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| + | 图2中的图式显示了量子电动力学中单圈对电子-电子散射的贡献之一。图左侧的电子,用实线表示,开始时是4动量的{{math|''p<sup>μ</sup>''}},结束时是4动量的{{math|''r<sup>μ</sup>''}}。它发射一个携带{{math|''r<sup>μ</sup>'' − ''p<sup>μ</sup>''}}的虚光子,将能量和动量传递给另一个电子。但在这张图中,在这之前,它发射了另一个4动量的{{math|''q<sup>μ</sup>''}}的虚光子,它在发射了另一个虚光子后重新吸收了这个。能量和动量守恒并不能唯一地决定4动量{{math|''q<sup>μ</sup>''}},所以所有的可能性都是相等的,我们必须积分。 |
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− | The diagram in Figure 2 shows one of the several one-loop contributions to electron–electron scattering in QED.
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− | The electron on the left side of the diagram, represented by the solid line, starts out with 4-momentum {{math|''p<sup>μ</sup>''}} and ends up with 4-momentum {{math|''r<sup>μ</sup>''}}.
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− | It emits a virtual photon carrying {{math|''r<sup>μ</sup>'' − ''p<sup>μ</sup>''}} to transfer energy and momentum to the other electron.
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− | But in this diagram, before that happens, it emits another virtual photon carrying 4-momentum {{math|''q<sup>μ</sup>''}}, and it reabsorbs this one after emitting the other virtual photon.
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− | Energy and momentum conservation do not determine the 4-momentum {{math|''q<sup>μ</sup>''}} uniquely, so all possibilities contribute equally and we must integrate.
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− | The diagram in Figure 2 shows one of the several one-loop contributions to electron–electron scattering in QED. The electron on the left side of the diagram, represented by the solid line, starts out with 4-momentum and ends up with 4-momentum . It emits a virtual photon carrying to transfer energy and momentum to the other electron. But in this diagram, before that happens, it emits another virtual photon carrying 4-momentum , and it reabsorbs this one after emitting the other virtual photon. Energy and momentum conservation do not determine the 4-momentum uniquely, so all possibilities contribute equally and we must integrate.
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− | 图2中的图式显示了量子电动力学中单圈对电子-电子散射的贡献之一。图左侧的电子,用实线表示,开始时是4动量的pμ,结束时是4动量的rμ。它发射一个携带rμ−pμ的虚光子,将能量和动量传递给另一个电子。但在这张图中,在这之前,它发射了另一个4动量的qμ的虚光子,它在发射了另一个虚光子后重新吸收了这个。能量和动量守恒并不能唯一地决定4动量qμ,所以所有的可能性都是相等的,我们必须积分。
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− | This diagram's amplitude ends up with, among other things, a factor from the loop of
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− | This diagram's amplitude ends up with, among other things, a factor from the loop of
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| 除去其他因素,该图的振幅最终成为下圈的一个因子: | | 除去其他因素,该图的振幅最终成为下圈的一个因子: |
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| 类似的环散度也出现在其他量子场论中。 | | 类似的环散度也出现在其他量子场论中。 |
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| == Renormalized and bare quantities == | | == Renormalized and bare quantities == |