July 15th, 2020

лошадь, диаграмма, Фейнман

Точная теория тормозного излучения электрона на электроне (нерелятивистских)

Exact Theory of Non-relativistic Electron-Electron Bremsstrahlung: https://arxiv.org/abs/2007.06592
Josef Pradler, Lukas Semmelrock
The quantum mechanical treatment of quadrupole radiation due to bremsstrahlung exact to all orders in the Coulomb interaction of two colliding unpolarized non-relativistic charged spin-1/2 particles is presented. We calculate the elements of the quadrupole tensor, and present analytical solutions for the double differential photon emission cross section of identical and non-identical particles. Contact is made to Born-level and quasi-classical results in the respective kinematic limits and effective energy loss rates are obtained. A generally valid formula for soft-photon emission is established and an approximate formula across the entire kinematic regime is constructed. The results apply to bremsstrahlung emission in the scattering of pairs of electrons and are hence relevant in the study of astrophysical phenomena. A definition of a Gaunt factor is proposed which should facilitate broad applicability of the results.
Comments: 19 pages, 6 figures
лошадь, диаграмма, Фейнман

Биография Чедвика

James Chadwick: ahead of his time: https://arxiv.org/abs/2007.06926
Gerhard Ecker
James Chadwick is known for his discovery of the neutron. Many of his earlier findings and ideas in the context of weak and strong nuclear forces are much less known. This biographical sketch attempts to highlight the achievements of a scientist who paved the way for contemporary subatomic physics.
Comments: 12 pages
лошадь, диаграмма, Фейнман

Игрушка для школьников об энергии связи ядер (и о нейтронных звездах до кучи)

с хорошим обширным введением:

From nuclei to neutron stars: simple binding energy computer modelling in the classroom: https://arxiv.org/abs/2007.06872
A. Pastore, A. M. Romero, C. Diget, A. Rios, K. Leech, P. Stokoe
We present a simple activity based on the liquid-drop model which allows secondary school students to explore the uses of mathematical models and gain an intuitive understanding of the concept of binding energy, and in particular the significance of positive binding energy. Using spreadsheets provided as Supplementary Material, students can perform simple manipulations on the different coefficients of the model to understand the role of each of its five terms. Students can use the spreadsheets to determine model parameters by optimising the agreement with real atomic mass data. This will subsequently be used to predict the limit of existence of the Segré chart and to find the minimum mass of a neutron star. This activity can be used as the starting point of a discussion about theoretical models, their validation when it comes to describing experimental data and their predictive power towards unexplored regimes.
лошадь, диаграмма, Фейнман

Дуговой разряд: история и современность

An integrated Approach to Understanding Vacuum Arcs: https://arxiv.org/abs/2007.06449
J. Norem, Z Insepov, A. Hassanein
Almost 120 years after the isolation of vacuum arcs as a phenomenon, the field continues to be somewhat unsettled. We outline a simple and general model of the vacuum arc that can incorporate all active mechanisms and aims to explain all relevant data. Our four stage model considers the trigger, plasma formation, plasma evolution and surface damage phases of the arc. This model provides a framework in which to evaluate all arcing phenomena, and should be a useful guide for future studies. We consider modeling problems such as the conditioning process and extension of modeling efforts to high power systems like tokamaks, HV transmission lines, as well as more detailed modeling of the arcs themselves. This work applies directly to the designs of future high energy colliders, as well as projects like the ITER tokamak.
Comments: 11 pages, 8 figures
лошадь, диаграмма, Фейнман

Лабораторные работы на дому в эпоху самоизоляции

С использованием приложения для смартфона PHYPHOX, упоминавшегося тут.

Meeting Laboratory Course Learning Goals Remotely via Custom Home Experiment Kits: https://arxiv.org/abs/2007.05390
Daniel Howard, Mariel Meier
In this paper, the use of cost-effective, custom home experiment kits for remote teaching of first-semester introductory physics labs is described. The kit experiments were designed to match the existing onsite lab experiment learning goals and the general laboratory course learning goals in remote teaching. Additionally, a revised group project approach optimized for remote use and that leverages the kits was developed and employed. Student survey results at the end of the Summer 2020 semester indicate that the critical learning goals were met, student satisfaction with the remote lab was maintained, and successful collaboration via video-conferencing breakout rooms was achieved.