Vol 105, No 11 (2017)

Nonperturbative effects in the quark–gluon thermodynamics are studied in the framework of vacuum correlator method. It is shown, that for T > T₀ = 175 MeV two correlators: colorelectric D₁^E(x) and colormagnetic D^H (x), provide the Polyakov line and the colormagnetic confinement in the spatial planes respectively. As a result, both effects produce the realistic behavior of p(T) and I(T), being in good agreement with numerical lattice data.

We discuss the polar phase of ³He, which is realized in the anisotropic aerogel. We consider it in the framework of the BCS model. In the absence of the spin–orbit interaction, this model predicts the appearance of the Fermi line. However, it is topologically unstable. We demonstrate that the spin–orbit interaction gives rise to the appearance of the two Fermi points instead of the Fermi line. In addition to the gapless Nambu–Goldstone bosons in this system the collective gapped bosonic states exist. Their gaps are calculated, and the corresponding Nambu sum rule is established.

An alternative treatment of the well-known effect of a decrease in the Morin transition temperature in hematite with a decrease in the size of crystallites to the complete disappearance of the transition for nanoparticles smaller than 20 nm is proposed. In contrast to the standard speculative explanation of this effect in terms of the effect of surface and defectiveness of grains, we suggest that the decisive factor is an increase in the contribution of the shape anisotropy of particles with a decrease in their size, which is responsible for the spread of orientations of the axes of the resulting magnetic anisotropy with respect to the crystallographic axes. Our reasons are confirmed by a numerical analysis of Mössbauer spectra of hematite nanoparticles within the continuous model of magnetic dynamics of an ensemble of antiferromagnetic nanoparticles in the two-sublattice approximation generalized to the existence of weak ferromagnetism (Dzyaloshinskii interaction).

Solutions of the equation for the superconducting gap including superexchange, spin–fluctuation, plasmon, and phonon pairing mechanisms are obtained. Solutions of the Bardeen–Cooper–Schrieffer equation are approximated by the expression Δ_k = Δ₀(B cos(2ϕ) + (1 − B)cos(6ϕ) at a carrier concentration close to optimal. It is found that the dependence proportional to cos(6ϕ) is due to the spin–fluctuation and phononmediated interactions.

Subablative exposure of tightly focused visible-range femtosecond laser pulses on a thin translucent nanocrystalline copper(I) oxide on a silica glass substrate results not only in its annealing (resolidification), but apparently also in reduction of copper ions to the metallic state via single-photon absorption and the following thermal decomposition (disproportioning). Partial or complete ablation of the film within the laser focal spot and also its subablative optically contrast modification through formation of colloidal nanoparticles or annealing (resolidification) make it possible to consider this material in the thin-film form as a novel optical platform for direct laser writing of vis-IR metasurfaces and thin-film sensing plasmonic and all-dielectric nanostructures.

Processes of single and pair production of heavy quarkonia under LHC conditions have been studied within nonrelativistic quantum chromodynamics. Constraints on the matrix elements of color-singlet and color-octet states have been obtained by analyzing the existing experimental data. It has been shown that the leading contribution to the cross sections for these processes comes from the color singlet mechanism with the singlet matrix elements exceeding phenomenological values obtained from the solutions of potential models or experimental decay widths of the corresponding mesons. It has also been found that the contribution from color-octet states should be taken into account to describe the ratio of the cross sections for the production of tensor and axial charmonia. These results have been used to analyze the single production of bottomonia, the pair production of heavy quarkonia, and the production of vector charmonium in jets. The resulting theoretical predictions are in good agreement with experimental data.