“School of Physics”

Back to Papers Home
Back to Papers of School of Physics

Paper   IPM / P / 17667
School of Physics
  Title:   A tilt instability in the cosmological principle
1.  Ch. Krishnan
2.  R. Mondol
3.  M.M. Sheikh-Jabbari
  Status:   Published
  Journal: Eur. Phys. J. C
  Vol.:  83
  Year:  2023
  Pages:   874
  Supported by:  IPM
We show that the Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) framework has an instability towards the growth of fluid flow anisotropies, even if the Universe is accelerating. This flow (tilt) instability in the matter sector is invisible to Cosmic No-Hair Theorem-like arguments, which typically only flag shear anisotropies in the metric. We illustrate our claims in the setting of ``dipole cosmology'', the maximally Copernican generalization of FLRW that can accommodate a flow. Simple models are sufficient to show that the cosmic flow need not track the shear, even in the presence of a positive cosmological constant. We also emphasize that the growth of the tilt hair is fairly generic if the total equation of state $w(t) \rightarrow -1$ at late times (as it does in standard cosmology), irrespective of the precise model of dark energy. {The generality of our theoretical result puts various recent observational claims about late time anisotropies and cosmic dipoles in a new light.

Download TeX format
back to top
scroll left or right