47 citations · 262 across the 16 of their papers we have counts for
6 papers · 1 filter
Resummation of infrared logarithms in de Sitter space via Dyson-Schwinger equations: the ladder-rainbow approximation
Ahmed Youssef, Dirk Kreimer
We study the infrared (large separation) behavior of a massless minimally coupled scalar quantum field theory with a quartic self interaction in de Sitter spacetime. We show that t…
Do scale-invariant fluctuations imply the breaking of de Sitter invariance?
Ahmed Youssef
The quantization of the massless minimally coupled (mmc) scalar field in de Sitter spacetime is known to be a non-trivial problem due to the appearance of strong infrared (IR) effe…
Lorentz-violating vs ghost gravitons: the example of Weyl gravity
Nathalie Deruelle, Misao Sasaki, Yuuiti Sendouda +1
We show that the ghost degrees of freedom of Einstein gravity with a Weyl term can be eliminated by a simple mechanism that invokes local Lorentz symmetry breaking. We demonstrate…
Inflation with a Weyl term, or ghosts at work
Nathalie Deruelle, Misao Sasaki, Yuuiti Sendouda +1
In order to assess the role of ghosts in cosmology, we study the evolution of linear cosmological perturbations during inflation when a Weyl term is added to the action. Our main r…
Various Hamiltonian formulations of f(R) gravity and their canonical relationships
Nathalie Deruelle, Yuuiti Sendouda, Ahmed Youssef
Various Hamiltonian formulations of f(R) gravity can be found in the literature. Some authors follow the Ostrogradsky treatment of higher derivative theories and introduce as extra…
A discrete nonetheless remarkable brick in de Sitter: the "massless minimally coupled field"
Jean-Pierre Gazeau, Ahmed Youssef
Over the last ten years interest in the physics of de Sitter spacetime has been growing very fast. Besides the supposed existence of a "de sitterian period" in inflation theories,…