On cosmic acceleration without dark energy
By E. Kolb, S. Matarrese, A. Riotto. 2005
270 citations recorded by the source corpus.
We elaborate on the proposal that the observed acceleration of the Universe is the result of the backreaction of cosmological perturbations, rather than the effect of a negative-pressure dark-energy fluid or a modification of general relativity. Through the effective Friedmann equations describing an inhomogeneous Universe after smoothing, we demonstrate that acceleration in our local Hubble patch is possible even if fluid elements do not individually undergo accelerated expansion. This invalidates the no-go theorem that there can be no acceleration in our local Hubble patch if the Universe only contains irrotational dust. We then study perturbatively the time behaviour of general-relativistic cosmological perturbations, applying, where possible, the renormalization group to regularize the dynamics. We show that an instability occurs in the perturbative expansion involving sub-Hubble modes. Whether this is an indication that acceleration in our Hubble patch originates from the backreaction of cosmological perturbations on observable scales requires a fully non-perturbative approach.
Subfields: Astronomy and Astrophysics
View Paper: https://www.semanticscholar.org/paper/96cb63220d1e6b70561cd4a20f29d4b90cff315c
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In Astronomy and Astrophysics
Citations in the corpus
- Modified Gravity-GADGET: A new code for cosmological hydrodynamical simulations of modified gravity models (2013, background): “…for example as a backreaction effect of the formation of nonlinear cosmic structures on the background expansion of the universe (see e.g. Kolb et al. 2006; Rasanen 2011; Clarkson et al. 2011) or through the presence of a very large void surrounding the Milky Way’s location and mimicking…”
- Dark Energy from structure: a status report (2007, methodology): “ition (29). Also, a cosmological constant need not be included into the cosmological equations, since QD can play this role [33], [47], [160], and can even provide a constant exactly, as was shown in [116] and [36]. The exact condition can be inferred from Eq. (24) and (31) and reads: 2 a2 D Zt ti d”
- Cosmological non-linearities as an effective fluid (2010, background): “(ρ̄+ p̄)θ = ma−3 k ∫ 4πp(2)dp p am f0(p)δ [1] f , (4.”
- Backreaction in Late-Time Cosmology (2011, background): “An alternative to standard perturbation theory is to employ gradient expansion techniques that allow to go substantially beyond the perturbative regime [67,91].”
- On the Growth of Perturbations as a Test of Dark Energy and Gravity (2006, background): “General relativity is correct but our understanding of it is not; e.g., long-wavelength density perturbations modify the Friedmann equation (Kolb et al. 2005, 2006).”
- The universe seen at different scales (2005, background): “Various papers suggest the effect may indeed be significant, for example the observed acceleration of the universe could possibly be the result of the backreaction of cosmological perturbations rather than the effect of a negative–pressure dark energy fluid [70], [47].”