MeV/nucleon, while it is only 10 fm/c at E = 600 MeV/nucleon. This clearly indicates that the matter shows high-density behavior only for a small time interval, which decreases with increasing incident energy. Since we are interested in the sensitivities of different kinds of fragments and their neutron-to-proton ratios, only those fragments that lie in the high-density region ($\rho>\rho_0$) will be sensitive to the high-density behavior of the symmetry energy.

![\[fig:2\](Color online) Time evolution of free nucleons (top), LCPs (middle), and IMFs (bottom) at semicentral geometry for $^{132}$Sn + $^{132}$Sn using the soft symmetry energy ($\gamma_i=0.5$). The different lines have the same meaning as in Fig. \[fig:1\]. The vertical line in each panel represents our time limit before which the system can be in the supra-saturation region (refer to Fig. 1).](figure2.eps){width="90mm"}

To check the sensitivities of different kind of fragments, in Fig. \[fig:2\] we display time evolution of free nucleons (top), LCPs (middle), and IMFs (bottom) at semicentral geometry for incident energies ranging from 50 to 600 MeV/nucleon. The behavior for all kinds of fragments is consistent with the results in the literature [@Kuma08]. The production of free nucleons increases with incident energy, and LCP production decreases after 400 MeV/nucleon. 