**5. Conclusions**

We studied the gluon propagators in *Nf* = 2 *SU*(2) QCD at *T* = 0 in the domain 0 < *μq* < 1.4 GeV, 0 < *p* < 6.5 GeV. It was found that both longitudinal and transverse propagators depend on the chemical potential both at low and high momenta.

**At low momenta,** we describe this dependence in terms of the chromoelectric (*mE*) and chromomagnetic (*mM*) screening masses using two definitions: Linde screening masses *mE*,*<sup>M</sup>* and proper screening masses *m*˜ *E*,*M*. We found a good agreemen<sup>t</sup> between the two definitions of the chromoelectric screening mass at least at *μq* > 0.3 GeV. *mE* increases substantially with *μq* and can be fitted by the function (17).

The case of the chromomagnetic screening mass is more complicated: we find only a rough agreemen<sup>t</sup> between the two definitions. The Linde mass *mM* can be evaluated more precisely; it depends only weakly on *μq* and can be fitted well by a constant at *μq* < 0.8 GeV. At higher *μq* one can see decreasing of *mM* which agrees with decreasing of *σs*. Results for higher values of *μq* are needed to decide whether *mM* goes to zero at large *μq* as was argued in Reference [43]. In any case, the difference between *mE* and *mM* shows a substantial growth with *μq* starting at *μq* ≈ 0.3 GeV (see Figure 2).

#### *Particles* **2020**, *3*

It should be emphasized that our findings do not agree with the results of Reference [24], where it was concluded that *(i) mM* comes close to *mE* for all *μq* and *(ii)* both screening masses depend only weakly on *μq*.

However, since the physical lattice size used in our study is not large, *DL*(0) and *DT*(0) are potentially subject to finite-volume effects, see discussion between Figures 2 and 3.

**At high momenta,** we used the perturbatively motivated fit function (21) and described *<sup>μ</sup>q*-dependence of the propagators *DT*,*<sup>L</sup>* in terms of the scaling parameters Λ*T*,*<sup>L</sup>* that appear in formulas like (21) for *DT* and *DL*.

Λ*L* shows a slow decrease with increasing *μq*, whereas Λ*T* =const at *μq* < 750 MeV and shows a linear growth at higher values of *μq*. A sharp change in the behavior of <sup>Λ</sup>*T*(*μq*) occurs at *μq* where the spatial string tension *σs* peaks (see Reference [16]).

**Author Contributions:** Conceptualization, R.R. and V.B.; Data curation, A.N.; Formal analysis, R.R. and A.K.; Investigation, R.R. and V.B.; Methodology, V.B. and A.K.; Project administration, V.B.; Software, A.K. and A.N.; Validation, A.K.; Visualization, R.R.; Writing—original draft, R.R.; Writing—review and editing, V.B. and A.N. All authors have read and agree to the published version of the manuscript.

**Funding:** The work was completed due to support of the Russian Foundation for Basic Research via gran<sup>t</sup> 18-02-40130 mega (analysis of gluon propagators) and via gran<sup>t</sup> 18-32-20172 (gauge fixing and Gribov copy effects analysis). A. A. N. acknowledges support from STFC via gran<sup>t</sup> ST/P00055X/1.

**Acknowledgments:** The authors are grateful to V. V. Braguta for useful discussions. Computer simulations were performed on the IHEP (Protvino) Central Linux Cluster, ITEP (Moscow) Linux Cluster, the shared research facilities of HPC computing resources at Lomonosov Moscow State University, and the federal collective usage center Complex for Simulation and Data Processing for Mega-science Facilities at NRC "Kurchatov Institute", http://ckp.nrcki.ru/.

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