= Momentum-space integral
{title2=$\int d^dp\,f(p)$}
= Momentum integral
{synonym}
An <integral> over <momentum space>. For example, state counting in $d$ spatial dimensions uses a measure proportional to $d^dp/(2\pi\hbar)^d$, whereas a relativistic <Feynman integral> commonly uses $d^dp/(2\pi)^d$ in <natural units>. The convention and any regulator must be specified. Independent <loop momenta> supply separate integration variables in a loop <Feynman diagram>; <ultraviolet divergences> and <infrared divergences> can require different regularizations.
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