есть вот такая корреляционная функция
![\begin{eqnarray}
\dot{F}_{rr^{\prime}}(\mathbf{k},\mathbf{k}^{\prime},t)
&=&ie(2\pi)^{-3/2}\int d^3 p_1 d^3 p_2 \Bigl\{\frac{1}{\sqrt{2k}} \delta(%
\mathbf{p}_1 -\mathbf{p}_2 -\mathbf{k}) \notag \\
&\cdot& [\bar{u}v]^{r}_{\beta\alpha}(\mathbf{p}_1 ,\mathbf{p}_2 ,\mathbf{k}%
;t) \langle b^{+}_{\beta}(-\mathbf{p}_{2},t)a^+_{\alpha}(\mathbf{p}_1,t)
A_{r^{\prime}}^{(-)}(\mathbf{k}^{\prime},t)\rangle \label{27e} \\
&+& \frac{1}{\sqrt{2k^{\prime}}} \delta(\mathbf{p}_1 -\mathbf{p}_2 +\mathbf{k%
}^{\prime}) [\bar{v}u]^{r^\prime}_{\beta\alpha} (\mathbf{p}_1,\mathbf{p}_2,%
\mathbf{k}^{\prime};t) \langle b_\alpha(-\mathbf{p}_1,t)a_{\beta}(\mathbf{p}%
_2,t) A_{r}^{(+)}(\mathbf{k},t)\rangle \Bigr\}~. \notag
\end{eqnarray} \begin{eqnarray}
\dot{F}_{rr^{\prime}}(\mathbf{k},\mathbf{k}^{\prime},t)
&=&ie(2\pi)^{-3/2}\int d^3 p_1 d^3 p_2 \Bigl\{\frac{1}{\sqrt{2k}} \delta(%
\mathbf{p}_1 -\mathbf{p}_2 -\mathbf{k}) \notag \\
&\cdot& [\bar{u}v]^{r}_{\beta\alpha}(\mathbf{p}_1 ,\mathbf{p}_2 ,\mathbf{k}%
;t) \langle b^{+}_{\beta}(-\mathbf{p}_{2},t)a^+_{\alpha}(\mathbf{p}_1,t)
A_{r^{\prime}}^{(-)}(\mathbf{k}^{\prime},t)\rangle \label{27e} \\
&+& \frac{1}{\sqrt{2k^{\prime}}} \delta(\mathbf{p}_1 -\mathbf{p}_2 +\mathbf{k%
}^{\prime}) [\bar{v}u]^{r^\prime}_{\beta\alpha} (\mathbf{p}_1,\mathbf{p}_2,%
\mathbf{k}^{\prime};t) \langle b_\alpha(-\mathbf{p}_1,t)a_{\beta}(\mathbf{p}%
_2,t) A_{r}^{(+)}(\mathbf{k},t)\rangle \Bigr\}~. \notag
\end{eqnarray}](https://dxdy-01.korotkov.co.uk/f/c/2/1/c213dbe62bbc17b9e30d64552707db0282.png)
Уравнения для корреляторов получаем из уравнений:
![\begin{eqnarray}
\dot{a}(\mathbf{p},t) &=& -i\omega(\mathbf{p},t)a(\mathbf{p},t)-U_{(1)}(%
\mathbf{p},t)a(\mathbf{p},t) -U_{(2)}(\mathbf{p},t)b^+ (-\mathbf{p},t)
\notag \\
&&+ ie(2\pi)^{-3/2}\int d^3 p_{1}\frac{d^3 k}{\sqrt{2k}}\; \delta(\mathbf{p}-%
\mathbf{p}_1 +\mathbf{k}) \Bigl\{a(\mathbf{p}_1,t)[\bar{u}u]^{r}(\mathbf{p},%
\mathbf{p}_1 ,\mathbf{k};t) \notag \\
&&+ b(-\mathbf{p}_1,t)[\bar{u}v]^{r}(\mathbf{p},\mathbf{p}_1,\mathbf{k} ;t) %
\Bigr\}A_r (\mathbf{k},t)~,, \notag \\
\dot{b}(-\mathbf{p},t)&=& -i\omega(\mathbf{p},t)b(-\mathbf{p},t)+b(-\mathbf{p%
},t)U_{(1)}(\mathbf{p},t) +a^+ (\mathbf{p},t)U_{(2)}(\mathbf{p},t) \notag \\
&&- ie(2\pi)^{-3/2}\int d^3 p_{1}\frac{d^3 k}{\sqrt{2k}}\; \delta(\mathbf{p}%
_1 -\mathbf{p}+\mathbf{k}) \Bigl\{[\bar{u}v]^{r}(\mathbf{p}_1,\mathbf{p},%
\mathbf{k};t) a^+ (\mathbf{p}_1,t) \notag \\
&&+ [\bar{v}v]^{r}(\mathbf{p}_1,\mathbf{p},\mathbf{k};t) b(-\mathbf{p}_1,t)%
\Bigr\}A_r (\mathbf{k},t)~, \notag \\
iA^{(\pm)}_r (\mathbf{k},t) &=& \mp k A^{(\pm)}_r (\mathbf{k},t)\mp
e(2\pi)^{-3/2}\frac{1}{\sqrt{2k}} \int d^3 p_1 d^3 p_2\; \delta(\mathbf{p}_1
-\mathbf{p}_2 \mp\mathbf{k}) \notag \\
&& \Bigl\{a^+(\mathbf{p}_1,t) [\bar{u}u]^{r}(\mathbf{p}_1 ,\mathbf{p}_2,%
\mathbf{k};t)a(\mathbf{p}_2 ,t) +a^+(\mathbf{p}_1,t) [\bar{u}v]^{r}(\mathbf{p%
}_1 ,\mathbf{p}_2 ,\mathbf{k};t)b^+(-\mathbf{p}_2 ,t) \notag \\
&& +b(-\mathbf{p}_1,t)[\bar{v}u]^{r}(\mathbf{p}_1 ,\mathbf{p}_2,\mathbf{k}%
;t) a(\mathbf{p}_2 ,t) + b(-\mathbf{p}_1,t)[\bar{v}v]^{r}(\mathbf{p}_1 ,%
\mathbf{p}_2,\mathbf{k};t) b^+ (-\mathbf{p}_2 ,t)\Bigr\}~. \label{24e}
\end{eqnarray} \begin{eqnarray}
\dot{a}(\mathbf{p},t) &=& -i\omega(\mathbf{p},t)a(\mathbf{p},t)-U_{(1)}(%
\mathbf{p},t)a(\mathbf{p},t) -U_{(2)}(\mathbf{p},t)b^+ (-\mathbf{p},t)
\notag \\
&&+ ie(2\pi)^{-3/2}\int d^3 p_{1}\frac{d^3 k}{\sqrt{2k}}\; \delta(\mathbf{p}-%
\mathbf{p}_1 +\mathbf{k}) \Bigl\{a(\mathbf{p}_1,t)[\bar{u}u]^{r}(\mathbf{p},%
\mathbf{p}_1 ,\mathbf{k};t) \notag \\
&&+ b(-\mathbf{p}_1,t)[\bar{u}v]^{r}(\mathbf{p},\mathbf{p}_1,\mathbf{k} ;t) %
\Bigr\}A_r (\mathbf{k},t)~,, \notag \\
\dot{b}(-\mathbf{p},t)&=& -i\omega(\mathbf{p},t)b(-\mathbf{p},t)+b(-\mathbf{p%
},t)U_{(1)}(\mathbf{p},t) +a^+ (\mathbf{p},t)U_{(2)}(\mathbf{p},t) \notag \\
&&- ie(2\pi)^{-3/2}\int d^3 p_{1}\frac{d^3 k}{\sqrt{2k}}\; \delta(\mathbf{p}%
_1 -\mathbf{p}+\mathbf{k}) \Bigl\{[\bar{u}v]^{r}(\mathbf{p}_1,\mathbf{p},%
\mathbf{k};t) a^+ (\mathbf{p}_1,t) \notag \\
&&+ [\bar{v}v]^{r}(\mathbf{p}_1,\mathbf{p},\mathbf{k};t) b(-\mathbf{p}_1,t)%
\Bigr\}A_r (\mathbf{k},t)~, \notag \\
iA^{(\pm)}_r (\mathbf{k},t) &=& \mp k A^{(\pm)}_r (\mathbf{k},t)\mp
e(2\pi)^{-3/2}\frac{1}{\sqrt{2k}} \int d^3 p_1 d^3 p_2\; \delta(\mathbf{p}_1
-\mathbf{p}_2 \mp\mathbf{k}) \notag \\
&& \Bigl\{a^+(\mathbf{p}_1,t) [\bar{u}u]^{r}(\mathbf{p}_1 ,\mathbf{p}_2,%
\mathbf{k};t)a(\mathbf{p}_2 ,t) +a^+(\mathbf{p}_1,t) [\bar{u}v]^{r}(\mathbf{p%
}_1 ,\mathbf{p}_2 ,\mathbf{k};t)b^+(-\mathbf{p}_2 ,t) \notag \\
&& +b(-\mathbf{p}_1,t)[\bar{v}u]^{r}(\mathbf{p}_1 ,\mathbf{p}_2,\mathbf{k}%
;t) a(\mathbf{p}_2 ,t) + b(-\mathbf{p}_1,t)[\bar{v}v]^{r}(\mathbf{p}_1 ,%
\mathbf{p}_2,\mathbf{k};t) b^+ (-\mathbf{p}_2 ,t)\Bigr\}~. \label{24e}
\end{eqnarray}](https://dxdy-03.korotkov.co.uk/f/e/d/b/edb5c246c3b7ce8a6eaf8c7ca593bd1082.png)
получаем
![\begin{eqnarray}
\biggl\{\frac{\partial}{\partial t}&+& i[\omega(\mathbf{p}_1,t)+\omega(%
\mathbf{p}_2,t)-k]\biggr\} \langle b_{\alpha}(-\mathbf{p}_{1},t)a_{\beta}(%
\mathbf{p}_2 ,t) A_{r} ^{(+)} (\mathbf{k},t)\rangle = \notag \\
&=&-ie(2\pi)^{-3/2}\int d^3 p^{\prime} \frac{d^3 k^{\prime}}{\sqrt{%
2k^{\prime}}}\Bigl\{ \delta(\mathbf{p}^{\prime}-\mathbf{p}_1 +\mathbf{k}%
^{\prime})\cdot \notag \\
&\cdot& \left[ [\bar{u}v]^{r^\prime}_{\alpha\beta^\prime} (\mathbf{p}^\prime,%
\mathbf{p}_1,\mathbf{k}^{\prime};t) \langle a^{+}_{\beta^{\prime}}(\mathbf{p}%
^{\prime},t) a_{\beta}(\mathbf{p}_2 ,t)A_{r^{\prime}} (\mathbf{k}%
^{\prime},t) A_{r}^{(+)} (\mathbf{k},t)\rangle \right. \label{29e} \\
&+&\left. [\bar{v}v]^{r^{\prime}}_{\alpha\beta^{\prime}} (\mathbf{p}%
^{\prime},\mathbf{p}_1 ,\mathbf{k}^{\prime};t) \langle b_{\beta^{\prime}}(-%
\mathbf{p}^{\prime},t) a_{\beta}(\mathbf{p}_2 ,t) A_{r^{\prime}} (\mathbf{k}%
^{\prime},t) A_{r} ^{(+)} (\mathbf{k},t)\rangle \right] \notag \\
&-&\delta(\mathbf{p}_2 -\mathbf{p}^{\prime}+\mathbf{k}^{\prime}) \cdot \left[
[\bar{u}u]^{r^{\prime}}_{\beta^{\prime}\beta} (\mathbf{p}_2 ,\mathbf{p}%
^{\prime},\mathbf{k}^{\prime};t) \langle b_{\alpha}(-\mathbf{p}%
_1,t)a_{\beta^{\prime}}(\mathbf{p}^{\prime},t) A_{r^{\prime}} (\mathbf{k}%
^{\prime},t) A_{r}^{(+)} (\mathbf{k},t)\rangle \right. \notag \\
&+& \left.[\bar{u}v]^{r^{\prime}}_{\beta^{\prime}\beta} (\mathbf{p}_2 ,%
\mathbf{p}^{\prime},\mathbf{k}^{\prime};t) \langle b_{\alpha}(-\mathbf{p}%
_1,t) b_{\beta^{\prime}}^+ (-\mathbf{p}^{\prime},t) A_{r^{\prime}} (\mathbf{k%
}^{\prime},t) A_{r} ^{(+)} (\mathbf{k},t)\rangle \right] \Bigr\} \notag \\
&+& S^r_{\alpha\beta}(\mathbf{p}_1 ,\mathbf{p}_2 ,\mathbf{k};t)
+U^r_{\alpha\beta}(\mathbf{p}_1 ,\mathbf{p}_2 ,\mathbf{k};t)~. \notag
\end{eqnarray} \begin{eqnarray}
\biggl\{\frac{\partial}{\partial t}&+& i[\omega(\mathbf{p}_1,t)+\omega(%
\mathbf{p}_2,t)-k]\biggr\} \langle b_{\alpha}(-\mathbf{p}_{1},t)a_{\beta}(%
\mathbf{p}_2 ,t) A_{r} ^{(+)} (\mathbf{k},t)\rangle = \notag \\
&=&-ie(2\pi)^{-3/2}\int d^3 p^{\prime} \frac{d^3 k^{\prime}}{\sqrt{%
2k^{\prime}}}\Bigl\{ \delta(\mathbf{p}^{\prime}-\mathbf{p}_1 +\mathbf{k}%
^{\prime})\cdot \notag \\
&\cdot& \left[ [\bar{u}v]^{r^\prime}_{\alpha\beta^\prime} (\mathbf{p}^\prime,%
\mathbf{p}_1,\mathbf{k}^{\prime};t) \langle a^{+}_{\beta^{\prime}}(\mathbf{p}%
^{\prime},t) a_{\beta}(\mathbf{p}_2 ,t)A_{r^{\prime}} (\mathbf{k}%
^{\prime},t) A_{r}^{(+)} (\mathbf{k},t)\rangle \right. \label{29e} \\
&+&\left. [\bar{v}v]^{r^{\prime}}_{\alpha\beta^{\prime}} (\mathbf{p}%
^{\prime},\mathbf{p}_1 ,\mathbf{k}^{\prime};t) \langle b_{\beta^{\prime}}(-%
\mathbf{p}^{\prime},t) a_{\beta}(\mathbf{p}_2 ,t) A_{r^{\prime}} (\mathbf{k}%
^{\prime},t) A_{r} ^{(+)} (\mathbf{k},t)\rangle \right] \notag \\
&-&\delta(\mathbf{p}_2 -\mathbf{p}^{\prime}+\mathbf{k}^{\prime}) \cdot \left[
[\bar{u}u]^{r^{\prime}}_{\beta^{\prime}\beta} (\mathbf{p}_2 ,\mathbf{p}%
^{\prime},\mathbf{k}^{\prime};t) \langle b_{\alpha}(-\mathbf{p}%
_1,t)a_{\beta^{\prime}}(\mathbf{p}^{\prime},t) A_{r^{\prime}} (\mathbf{k}%
^{\prime},t) A_{r}^{(+)} (\mathbf{k},t)\rangle \right. \notag \\
&+& \left.[\bar{u}v]^{r^{\prime}}_{\beta^{\prime}\beta} (\mathbf{p}_2 ,%
\mathbf{p}^{\prime},\mathbf{k}^{\prime};t) \langle b_{\alpha}(-\mathbf{p}%
_1,t) b_{\beta^{\prime}}^+ (-\mathbf{p}^{\prime},t) A_{r^{\prime}} (\mathbf{k%
}^{\prime},t) A_{r} ^{(+)} (\mathbf{k},t)\rangle \right] \Bigr\} \notag \\
&+& S^r_{\alpha\beta}(\mathbf{p}_1 ,\mathbf{p}_2 ,\mathbf{k};t)
+U^r_{\alpha\beta}(\mathbf{p}_1 ,\mathbf{p}_2 ,\mathbf{k};t)~. \notag
\end{eqnarray}](https://dxdy-02.korotkov.co.uk/f/1/3/1/131e3811eb242d6d04e6b0ffc6d9a37e82.png)
могут быть опечатки. Вопрос, как получается последнее выражение, желательно на пальцах объяснить)
Я не профессиональный физик. Я любитель, физических факультетов не заканчивал (
Надеюсь, что найдется человек, который сможет помочь