Week 26.10.2026 – 01.11.2026

We will discuss how to bootstrap string theory in AdS, using N=4 SYM as a concrete example. The first lecture will review the basic ingredients of AdS/CFT: the definitions of AdS and CFT, the correspondence between Kaluza–Klein modes and single-trace operators, and the relation between string scattering in AdS and correlation functions of Kaluza–Klein modes in the CFT. The second lecture will focus on the stress-tensor multiplet four-point function, including its conformal block expansion, the constraints imposed by superconformal Ward identities, and its formulation in Mellin space. The third lecture will introduce the flat-space limit, explain how it acts on the conformal block expansion, and discuss the spectrum of single-trace operators that survives at strong coupling. In the final lecture, we will go beyond the flat-space limit and study the first AdS correction. We will introduce a worldsheet ansatz for this correction and show how matching it to the conformal block expansion fixes the correction completely.

In this talk, we establish a microstructural foundation of the rough Bergomi model. Specifically, we consider financial market models where orders to buy or sell an asset arrive according to a Poisson process, with order sizes depending on a hidden volatility state that takes into account the entire order history. Consequently, each order has a long-lasting impact on volatility.

We show weak convergence of the price-volatility process to a log-normal rough volatility model on the Skorokhod space of right-continuous functions using a recent C-tightness result for càdlàg processes.
This weak convergence result is complemented by providing explicit weak error rates for the marginal distributions. To obtain these rates, we employ a recently established Clark-Ocone formula for Poisson processes.
Together, these results establish our microstructure model as a viable alternative to classical simulation schemes.

The talk is based on joint work with Paul Hager, Ulrich Horst and Wei Xu.

I explain how to take a well-defined flat-space limit of brane models of AdS coupled to a non-gravitating bath. In the dual BCFT this amounts to a triple-scaling limit where both the number of boundary degrees of freedom and the boundary coupling are taken to infinity while the BCFT boundary piecewise approaches a lightcone. This procedure acts on the conformal generators as a Wigner-İnönü contraction, reducing the global BCFT symmetry algebra to the global symmetry algebra of flat space.
I will discuss two natural notions of entanglement entropy of the flat-space dual. These are distinguished by whether modes that have left through future null infinity are included or not and give rise to a vanishing and non-trivial Page curve, respectively. Taking the flat-space limit of topological black holes, the Page time remains finite in two-dimensions. In d > 2 the Page time diverges in the flat limit, since AdS topological black holes become flat-space Rindler horizons.

We address the brittleness of Bayesian experimental design under model misspecification by formulating the problem as a max--min game between the experimenter and an adversarial nature subject to information-theoretic constraints. We demonstrate that this approach yields a robust objective governed by Sibson's α-mutual information (MI), which identifies the α-tilted posterior as the robust belief update and establishes the Rényi divergence as the appropriate measure of conditional information gain. To mitigate the bias and variance of nested Monte Carlo estimators needed to estimate Sibson's α-MI, we adopt a PAC-Bayes framework to search over stochastic design policies, yielding rigorous high-probability lower bounds on the robust expected information gain that explicitly control finite-sample error.