= One-point correlation function
{title2=$G_1(x)=\langle\phi(x)\rangle$}
= One-point function
{synonym}
The <correlation function> with a single field insertion is its <expectation value>. In a translation-invariant vacuum it is independent of position. A <tadpole subtraction> chooses a linear <counterterm>, or shifts the expansion point of the field, so that this expectation is zero. This removes attached <tadpole diagrams> from higher connected <correlation functions> without discarding the physical need to renormalize the chosen vacuum.
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