Korea-France Joint Workshop on String Theory

15 sept. 2026, 09:00 → 18 sept. 2026, 17:45 Europe/Paris

Centre de conférences Marilyn et James Simons (Le Bois-Marie)

Korea-France Joint Workshop on String Theory    

September 15-18, 2026    
at IHES - Marilyn and James Simons Conference Center

Registration deadline (required) : September 10, 2026    

How to get to IHES

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This workshop will bring together experts in string theory and quantum field theory to discuss recent advances in these fields, and also to foster collaboration between the Korean and French theoretical and mathematical physics communities.

Key topics will include conformal field theory, generalized symmetries and topological quantum field theory, scattering amplitudes, quantum gravity/holography, black-hole physics.

The event will mark the second edition of a new biennial series, alternating between the Korea Institute for Advanced Study (KIAS) and institutions in the Saclay region, near Paris, and it will feature speakers both from Saclay and Korea, as well as worldwide experts in these areas. 

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Organizing Committee:

Piljin Yi (KIAS), Sangmin Lee (KIAS), Sungjay Lee (KIAS), Ruben Minasian (IPhT, CEA Saclay), Julio Parra Martinez (IHES), Eric Perlmutter (IPhT, CEA Saclay).

Invited speakers:

• Stefano de Angelis (IPhT, CEA Saclay)
• Jan de Boer (Univ. of Amsterdam)
• Anna Biggs (Princeton Univ.)
• Thibault Damour (IHES)
• Matilda Delgado (Harvard Univ. & MPI Munich)
• Anatoly Dymarsky (University of Kentucky)
• Dongmin Gang (Seoul National Univ.)
• Elliott Gesteau (MIT & Harvard CMSA)
• Rajesh Gopakumar (ICTS, Bangalore)
• Mariana Graña (IPhT, CEA Saclay)
• Robin Karlsson (Oxford Univ.)
• Anton Kapustin (Caltech & IHES)
• Jung-Wook Kim (CERN)
• Seung-Joo Lee (Yonsei Univ.)
• Hong Liu (MIT)
• Shiraz Minwalla (TIFR Mumbai)
• Mukund Rangamani (QMAP, UC Davis)
• Diandian Wang (Harvard Univ.)
• Anna Wolz (UCLA)
• Alberto Zaffaroni (Milano Bicocca Univ.)

 

Sponsors & Partners:

KFWorkshop_Poster_NUM2.pdf

mar. 15 septembre

09:00 → 10:00 Registration and name tags

10:00 → 11:00 From Z to a: Universal Constraints on Rotating Partition Functions and Conformal Anomalies

The free energy of any CFT, $ \ln Z(\beta; \omega_i)$, admits two expansions: high temperature ($\beta \rightarrow 0$) and fast rotation ($\omega_i \rightarrow 1$). We demonstrate that locality of the thermal effective action forces $\ln Z$ to take a simple analytic form at all orders in the high temperature expansion, and further imposes an infinite number of sharp relations on the coefficients in this expansion. All are homogeneous, except at order $\beta^1$ due to the Weyl anomaly. From this, the $a$-anomaly can be extracted from the counting of operators. The relations resum in the fast-spinning expansion into differential equations in $\beta$ obeyed by the semi-universal limit and its corrections. We verify the relations in a variety of CFTs. We generalize to any even $d$, but find no similar relations at odd $d$.

Orateur: Shiraz Minwalla (TIFR Mumbai)

11:00 → 11:30 Coffee Break

11:30 → 12:30 Conformal Colliders: Strings, Membranes and the Bootstrap

I will discuss the energy-energy correlator (EEC) in maximally supersymmetric conformal field theories. In four-dimensional $N=4$ SYM, I will describe how nonperturbative bootstrap methods can be used to obtain bounds on this collider observable at finite coupling. I will then discuss the same collider setup in theories dual to M-theory, notably three-dimensional $N=8$ ABJM theory and six-dimensional (2,0) theory. The EEC provides a window into the UV regime of these theories and probes both the bulk geometry and the internal structure of bulk objects, be they strings, membranes or something else.

Orateur: Robin Karlsson (University of Oxford)

12:30 → 14:00 Lunch

14:00 → 15:00 A Melonic Quantum Mechanical Model Without Disorder

I will describe a quantum mechanical model involving $N$ interacting fermions without disorder that has a large $N$ melonic expansion. In particular, it has the same Schwinger-Dyson equations and low energy physics as the $\mathcal{N} = 2$ supersymmetric SYK model. The model is SU(2) invariant, and the supercharge involves the SU(2) 3j symbol. I will conceptually explain why the model has a melonic expansion, discuss various solvable corners, and present some results of exact diagonalization for small values of $N$. Expanded around states with maximal angular momentum, the model is approximated by a two dimensional CFT. The BPS states have a simple description in that regime. Based on arXiv:2601.08908 with L. Lin and J. Maldacena.

Orateur: Anna Biggs (Princeton University)

15:00 → 15:15 Break

15:15 → 16:15 Sum over Topologies, Symmetry-Based Ensembles of 2d CFTs, and a Solvable Model of 3d Gravity

Two of the central open problems in three-dimensional quantum gravity are how to sum over all 3d topologies, which is necessary for self-consistency, and how to define the dual ensemble, which is believed to include all CFTs at large central charge.

In this talk I present a model of 3d gravity in which both of these questions can be addressed explicitly. The model, formulated within the framework of TQFT gravity, is built from n copies of the rational version of Virasoro TQFT at central charge $c = 1/2$, summed over all 3d topologies according to a universal, TQFT-independent prescription. The resulting 3d gravitational theory is dual to the ensemble of all 2d CFTs with central charge $c = n/2$ and chiral algebra $(Vir_{c=1/2})^n$, which can be verified by comparing the partition functions on both sides of the duality. I will explain how the sum over topologies is defined and performed, and describe the structure of the resulting partition function. I will then discuss the large central charge limit and close with the lessons for conventional 3d gravity.

Orateur: Anatoly Dymarsky (University of Kentucky)

16:15 → 16:45 Coffee Break

16:45 → 17:45 Open and Closed Triangulations of 3d Gravity

Virasoro TQFT provides a powerful framework for computing amplitudes in quantum three-dimensional gravity. Conformal Turaev–Viro theory offers a closely related, triangulation-based formulation of the same underlying structure. We develop a BCFT perspective on both theories and give an alternative derivation of the relation between them.

Orateur: Diandian Wang (Harvard University)

17:45 → 18:00 Congratulatory Remarks by the Korean Embassy to France

Orateur: Mme Hyekyoung Jung (Attachée scientifique, ambassade de Corée en France)

18:00 → 19:30 Cocktail

mer. 16 septembre

10:00 → 11:00 Euclidean Wormholes, Quantum Chaos, and the Factorization Puzzle

I propose a resolution of the factorization puzzle in AdS/CFT based on quantum-chaotic behavior in the large-N limit. In this framework, Euclidean wormhole contributions admit a boundary description within a single quantum theory, without invoking an ensemble average.

Orateur: Hong Liu (Massachusetts Institute of Technology)

11:00 → 11:30 Coffee Break

11:30 → 12:30 Connectivity and Spacetime Emergence

Recent developments in holography have put forward examples of spacetimes with disconnected closed components. In this talk, I will present some insights that have been obtained from attempts to understand the holographic emergence of such spacetimes, and in particular, their connection to the subtle nature of some large-N observables in AdS/CFT.

Orateur: Elliott Gesteau (MIT & Harvard CMSA)

12:30 → 14:00 Lunch

14:00 → 15:00 EFTs 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 known string theory landscape, while a handful of them seem impossible to get from M or string theory.

Orateur: Mariana Graña (IPhT, CEA Saclay)

15:00 → 15:15 Break

15:15 → 16:15 Towards Explicit Bounds in Supergravity

Effective theories that admit a UV completion into quantum gravity are subject to a set of universal consistency constraints. Those constraints can sometimes lead to explicit, uniform bounds on concrete physical quantities of the effective theories. In the context of supersymmetric string compactifications, such physical bounds in turn translate into bounds on corresponding geometric quantities of Calabi-Yau varieties, and conversely. In this talk, focusing for concreteness on six-dimensional F-theory vacua, or equivalently on elliptically fibered Calabi-Yau three-folds, we will illustrate the bounding program with examples of explicit bounds.

Orateur: Seung-Joo Lee (Yonsei University)

16:15 → 16:45 Coffee Break

16:45 → 17:45 Anomalies and the Structure of String Theory

I will discuss recent progress in understanding non-supersymmetric string theory using anomalies. I will focus on two complementary aspects: anomalies in spacetime and anomalies on the worldsheet. Spacetime anomalies provide constraints on candidate theories and offer evidence that certain non-supersymmetric string constructions are well-defined at the quantum level. Worldsheet anomalies, on the other hand, encode restrictions on the two-dimensional theory describing string propagation and, in turn, constrain the allowed target-space backgrounds. I will explain how these worldsheet considerations can be used to identify and establish the viability of certain non-supersymmetric backgrounds in type II string theory. Based mostly on [2606.18380] but also [2310.06895].

Orateur: Matilda Delgado (Harvard University & MPI Munich)

jeu. 17 septembre

10:00 → 11:00 Microstate Counting from Defects in de Sitter

I will explain how one can obtain de Sitter entropy by counting states composed of thin shells and end of the world branes, and what assumptions have to be made to make this work. If time permits, some other aspects of thin shells will be discussed as well.

Orateur: Jan de Boer (University of Amsterdam)

11:00 → 11:30 Coffee Break

11:30 → 12:30 Curiosities of Superstring Perturbation Theory at One Loop

I will discuss aspects of superstring perturbation theory at one loop, i.e., on a toroidal worldsheet, focusing on zero and one-point functions.
Specifically, I will exhibit some non-trivial aspects in both critical and non-critical string theories, owing to the presence of Ramond zero modes when the spin structure is odd. String dualities will prove a helpful guide in sorting out the subtleties we encounter.

Orateur: Mukund Rangamani (QMAP, UC Davis)

12:30 → 14:00 Lunch

14:00 → 15:00 Worldsheet Duals for One Matrix Models

I will describe a concrete closed string dual to a general interacting Hermitian one matrix model, away from the double scaling limit. The correspondence holds for all genus and to all orders in the 't Hooft coupling(s). The worldsheet theory consists of a supersymmetric B-twisted Landau--Ginzburg model coupled to 2d topological gravity. A precise dictionary between traces of the matrix and vertex operators on the worldsheet enables matrix model correlators to be explicitly mapped to computable integrals over the moduli space of Riemann surfaces. We perform several independent cross-checks on both sides of the duality using a computational implementation of the integrands as well as integrals over moduli space. (Work with A. Giacchetto and E. Mazenc)

Orateur: Rajesh Gopakumar (ICTS, Bangalore)

15:00 → 15:15 Break

15:15 → 16:15 Equivariant Volumes and Holography

I discuss applications of equivariant localization to holography, emphasizing the special role played by the equivariant volume of the internal or spacetime manifold. In particular, I describe the localization of the on-shell action in five-dimensional gauged supergravity for solutions with nontrivial topology and the resulting predictions for a variety of black objects in AdS5 still to be found.

Orateur: Alberto Zaffaroni (Milano Bicocca University)

16:15 → 16:45 Coffee Break

16:45 → 17:45 Non-Unitary Bulk-Boundary Correspondence

I will review recent developments in extending the bulk–boundary correspondence between three-dimensional topological quantum field theories (TQFTs) and two-dimensional rational conformal field theories (RCFTs) to the non-unitary setting. This correspondence can be viewed as a generalization of the celebrated Chern–Simons/Wess–Zumino–Witten (CS/WZW) correspondence. Remarkably, the corresponding bulk TQFTs can be physically realized as topological twists of an exotic class of three-dimensional N=4 superconformal field theories known as rank-zero SCFTs. I will present several non-trivial dictionaries of the correspondence and describe their verification through concrete examples. I will also discuss mathematical and physical applications of this non-unitary bulk–boundary correspondence.

Orateur: Dongmin Gang (Seoul National University)

ven. 18 septembre

10:00 → 11:00 The Hidden Simplicity of the Classical Limit

I will illustrate the hidden simplicity relating the classical limits of different theories, including N=8 supergravity, electrodynamics, and certain scalar theories. Despite this simplicity, extracting observables from the classical limit becomes rapidly computationally expensive at higher orders. This motivates a complementary approach to weak-field gravity, based on the Schwinger–Keldysh path integral, in which the dynamics and waveform are computed for generic relativistic worldlines, bypassing several technical intermediate steps in the computation of gravitational-wave observables.

Orateur: Stefano de Angelis (IPhT, CEA Saclay)

11:00 → 11:30 Coffee Break

11:30 → 12:30 Locality, Higher Symmetries, and Anomalies: an Operator-Algebraic Approach

In the usual Euclidean path-integral picture, higher symmetries are represented by invertible topological defects, and ’t Hooft anomalies are described by anomaly inflow from a topological action in one dimension higher. Is there a corresponding construction that starts directly from the algebra of local operators and its symmetries? To address this question, I will describe a mathematically precise framework based on localized symmetry transformations and their commutators. To each spatial region U, one associates a group of transformations localized in U. Locality implies that the commutator of transformations localized in regions U and V is localized in their intersection. Organizing these groups and commutator data over covers of space produces a canonical map of homotopy types. Its homotopy fiber is the proposed higher-symmetry type, while composing the map with an ordinary group action gives an obstruction to gauging. The framework is designed to treat algebraic QFT and quantum lattice systems in a common language. The guiding idea is that topology emerges from the interplay of symmetry and locality.

Orateur: Anton Kapustin (Caltech & IHES)

12:30 → 14:00 Lunch

14:00 → 15:00 A First Look at Magnusian Bootstrap

The Magnus series is the formal expansion for the logarithm of the S-matrix, similar to the Dyson series being the formal expansion for the S-matrix itself. Magnus amplitudes refer to the matrix elements of the log of the S-matrix. As is well known, string theory has its roots in the bootstrap programme. What can we learn by bootstrapping Magnus amplitudes? I will report on some preliminary explorations in this direction.

Orateur: Jung-Wook Kim (CERN)

15:00 → 15:15 Break

15:15 → 16:15 Gravitational Scattering off Compact Objects from Partial Waves

In this talk, I will describe the scattering of gravitational waves from compact objects in worldline effective field theory. The Feynman-diagram expansion can be reorganized as the Born series of an effective wave equation, with distinct contributions from long-distance gravitational interactions and short-distance tidal effects. I will explain how the resulting partial-wave amplitudes can be summed to obtain the momentum-space gravitational Compton amplitude, revealing an underlying elliptic function space. Our results through $\mathcal{O}(G^7)$ show the contributions of static, dynamical, and dissipative Love numbers, and the first ultraviolet divergence which requires finite-size worldline operators as counterterms. Finally, I will discuss matching to black-hole perturbation theory and the on-shell vanishing of static Schwarzschild Love numbers.

Orateur: Anna Wolz (UCLA)

16:15 → 16:45 Coffee Break

16:45 → 17:45 Gravitational Scattering at Null Infinity: Asymptotics, BMS Symmetries, Angular Momentum, and Peeling Violation

We present some results about the asymptotic structure of the gravitational field emitted during the gravitational scattering of two
point masses. This problem has recently been investigated from several complementary angles: the Multipolar Post-Minkowskian formalism,
Effective-Field-Theory approaches, Soft theorems, Celestial Holography, and extension of the Bondi-Metzner-Sachs (BMS) group of asymptotic symmetries to the five infinities of asymptotically flat spacetimes. The comparison between these approaches has raised interesting conceptual issues and has given new vistas on old problems (notably on the definition of angular momentum, and peeling violations).

Orateur: Thibault Damour (IHES)