On the creation of spin 1/2 particles and adiabatic renormalization in FLRW spacetimes

Within the framework of adiabatic regularization scheme, developed by Parker & Fulling, 

we have computed particle number density and renormalized stress energy tensor of spin 

1/2 particles. In the process, we have extended the approach of Zeldovich & Starobinskii 

(n-wave regularisation method), introduced for scalar fields, to spin-1/2 fields in FLRW 

background, using appropriate WKB ansatz for the adiabatic expansion for field modes. 

The conformal and axial anomalies thus found are in exact agreement with those obtained 

from other renormalization method. This work gives us an alternative to [Phys. Rev. D 

88, 061501 (2013)] as an appropriate extension of adiabatic renormalization scheme, 

originally introduced for scalar fields, applicable to fermions.