Том 117, № 9-10 (5) (2023)

It becomes difficult and expensive to control TeV-particle trajectories using electromagnets to obtain extracted beams at accelerators. For these purposes, high-gradient devices based on bent crystals are more suitable. These crystals can serve as superstrong lenses with a focal length of less than 1 m with an equivalent magnetic field of 1000 T. In this work, a scheme based on two successive focusing crystals has been implemented to form a 50 GeV axially symmetric beam with a small divergence of 30 μrad in both the horizontal and vertical planes. One of the promising applications of this scheme is the creation of high-energy neutrino beams.

The lateral distribution of particles in extensive air showers from cosmic rays with energy above 1017 eV registered at the Yakutsk complex array was analyzed. Experimentally measured particle densities were compared to the predictions obtained within frameworks of three ultra-high energy hadron interaction models. The cosmic ray mass composition estimated from the readings of surface-based and underground detectors of the array is consistent with estimations obtained from measurements of lateral distribution of the air showers Cherenkov light emission. A comparison was made with the results of direct measurement of the muon component performed at the Pierre Auger Observatory. It is demonstrated that the densities of muon flux measured at Yakutsk array are consistent with results of fluorescent light measurements and disagree with results on muons obtained at the Auger array.

Media with the dielectric permittivity 
 close to zero (epsilon-near-zero or ENZ) maintain conditions for enhanced light-matter interactions. In this paper, we propose to use these media to enhance the optomechanical coupling of vibrational excitations of the medium with the optical near-field of the nanoantenna. It is shown that the ENZ medium significantly increases the optically induced decay rate of a vibration, which can be used for cooling (when the incident light frequency is less than the ENZ frequency) or heating (when the incident light frequency is greater than the ENZ frequency). Due to the proximity of the refractive index to zero as well, oscillations of the polarization of the medium are coherent, which further enhances the optomechanical effects. Analytical expressions are obtained for the optical shift of the resonance and the induced decay rate.

Using stereographic projection approach, we develop a theory for calculation of dynamic susceptibility tensor of Skyrmion crystals (SkX), formed in thin ferromagnetic films with Dzyaloshinskii–Moriya interaction and in the external magnetic field. Staying whenever possible within analytical framework, we employ the model ansatz for static SkX configuration and discuss small fluctuations around it. The obtained formulas are numerically analyzed in the important case of uniform susceptibility, accessible in magnetic resonance experiments. We show that, in addition to three characteristic magnetic resonance frequencies discussed earlier both theoretically and experimentally, one should also expect several resonances of smaller amplitude at somewhat higher frequencies.

Full-potential, linearized augmented plane wave approach (FP LAPW), as employed in Wien2K code was utilized to analyze structural, elastic, optoelectronic, and transport features of NaCaSb and KCaSb half–Heusler (HH) compounds. Generalized gradient approximation (GGA) was considered for structural optimization. The predicted lattice constants are in line with the prior theoretical and experimental findings. The examined NaCaSb and KCaSb compounds are inherently ductile and mechanically stable. The investigated HHs are semiconductors with a band gap 1.27 and 1.23 eV for NaCaSb and KCaSb, respectively, in the modified Becke–Johnson (mBJ) approximation. Calculated optical characteristics of NaCaSb and KCaSb point to their potential applicability in optoelectronic devices. Thermoelectric features were analyzed employing the Boltzmann transport provided in the BoltzTraP software. At room temperature, the significant figure of merit (ZT) values indicates that the investigated NaCaSb and KCaSb can be used for fabricating thermoelectric devices with the highest possible efficiency.

Features of the formation of the magnetic structure and the exciton Bose–Einstein condensate phase of magnetic excitons in strongly correlated systems near the spin crossover have been considered with the effective Hamiltonian obtained from the two-band Hubbard–Kanamori model. The coexistence of antiferromagnetism and exciton condensate, as well as the appearance of the long-range excitonic antiferromagnetic order even in the absence of the interatomic exchange interaction, has been revealed. The role of the electron–phonon coupling has been considered.

An expression for the chiral separation effect in a quark–gluon plasma has been derived using the method of field correlators by expanding in Landau levels.

Anisotropic focusing by a mesoscopic (Mie size parameter of about 18) acoustic cubic lens based on V-shaped plate structures has been simulated numerically and confirmed experimentally. It has been shown for the first time that this lens with an edge dimension of about three wavelengths ensures the focusing of an acoustic wave in air into a diffraction-limited region. In the inverse geometry of the structure, the lens completely reflects the incident acoustic wave.

Design methods in the reciprocal space allow one to obtain structures with desired properties. Quasicrystalline photonic structures, which ensure the selective scattering of an electromagnetic wave incident on the sample, have been designed. The maxima of the Fourier transform of the desired distribution of the permittivity in the reciprocal space are located along two arcs on the Ewald sphere, which corresponds to the scattering of the wave with the required wavelength and angle of incidence. The material distribution has been determined by the transition to the real space. A structure with a low dielectric contrast has been formed after the binarization of the refractive index. The theoretical analysis of the properties of the structure has confirmed the frequency–angular selectivity of scattering. The numerical calculations show the possibility of achieving the effective scattering and absorption of the electromagnetic energy up to 94% in a narrow frequency range and in a narrow interval of angles of incidence at a dielectric contrast of two materials of 1.07.

The studies of a number of systems treated in terms of an inhomogeneous (spatially separated) Fermi–Bose mixture with superconducting clusters or droplets of the order parameter in a host medium with unpaired normal states are reviewed. A spatially separated Fermi–Bose mixture is relevant to superconducting Ba-KBiO3 bismuth oxides. Droplets of the order parameter can occur in thin films of a dirty metal, described in the framework of the strongly attractive two-dimensional Hubbard model at a low electron density with a clearly pronounced diagonal disorder. The Bose–Einstein condensate droplets are formed in mixtures and dipole gases with an imbalance in the densities of the Fermi and Bose components. The Bose–Einstein condensate clusters also arise at the center or at the periphery of a magnetic trap involving spin-polarized Fermi gases. Exciton and plasmon collapsing droplets can emerge in the presence of the exciton–exciton or plasmon–plasmon interaction. The plasmon contribution to the charge screening in MgB2 leads to the formation of spatially modulated inhomogeneous structures. In metallic hydrogen and metal hydrides, droplets can be formed in shock-wave experiments at the boundary of the first-order phase transition between the metallic and molecular phases. In a spatially separated Fermi–Bose mixture arising in an Aharonov–Bohm interference ring with a superconducting bridge in a topologically nontrivial state, additional Fano resonances may appear and collapse due to the presence of edge Majorana modes in the system.

The Mössbauer spectra of FeBO3 single crystals are studied at temperatures above and below the magnetic transition point at different orientations of the crystals with respect to the propagation direction of γ rays. To describe the Mössbauer spectra, a theoretical model is developed with allowance for different orientations of magnetic moments in the crystal plane. It is found that the magnetic domain structure in iron borate significantly affects the shape of the Mössbauer spectra and the intensity of resonant transitions. The proposed model may be useful for determining the configuration of the magnetic domain structure of materials from Mössbauer spectroscopy data.

COVID-19 has resulted in epidemic conditions over the world. Despite efforts by scientists from all over the world to develop an effective vaccine against this virus, there is presently no recognized cure for COVID-19. The most succeed treatments for various ailments come from natural components found in medicinal plants, which are also crucial for the development of new medications. This study intends to understand the role of the baimantuoluoamide A and baimantuoluoamide B molecules in the treatment of Covid19. Initially, density functional theory (DFT) used to explore their electronic potentials along with the Becke3–Lee–Yang–Parr (B3LYP) 6-311 + 
 basis set. A number of characteristics, including the energy gap, hardness, local softness, electronegativity, and electrophilicity, have also been calculated to discuss the reactivity of molecules. Using natural bond orbital, the title compound’s bioactive nature and stability were investigated. Further, both compounds potential inhibitors with main protease (Mpro) proteins, molecular dynamics simulations and AlteQ investigations also studied.