• Sep 30:  Luca Delacrétaz (Chicago U., EFI) on 2505.06869

EFTs for thermal dynamics in QFT 

Abstract:  After a brief review of how thermal effective actions capture equilibrium physics in QFT, I will turn to dynamics and describe the Schwinger-Keldysh EFTs that control the near-equilibrium, real time, behavior. I will describe precision tests of these EFTs in lattice models that are simpler to simulate. I will show how one can identify a strong coupling scale in these EFTs, which bounds how fast a system can thermalize and let hydrodynamics emerge. For generic QFTs and CFTs, this establishes the Planckian bound on their thermalization time, tau_{eq}> hbar / T. If time permits, I may discuss the special case of 1+1d QFTs, where low dimensionality allows for additional control on the thermalization dynamics.

• Oct 7:  Ilija Burić (TCD) on 2508.08373

Holographic Correlators from Thermal Bootstrap

Abstract:  The thermal bootstrap, a method based on the partial wave decomposition and Euclidean-time periodicity (KMS invariance) of finite-temperature two-point functions, has recently led to various results in the critical Ising and O(N) models. In this talk, we apply the thermal bootstrap to holographic CFTs. Starting from the well-understood thermal coefficients of the stress tensor and its composites, we use the KMS sum rules and Pade-Borel resummation techniques to obtain thermal coefficients of double-trace operators. The result passes several checks, including a comparison with solutions to the Klein-Gordon equation on the planar AdS black hole. The talk is based on the joint work with Ivan Gusev and Andrei Parnachev, 2508.08373. 

• Oct 14:  Vasilis Niarchos (ITCP & CCTP) on 2508.08560

Deep Finite Temperature Bootstrap

Abstract:  I will discuss a new way to bootstrap crossing equations in CFT that relies on the use of dispersion relations and efficient ways to optimize over spaces of functions. In this approach, one does not only bootstrap specific CFT data, but also full tails of OPE expansions, reconstructing approximate crossing-symmetric correlation functions. As a concrete demonstration, I will present how the method works in the context of the thermal bootstrap, highlighting the differences from previous approaches, comparative advantages and potential pitfalls and difficulties that can arise.

• Oct 21:  Maria Knysh (VUB) on 2508.05444

Krylov exponents and power spectra for maximal quantum chaos: an EFT approach

• Oct 28:  Anastasios C. Petkou (Aristotle University of Thessaloniki) on 2508.16718

The thermal representation of conformal ladder integrals

• Nov 4:  Srijan Kumar (ICTS-TIFR) on 2508.14872

High to low temperature: O(N) model at large N

Abstract:  We study the O(N) vector model for scalars with quartic interaction at large N on S^1\times S^2 without the singlet constraint. The non-trivial fixed point of the model is described by a thermal mass satisfying the gap equation at large N. We obtain the partition function and the energy density for the model as a series at low temperature in units of the radius of the sphere. We show these results agree with the Borel-Pad\'{e} extrapolations of the high temperature expansions of the partition function and energy density obtained in our previous work. This agreement validates both the expansions and demonstrates that low temperature expansions obtained here correspond to the same fixed point studied earlier at high temperature. We obtain the ratio of the partition function of the theory at the non-trivial fixed point to that of the Gaussian theory at all values of temperature. This ratio begins at 4/5 when the temperature is infinity, decreases to a minimum value of 0.760937, then increases and approaches unity as the temperature is decreased.  

• Nov 18:  Andrew Gomes (EPFL) on 2508.18346 (Note: This seminar will not be recorded!) 

Schwinger-Keldysh effective theory of charge transport: redundancies and systematic ω/T expansion

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