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From Eq. (17) one can see that for the first-order self-energycorrection the divergent part is zero. However, in case of the higher-order diagrams under consideration the contributions of par- ticular diagrams are divergent. Nevertheless, as it is shown below, the sum of all the contributions to the screened self-energy correction is finite. 

## A. ”Modified self-energy” diagrams 

The irreducible parts of the diagrams A , B and E can be presented as the matrix elements of the self-energy operator 〈 X | Σ( ε ) | Y 〉 with various wave functions 〈 X | and | Y 〉 . The formulas for these contributions are as follows, 

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All the reducible terms of the similar structure are denoted as Δ E SE( G ) $_{SQED}$, 

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