June 20th, 2020

лошадь, диаграмма, Фейнман

Бразильцы (но на английском) учат методу изображений

Green's functions and method of images: an interdisciplinary topic usually cast aside in physics textbooks^ https://arxiv.org/abs/2006.09999

Glauco Cohen Ferreira Pantoja, Walace S. Elias
In the present work we discuss how to address the solution of electrostatic problems, in professional cycle, using Green's functions and the Poisson's equation. By using this procedure, it was possible to verify its relation with the method of images as an interdisciplinary approach in didactic physics textbooks. For this, it was considered the structural role that mathematics, specially the Green's function, have in physical thought presented in the method of images.
Comments: 21 pages, 2 tables, 4 figures
лошадь, диаграмма, Фейнман

Экситоны и уравнение Бете-Солпитера

The Bethe-Salpeter Equation Formalism: From Physics to Chemistry: https://arxiv.org/abs/2006.09440
Xavier Blase, Ivan Duchemin, Denis Jacquemin, Pierre-François Loos

The many-body Green's function Bethe-Salpeter equation (BSE) formalism is steadily asserting itself as a new efficient and accurate tool in the ensemble of computational methods available to chemists in order to predict optical excitations in molecular systems. In particular, the combination of the so-called GW approximation of many-body perturbation theory, giving access to reliable ionization energies and electron affinities, and the BSE formalism, able to model UV/Vis spectra by catching excitonic effects, has shown to provide accurate singlet excitation energies in many chemical scenarios with a typical error of 0.1--0.3 eV. With a similar computational cost as time-dependent density-functional theory (TD-DFT), the BSE formalism is able to provide an accuracy on par with the most accurate global and range-separated hybrid functionals without the unsettling choice of the exchange-correlation functional, resolving further known issues (e.g., charge-transfer excitations) and offering a well-defined path to dynamical kernels. In this \textit{Perspective} article, we provide a historical overview of the BSE formalism, with a particular focus on its condensed-matter roots. We also propose a critical review of its strengths and weaknesses in different chemical situations. Future directions of developments and improvements are also discussed.
Comments: 13 pages, 3 figures, invited Perspective article
лошадь, диаграмма, Фейнман

Материалы очередной ЦЕРНовской школы по ускорителям. На сей раз - компьютерные методы

CAS - CERN Accelerator School: Numerical Methods for Analysis, Design and Modelling of Particle Accelerators, 11-23 November 2018, Thessaloniki, Greece

Simulation of Particle-Material Interactions: https://arxiv.org/abs/2006.09866
Nikolai Mokhov
This paper gives an overview of the particle transport theory essentials, the basics of particle-material interaction simulation, physical quantities needed to simulate particle transport and interactions in materials, Monte Carlo simulation flow, response of additive detectors, statistical weights and other techniques to minimize statistical errors. Effects in materials under irradiation, materials response related to component lifetime and performance are considered with a focus on high-energy and high-power accelerator applications. Implementation of simulation of particle-material interactions in the modern Monte Carlo codes along with the code s main features and results of recent benchmarking are described.
Comments: 24 pages

Finite-Element Simulation of an Accelerator Magnet: an Exercise: https://arxiv.org/abs/2006.10463
H. De Gersem, I. Kulchytska-Ruchka, S. Schöps
This note describes an extended exercise on the finite-element (FE) simulation of an accelerator magnet. The students construct and simulate a magnet model using the FEMM freeware. They get the opportunity to exercise on the theory of FEs, including Maxwell equations, magnetoquasistatic formulation, weighted residual approach, choice of appropriate FE shape functions and algebraic system of equations, thereby guided by fill-in sheets. They are invited to implement the most crucial parts of a simple FE solver. Finally, the own software is used to simulate the magnet once more and to develop some problem-dedicated post-processing routines. The exercise educates students in accelerator physics and electrical engineering on the construction and simulation of accurate and manageable FE models, the algorithms behind a standard FE solver and some ideas to extend a FE solver for own purposes. All necessary files to carry out the exercise are freely available.
Comments: 32 pages

Dynamical Systems, Representation of Particle Beams: https://arxiv.org/abs/2006.14332
Alex Chao
An overview of dynamical systems in accelerator physics is presented with a suggestion of a few issues to be addressed. Also mentioned are a few possible developments in the future. Technical details supporting the views are not presented.
Comments: 13 pages

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лошадь, диаграмма, Фейнман

Очередное предложение по использованию каналирования в нанотрубках

Nanostructure Accelerators: Novel concept and path to its realization: https://arxiv.org/abs/2006.10261

A. Sahai, M. Golkowski (Univ. of Colorado Denver), F. Zimmermann (CERN), J. Resta-Lopez (Univ. of Liverpool & Cockcroft Inst.), T. Tajima (UC Irvine), V. Shiltsev (Fermilab)
TeV/m acceleration gradients using crystals as originally envisioned by R. Hofstadter, an early pioneer of HEP, have remained unrealizable. Fundamental obstacles that have hampered efforts on particle acceleration using bulk-crystals arise from collisional energy loss and emittance degradation in addition to severe beam disruption despite the favorable effect of particle channeling along interatomic planes in bulk. We aspire for the union of nanoscience with accelerator science to not only overcome these problems using nanostructured tubes to avoid direct impact of the beam on bulk ion-lattice but also to utilize the highly tunable characteristics of nanomaterials. We pioneer a novel surface wave mechanism in nanostructured materials with a strong electrostatic component which not only attains tens of TeV/m gradients but also has focusing fields. Under our initiative, the proof-of-principle demonstration of tens of TeV/m gradients and beam nanomodulation is underway. Realizable nanostructure accelerators naturally promise new horizons in HEP as well as in a wide range of areas of research that utilize beams of high-energy particles or photons.
Comments: submission to Snowmass'21 Accelerator Frontier