Can non-linear structure form at the era of decoupling?

Nir J. Shaviv*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


The effects of large-scale fluctuations on small-scale isothermal modes at the epoch of recombination are analysed. We find the following. (a) Albeit the fact that primordial fluctuations were at this epoch still well in the linear regime, a significant non-linear radiation hydrodynamic interaction could have taken place. (b) Short-wavelength isothermal fluctuations are unstable. Their growth rate is an exponential function of the amplitude of the large-scale fluctuations and is therefore very sensitive to the initial conditions. (c) The observed cosmic microwave background radiation (CMBR) fluctuations are of order of the limit above which the effect should be significant. Thus, depending on their exact value, the effect may be negligible or lead to structure formation out of the isothermal fluctuations within the period of recombination. (d) If the cosmological parameters are within the prescribed regime, the effect should be detectable through induced deviations in the Planck spectrum. (e) The sensitivity of the effect to the initial conditions provides a tool to set limits on various cosmological parameters with emphasis on the type and amplitude of the primordial fluctuation spectrum. (f) Under proper conditions, the effect may be responsible for the formation of sub-globular-cluster sized objects at particularly high redshifts. (g) Under certain circumstances, it can also affect horizon-sized large-scale structure.

Original languageAmerican English
Pages (from-to)1245-1260
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - 11 Jul 1998
Externally publishedYes


  • Cosmic microwave background
  • Cosmology: theory
  • Large-scale structure of Universe


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