### Tranfer function: Relative CDM Baryon Velocity

Posted:

**October 26 2015**Hi! I am new to CAMB and have been trying to use it to get the relative velocity between CDM and Baryons using the transfer function. I have a few questions and I would be really glad if someone could answer them:

1. What is the exact formula used for getting the 13th column of the transfer function data file? (Including the constants if any)

2. For some reason when I try to get the transfer function for a redshift >3000, the transfer function gives incomprehensible values. There is a lot of repetition in the rows and the first column (with k values) is of the order 10^(-18). So I am assuming it is some sort of numerical problem. Are there changes that I have to make in the params.ini file apart from the usual ones to get meaningful transfer function for high redshifts?

1. What is the exact formula used for getting the 13th column of the transfer function data file? (Including the constants if any)

2. For some reason when I try to get the transfer function for a redshift >3000, the transfer function gives incomprehensible values. There is a lot of repetition in the rows and the first column (with k values) is of the order 10^(-18). So I am assuming it is some sort of numerical problem. Are there changes that I have to make in the params.ini file apart from the usual ones to get meaningful transfer function for high redshifts?