Constraints on small-scale primordial density fluctuation from cosmic microwave background through dark matter annihilation

Abstract

The cosmic microwave background (CMB) observation by the Planck satellite precisely determines primordial curvature fluctuations on larger scales than $\mathcal{O}(1)\mathrm{Mpc}$, while the small-scale curvature fluctuation is still less constrained. The constraint on small-scale fluctuations is highly improved if we assume the standard thermal relic dark matter scenario. When small-scale fluctuations are large enough, dense regions collapse to form small halos even in a redshift $z\gtrsim 10^3$, which is called ultracompact minihalos. These minihalos enhance the annihilation of the dark matter and it is constrained by observations such as extragalactic gamma rays and the CMB. We revisit the effect of minihalos formed by the small-scale density fluctuations and calculate the ionization history modified by the dark matter annihilation. We perform the Markov Chain Monte Carlo method to constrain the size of small-scale curvature fluctuations by the CMB power spectrum. It is found that the constraint from the CMB power spectrum is comparable to that from the extragalactic gamma rays. We confirm that our constraint mainly comes from the energy injection in early time ($z\gtrsim 100$) and hence it is independent of the uncertainty of minihalo properties in the late time.

15 pages, 8 figures

References in corpus (11)

• The Clustering of the SDSS DR7 Main Galaxy Sample I: A 4 per cent Distance Measure at z=0.15
• Precise Relic WIMP Abundance and its Impact on Searches for Dark Matter Annihilation
• CMB Constraints on WIMP Annihilation: Energy Absorption During the Recombination Epoch
• The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in Fourier-space
• Silk damping at a redshift of a billion: a new limit on small-scale adiabatic perturbations
• The impacts of dark matter particle annihilation on recombination and the anisotropies of the cosmic microwave background
• Gamma-rays from ultracompact minihalos: potential constraints on the primordial curvature perturbation
• 3D simulations with boosted primordial power spectra and ultracompact minihalos
• CMB anisotropy and BBN constraints on pre-recombination decay of dark matter to visible particles
• Electron and Photon Energy Deposition in Universe
• Constraining Mixed Dark-Matter Scenarios of WIMPs and Primordial Black Holes from CMB and 21-cm observations

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• Constraining first-order phase transitions with curvature perturbations
• Comparing sharp and smooth transitions of the second slow-roll parameter in single-field inflation
• Minihalos as probes of the inflationary spectrum: accurate boost factor calculation and new CMB constraints
• Implications for Pulsar Timing Arrays of Sub-solar Black Hole Detections: From LVK to Einstein Telescope and Cosmic Explorer
• Generating large primordial fluctuations in single-field inflation for PBH formation
• Enhanced Small-Scale Structure in the Cosmic Dark Ages