Formula_1356

\[\begin{gathered}\frac{\partial B_{L L}}{\partial t}=\left(\frac{\partial}{\partial r}+\frac{4}{r}\right)\left(B_{L L, L}+2 v \frac{\partial B_{L L}}{\partial r}\right) ; \\B_{L L}(r, t)=\left\langle u_{L}(\boldsymbol{x}, t) u_{L}(\boldsymbol{x}+\boldsymbol{r}, t)\right\rangle ; \\B_{L L, L}(r, t)=\left\langle u_{L}^{2}(\boldsymbol{x}, t) u_{L}(\boldsymbol{x}+\boldsymbol{r}, t)\right\rangle .\end{gathered}\]