逐字来源、作者主张与候选译文分别保留。工程核验不批准 OCR、译文或数学正确性。

概念与作者路径

§13 自旋–统计回顾与反对易关系

作者据自旋–统计定理要求旋量产生和湮灭算符反对易。

条件与约定:旋量场;关系中的动量归一化和自旋指标按 Schwartz 保留。

逐字作者来源与版本
The creation and annihilation operators for spinors must anticommute by the spin-statistics theorem:
$$
\left\{a _ {p} ^ {s \dagger}, a _ {q} ^ {s ^ {\prime} \dagger} \right\} = \left\{a _ {p} ^ {s}, a _ {q} ^ {s ^ {\prime}} \right\} = \left\{b _ {p} ^ {s \dagger}, b _ {q} ^ {s ^ {\prime} \dagger} \right\} = \left\{b _ {p} ^ {s}, b _ {q} ^ {s ^ {\prime}} \right\} = 0 \tag {13.4}
$$
and
$$
\left\{a _ {p} ^ {s}, a _ {q} ^ {s ^ {\prime} \dagger} \right\} = \left\{b _ {p} ^ {s}, b _ {q} ^ {s ^ {\prime} \dagger} \right\} = \delta_ {s s ^ {\prime}} (2 \pi) ^ {3} \delta^ {3} (p - q). \tag {13.5}
$$

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使用前置陈述:第12章自旋–统计陈述(既有种子)。作者有明确编号回指。

证据:作者编号回指
The creation and annihilation operators for spinors must anticommute by the spin-statistics theorem:

§13 费米子负号的自旋–统计回指

额外负号归因于自旋统计,作者说稍后解释。

条件与约定:这是回指和后文承诺,不在此处补证明。

逐字作者来源与版本
The extra minus sign is due to spin-statistics, as will be explained shortly. Contracting all the spinor indices and replacing  $p_1^\mu$  by  $p^\mu + k^\mu$  and  $p_2^\mu$  by  $k^\mu$ :

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§13 无质量电子极限的螺旋度守恒

三枚伽马矩阵的耦合保持左右手态;作者限定无质量电子极限下左右手态解耦。

条件与约定:不能把有质量粒子的手征性与螺旋度普遍等同。

逐字作者来源与版本
In particular, our interaction  $\mathcal{M}_t$  has three  $\gamma$ -matrices, so it couples  $RR$  and  $LL$ . Thus,
$$
\mathcal {M} _ {t} = - \frac {e ^ {2}}{\omega \phi} \left[ \bar {u} _ {L} \left(p _ {3}\right) \epsilon_ {1} / k \epsilon_ {4} ^ {*} u _ {L} \left(p _ {2}\right) + \bar {u} _ {R} \left(p _ {3}\right) \epsilon_ {1} / k \epsilon_ {4} ^ {*} u _ {R} \left(p _ {2}\right) \right], \tag {13.157}
$$
which is helicity conserving. So,  $u(p_2)$  and  $\bar{u}(p_3)$  should be either both right-handed or both left-handed. This is consistent with a general property of QED, that in the limit of a massless electron, the left- and right-handed states completely decouple.

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§13 光子螺旋度与左右手约定检查

作者用光子和电子的自旋沿动量投影检查左右手符号一致。

条件与约定:动量沿 z 轴,光子本征值 ±1,电子 ±1/2;保留 E 与角动量矩阵约定。

逐字作者来源与版本
For the photons, we need to use the helicity eigenstates:
$$
\epsilon_ {R} ^ {\mu} = \frac {1}{\sqrt {2}} (0, 1, i, 0), \quad \epsilon_ {L} ^ {\mu} = \frac {1}{\sqrt {2}} (0, 1, - i, 0). \tag {13.159}
$$
To see that the convention for "left" and "right" is being used consistently, it is easy to check that  $\frac{\vec{S} \cdot \vec{p}}{E} \epsilon_{L} = -\epsilon_{L}$  and  $\frac{\vec{S} \cdot \vec{p}}{E} u_{L} = -\frac{1}{2} u_{L}$  using  $p^{\mu} = (E, 0, 0, p_{z})$  and  $S_{z} = S_{12}$  or  $S_{z} = V_{12}$  in Eqs. (10.117) and (10.113) respectively.

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