Opening Remarks

• Masazumi Honda (RIKEN iTHEMS / Saitama University)

Room: 8F Lecture theatre

Recent developments in double-scaled SYK

• Kazumi Okuyama

Room: 8F Lecture theatre SYK model is an interesting toy model of holographic duality. In particular, the so-called double-scaled SYK (DSSYK), which is defined by taking a large N limit with the number p of the p-body interaction scaled as p=N^(1/2), has attracted a lot of attention recently since DSSYK is exactly solvable thanks to the underlying quantum group symmetry. In this talk, I will briefly review the recent developments in DSSYK.

T Tbar and Sqrt(T Tbar) deformations in 4d Chern-Simons Theory

• Masahito Yamazaki

Room: 8F Lecture theatre

Higher point N=4 SYM correlators

• Paul Heslop

Room: 8F Lecture theatre

Giant Gravitons, Volume Minimisation, M2/M5 Duality, and Vertex Algebras

• Nick Dorey

Room: 8F Lecture theatre

Resonances, Spectral Theory, and the Resurgent Structure

• Okuto Morikawa

Room: 8F Lecture theatre An attempt is made to unify the understanding of resonance phenomena, analytic spectra, and resurgence by developing and applying a mature exact-WKB framework. We begin by formulating non-perturbative resonances in quantum mechanics via the exact WKB method, demonstrated concretely in the inverted Rosen–Morse potential, where barrier resonances and quasi-stationary states are shown to match exact and WKB predictions. Next, we extend this framework to incorporate Zel’dovich regularization, complex scaling, and a modified rigged Hilbert space, thereby clarifying the equivalence and complementarity of these regularization methods and the functional analytic structure they define. Finally, we apply exact WKB and complex scaling to scattering problems, compute the continuum spectrum and the S-matrix, and reinterpret classical theorems such as Aguilar-Balslev-Combes and the Siegert boundary condition in this unified setting. The result is a coherent picture in which resonant poles, continuum spectra, and resurgent structures are seamlessly interconnected, giving new insight into the spectral theory of unstable quantum states.

AdS string amplitudes from single-valuedness

• Tobias Hansen (Durham University)

Room: 8F Lecture theatre It has long been known that string theory amplitudes have intriguing single-valuedness properties. When considering string theories on curved backgrounds, which are still lacking a complete worldsheet description, these properties become even richer. For AdS/CFT, single-valuedness can be combined with the structure of the OPE in the dual CFT to fix AdS string amplitudes in a small curvature expansion. In this way we found curvature corrections to the AdS Virasoro-Shapiro amplitude for graviton scattering in type IIB on AdS5xS5, type IIA on AdS4xCP3 and the AdS Veneziano amplitude for gluon scattering in orientifolds of type IIB on AdS5xS5. The results have the form of worldsheet integrals involving single-valued multiple polylogarithms. Our answers determine the CFT data for unprotected operators in planar N=4 SYM theory, ABJM theory and certain N=2 SCFTs at strong coupling, making contact with integrability, localization and conformal bootstrap. Furthermore, the high energy limit of the amplitudes agrees with classical scattering computations in AdS.

Extremal Couplings and Gluons in AdS/CFT

• Rishi Mouland

Room: 8F Lecture theatre In AdS/CFT, extremal couplings induce a mixing between single- and double-trace operators. I will diagnose this mixing and compute it coefficient using the conformal block expansion of 4-point Witten diagrams involving extremal couplings. I will then study the simplest dual pair in which such couplings arise: 4d N=2 theories dual to AdS5 x S5 with some 7-branes. Summing a tower of extremal Witten diagrams provides the final piece of the gluon 4-point function to order 1/N^2.

Yang-Mills/QCD on R2xT2, adiabatic continuity, and eta' potential

• Yuya Tanizaki

Room: 8F Lecture theatre We show that 4d Yang-Mills/QCD can be semi-classically solved on R2xT2 with nontrivial 't Hooft flux. In this setup, 4d instanton splits into N center-vortex fractional instantons, and its dilute gas describes qualitative features of 4d confinement vacua via the adiabatic continuity. When we apply this technique to QCD with fundamental quarks, we can learn about the global structure of the eta' potential.

Towards Celestial Holography for Self-Dual Einstein Gravity

• David Skinner

Room: 8F Lecture theatre Celestial Holography posits the existence of a holographic description of gravitational theories in asymptotically flat space-times. To date, top-down constructions of such dualities involve a combination of twisted holography and twistor theory. The gravitational theory is the closed string B model living in a suitable twistor space, while the dual is a chiral 2d gauge theory living on a stack of D1 branes wrapping a twistor line. I’ll talk about a variant of these models that yields a theory of self-dual Einstein gravity in four dimensions. This is based on work in progress with Roland Bittleston, Kevin Costello and Atul Sharma.

Quantum Cosmology from Perturbative and Non-Perturbative Perspective

• Hiroki Matsui

Room: 8F Lecture theatre

Integrable Regge Trajectories of N=4 SYM

• Simon Ekhammar

Room: 8F Lecture theatre Maximally supersymmetric four-dimensional Yang-Mills appear to be solvable in the planar limit. In particular, the non-perturbative spectrum of local operators can be calculated using the integrability-based Quantum Spectral Curve (QSC) formalism. However, the usefulness QSC extends beyond local operators. I will demonstrate how it can be used to understand what happens upon analytic continuation to negative spin, into the regime of horizontal Regge trajectories. Taking a weak coupling limit I will formulate a novel ”Asymptotic Baxter-Bethe Ansatz”: a set of equations, reminiscent of the Beisert-Eden-Staudacher equations, that controls the trajectories.

Comments on Deep Learning as a String Theory

• Simeon Hellerman

Room: 8F Lecture theatre

Photo Room: 8F Lecture theatre

Gravitational Waveform from Amplitudes

• Alessandro Georgoudis

Room: 8F Lecture theatre In this talk I will present some recent developments in the study of classical observables for gravitational waves physics. This topic has received a lot of attention in the recent years due to the observation of gravitational waves emitted by black hole mergers. Our approach will be based on quantum scattering amplitudes methods, which have been developed to study scattering of fundamental particles. We will describe how the same tools can be used to also study binary black hole processes in the largely separated and weakly interacting post-Minkowskian (PM) regime. I will focus in particular on the 2 to 3 amplitude, which can be connected to the emitted gravitational waveform itself, and after introducing the amplitude methods used for the one-loop computation I will show how the choice of the asymptotic BMS frame is crucial for comparing with more traditional methods (i.e. the multipolar post-Newtonian (PN) expansion). I will conclude by presenting some recent results at two-loop for the non-linear memory.

Resumming perturbations in curved spacetime - Black hole QNMs via exact WKB

• Ryo Namba

Room: 8F Lecture theatre Divergences in perturbative expansions often signal the presence of rich physics. Perturbations around curved spacetime can be systematically handled using the (J)WKB series. However, while being asymptotic expansions, these series are typically divergent. Recent developments have demonstrated that exact WKB analysis, combined with Borel resummation, provides a powerful framework to go beyond the limitations of perturbation theory and to access the global structure of exact solutions. This approach unveils nonperturbative effects that cannot be captured by standard expansions and thus offers deeper insights into the dynamics in curved spacetime. In this talk, I will focus on black hole perturbations as a particularly illuminating application and discuss how exact WKB techniques clarify the role of singularities, providing a novel analytical technique to compute quasi-normal modes (QNMs).

To boost or not to boost, that’s the question: dS/CFT vs dS/SFT

• Yu Nakayama

Room: 8F Lecture theatre

Multiparty entanglement and holography

• Simon Ross

Room: 8F Lecture theatre

Concluding Remarks Room: 8F Lecture theatre