Triangle Seminars
Tuesday, 17 Nov 2026
High-frequency limits in general relativity
📍 London
Jonathan Wing-hong Luk
(Stanford)
Abstract:
It is known that a high-frequency limit of solutions to the Einstein vacuum equation need not be vacuum, and that "effective matter" may arise in the limiting spacetime. I will discuss results about the characterization of such limits, and in particular present a recent construction such that the limiting effective matter is given by a massless Vlasov field. This is a joint work with Cécile Huneau.
It is known that a high-frequency limit of solutions to the Einstein vacuum equation need not be vacuum, and that "effective matter" may arise in the limiting spacetime. I will discuss results about the characterization of such limits, and in particular present a recent construction such that the limiting effective matter is given by a massless Vlasov field. This is a joint work with Cécile Huneau.
Posted by: Alan Rios Fukelman
Wednesday, 18 Nov 2026
Quark Anti-Quark Fusion and Walking RG Flows
📍 London
Amit Sever
(Tel Aviv University)
Abstract:
We study the fusion of two conjugate conformal line defects on the sphere. At small separation, their spectrum is governed by a universal Fusion Master Equation. Below a critical coupling, the fused defect has two conformal fixed points; at criticality, they collide and move into the complex plane, producing walking RG behaviour. Although individual energy levels then drift with the UV scale and are scheme dependent, the SL(2,R) Casimir continues to commute with the Hamiltonian below that scale. This organises the spectrum into conformal families and fixes a universal, scheme-independent density of states. We derive this structure in the planar ladder model and obtain an exact finite-coupling description of conjugate 1/2-BPS Wilson-line fusion in planar N=4 SYM using the Quantum Spectral Curve. We test our results against perturbation theory and semiclassical string theory.
We study the fusion of two conjugate conformal line defects on the sphere. At small separation, their spectrum is governed by a universal Fusion Master Equation. Below a critical coupling, the fused defect has two conformal fixed points; at criticality, they collide and move into the complex plane, producing walking RG behaviour. Although individual energy levels then drift with the UV scale and are scheme dependent, the SL(2,R) Casimir continues to commute with the Hamiltonian below that scale. This organises the spectrum into conformal families and fixes a universal, scheme-independent density of states. We derive this structure in the planar ladder model and obtain an exact finite-coupling description of conjugate 1/2-BPS Wilson-line fusion in planar N=4 SYM using the Quantum Spectral Curve. We test our results against perturbation theory and semiclassical string theory.
Posted by: Kiarash Naderi
Thermal Giant Graviton Expansion
📍 London
Kasia Budzik
(Harvard University)
Abstract:
In this talk, I will present the Giant Graviton Expansion of the thermal partition function of free N=4 super Yang-Mills. We use the twistorial uplift of self-dual N=4 SYM, which can be engineered in the topological B-model on a Calabi-Yau 7-fold (a version of Witten's twistor string). We reproduce the Giant Graviton Expansion from closed string and D-brane contributions. In particular, we recover the Hagedorn temperature of the free gauge theory from the bulk computation on CY7. This is based on work with Atul Sharma.
In this talk, I will present the Giant Graviton Expansion of the thermal partition function of free N=4 super Yang-Mills. We use the twistorial uplift of self-dual N=4 SYM, which can be engineered in the topological B-model on a Calabi-Yau 7-fold (a version of Witten's twistor string). We reproduce the Giant Graviton Expansion from closed string and D-brane contributions. In particular, we recover the Hagedorn temperature of the free gauge theory from the bulk computation on CY7. This is based on work with Atul Sharma.
Posted by: Elia de Sabbata
Thursday, 19 Nov 2026
TBD
📍 London
Mattia Serrani
(Mons)
Abstract:
TBD.
TBD.
Posted by: Kymani Armstrong-Williams
Kinematical algebras: the simplicity of self-duality
📍 London
Mattia Serrani
(Mons)
Abstract:
Self-dual (SD) theories are powerful toy models of their unitary completions. It was shown recently that there are infinitely many SD (higher-spin) theories in 4d flat space with non-trivial local interactions, all of which are governed by kinematical algebras. The maximal SD theory is chiral higher-spin gravity, whose kinematical algebra is given by the Moyal–Weyl commutator. In light of the recent work of Guevara et al. [2602.12176], we show that all these SD theories have non-trivial tree-level amplitudes, which can be written as self-dual Yang–Mills (SDYM) amplitudes times a kinematical factor. This non-triviality provides the missing ingredient for a celestial analogue of the CFT_3 vector-model/AdS_4 higher-spin duality.
Self-dual (SD) theories are powerful toy models of their unitary completions. It was shown recently that there are infinitely many SD (higher-spin) theories in 4d flat space with non-trivial local interactions, all of which are governed by kinematical algebras. The maximal SD theory is chiral higher-spin gravity, whose kinematical algebra is given by the Moyal–Weyl commutator. In light of the recent work of Guevara et al. [2602.12176], we show that all these SD theories have non-trivial tree-level amplitudes, which can be written as self-dual Yang–Mills (SDYM) amplitudes times a kinematical factor. This non-triviality provides the missing ingredient for a celestial analogue of the CFT_3 vector-model/AdS_4 higher-spin duality.
Posted by: Kymani Armstrong-Williams