The next cosmology seminar takes place on Friday 20th of November, room E349 at 2pm. We will have the pleasure to listen to Angelo Caravano from the University of Amsterdam (Netherlands).
At 2pm, room E349, Angelo Caravano will be talking about
Lattice Monte Carlo of quantum field theory on de Sitter space
Quantum fields in de Sitter space behave in ways that have no counterpart in flat space. Because of the accelerated expansion, light fields become strongly coupled on large scales, however weak their interaction. In particle physics, strongly coupled theories are studied with lattice Monte Carlo methods, but bringing these tools to curved spacetime has been a major challenge, because discretizing a curved geometry typically breaks its symmetries. In this talk I will introduce a new lattice formulation that keeps the de Sitter symmetries exact, and show the first Monte Carlo simulations of an interacting scalar field on Euclidean de Sitter space. At weak coupling, the simulations reproduce the equilibrium of stochastic inflation to a few parts per thousand, without ever invoking a Langevin equation. Small deviations from this distribution closely follow the one-loop renormalization of the coupling. At strong coupling, the effective interaction saturates while the field distribution stays close to the stochastic prediction. This saturation is the de Sitter counterpart of the mechanism behind the lattice bound on the Higgs mass in flat space. More broadly, this new discretization opens up de Sitter space to lattice Monte Carlo methods.