Hamiltonian formalism for cosmological perturbations: the separate-universe approach

@article{Artigas2021HamiltonianFF,
  title={Hamiltonian formalism for cosmological perturbations: the separate-universe approach},
  author={Danilo Artigas and Julien Grain and Vincent Vennin},
  journal={Journal of Cosmology and Astroparticle Physics},
  year={2021},
  volume={2022}
}
The separate-universe approach provides an effective description of cosmological perturbations at large scales, where the universe can be described by an ensemble of independent, locally homogeneous and isotropic patches. By reducing the phase space to homogeneous and isotropic degrees of freedom, it greatly simplifies the analysis of large-scale fluctuations. It is also a prerequisite for the stochastic-inflation formalism. In this work, we formulate the separate-universe approach in the… 

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