Browsing Institutt for teoretisk astrofysikk by Author "Wittwer, Peter"

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  • A generic instability in clustering dark energy? 
    Hassani, Farbod; Adamek, Julian; Kunz, Martin; Shi, Pan; Wittwer, Peter (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
    In this paper, we study the effective field theory (EFT) of dark energy (DE) for the k-essence model beyond linear order. Using particle-mesh N-body simulations that consistently solve the DE evolution on a grid, we find ...
  • New nonlinear instability for scalar fields 
    Hassani, Farbod; Shi, Pan; Adamek, Julian; Kunz, Martin; Wittwer, Peter (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2022)
    In this Letter, we introduce the nonlinear partial differential equation ∂2τπ∝(→∇π)2 showing a new type of instability. Such equations appear in the effective field theory (EFT) of dark energy for the k-essence model as ...