Triangle Seminars

Abstract:
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.

Abstract:
TBA

Abstract:
Please register here: https://forms.gle/7zfqxHjCDSdDesmy7

The recent discovery of a known infinite-dimensional algebra, w(1+infinity), among the asymptotic symmetries of four-dimensional asymptotically flat spacetimes has been interpreted as key evidence in support of a bottom-up approach to flat-space (a.k.a. celestial) holography.  In particular, since a holographic theory must realize the symmetries of its associated gravitational dual, large universal symmetries in principle impose fairly stringent constraints on a holographic correspondence. Of course, concrete progress relies crucially on the precise strength of the constraints from symmetry. Thus in pursuit of this larger goal, in this seminar, I will present a precise avatar of the universal  w(1+infinity) symmetry algebra that persists in the absence of gravity and in particular is realized in generic interacting four-dimensional conformal field theories.  The generators of the algebra are light-ray operators formed from null integrals of the stress tensor that generalize the average null energy operator.  I will discuss potential implications for conformal field theories in spacetime dimensions greater than two and celestial holography.

Abstract:
Please register here: https://forms.gle/7zfqxHjCDSdDesmy7

I will address the question: In what situations are perturbative quantum gravity effects important at distances much longer than the Planck scale? Among other examples, I will calculate the `quantum width' of the black hole horizon.

Abstract:
This talk explores the role of Schur–Weyl duality between unitary and symmetric groups in random matrix theory and the large-N limits of lattice gauge theories, from a combinatorial perspective.

I shall present a combinatorial approach based on a variant of Schur–Weyl duality for mixed tensors, recently used to establish asymptotic expansions of the partition function and convergence of Wilson loops in two-dimensional Yang–Mills theory. I will revisit the work of Gross and Taylor, “2D QCD Is a String Theory,” sketch an alternative proof of a formula due to Kimura and Ramgoolam, and discuss applications to surface expansions of Wilson loops and the determination of the master field on closed orientable surfaces.

This talk is based on the arXiv preprint arXiv:2603.1137.