Polarization variables in inclusive <Emphasis Type=Italic>J</Emphasis>/Ψ production at HERA in the <Emphasis Type=Italic>k</Emphasis><Subscript><Emphasis Type=Italic>t</Emphasis></Subscript>-factorization approach

In the framework of k _t -factorization approach, the process of inclusive photoproduction of J/Ψ mesons at HERA conditions is considered. The spin density matrix elements are calculated, and the predictions are compared with recent experimental data. The article is published in the original.     

<Emphasis Type=Italic>Q</Emphasis> kink of the nonlinear <Emphasis Type=Italic>O</Emphasis>(3) <Emphasis Type=Italic>σ</Emphasis> model involving an explicitly broken symmetry

The (1 + 1)-dimensional nonlinear O(3) σ model involving an explicitly broken symmetry is considered. Sphalerons are known to exist in this model. These sphalerons are of a topological origin and are embedded kinks of the sine-Gordon model. In the case of a compact spatial manifold S ¹, sine-Gordon multikinks exist in the model. It is shown that the model admits a nonstatic generalization of the sine-Gordon kink/multikink, Q kink/multikink. Explicit expressions are obtained for the dependence of the Q kink energy and charge on the phase frequency of rotation. The Q kink is studied for stability, and expressions are obtained for the eigenfunctions and eigenfrequencies of the operator of quadratic fluctuations. It is shown that the Q kink is unstable over the entire admissible frequency range ω ∈ [−1, 1]. The one-loop quantum correction to the static-kink mass is calculated, and the Q-kink zero mode is quantized. It is shown that, in a general static case, the field equations of the model are integrable in quadratures.     

On the role of FSI in <Emphasis Type=Italic>K</Emphasis> → 2<Emphasis Type=Italic>π</Emphasis> decay

Contrary to widespread opinion that the final-state interaction (FSI) enlarges the amplitude 〈2π; I = 0|K ⁰〉, we argue that FSI is not able to increase the absolute value of this amplitude. The text was submitted by the author in English.     

Quantum Key Distribution Using Four-Qubit W State

A new theoretical quantum key distribution scheme based on entanglement swapping is proposed, where four-qubit symmetric W state functions as quantum channel. It is shown that two legitimate users can secretly share a series of key bits by using Bell-state measurements and classical communication.     

Radiative corrections to the cross section for <Emphasis Type=Italic>e</Emphasis><Superscript>−</Superscript> + <Emphasis Type=Italic>p</Emphasis> → <Emphasis Type=Italic>v + n</Emphasis> and the crossed processes

The Born cross section and the radiative corrections to its lowest order are considered in the framework of QED with structureless nucleons including the emission of virtual and real photons. The result is generalized to take into account the radiative corrections in higher orders of the perturbation theory in the leading and next-to-leading logarithmic approximation. The crossing processes are considered in the leading approximation. The text was submitted by the authors in English.     

Hawking radiation of black holes in non-minimal <Emphasis Type=Italic>R</Emphasis><Superscript><Emphasis Type=Italic>β</Emphasis></Superscript><Emphasis Type=Italic>F</Emphasis><Superscript>2</Superscript>-type coupled Einstein–Maxwell theory

We investigate the Hawking radiation and greybody factor for a scalar field on the background of the black holes in the theory of the non-minimal R ^β F ²-coupled electromagnetic fields to gravity. For different asymptotic structures caused by the real power number β, we find that the influences of the real power number on the Hawking radiation and greybody factor are different. We also show that the different coupling constant also affects the Hawking radiation and greybody factor.     

Geometric Phase in a Time-Dependent <Emphasis Type=Italic>k</Emphasis>-Photon Λ-Type Jaynes–Cummings Model

By using the Lewis–Riesenfeld invariant theory, we have studied the dynamical and the geometric phases in a generalized time-dependent k-photon Λ-type Jaynes–Cummings model. It is found that, different from the dynamical phases, the geometric phases in a cycle case are independent of the photon numbers, the frequency of the photon field, the coupling coefficient between photons and atoms, and the atom transition frequency.