Triangle Seminars
Wednesday, 27 May 2026
Stochastic inflation from a non-equilibrium renormalization group
📍 London
Sebastian Cespedes
(Imperial College London)
Abstract:
Understanding stochastic inflation, and in particular how to compute controlled corrections, remains an important open problem. In this talk, we study this problem using an effective field theory description of light fields in de Sitter space. Starting from a coarse-grained description, we derive an effective theory for the infrared dynamics of long-wavelength modes. As the coarse-graining scale is pushed below the Hubble scale, the dynamics becomes dominated by stochastic fluctuations and diffusion, reproducing stochastic inflation at leading order while allowing systematic corrections to be computed. We then analyse the renormalisation-group flow of the reduced density matrix under changes of the coarse-graining scale. In the infrared limit, the flow approaches a local stochastic regime described by a generalised Fokker–Planck equation. These results provide a unified framework for understanding stochastic inflation as the infrared limit of an effective field theory in de Sitter space
Understanding stochastic inflation, and in particular how to compute controlled corrections, remains an important open problem. In this talk, we study this problem using an effective field theory description of light fields in de Sitter space. Starting from a coarse-grained description, we derive an effective theory for the infrared dynamics of long-wavelength modes. As the coarse-graining scale is pushed below the Hubble scale, the dynamics becomes dominated by stochastic fluctuations and diffusion, reproducing stochastic inflation at leading order while allowing systematic corrections to be computed. We then analyse the renormalisation-group flow of the reduced density matrix under changes of the coarse-graining scale. In the infrared limit, the flow approaches a local stochastic regime described by a generalised Fokker–Planck equation. These results provide a unified framework for understanding stochastic inflation as the infrared limit of an effective field theory in de Sitter space
Posted by: Riccardo Gonzo
TBA
📍 London
Ohad Mamroud
(SISSA)
Abstract:
TBA
TBA
Posted by: Kiarash Naderi
Thursday, 28 May 2026
On bulk reconstruction in Lorentzian AdS and its flat space limit
📍 London
Ana-Maria Raclariu
(KCL)
Abstract:
We revisit the reconstruction of a free scalar in 4-dimensional Lorentzian Anti-de-Sitter spacetime in terms of primary operators in the boundary 3d CFT. We show that the positive and negative energy subspaces of solutions to the Klein–Gordon equation in AdS can be spanned with bulk-to-boundary propagators with appropriate time orderings. As a result, free scalar fields on a codimension-1 bulk hypersurface can be expressed in terms of operators integrated over boundary regions in the past or future of the hypersurface with kernels given by time-ordered or anti-time-ordered propagators. We will explain how to obtain a similar decomposition of the free field in terms of boundary operators transforming in representations of an so(3,1) subalgebra of the 4d AdS isometry algebra by constructing the appropriate wavefunctions. We conclude by showing that the expansion of a free scalar in Minkowski space in plane wave, Carrollian and conformal primary bases follow from these results in various flat space limits.
We revisit the reconstruction of a free scalar in 4-dimensional Lorentzian Anti-de-Sitter spacetime in terms of primary operators in the boundary 3d CFT. We show that the positive and negative energy subspaces of solutions to the Klein–Gordon equation in AdS can be spanned with bulk-to-boundary propagators with appropriate time orderings. As a result, free scalar fields on a codimension-1 bulk hypersurface can be expressed in terms of operators integrated over boundary regions in the past or future of the hypersurface with kernels given by time-ordered or anti-time-ordered propagators. We will explain how to obtain a similar decomposition of the free field in terms of boundary operators transforming in representations of an so(3,1) subalgebra of the 4d AdS isometry algebra by constructing the appropriate wavefunctions. We conclude by showing that the expansion of a free scalar in Minkowski space in plane wave, Carrollian and conformal primary bases follow from these results in various flat space limits.
Posted by: Kymani Armstrong-Williams