The cosmological background of vector modes

Understand

We investigate the spectrum of vector modes today which is generated at second order by density perturbations.

• The vector mode background that is generated by structure formation is small but in principle it contributes to the integrated Sachs-Wolfe effect, to redshift-space distortions and to weak lensing.
• We recover, clarify and extend previous results, and explain carefully why no vorticity is generated in the fluid at second order.
• The amplitude of the induced vector mode in the metric is around 1% that of the first-order scalars on small scales.