June 25th, 2021

лошадь, диаграмма, Фейнман

Педагогическое введение в голографическую физику адронов

Возможно, будет интересно уважаемому istanaro.

A Pedagogical Introduction to Holographic Hadrons: https://arxiv.org/abs/2106.13136
Sophia K Domokos, Robert Bell, Trinh La, Patrick Mazza
String theory's holographic QCD duality makes predictions for hadron physics by building models that live in five-dimensional (5D) curved space. In this pedagogical note, we explain how finding the hadron mass spectrum in these models amounts to finding the eigenvalues of a time-independent, one-dimensional Schroedinger equation. Changing the structure of the 5D curved space is equivalent to altering the potential in the Schroedinger equation, which in turn alters the hadron spectrum. We illustrate this concept with three holographic QCD models possessing exact analogs in basic quantum mechanics: the free particle, the infinite square well, and the harmonic oscillator. In addition to making aspects of holographic QCD accessible to undergraduates, this formulation can provide students with intuition for the meaning of curved space. This paper is intended primarily as a tool for researchers interested in involving early-stage undergraduates in research, but is also a suitable introduction to elements of holographic QCD for advanced undergraduate- and beginning graduate students with some knowledge of general relativity and classical field theory.
Comments: 12 pages, 4 figures, a slightly revised version has been submitted to the European Journal of Physics
лошадь, диаграмма, Фейнман

Проектирование гитарного грифа по-научному: проект для студентов

Design of a fretboard using the stiff string equation: https://arxiv.org/abs/2106.13030
Nicolás Guarín Zapata
Guitar fretboards are designed based on the equation of the ideal string. That is, it neglecs several factors as nonlinearities and bending stiffness of the strings. Due to this fact, intonation of guitars along the whole neck is not perfect, and guitars have right tuning just in an \emph{average} sense. There are commercially available fretboards that differ from the tradictional design.\footnote{One example is the \cite{patent} by the Company True Temperament AB, where each fretboard is made using CNC processes.} As a final application of this work we would like to redesign the fretboard layout considering the effects of bending stiffness. The main goal of this project is to analyze the differences between the differences in the solution for vibrations of the ideal string and a stiff string. These differences should lead to changes in the fret distribution for a guitar, and, hopefully improve the overall intonation of the instrument. We will start analyzing the ideal string equation and after a good understanding of this analytical solution we will proceed with the, more complex, stiff equation. Topics like separation of variables, Fourier transforms, and Perturbation analysis might prove useful during the course of this project
Comments: 12 pages, 5 figures
лошадь, диаграмма, Фейнман

Снова о торможении протонов

A Proton Computed Tomography Demonstrator for Stopping Power Measurements: https://arxiv.org/abs/2106.12890
Felix Ulrich-Pur, Thomas Bergauer, Alexander Burker, Albert Hirtl, Christian Irmler, Stefanie Kaser, Florian Pitters
Particle therapy is an established method to treat deep-seated tumours using accelerator-produced ion beams. For treatment planning, the precise knowledge of the relative stopping power (RSP) within the patient is vital. Conversion errors from x-ray computed tomography (CT) measurements to RSP introduce uncertainties in the applied dose distribution. Using a proton computed tomography (pCT) system to measure the SP directly could potentially increase the accuracy of treatment planning. A pCT demonstrator, consisting of double-sided silicon strip detectors (DSSD) as tracker and plastic scintillator slabs coupled to silicon photomultipliers (SiPM) as a range telescope, was developed. After a significant hardware upgrade of the range telescope, a 3D tomogram of an aluminium stair phantom was recorded at the MedAustron facility in Wiener Neustadt, Austria. In total, 80 projections with 6.5x10^5 primary events were acquired and used for the reconstruction of the RSP distribution in the phantom. After applying a straight-line approximation for the particle path inside the phantom, the most probable value (MPV) of the RSP distribution could be measured with an accuracy of 0.59%. The RSP resolution inside the phantom was only 9.3% due to a limited amount of projections and measured events per projection.
Comments: Preprint submitted to the open-access Journal of Physics: Conference Series. (TIPP2021 conference proceedings). IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it