PIRSA:26050037 Scientific Series Particle Physics

DOI10.48660/26050037

Series: Particle Physics

Cheong, D.Y. (2026). Kinetic Isocurvature Perturbations. Perimeter Institute. https://pirsa.org/26050037

Cheong, Dhong Yeon. Kinetic Isocurvature Perturbations. Perimeter Institute, May. 05, 2026, https://pirsa.org/26050037 

@misc{ pirsa_PIRSA:26050037,
  doi = {10.48660/26050037},
  url = {https://pirsa.org/26050037},
  author = {Cheong, Dhong Yeon},
  keywords = {Particle Physics},
  language = {en},
  title = {Kinetic Isocurvature Perturbations},
  publisher = {Perimeter Institute},
  year = {2026},
  month = {may},
  note = {PIRSA:26050037 see, \url{https://pirsa.org}}
}

Abstract

In this talk, I will formulate a new class of primordial perturbations called kinetic isocurvature perturbations, where the mass density of dark matter is constant relative to the photon number density while the kinetic energy of dark matter fluctuates in space. Such perturbations naturally arise in scenarios where a nonrelativistic heavy field decays into relativistic dark matter particles with a spatially modulated rate. As dark matter cools and becomes nonrelativistic, these fluctuations in kinetic energy leave large-scale density perturbations essentially unaffected and therefore evade the Cosmic Microwave Background bounds on isocurvature perturbations, yet survive as spatial variations in the free-streaming scale, resulting in patch-by-patch variation of the matter power spectrum.

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