Undergrad Why is there an additional prefactor in equation (12.52) of Peskin's QFT book?

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The discussion revolves around the additional prefactor of (-ig) in equation (12.52) of Peskin's QFT book, specifically concerning external leg corrections. The user expresses confusion about why this coupling constant is included, as it is not typically seen with external leg prefactors. The conversation highlights the importance of understanding the role of coupling constants in field renormalization counterterms. Clarifications are sought regarding the implications of this prefactor on calculations and physical interpretations. Understanding this aspect is crucial for accurate application of quantum field theory principles.
thatboi
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Hey all,
I am currently having trouble understanding equation (12.52) in Peskin's QFT book. Specifically the term for external leg corrections, in which they tack on an additional prefactor of ##(-ig)##. Normally with external leg prefactors, we don't see the coupling constant multiplied onto the field renormalization counterterm so why is such a prefactor included here?
Thanks.
 

Thread 'Two equivalent statements of time reversal symmetric Hamiltonian'

Time reversal invariant Hamiltonians must satisfy ##[H,\Theta]=0## where ##\Theta## is time reversal operator. However, in some texts (for example see Many-body Quantum Theory in Condensed Matter Physics an introduction, HENRIK BRUUS and KARSTEN FLENSBERG, Corrected version: 14 January 2016, section 7.1.4) the time reversal invariant condition is introduced as ##H=H^*##. How these two conditions are identical?
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