Comment on "Fermion production in a magnetic field in a de Sitter universe"

Understand

We point out that the transition probabilities used in a recent perturbative calculation of pair creation in an external magnetic field in the expanding de Sitter space with the $in$ and $out$ fermion states defined by the Bunch-Davies modes [C.

• Crucean et al., Phys.
• Rev.
• D 73 044019 (20016)] are gauge dependent quantities.