for the non-toric case. I will present a framework to construct probe-brane theories for compound Du Val (cDV) singularities, based on a Higgs field Φ(w) that encodes the ADE fibration.

Valandro_talk_S&G2026.pdf

10:00 → 10:25 Lüst: Continuity on the Boundary of Moduli Space

I discuss whether period maps and their Kähler-covariant derivatives can be continuously extended to the boundary of the complex structure moduli space of a Calabi-Yau fourfold. This continuity makes it possible to define a topological contour integral along the boundary, which in turn yields a sufficient condition for the existence of flux vacua in the interior of moduli space.

stringsandgeometry26_SL.pdf

10:30 → 11:00 Coffee break

11:00 → 11:25 Wang: Higgs branch and VOA of 4d N=2 SCFTs from IIB

We study the Higgs branch and VOA of 4d N=2 SCFTs from the geometric engineering of IIB superstring on canonical threefold singularities. We cover examples of terminal singularities as well as hypersurface singularities with smooth or singular exceptional divisors in their crepant resolution. We found many new VOAs with no known W-algebra descriptions, as well as examples of 4d N=2 SCFTs with the E-type Kleinian singularities as their Higgs branches.

2026-05-Sweden-2.pdf

11:30 → 11:55 De Marco: Discrete gauging in theories with 8 supercharges

I will discuss how gauging 0-form discrete symmetries modifies the Higgs and Coulomb branches of theories with eight supercharges. I will focus on two classes of examples: 4d N = 2 SQCD and 5d rank-one SCFTs. In the latter case, I will discuss how string theory connects the HB and CB realizations of these symmetries, and how the construction suggests the existence of 5d rank-one SCFTs with non-simply laced flavour groups.