Dispersion Distance and the Matter Distribution of the Universe in Dispersion Space

Understand

We propose that "standard pings", brief broadband radio impulses, can be used to study the three-dimensional clustering of matter in the Universe even in the absence of redshift information.

• The dispersion of radio waves as they travel through the intervening plasma can, like redshift, be used as a cosmological distance measure.
• Because of inhomogeneities in the electron density along the line of sight, dispersion is an imperfect proxy for radial distance and we show that this leads to calculable dispersion-space distortions in the apparent clustering of sources.
• Fast radio bursts (FRBs) are a new class of radio transients that are the prototypical standard ping and, due to their high observed dispersion, have been interpreted as originating at cosmological distances.