September 12th, 2020

лошадь, диаграмма, Фейнман

Громадный обзор по КХД

The QCD Running Coupling: https://arxiv.org/abs/1604.08082

A. Deur, S. J. Brodsky, G. F. de Teramond
We review the present knowledge for αs, the fundamental coupling underlying the interactions of quarks and gluons in QCD. The dependence of αs(Q2) on momentum transfer Q encodes the underlying dynamics of hadron physics -from color confinement in the infrared domain to asymptotic freedom at short distances. We review constraints on αs(Q2) at high Q2, as predicted by perturbative QCD, and its analytic behavior at small Q2, based on models of nonperturbative dynamics. In the introductory part of this review, we explain the phenomenological meaning of αs, the reason for its running, and the challenges facing a complete understanding of its analytic behavior in the infrared domain. In the second, more technical, part of the review, we discuss the behavior of αs(Q2) in the high Q2 domain of QCD. We review how αs is defined, including its renormalization scheme dependence, the definition of its renormalization scale, the utility of effective charges, as well as Commensurate Scale Relations which connect the various definitions of αs without renormalization-scale ambiguity. We also report recent measurements and theoretical analyses which have led to precise QCD predictions at high energy. In the last part of the review, we discuss the challenge of understanding the analytic behavior αs(Q2) in the infrared domain. We also review important methods for computing αs, including lattice QCD, the Schwinger-Dyson equations, the Gribov-Zwanziger analysis and light-front holographic QCD. After describing these approaches and enumerating their conflicting predictions, we discuss the origin of these discrepancies and how to remedy them. Our aim is not only to review the advances in this difficult area, but also to suggest what could be an optimal definition of αs in order to bring better unity to the subject.
Comments: Invited review article for Progress in Particle and Nuclear Physics. 195 pages, 18 figures. V3: Minor corrections and addenda compared to V1 and V2. V4: typo fixed in Eq. (3.21)
Subjects: High Energy Physics - Phenomenology (hep-ph)
Journal reference: Prog. Part. Nuc. Phys. 90 1 (2016)
лошадь, диаграмма, Фейнман

Мертвая область в резерфордовском рассеянии отталкивающихся частиц

Великолепный материал к спецкурсу по теории рассеяния, который я сейчас читаю! Тут и ссылки на оригинальные работы Гейгера и Марсдена, и всякие полезные упражнения, много всего:

A shadow of the repulsive Rutherford scattering in the fixed-target and the center-of-mass frame: https://arxiv.org/abs/2009.04920

Petar Žugec, Ivan Topić
The paper explores the shadow of the repulsive Rutherford scattering - the portion of space entirely shielded from admitting any particle trajectory. The geometric properties of the projectile shadow are analyzed in detail in the fixed-target frame as well as in the center-of-mass frame, where both the charged projectile and the charged target cast their own respective shadows. In both frames the shadow is found to take an extremely simple, paraboloidal shape. In the fixed-target frame the target is precisely at the focus of this paraboloidal shape, while the focal points of the projectile and target shadows in the center-of-mass frame coincide. In the fixed-target frame the shadow takes on a universal form, independent of the underlying physical parameters, when expressed in properly scaled coordinates, thus revealing a natural length scale to the Rutherford scattering.
Comments: 14 pages (8 main paper + 6 supplementary note), 10 figures
лошадь, диаграмма, Фейнман

Семь способов вывести закон Ламберта-Бэра

Не так уж и давно в своей жизни (лет 12 назад) я узнал, что немудреная формула, описывающая экспоненциальное ослабление интенсивности проходящего через вещество пучка (например, рентгеновского излучения) носит звучное название закона Бугера-Ламберта-Бэра! И вот педагогическая статейка с выводами этого закона на любой вкус:))

Seven derivations of the Lambert-Beer law
Hernán R. Sánchez
Seven derivations of the Lambert-Beer law are proposed in this paper. They were designed to be simple and intuitive. Most of them are suitable for the classroom. Readers can also benefit from them by looking at the phenomenon from different perspectives, which gives valuable resources when explaining it in class.
лошадь, диаграмма, Фейнман

Начало ядерной эры

Лекция уважаемого Михаила Шифмана traveller2:

The Beginning of the Nuclear Age: https://arxiv.org/abs/2009.05001
M. Shifman
The article below is based on lectures delivered to new students remotely in the course of orientation. It presents the quantum theory tree from its inception a century ago till today. The main focus is on the nuclear physics - HEP branch.
Comments: 35 pages, 18 figures
лошадь, диаграмма, Фейнман

Биомеханика дзюдо

Специально для уважаемого ahiin'а:))

Suwari Seoi Safety: from children Dojo to High Level Competition (Biomechanical Part): https://arxiv.org/abs/2009.02906

Attilio Sacripanti
In this paper we face the problem of safety connected to a class of throws that are more often applied in every level of competitions. However, to our knowledge it has never been a scientific study on this subject in Japan and, to our great amazement, in Europe, only one, and in very recent times. While the family of techniques that is applied with two knees on the ground has gone over time, increasing, without increasing the immediate traumas. this posed the problem if these techniques were really dangerous. It was decided to investigate in a comprehensive way, on the immediate traumas, by Biomechanics of the technique aimed at the safety of Tori, from children in the dojo up to high-level competitions. With the purpose to clarify: if the technique is dangerous, in its correct execution, for children and athletes, if the technique is dangerous for the accumulation of traumas in the long run build up a mathematical model of interaction between knees and Tatami. The experimental part was developed with a thermal imaging camera that allowed to highlight the actual impact surfaces and therefore to trace the stress received by the knees, both for the children and for the athletes of the Italian National Team. the results have made clear that, if well done and on a certified tatami, the technique has a negligible probability of immediate trauma.
Comments: 51 pages, 68 Figures, 19 Tables, 12 Diagrams