in QF, every dirac delta function is accompanied by [itex]2\pi[/itex],i.e.[itex](2\pi)\delta(p-p_0)[/itex] or [itex](2\pi)^3\delta(\vec{p}-\vec{p_0})[/itex](adsbygoogle = window.adsbygoogle || []).push({});

the intergral element in QF is [itex]\int\frac{d^3p}{(2\pi)^3}\frac{1}{2E_P}[/itex], it comes from the integral element [itex]\int\frac{d^4p}{(2\pi)^4}(2\pi)\delta(p^2-m^2)[/itex],I want to know why there is [itex]2\pi[/itex]in the second equation. Is it a convention? Is so where does the [itex]2\pi[/itex]comes from originally.

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# Why there is 2[itex]\pi[/itex] in every dirac delta function

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