A calculation on the self-field of a point charge and the Unruh effect

Within the context of quantum field theory in curved spacetimes, Hacyan and Sarmiento defined the vacuum stress-energy tensor with respect to the acce lerated observer. They calculated it for uniform acceleration and circular motion, and derived that the rotating observer perceives a flux. Mane relat ed the flux to synchrotron radiation. In order to investigate the relation between the vacuum stress and bremsstrahlung, we estimate the stress-energy tensor of the electromagnetic field generated by a point charge, at the po sition of the charge. We use the retarded field as a self-field of the poin t charge. Therefore the tensor diverges if we evaluate it as it is. Hence w e remove the divergent contributions by using the expansion of the tensor i n powers of the distance from the point charge. Finally, we take an average for the angular dependence of the expansion. Mie calculate it for the case of uniform acceleration and circular motion, and it is found that the orde r of the vacuum stress multiplied by pi alpha (alpha = e(2)/(h) over bar c is the fine structure constant) is equal to that of the self-stress. In the Appendix, we give another trial approach with a similar result.