Covering-based rough sets are important generalizations of the classical rough sets of Pawlak. A common way to shape lower and upper approximations within this framework is by means of a neighborhood operator. In this article, we study 24 such neighborhood operators that can be derived from a single covering. We verify equalities between them, reducing the original collection to 13 different ne...

It is argued that in the antiproton-proton annihilation into two mesons p̄p −→ m1m2, the origin of different angular momentum selection rules commonly obtained for planar annihilation diagrams A2 and for non-planar rearrangement diagrams R2 lies in the omission of momentum transfer between an annihilated antiquark-quark pair and a remaining quark or antiquark. Therefore, there is no reason for d...

We study the production of J/ψ + cc̄ in ee annihilation through two virtual photons. The cross section is estimated to be 23 fb at √ s = 10.6 GeV, which is smaller by a factor of six than the calculated cross section for the same process but through one virtual photon. As a result, while the annihilation into two photons may be important for certain exclusive production processes, the big gap be...

Positron annihilation on many molecules occurs via positron capture into vibrational Feshbach resonances, with annihilation rates often further enhanced by energy transfer to vibrational excitations weakly coupled to the positron continuum. Data presented here uncover another scenario in which the positron couples directly to a quasicontinuum of multimode vibrational states. A model that assume...

Some most representative results for semicrystalline polymers by positron annihilation spectroscopy method, showing the influence of crystallinity and morphology of samples on positron annihilation characteristics, are reminded. The latest finding of the author’s experiment on modified polyamide 6 is presented. The latter reveals that the interfacial zone between a lamella and an amorphous regi...

A general method for calculating next-to-leading order cross sections in perturbative QCD is presented. The algorithm is worked out for calculating N -jet cross sections in hadron-hadron collisions. The generalization of the scheme to performing caclulations for other QCD process, such as electron-positron annihilation or in deep inelastic scattering is also straightforward. As an illustration ...

We present a theoretical analysis of positron annihilation studies of two isostructural f -electron compounds CeIn3 and UGa3. The interpretation of twodimensional angular correlation of annihilation radiation experiment (2D-ACAR) is based on a parameter-free density functional theory calculations. Our analyses show, that the f -electrons in CeIn3 behave as well localized while in UGa3 it was th...

We analyze the transition from annihilation to preservation of colliding waves. The analysis exploits the similarity between the local and global phase portraits of the system. The transition is shown to be the infinite-dimensional analog of the creation and annihilation of limit cycles in the plane via a homoclinic Andronov bifurcation, and has parallels to the nucleation theory of first-order...

The Wigner equation provides an interesting mathematical limit, which recovers the constant field, ballistic Boltzmann equation. The peculiarities of a recently proposed Monte Carlo approach for solving the transient Wigner problem, based on generation and annihilation of particles are summarized. The annihilation process can be implemented at consecutive time steps to improve the Monte Carlo r...