Probabilities of delayed processes for nuclei involved in the r-process

Delayed fission, along with induced and spontaneous fission, is responsible for the suppression of the production of superheavy elements both during the r-process and after its completion. Beta-decay strength functions are required for calculating delayed fission. In the present study, respective strength functions are calculated by relying on the theory of finite Fermi systems and by predominantly employing nuclear masses and fission barriers predicted by a generalized Thomas-Fermi model. The probabilities for delayed fission and for the emission of delayed neutrons are calculated for a number of isotopes. On the basis of calculations performed in order to determine the probabilities for delayed processes, it is shown that some of the delayed-fission probabilities calculated thus far were substantially overestimated. The application of these new results to calculating the r-process may change substantially both the r-process path and the yields of superheavy nuclei.     

Charge distribution in surface layers of polarized electret ceramics according to electron spectroscopy measurements

The anomalous electron emission (AEE) from the negative surface of a polarized SrTiO₃ ceramic sample is studied both experimentally and theoretically. The form of the low-energy edge and the fine structure of AEE spectra are interpreted within the “brick wall” model. The distribution of electric potential over the charged surface is calculated using Green’s functions under the assumption of p-type conduction of intergrain boundaries. It is demonstrated that the AEE spectra of SrTiO₃ ceramic surface mainly reflect the charge distribution in the polarized electret SrTiO₃ sample.     

Reaction-diffusion processes of hard-core particles

We study a 12-parameter stochastic process involving particles with two-site interaction and hard-core repulsion on ad-dimensional lattice. In this model, which includes the asymmetric exclusion process, contact processes, and other processes, the stochastic variables are particle occupation numbers taking valuesn _x=0,1. We show that on a ten-parameter submanifold thek-point equal-time correlation functions n _x1...n _xk satisfy linear differential-difference equations involving no higher correlators. In particular, the average density n _x satisfies an integrable diffusion-type equation. These properties are explained in terms of dual processes and various duality relations are derived. By defining the time evolution of the stochastic process in terms of a quantum HamiltonianH, the model becomes equivalent to a lattice model in thermal equilibrium ind+1 dimensions. We show that the spectrum ofH is identical to the spectrum of the quantum Hamiltonian of ad-dimensional anisotropic, spin-1/2 Heisenberg model. In one dimension our results hint at some new algebraic structure behind the integrability of the system.     

Self-organization of a system of dipole particles according to the keesom model

Self-organization of dipolar hard spherical particles at low temperatures was studied using the Monte Carlo method. Configurations of the principal stable structures formed by the particles upon the destabilization of homogeneous distribution were described. The possibility of the formation of structural domains of different symmetries and sizes commensurate with the volume of the system under certain circumstances was demonstrated. The dipole moment of the domains thus formed is considerably higher than that of the entire system. The existence of dipole interactions in the model apparently leads to the appearance of layered structures. The results we obtained can be used in the development of biotechnologies involving the use of synthetic magnetic particles for targeted delivery of chemotherapeutics into an affected organ, as contrast agents in magnetic resonance imaging, and for the studies of magnitotaxis mechanisms.     

Effect of triple gluon coupling in semi-inclusive polarized scattering processes

We show that the gluon helicity inside a proton and a photon can be deduced from a knowledge of a special combination of cross sections of the semi-inclusive processese+p→e+π+π+... ande ⁺+e ^?→e ⁺+e ^?+π+π+... Such a measurement could thus be used to check the QCD prediction that the gluon helicity increases linearly with lnQ ².     

Trapping Rayleigh particles using highly focused higher-order radially polarized beams

The optical trapping characteristics of highly focused higher-order radially polarized beams (R-TEM_p1*) acting on a Rayleigh particle are studied theoretically. Numerical results show that as the order p of beam increases and the numerical aperture NA_o of the objective decreases, the axial trap distance increases but the trap depth and maximum restoring force decreases. In a limit of NA_o = 1, three higher-order R-TEM_p1* beams of p = 1, 2, 3, like the fundamental lowest-order radially polarized beam of p = 0, can three-dimensionally trap a particle to the focus but the axial trap stiffness decreases with the increase of p. When NA_o = 0.95, the focus is still a stable trap point for the two beams of p = 0 and 1 but it becomes an unstable trap point for the two beams of p = 2 and 3. The trap stability is also discussed for higher-order radially polarized beam illumination.     

Lagrangian dynamics of spinning particles and polarized media in general relativity

The general form of the Lagrangian equations of motion is derived for a spinning particle having arbitrary multipole structure in arbitrary external fields. It is then shown how these equations, together with the complete system of field equations can be recovered from a fourdimensional action integral representing a polarized dustlike medium interacting with an arbitrary set of fields. These general results are then specialized to the case of Einstein-Maxwell fields in order to obtain the general-relativistic extension of Lorentz's dielectric theory.     

From Quantum Probabilities to Quantum Amplitudes

The task of reconstructing the system’s state from the measurements results, known as the Pauli problem, usually requires repetition of two successive steps. Preparation in an initial state to be determined is followed by an accurate measurement of one of the several chosen operators in order to provide the necessary “Pauli data”. We consider a similar yet more general problem of recovering Feynman’s transition (path) amplitudes from the results of at least three consecutive measurements. The three-step histories of a pre- and post-selected quantum system are subjected to a type of interference not available to their two-step counterparts. We show that this interference can be exploited, and if the intermediate measurement is “fuzzy”, the path amplitudes can be successfully recovered. The simplest case of a two-level system is analysed in detail. The “weak measurement” limit and the usefulness of the path amplitudes are also discussed.     

Azimuthal asymmetry in processes of nonlinear QED for linearly polarized photon

Cross sections of nonlinear QED processes (photon-photon scattering, photon splitting in a Coulomb field, and Delbrück scattering) are considered for linearly polarized initial photon. The cross sections have sizeable azimuthal asymmetry.     

Quantum mechanical equations of motion of particles and spin in polarized media

Quantum mechanical equations of motion are obtained for particles and spin in media with polarized electrons in the presence of external fields. The motion of electrons and their spins is governed by the exchange interaction, while the motion of positrons and their spin is governed by the annihilation interaction. For particles with spin S ≥ 1, second-order terms in spin are taken into account. The equations obtained can be applied to describe the motion of particles and spin both in magnetic and nonmagnetic media.     

Multiple ionization processes involving fast charged particles

This review is devoted to certain aspects of the theory of multiple ionization of a quantum target by a fast charged particle. Atoms and molecules, and their ions as well, are considered as targets, while electrons and protons are considered as projectiles. Special attention is paid to the effective charge approximation while constructing continuum wave functions for several charged fragments in the exit channel of the reaction. Theoretical calculations of differential and total cross sections of various multiple ionization processes are presented and, where possible, comparison of the results of these calculations with experimental data is carried out.     

Electroweak radiative effects in the Møller scattering of polarized particles

Physics of Atomic Nuclei - Bremsstrahlung-induced electroweak radiative corrections to observables of the Møller scattering of polarized particles are calculated. The covariant method is used...     

On the splitting of aspherical structure submitted to an acoustic polarized excitation

We experimentally show how the deviations from spherical symmetry such as the inhomogeneity, the removal mass or the asphericity affect the frequency spectrum of a single elastic sphere. The recorded spectrograms point out the great influence of the polarization of the source on the splitting and the shift of the peaks. Qualitatively, the results are consistent with the data reported in Geophysics although the present study is concerned with a low degree and low- [Formula: see text] modes in contrast to those usually encountered in seismic investigations. From a practical point of view, this study suggests that Geophysics phenomena could be analyzed through spherical beads reproducing the imperfections encountered in the mantle and in the core of the earth.     

Photo-production of scalar particles in the field of a circularly polarized laser beam

The photo-production of a pair of scalar particles in the presence of an intense, circularly polarized laser beam is investigated. Using the optical theorem within the framework of scalar quantum electrodynamics, explicit expressions are given for the pair production probability in terms of the imaginary part of the vacuum polarization tensor. Its leading asymptotic behavior is determined for various limits of interest. The influence of the absence of internal spin degrees of freedom is analyzed via a comparison with the corresponding probabilities for production of spin-1/2 particles; the lack of spin is shown to suppress the pair creation rate, as compared to the predictions from Dirac theory. Potential applications of our results for the search of minicharged particles are indicated.     

Topological defects and magnetization processes for the triangular lattice of ising particles with an antiferromagnetic interaction

For the frustrated triangular lattice of Ising magnetic moments with an antiferromagnetic interaction, which is in a state with two sublattices, a new type of topological defects with zero energy in the approximation of the interaction between only the nearest-neighbors has been found. These defects have a nonzero magnetic moment, and the magnetization in a low field occurs via the formation of a system of such defects. These properties are valid for a 2D superstructure in the form of a triangular lattice of single-domain magnetic particles with perpendicular anisotropy and dipole coupling.