Relativistic dynamical polarizability of hydrogen-like atoms

Using the operator representation of the Dirac Coulomb Green function the analytical method in perturbation theory is employed in obtaining solutions of the Dirac equation for a hydrogen-like atom in a time-dependent electric field. The relativistic dynamical polarizability of hydrogen-like atoms is calculated and analysed.Comment: 15 pages, 3 figures (not included, but hard copies are available upon request

Quantum tops as examples of commuting differential operators

We study the quantum analogs of tops on Lie algebras $so(4)$ and $e(3)$ represented by differential operators.Comment: 24 p

Electromagnetic field of a charge asymptotically approaching spherically symmetric black hole

We consider a test charged particle falling onto a Schwarzschild black hole and evaluate its electromagnetic field. The Regge-Wheeler equation is solved analytically by approximating the potential barrier with Dirac delta function and rectangular barrier. We show that for asymptotically large time measured by a distant observer the electromagnetic field approaches the spherically symmetric electrostatic field exponentially fast. This implies that in the region accessible to a distant observer the initial state of separated charge and Schwarzschild black hole becomes asymptotically indistinguishable from the Reisnner-Nordstr\"om solution. Implications of this result for models with plasma accretion on black holes are discussed.7 aComment: 7 pages, 2 figure

Neutron and Proton Transverse Emission Ratio Measurements and the Density Dependence of the Asymmetry Term of the Nuclear Equation of State

Recent measurements of pre-equilibrium neutron and proton transverse emission from (112,124)Sn+(112,124)Sn reactions at 50 MeV/A have been completed at the National Superconducting Cyclotron Laboratory. Free nucleon transverse emission ratios are compared to those of A=3 mirror nuclei. Comparisons are made to BUU transport calculations and conclusions concerning the density dependence of the asymmetry term of the nuclear equation-of-state at sub-nuclear densities are made. The double-ratio of neutron-proton ratios between two reactions is employed as a means of reducing first-order Coulomb effects and detector efficiency effects. Comparison to BUU model predictions indicate a density dependence of the asymmetry energy that is closer to a form in which the asymmety energy increases as the square root of the density for the density region studied. A coalescent-invariant analysis is introduced as a means of reducing suggested difficulties with cluster emission in total nucleon emission. Future experimentation is presented

Electromagnetic radiation and electromagnetic self-force of a point charge in the vicinity of Schwarzschild black hole

Point charge, radially moving in the vicinity of a black hole is considered. Electromagnetic field in wave zone and in the small neighbourhood of the charge is calculated. Numerical results of the calculation of the spectrum of electromagnetic radiation of the point charge are presented. Covariant approach for the calculation of electromagnetic self-force is used for the case of the slowly moving charge. Numerical results for the self-force in the case of slow motion of the particle are obtained and compared to the results in literature.Comment: 5 pages, 3 figure

Fréchet mimo-filters

Медианная фильтрация получила широкое распространение при обработке скалярных изображений в качестве методов фильтрации, сохраняющих перепады яркости. Главная идея медианной фильтрации состоит в том, что центральный пиксель сканирующей маски заменяется медианой всех пикселей, содержащихся в маске. В этой работе идея расширяется на векторно-значные изображения. Расширение основывается на том факте, что медиана является также точкой, которая минимизирует сумму расстояний между ней и всеми скалярными пикселями внутри маски. Точкой Фреше конечного множества векторно-значных пикселей в некотором метрическом пространстве (с заданной метрикой) является такой вектор, сумма расстояний до которого от всех векторных пикселей (находящихся внутри маски) имеет минимальное значение. В данной статье понятие точки Фреше расширяется до обобщенной медианы Фреше, в которой используется агрегация расстояний, а не их сумма. Более того, при обобщении используются не классические расстояния, а их агрегационные обобщения. Обобщенные медианы Фреше используются для построения новых медианных MIMO-фильтров

Controlling Boron Diffusion during Rapid Thermal Annealing with CoImplantation by Amphoteric Impurity Atoms

A model for simulating the rapid thermal annealing of silicon structures implanted with boron and carbon is developed. The model provides a fair approximation of the process of boron diffusion in silicon, allowing for such effects as the electric field, the impact of the implanted carbon, and the clustering of boron. The migration process of interstitials is described according to their drift in the field of internal elastic stress

Target mass number dependence of subthreshold antiproton production in proton-, deuteron- and alpha-particle-induced reactions

Data from KEK on subthreshold \bar{\mrm{p}} as well as on $\pi^\pm$ and \mrm{K}^\pm production in proton-, deuteron- and $\alpha$-induced reactions at energies between 2.0 and 12.0 A GeV for C, Cu and Pb targets are described within a unified approach. We use a model which considers a nuclear reaction as an incoherent sum over collisions of varying numbers of projectile and target nucleons. It samples complete events and thus allows for the simultaneous consideration of all final particles including the decay products of the nuclear residues. The enormous enhancement of the \bar{\mrm{p}} cross section, as well as the moderate increase of meson production in deuteron and $\alpha$ induced compared to proton-induced reactions, is well reproduced for all target nuclei. In our approach, the observed enhancement near the production threshold is mainly due to the contributions from the interactions of few-nucleon clusters by simultaneously considering fragmentation processes of the nuclear residues. The ability of the model to reproduce the target mass dependence may be considered as a further proof of the validity of the cluster concept.Comment: 9 pages, 4 figure