Heavy Hadrons and QCD Instantons

Heavy hadrons are analyzed in a random and dilute gas of instantons. We derive the instanton-induced interactions between heavy and light quarks at next to leading order in the heavy quark mass and in the planar approximation, and discuss their effects on the hadronic spectrum. The role of these interactions in the formation of exotic hadrons is also discussed.Comment: 26 pages, REVTeX, 2 tables, 5 figures, uses FEYNMAN.st

Field-induced decay dynamics in square-lattice antiferromagnet

Dynamical properties of the square-lattice Heisenberg antiferromagnet in applied magnetic field are studied for arbitrary value S of the spin. Above the threshold field for two-particle decays, the standard spin-wave theory yields singular corrections to the excitation spectrum with logarithmic divergences for certain momenta. We develop a self-consistent approximation applicable for S >= 1, which avoids such singularities and provides regularized magnon decay rates. Results for the dynamical structure factor obtained in this approach are presented for S = 1 and S = 5/2.Comment: 12 pages, 11 figures, final versio

Using the simulation modeling with stochastic estimation of trafficability of forest transport systems

Forecasting trafficability of logging and forest transport systems on the ground, which have a multi-sectional layout solution is considered in the paper. Trafficability problems are evaluated from the point of view of the stochastic character of indicators of traction properties - the forces of resistance to movement and the adhesion force of the driving wheels with the supporting surface. With the stochastic estimation of trafficability the law of Gaussian distribution for random values of the rolling resistance coefficient and the two-parameter Weibull distribution law with a negative asymmetry coefficient or values of the shape parameter greater than 4 for the cohesion coefficient was adopted. A stochastic approach to the evaluation of trafficability allows to ensure a rational distribution of the power flows between propulsors of the transport-technological system, which is shown in this paper. © 2019 Published under licence by IOP Publishing Ltd

Acoustic instability of a circular vortex with a smoothed vorticity profile

It is known that a localized vortex can have two specific mechanisms of interaction with the ambient flow. The first mechanism is associated with acoustic radiation, which is accompanied by a loss of energy and causes instability in the case of negative energy of vortex disturbances. The second is a Miles mechanism of interaction of the vortex core oscillations with disturbances in the vicinity of the critical layer (where the phase velocity of the disturbances coincides with the velocity of the mean flow), accompanied by an energy flux from the critical layer vicinity, which leads to damping in the case of negative energy of the oscillations. For the first time, the flow with both of these mechanisms is considered. The problem is solved from the first principles. It is shown that the Miles mechanism can completely suppress acoustic instability, however, in the case of a stronger loss of energy due to acoustic radiation, acoustic instability will dominate. The role of various parameters is analyzed and a quantitative criterion for the acoustic instability of a vortex with a smoothed vorticity profile is obtained

Using the simulation modeling with stochastic estimation of trafficability of forest transport systems

Forecasting trafficability of logging and forest transport systems on the ground, which have a multi-sectional layout solution is considered in the paper. Trafficability problems are evaluated from the point of view of the stochastic character of indicators of traction properties - the forces of resistance to movement and the adhesion force of the driving wheels with the supporting surface. With the stochastic estimation of trafficability the law of Gaussian distribution for random values of the rolling resistance coefficient and the two-parameter Weibull distribution law with a negative asymmetry coefficient or values of the shape parameter greater than 4 for the cohesion coefficient was adopted. A stochastic approach to the evaluation of trafficability allows to ensure a rational distribution of the power flows between propulsors of the transport-technological system, which is shown in this paper. © 2019 Published under licence by IOP Publishing Ltd