Adsorption of Oil Substances by Carbon Monolith and Their Subsequent Determination by GC/GC/MS

Moscow University Chemistry Bulletin - A monolith based on foamed graphite is used for the sorption of hydrocarbons (alkanes, cycloalkanes, arenes) as markers of oil pollution. This material is...     

Behavior of solutions to the pion dispersion equation in the complex frequency plane

Solutions to the pion dispersion equation in the complex plane of the pion frequency ω are obtained for symmetric nuclear matter. Three well-known solution branches—a sound, a pion, and an isobar one—exist on the physical sheet at the medium density below its critical value (ρ<ρ_c). For ρ>ρ_c, the fourth branch ω_c appears on the physical sheet. The condition ω _c ² ≤0 is valid for this branch (in general, Re ω _c ² ≤0). This suggests ground-state instability, possibly associated with pion condensation. The behavior of these solutions is analyzed for various medium densities. The appearance of each solution on the physical sheet of the complex frequency plane and its disappearance are also studied.     

Influence of a polarization operator’s imaginary part on dispersion equation solutions

We consider solutions of the zero sound dispersion equation in the standard model of random phase approximation. A method for calculating solutions in the region of overlap between collective excitations and real particle-hole pairs is proposed. The method takes advantage of the analytical structure of the polarization operator. The solutions of dispersion equation with the full polarization operator Π(ω, k) and with the Re Π(ω, k) are compared.     

Evaluating emission widths of giant dipole resonances in a Fermi liquid model

It is shown in the theory of finite Fermi systems that giant resonances can be considered as zero-sound excitations in concrete nuclei. Solutions to the zero-sound dispersion equation in symmetric nuclear matter, ωs(k), are obtained. Hydrodynamic models determine the wave vector k _A corresponding to giant resonance in a nucleus with atomic number A. The real and imaginary parts of ωs(k _A ) compare to the energy and escape width of giant resonance. Calculations are performed for giant dipole resonances.     

Dependence of nucleon parameters on condensates in QCD sum rules

The vacuum-condensate dependence of nucleon parameters is investigated within QCD sum rules. It is shown that, without allowance for radiative corrections, a solution to the sum-rule equations exists only under stringent constraints on condensate values. There is only an unphysical solution beyond the region specified by these constraints. It is found that the nucleon-mass value is stabilized upon taking into account radiative corrections.     

Connection between Zero-Sound Excitations in Symmetric and Asymmetric Nuclear Matter

Physics of Atomic Nuclei - A method for calculating frequencies of zero-sound excitations in symmetric and isospin-asymmetric nuclear matter is presented. In asymmetric matter, three branches of...     

Branches of zero sound excitations in asymmetric nuclear matter: The dependence on density

Results from calculating zero sound excitations in isospin asymmetric nuclear matter are presented. A polarization operator constructed in the random phase approximations is used in the calculations. Three branches of the complex solutions ω_sτ(k), τ = p,n,np are presented. The type of branch depends on that of the considered branch damping. An imaginary part of the solution corresponds to the damping of collective excitations due to mixing with the background of noninteracting (1) proton particle–hole pairs (ω _sp (k)), (2) neutron particle–hole pairs (ω _sn (k)), and (3) both proton and neutron particle–hole pairs (ω _snp (k)). The behavior of the solutions upon variations in density depends on the value of the asymmetry parameter.     

Use of the Bogoliubov method of compensating “dangerous” diagrams to investigate magnetic superconductors

The gauge model in superconductivity theory describes a multiparticle dynamic system in a constant external field of the vector (electromagnetic) potential. The Hamiltonian of this dynamic system models a superconducting antiferromagnet and contains electron-boson interactions of the second (Fröhlich Hamiltonian) and fourth (exchange interaction)_orders in the electron operators. This Hamiltonian accounts for the interaction of the magnetic moments of the conductance electrons. The bosonic spectrum of the system consists of normal modes of the coupled phonon-magnon oscillations. We obtain a system of equations describing a simultaneous compensation of the “dangerous” diagrams (those leading to energy divergence in the perturbation theory) corresponding to the creation of two (bivertex) or four (tetravertex) electron excitations from the vacuum. We find a solution of this system of equations corresponding to the superconducting state.