Cosmic Lightning: How Fast Radio Bursts Illuminate Hidden Baryons

Original: "Measuring the Angular Auto-power Spectrum of Fast Radio Burst Dispersion Measures as a Robust Cosmological Probe and Baryon Tracer"

· Bao Wang, Zhiyu Lu, Yang Liu, Jun-Jie Wei, Xue-Feng Wu

arXiv:2607.04106v1 · 2026-07-05 · CC BY 4.0 · ⏱ 1 min · High Energy Cosmology

The angular power spectrum of FRB dispersion measures has for the first time measured large-scale inhomogeneities in electron plasma, opening a new path to independent cosmology.

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Every fast radio burst is like a lightning strike on a cloudless night: we don't see the storm, but the delay of thunder betrays the clouds. 3455 such 'thunderous' signals gathered by the CHIME telescope have outlined the contours of the baryonic web for the first time. When we count them in the hundreds of thousands, we'll not only find all the missing baryons, but perhaps even hear the breath of dark energy.

🎯 Fast radio bursts are so energetic that a single millisecond pulse releases as much energy as the Sun does in several days. Moreover, they come from all directions and can serve as 'lighthouses' that illuminate the cosmic web.

🎬 The idea of using distant pulses to study hidden matter echoes the concept of 'interstellar radio beacons' from Carl Sagan's novel 'Contact,' where an extraterrestrial signal carries information about the structure of the Universe.

DM_{\rm obs} = DM_{\rm MW\,ISM} + DM_{\rm MW\,halo} + DM_{\rm LSS}(z) + \frac{DM_{\rm host}}{1+z}

This equation shows how to extract the cosmologically significant part from the total effect.

C_{\rm LSS-LSS}^{\ell} = \int dz \frac{H(z)}{c\chi^2(z)} W_{\rm LSS}^2(z) P_{\rm ee}\left(k=\frac{\ell+1/2}{\chi(z)},z\right)

This formula is the core of the method, transforming inhomogeneities in electron distribution into a measurable angular signal.

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Cosmic Lightning: How Fast Radio Bursts Illuminate Hidden Baryons