Do baryons trace dark matter in the early universe?

Abstract

Baryon-density perturbations of large amplitude may exist if they are compensated by dark-matter perturbations so that the total density remains unchanged. Big-bang nucleosynthesis and galaxy clusters allow the amplitudes of these compensated isocurvature perturbations (CIPs) to be as large as $\sim 10$. CIPs will modulate the power spectrum of cosmic microwave background (CMB) fluctuations---those due to the usual adiabatic perturbations---as a function of position on the sky. This leads to correlations between different spherical-harmonic coefficients of the temperature/polarization map, and it induces B modes in the CMB polarization. Here, the magnitude of these effects is calculated and techniques to measure them are introduced. While a CIP of this amplitude can be probed on the largest scales with WMAP, forthcoming CMB experiments should improve the sensitivity to CIPs by at least an order of magnitude.

4 pages, 3 figures, updated with version published in Phys. Rev. Lett. Results unchanged. Added expanded discussion of how to disentangle compensated isocurvature perturbations from weak lensing of the CMB. Expanded discussion of early universe motivation for compensated isocurvature perturbations

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Cited by in corpus (26)

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• Planck 2018 results. V. CMB power spectra and likelihoods
• Planck 2013 results. XXII. Constraints on inflation
• CMB-S4 Science Case, Reference Design, and Project Plan
• Gravity and Large-Scale Non-local Bias
• The Pesky Power Asymmetry
• CMB spectral distortions from small-scale isocurvature fluctuations
• Search for Compensated Isocurvature Perturbations with Planck Power Spectra
• Baryons do trace dark matter 380,000 years after the big bang: Search for compensated isocurvature perturbations with WMAP 9-year data
• Power spectra in the eikonal approximation with adiabatic and non-adiabatic modes
• Probing correlated compensated isocurvature perturbations using scale-dependent galaxy bias
• Dark Matter Assimilation into the Baryon Asymmetry
• Baryons still trace dark matter: probing CMB lensing maps for hidden isocurvature
• Statistical diagnostics to identify Galactic foregrounds in B-mode maps
• Probing spatial variation of the fine-structure constant using the CMB
• Lensing Bias to CMB Measurements of Compensated Isocurvature Perturbations
• Probing Compensated Isocurvature with the 21-cm Signal during Cosmic Dawn
• BAO Modulation as a Probe of Compensated Isocurvature Perturbations
• Uncorrelated Compensated Isocurvature Perturbations from kSZ Tomography
• Probing vector chirality in the early Universe
• Lensing Bias to CMB Polarization Measurements of Compensated Isocurvature Perturbations
• Magnetic Fields from Compensated Isocurvature Perturbations
• Phenomenology of a vector-field-induced (and possibly parity breaking) compensated isocurvature perturbation
• Generalized neutrino isocurvature
• The intrinsic bispectrum of the CMB from isocurvature initial conditions
• Probing small-scale baryon and dark matter isocurvature perturbations with cosmic microwave background anisotropies