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Сегодняшнее из арХива

Плотно и содержательно на 45 страниц.

Elastic and diffractive scattering in the LHC era: https://arxiv.org/abs/1902.05614

We review elastic and diffractive scattering of protons (called also "forward physics") with emphasis on the LHC data, especially those deviating from the expectations based on extrapolations from earlier measurements at the ISR, Fermilab and thus triggering searches for new ideas, models and theories. We list these new data and provide a brief introduction of available theoretical approaches, mainly those based on analyticity, crossing symmetry and unitarity, particularly the Regge-pole model realizing these concepts. Fits to the data are presented and tensions between theoretical predictions and the data that may indicate the way to further progress are in the focus of our paper.

Comments: 45 pages, 38 figures, 2 tables
Journal reference: International Journal of Modern Physics E Vol. 27, No. 08, 1830005 (2018)

И вот такое (даже с двумя задачками):

Feynman's different approach to electrodynamics: https://arxiv.org/abs/1902.05799

We discuss a previously unpublished description of electromagnetism developed by Richard P. Feynman in the 1960s. Though similar to the existing approaches deriving electromagnetism from special relativity, the present one extends a long way towards the derivation of Maxwell's equations with minimal physical assumptions (in particular, without postulating Coulomb's law). Homogeneous Maxwell's equations are, indeed, derived by following a route different to the standard one, i.e. first introducing electromagnetic potentials in order to write down a relativistic invariant action, which is just the inverse approach to the usual one. Also, Feynman's derivation of the Lorentz force exclusively follows from its linearity in the charge velocity and from relativistic invariance. The obvious historical significance of such approach is then complemented by its possible relevance for didactics, providing a novel way to develop the foundations of electromagnetism, which can fruitfully supplement usual treatments.

Comments: 14 pages, no figures, submitted for publication to The American Journal of Physics


Сегодня у меня была необыкновенная удача! Я выглянул в окно посмотреть, какая погода, и в первое мгновение мне показалось, что вдоль улицы несет хлопья снега. Правда, они оказались какими-то чересчур крупными и не очень белыми. Спустя мгновение стая "хлопьев" сделала разворот на перекрестке и уселась на березу на другой стороне улицы. А благодаря уважаемому prokhozhyj я недавно узнал, где эти волшебные твари обитают и где их искать, так что сразу рванул за фотоаппаратом. Выкладываю лучшее из того, что получилось:

+ 2Collapse )
WavePacket: A Matlab package for numerical quantum dynamics. III: Quantum-classical simulations and surface hopping trajectories: https://arxiv.org/abs/1902.05092

WavePacket is an open-source program package for numerical simulations in quantum dynamics. Building on the previous Part I [Comp. Phys. Comm. 213, 223-234 (2017)] and Part II [Comp. Phys. Comm. 228, 229-244 (2018)] which dealt with quantum dynamics of closed and open systems, respectively, the present Part III adds fully classical and mixed quantum-classical propagations to WavePacket. In those simulations classical phase-space densities are sampled by trajectories which follow (diabatic or adiabatic) potential energy surfaces. In the vicinity of (genuine or avoided) intersections of those surfaces trajectories may switch between surfaces. To model these transitions, two classes of stochastic algorithms have been implemented: (1) J. C. Tully's fewest switches surface hopping and (2) Landau-Zener based single switch surface hopping. The latter one offers the advantage of being based on adiabatic energy gaps only, thus not requiring non-adiabatic coupling information any more.
The present work describes the MATLAB version of WavePacket 6.0 which is essentially an object-oriented rewrite of previous versions, allowing to perform fully classical, quantum--classical and quantum-mechanical simulations on an equal footing, i.~e., for the same physical system described by the same WavePacket input. The software package is hosted and further developed at the Sourceforge platform, where also extensive Wiki-documentation as well as numerous worked-out demonstration examples with animated graphics are available.
Обратите внимание на имя второго автора:

An improved physics model for multi-material identification in photon counting CT: https://arxiv.org/abs/1902.03360

Снова о теории радуги

На этот раз в виде задачи на Элементах: https://elementy.ru/problems/1999/Razmer_radugi

Выкладки для предела геометрической оптики проделаны подробно. Текст просмотрел по диагонали, не без погрешностей.

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