2025/11/19 by Gabriela Barenboim, Aurora Ireland, Barenboim, Gabriela +3
Physics and Astronomy · #COSMIC cancer database #Cosmology #Cosmology and Gravitation Theories #Coupling (piping) #Cutoff #Galaxies: Formation, Evolution, Phenomena #Mode (computer interface) #Noise (video) #Observable #Radio Astronomy Observations and Technology #Spectral density #Universe #White noise #astro-ph.CO #gr-qc #hep-ph
paper · pdf · doi:10.48550/arxiv.2511.15803
openalex publication_date 2025/11/19 · openalex created_date 2025/11/23 · openalex updated_date 2026/07/28
We present observational constraints on large-scale white noise (LSWN) in the cosmic density field, a phenomenon predicted to arise from non-linear mode coupling during cosmological evolution. Building on the theoretical framework of Paper I, where we demonstrated that non-linearities inevitably redistribute power from small to large scales through mode mixing, we confront these predictions with current cosmological data. We modify the CLASS Boltzmann code to incorporate a white noise component kBH/k in the primordial power spectrum and perform parameter estimation using current cosmological data. The non-detection of excess power on the largest observable scales places stringent upper bounds: kBH ≤ 1.80 × 10-13~Mpc-1 at 99% confidence. These constraints imply the primordial power spectrum must deviate from perfect scale invariance on small scales, either through a cutoff at kcut \lesssim 3~pc-1 or through running of the spectral index with αs \lesssim -0.015. Our results demonstrate that LSWN provides a powerful probe of the primordial spectrum at scales orders of magnitude smaller than directly observable, offering unique constraints on early-universe physics.