Model of formation of broken dislocation boundaries at joint disclinations

We propose a physical model of formation of broken dislocation boundaries (partial disclinations of deformation origin) at the joints of large-angle grain boundaries. The model explains why and how rotational-type defects are necessarily formed in polycrystals in which plastic deformation at the microscopic level occurs exclusively via translational slips for strains ε > 0.2.     

Model of local melting of grain boundaries containing impurity atom clusters

A model describing the initial stages of the local melting of grain boundaries containing impurity atom clusters is developed. The local melting process is considered as the formation of liquid zones whose geometry and number depend on the initial concentration and thermodynamic characteristics of the impurity atoms, as well as on the material parameters and temperature. The evolution of the liquid-solid interface structure with increasing temperature is discussed. The dependences of the liquid-solid interface parameters on temperature are obtained at various initial concentrations and thermodynamic characteristics of the impurity atoms.     

Comparison of the processes of Higgs boson pair production and associated production of a radion and a Higgs boson

It is demonstrated that a radion and a Higgs boson are similar up to the replacement of masses and coupling constants (m _r → m _h and Λ _r → v ₀) in the processes of their single production and the additional rescaling of the coupling constant at the cubic self-action of a Higgs boson \(\left( {1 \to 1 + \frac{{m_r^2 - m_h^2}}{{3m_h^2}}} \right)\) in the processes of their associated production.     

Spontaneous phase symmetry breaking in a four-frequency ring gas laser

Lasing regimes of a single-mode four-frequency class-A ring gas laser with elliptical polarization of the emitted waves are studied numerically. Stationary regimes typical of both standing-and traveling-wave lasing are discovered. Self-oscillations exhibiting the properties of asymmetric and symmetric limit cycles are also found. It is shown that transition between cycles with different symmetry may result in the spontaneous phase symmetry breaking and the appearance of chaos arising due to the period doubling bifurcation cascade of the asymmetric limit cycle.     

Similarity and differences between the radion and Higgs boson production and decay processes involving off-shell fermions

The radion is a scalar particle that occurs in brane world models and interacts with the trace of the energy–momentum tensor of the Standard Model (SM). The radion–SM fermion interaction Lagrangian differs from the Higgs boson–fermion interaction Lagrangian for off-shell fermions. It is shown that all additional, as compared to the Higgs boson, contributions to the amplitudes of radion production and decay processes involving off-shell fermions are canceled out for both massless and massive fermions. Thus, additional terms in the interaction Lagrangian do not change properties of these processes for the radion and the Higgs boson, except for the general normalization factors. This similarity is a consequence of gauge invariance for the processes with production of gauge bosons. When an additional scalar particle is produced, there are no apparent reasons for the above cancellation, as confirmed, for example, by the process with production of two scalar particles, which features an additional contribution of the radion in comparison with the Higgs boson.     

Polarization-phase dynamics in a four-frequency gas ring laser with elliptical polarization of counter-propagating waves

Based on a developed and experimentally tested model, self-oscillatory lasing regimes have been studied for a Class A four-frequency gas ring laser with linear coupling of elliptically polarized counter-propagating waves. In the self-oscillatory regime, switching of the intensities, polarization states, and phase differences of the counter-propagating waves is observed, and also a polarization-phase dynamics effect involving displacement of the intensity switching point (with respect to detuning), due to the phase shift as a result of an ellipticity different from zero. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 620–625, September–October, 2006.     

Structural transformations at the initial stages of fragmentation of plastically deformed polycrystals: A computer experiment

Results have been presented for a computer experiment on concurrent micro-, meso-, and macroscopic studies of the evolution of dislocation structure in a large (adjacent to one of the junctions) domain of a grain after its constant-rate macroplastic deformation to an extent that corresponds to the onset of the stage of developed plastic deformation. The type of dislocation-density and dislocation-charge distributions, as well as amounts and degrees of inhomogeneity in local plastic deformation, have been analyzed. The type of dislocation rearrangements at the junctions and fractures of high-angle grain boundaries has been established, which is responsible for the formation of the first dangling dislocation boundaries, which are mesodefects that trigger fragmentation.     

High-speed superplasticity of microcrystalline alloys under conditions of local grain boundary melting

A model is proposed for the high-speed superplasticity of materials under conditions of local grain boundary melting at temperatures close to solidus. It is shown that the local melting of grain boundaries containing segregations of impurity atoms, results in the formation of a structure consisting of liquid-phase regions and solid intergranular bridges which provide cohesion of the grains during the deformation process. The equilibrium concentration, dimensions, and activation energy for the formation of solid bridges are determined as a function of the temperature, initial impurity concentration in the boundary, and the boundary thickness. A mechanism is proposed for grain-boundary slip under conditions of local grain boundary at anomalously high strain rates. Zh. Tekh. Fiz. 68, 38–42 (December 1998)     

Polarization instability in lasers with weakly anisotropic cavities

A theoretical study is made of the influence of the active medium and the cavity parameters, as well as that of an external magnetic field, on the properties of spontaneous pulsation regimes of lasers with weakly anisotropic cavities. Our results provide a physical interpretation of recently reported experimental data for spontaneous intensity pulsations of orthogonal components of the electromagnetic field generated by a single-mode, Fabry-Perot, HeNe gas laser at λ = 3.3922 μm and by a HeXe laser at λ = 3.51 μm.