**5. Conclusions**

We have presented a study of D *χ*SB in QED3, including an exact computation of 1/*N*<sup>2</sup> corrections to the SD equation and considering the full *ξ*-dependence of the gap equation. Following Nash, the renormalization constant of the wave function was resummed at the level of the gap equation, which led to a gauge-invariant critical number of fermion flavours, *Nc* = 2.85, in full accordance with the result of Ref. [29].

As noted in [49,52–54], the limit of the large *N* for the photon propagator in QED3 has exactly the same dependence on momentum as in the so-called reduced QED [55–59]. One of the differences is that the gauge fixing parameter in reduced QED is half as much as in QED3. This difference can be accounted for using our current QED3 results along with multi-loop results obtained in [48,49,52–54]. The case of reduced QED and its relation to the generation of a dynamic gap in graphene, which is the subject of active current research, see, e.g., reviews [60–62], were considered in our article [63].

**Author Contributions:** Investigation, A.V.K. and S.T., Writing—original draft, A.V.K. and S.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** A.V.K. thanks the Organizing Committee of II International workshop Theory of Hadronic Matter under Extreme Conditions for their invitation.

**Conflicts of Interest:** The authors declare no conflict of interest.
