the system remains disordered up to a certain incubation time $\tau_{inc}$. The metastability of the ordered phase is reflected by plateaus in $\Delta E(t)$, which develop near $T_f\simeq T_{sp}$, and extend with increasing $T_f$. Second, $\Delta E(t)$ drops markedly when overcritical nuclei are produced by thermal fluctuations. We define $\tau_{inc}(T)$ as precisely that moment after the quench at which, for a given temperature $T$, $\Delta E(t)$ drops notably (by about 10 percent) below its plateau–value. The ordered nuclei formed within the incubation time grow against the disordered bulk until, in a third stage, ordered regions meet and slow coarsening processes set in.

In addition to $\Delta E(t)$, we also show in Figure 5b and 5c how the corresponding first moments of the structure factors $S_{\alpha}(k_x,k_y,k_z,t)$ change with time. To account for the anisotropy illustrated in the domain patterns in Fig. 3a and b, we consider the two kinds of structure factors

$$S_{\parallel}(k,t) = \frac{1}{3}
                   (S_1(k,0,0,t)+S_2(0,k,0,t)+S_3(0,0,k,t)),$$

and

$$\begin{aligned}
S_{\perp}(k,t) &=& \frac{1}{N_k}\sum \limits_{q_1^2 + q_2^2=k^2}
     (S_1(0,q_1,q_2,t) \nonumber\\
   &&  + S_2(q_1,0,q_2,t) + S_3(q_1,q_2,0,t)),\end{aligned}$$

where $N_k$ denotes here the number of $(q_1,q_2)$ pairs that fulfill $q_1^2 + q_2^2 = k^2$, as well as their first moments

$$k_{\parallel}(t) = \frac{\sum_{k>0} k S_{\parallel}(k,t)}
                        {\sum_{k>0} S_{\parallel}(k,t)},$$

$$k_{\perp}(t) 