## 8 Conclusions  
We have obtained on a nonperturbative basis the KE for describing electron-hole excitations in graphene under the action of a spatially homogeneous time dependent electric field. To this end the analogy with the well-developed case of kinetic theory of vacuum \(e^{+}e^{-}\) plasma generation in strong fields [8; 10] in \(D=3+1\) QED has been used. As a rule, we used the simplest low energy model. However, the used method admits a straightforward generalization to other realistic models of the carrier dynamics as, e.g., the tight binding model of nearest neighbour interaction. The derivation of the KE is based on the transition to the quasiparticle representation [6]. As shown in Section 2, in the \(D=2+1\) QED model of graphene such a derivation can be given in an explicit form with the help of a unitary transformation first introduced in the work [15] for the linearly polarized electric field. It is important that the final KE is valid in the general case of an arbitrarily polarized electric field. Some features of the obtained KE are discussed in that Section. In particular, the non applicability of the standard perturbation theory in vicinity of the Dirac lines has been demonstrated. However, the corresponding approximate analytical and numerical nonperturbative solutions (e.g., the Markovian approximation) of the KE provide a correct description in physical terms in the entire momentum space. In Section 2.2 we consider also some general properties of the evolution of the excited electron-hole plasma that allow to interpret this phenomenon as a specific field induced phase transition [10, 16]. An important characteristics of this process is an order parameter that continues to oscillate in the out-state after the external field pulse ceases. The connection of the observables with both, the distribution function and the polarization functions has been discussed in Section 3. The damped oscillations of the residual polarization current on the background of a conduction current were considered in Section 4. The character of these oscillations is related to features of the external field pulse. The damped oscillations of the polarization current in a constant electric field have demonstrated a similar nature. Apparently, these effects are accessible to experimental observation. It can be assumed that similar phenomena occur in \(D=3+1\) QED. Here too it was shown that the polarization current dominates over the conduction current. We have performed a systematic numerical investigation based on the KE for the distribution function of quasiparticle excitations and the corresponding observable values for various models of the external electric field. We have discussed the possibility of using graphene as an active medium excited by the basic electric field to be probed by another signal current (\"pump-and-probe\"). Finally, we have derived an analogous KE for the tight binding model that is substantially nonperturbative. In the framework of this model we have obtained and discussed the conduction and polarization currents. A verification of the developed theory was obtained in the work [31], where good agreement with experiment has been shown for the case of a constant electric field [32]. Let us note that both models considered here led KE's of identical form. Moreover, this form invariance is conserved also in the standard QED in the case of a linearly polarized electric field when the spin degrees of freedom are frozen. Conceptualization, S.A.S. and A.D.P. ; Validation, all authors; Data Curation, A.D.P. and N.T.G. ; Writing--Original Draft Preparation, S.A.S. and A.D.P. ; Writing--Review & Editing, D.B.B. and N.T.G. ; Visualization, A.D.P. and N.T.G. ; Funding Acquisition, S.A.S. and D.B.B. This research was supported in part by the \"RUDN University Program 5-100\", by RFBR according to the research project No 17-02-00375 A, and by the Polish NCN under grant number UMO-2014/15/B/ST2/03752. The authors thank [PERSON]. [PERSON], [PERSON], [PERSON] and [PERSON] for useful discussions.