Speaker:   Rodolfo Russo
Title:   "Holographic correlators with 1/2-BPS bound states"
Abstract:   In holographic CFT's, such as N=4 SYM, it is natural to organise the spectrum in single and multi particle states. By now we have a wealth of information about 4-point correlators with BPS single particle states, but very little is known about 4-point correlators involving multi particle states. I will discuss how we can calculate such correlators at strong coupling focusing in particular on a bulk approach based on 1/2-BPS asymptotically AdS supergravity solutions. I will provide some explicit examples of correlators with multi-particle states both in AdS3 and AdS5. The results involve a natural generalisation of the D-functions appearing in the 4-point correlators with single particle states at strong coupling.

Speaker:   Justin David
Title:   The large N vector model on $S^1\times S^2$
Abstract:   The $O(N)$ vector model with a quartic interaction in 3 dimensions is one of the most well studied quantum field theories. It is important to describe strongly correlated physics and its non-trivial fixed point at large $N$ serves as the holographic dual to Vasiliev's higher spin theory on $AdS_4$. In spite of the extensive studies, there is no systematic study of the model on $S^1\times S^2$. We develop a method to evaluate the partition function and energy density of a massive scalar on a 2-sphere of radius $r$ and at finite temperature $\beta$ as power series in $\beta/r$. Each term in the power series can be written in terms of polylogarithms. We use this result to obtain the gap equation for the large $N$, critical $O(N)$ model in the large radius expansion. Solving the gap equation perturbatively we obtain the leading finite size corrections to thermal one-point functions in the model. This includes one-point functions of the higher spin, $s>2$ currents of the model for which we use the Euclidean inversion formula. The talk will also review the relevance of one point functions in holography and summarize earlier results.

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Title:   2025 Mathematics Commencement


Abstract:  
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Public holiday

Speaker:   Richard Davison
Title:   Universal thermalization dynamics in (1+1)d QFTs
Abstract:   Interacting quantum field theories typically thermalize, leading to the emergence of hydrodynamics at late times. I will talk about (1+1)d QFTs at high temperatures, where the proximity to a CFT results in parametrically slow thermalization, with much of the associated dynamics tractable. I will first explain how the UV effective theory – conformal perturbation theory – breaks down at late times giving room for hydrodynamics to emerge. Specialising to the case of large central charge, I will then argue that the IR effective theory – hydrodynamics -- has universal transport coefficients and use this to show that it breaks down at early times due to the existence of thermal CFT excitations. The timescales at which the two effective theories break down agree.

Speaker:   Kostas Skenderis
Title:   The AdS/CFT correspondence to all order
Abstract:   We show that AdSd+1 gravity is a d-dimensional CFT by showing that the AdS amplitudes to all orders in bulk perturbation theory satisfy the appropriate CFTd Ward identities. We explain how to renormalize UV and IR divergences in AdS and how these are related to renormalization in CFT and illustrate the renormalization via loop computations.

Speaker:   Elli Pomoni
Title:   Bootstrapping Thermal CFTs
Abstract:   In this talk, we explore the structure and solution of thermal conformal field theories (CFTs) using the conformal bootstrap approach. At finite temperature, the role of crossing symmetry is played by the Kubo-Martin Schwinger (KMS) condition, which imposes periodicity on thermal correlation functions. We present two methods for solving the resulting KMS sum rules for thermal one-point functions, assuming knowledge of the zero-temperature CFT data. The first is a numerical method that incorporates the asymptotic operator product expansion (OPE) density of heavy operators, derived using Tauberian theorems. The second is an analytical approach based on dispersion relations. We benchmark both methods against known results in free theories and two dimensional CFTs, and subsequently apply them to O(N) models for N=1,2,3, as well as in the large-N limit.

Speaker:   Blaise Gouteraux and Amos Yarom 
Discussion on Hydrodynamics