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Force on a moving object in an ideal quantum gas 在理想量子气体中作用在运动物体上的力
4区 教育学
American Journal of Physics Pub Date : 2023-11-01 DOI: 10.1119/5.0127334
Wittaya Kanchanapusakit, Pattarapon Tanalikhit
{"title":"Force on a moving object in an ideal quantum gas","authors":"Wittaya Kanchanapusakit, Pattarapon Tanalikhit","doi":"10.1119/5.0127334","DOIUrl":"https://doi.org/10.1119/5.0127334","url":null,"abstract":"We consider a heavy external object moving in an ideal gas of light particles. Collisions with the gas particles transfer momentum to the object, leading to a force that is proportional to the object's velocity but in the opposite direction. In an ideal classical gas at temperature T, the force acting on the object is proportional to T. Quantum statistics causes a deviation from the T-dependence and shows that the force scales with T2 at low temperatures. At T = 0, the force vanishes in a Bose gas but is finite in a Fermi gas.","PeriodicalId":7589,"journal":{"name":"American Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135112048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
In this issue: November 2023 本期:2023年11月
4区 教育学
American Journal of Physics Pub Date : 2023-11-01 DOI: 10.1119/5.0177701
John Essick, Jesse Kinder, Beth Parks, Donald Salisbury, Todd Springer, Keith Zengel
{"title":"In this issue: November 2023","authors":"John Essick, Jesse Kinder, Beth Parks, Donald Salisbury, Todd Springer, Keith Zengel","doi":"10.1119/5.0177701","DOIUrl":"https://doi.org/10.1119/5.0177701","url":null,"abstract":"","PeriodicalId":7589,"journal":{"name":"American Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135112049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The first Global e-Competition on Astronomy and Astrophysics 首届全球天文学和天体物理学电子竞赛
4区 教育学
American Journal of Physics Pub Date : 2023-11-01 DOI: 10.1119/5.0121242
Charles Barclay, Tonis Eenmae, Taavet Kalda, Hara Papathanassiou, Nikita Poljakov, Gustavo A. Rojas, Tiit Sepp, Greg Stachowski, Aniket Sule, Ioana A. Zelko
{"title":"The first Global e-Competition on Astronomy and Astrophysics","authors":"Charles Barclay, Tonis Eenmae, Taavet Kalda, Hara Papathanassiou, Nikita Poljakov, Gustavo A. Rojas, Tiit Sepp, Greg Stachowski, Aniket Sule, Ioana A. Zelko","doi":"10.1119/5.0121242","DOIUrl":"https://doi.org/10.1119/5.0121242","url":null,"abstract":"The first global e-competition on astronomy and astrophysics was held online in September–October 2020 as a replacement for the International Olympiad on Astronomy and Astrophysics, which was postponed due to the COVID-19 pandemic. Despite the short time available for organization, 8 weeks, the competition was run successfully, with 325 students from over 42 countries participating with no major issues. The feedback from the participants was positive and reflects the ways in which such events can boost interest in astronomy and astronomy education. With online activities set to become more prevalent in the future, we present an overview of the competition process, the challenges faced, and some of the lessons learned, aiming to contribute to the development of best practices for organizing online competitions.","PeriodicalId":7589,"journal":{"name":"American Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136103250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Leading quantum correction to the classical free energy 引导量子修正到经典自由能
4区 教育学
American Journal of Physics Pub Date : 2023-11-01 DOI: 10.1119/5.0106687
Markus Deserno, O. Teoman Turgut
{"title":"Leading quantum correction to the classical free energy","authors":"Markus Deserno, O. Teoman Turgut","doi":"10.1119/5.0106687","DOIUrl":"https://doi.org/10.1119/5.0106687","url":null,"abstract":"The quantum free energy of a system governed by a standard Hamiltonian is larger than its classical counterpart. The lowest-order correction, first calculated by Wigner, is proportional to ℏ2 and involves the sum of the mean squared forces. We present an elementary derivation of this result by drawing upon the Zassenhaus formula, an operator-generalization for the main functional relation of the exponential map. Our approach highlights the central role of non-commutativity between kinetic and potential energy and is more direct than Wigner's original calculation, or even streamlined variations thereof found in modern textbooks. We illustrate the quality of the correction for the simple harmonic oscillator (analytically) and the purely quartic oscillator (numerically) in the limit of high temperature. We also demonstrate that the Wigner correction fails in situations with sufficiently rapidly changing potentials, for instance, the particle in a box.","PeriodicalId":7589,"journal":{"name":"American Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135112045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Multiplicity counting using organic scintillators to distinguish neutron sources: An advanced teaching laboratory 利用有机闪烁体识别中子源的多重计数:一个先进的教学实验室
4区 教育学
American Journal of Physics Pub Date : 2023-11-01 DOI: 10.1119/5.0139531
Flynn B. Darby, Michael Y. Hua, Oskari V. Pakari, Shaun D. Clarke, Sara A. Pozzi
{"title":"Multiplicity counting using organic scintillators to distinguish neutron sources: An advanced teaching laboratory","authors":"Flynn B. Darby, Michael Y. Hua, Oskari V. Pakari, Shaun D. Clarke, Sara A. Pozzi","doi":"10.1119/5.0139531","DOIUrl":"https://doi.org/10.1119/5.0139531","url":null,"abstract":"In this advanced instructional laboratory, students explore complex detection systems and nondestructive assay techniques used in the field of nuclear physics. After setting up and calibrating a neutron detection system, students carry out timing and energy deposition analyses of radiation signals. Through the timing of prompt fission neutron signals, multiplicity counting is used to carry out a special nuclear material (SNM) nondestructive assay. Our experimental setup is comprised of eight trans-stilbene organic scintillation detectors in a well-counter configuration, and measurements are taken on a spontaneous fission source as well as two (α,n) sources. By comparing each source's measured multiplicity distribution, the resulting measurements of the (α,n) sources can be distinguished from that of the spontaneous fission source. Such comparisons prevent the spoofing, i.e., intentional imitation, of a fission source by an (α,n) neutron source. This instructional laboratory is designed for nuclear engineering and physics students interested in organic scintillators, neutron sources, and nonproliferation radiation measurement techniques.","PeriodicalId":7589,"journal":{"name":"American Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135112044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
An alternative derivation of propagator for a linear potential 线性势的传播子的另一种推导
4区 教育学
American Journal of Physics Pub Date : 2023-11-01 DOI: 10.1119/5.0103857
Xi-Jun Ren
{"title":"An alternative derivation of propagator for a linear potential","authors":"Xi-Jun Ren","doi":"10.1119/5.0103857","DOIUrl":"https://doi.org/10.1119/5.0103857","url":null,"abstract":"","PeriodicalId":7589,"journal":{"name":"American Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135112046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Coupled oscillations of the Wilberforce pendulum unveiled by smartphones 智能手机揭示了威尔伯福斯摆的耦合振荡
4区 教育学
American Journal of Physics Pub Date : 2023-11-01 DOI: 10.1119/5.0138680
Thomas Gallot, Daniel Gau, Rodrigo García-Tejera
{"title":"Coupled oscillations of the Wilberforce pendulum unveiled by smartphones","authors":"Thomas Gallot, Daniel Gau, Rodrigo García-Tejera","doi":"10.1119/5.0138680","DOIUrl":"https://doi.org/10.1119/5.0138680","url":null,"abstract":"The Wilberforce pendulum illustrates important properties of coupled oscillators including normal modes and beat phenomena. When helical spring is attached to a mass to create the Wilberforce pendulum, the longitudinal and torsional oscillations are coupled. A Wilberforce can be constructed simply from a standard laboratory spring, and a smartphone's accelerometer and gyroscope can be used to monitor the oscillations. We show that the resulting time-series data match theoretical predictions, and we share the procedures for observing both normal modes and beats.","PeriodicalId":7589,"journal":{"name":"American Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135112050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
The emergence of classical mixtures from an entangled quantum state 纠缠量子态中经典混合物的出现
4区 教育学
American Journal of Physics Pub Date : 2023-10-01 DOI: 10.1119/5.0063636
Mark G. Kuzyk
{"title":"The emergence of classical mixtures from an entangled quantum state","authors":"Mark G. Kuzyk","doi":"10.1119/5.0063636","DOIUrl":"https://doi.org/10.1119/5.0063636","url":null,"abstract":"","PeriodicalId":7589,"journal":{"name":"American Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135324251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Damped harmonic oscillator revisited: The fastest route to equilibrium 重访阻尼谐振子:达到平衡的最快途径
4区 教育学
American Journal of Physics Pub Date : 2023-10-01 DOI: 10.1119/5.0112573
Karlo Lelas, Nikola Poljak, Dario Jukić
{"title":"Damped harmonic oscillator revisited: The fastest route to equilibrium","authors":"Karlo Lelas, Nikola Poljak, Dario Jukić","doi":"10.1119/5.0112573","DOIUrl":"https://doi.org/10.1119/5.0112573","url":null,"abstract":"Theoretically, solutions of the damped harmonic oscillator asymptotically approach equilibrium, i.e., the zero energy state, without ever reaching it exactly, and the critically damped solution approaches equilibrium faster than the underdamped or the overdamped solution. Experimentally, the systems described with this model reach equilibrium when the system's energy has dropped below some threshold corresponding to the energy resolution of the measuring apparatus. We show that one can (almost) always find an optimal underdamped solution that will reach this energy threshold sooner than all other underdamped solutions, as well as the critically damped solution, no matter how small this threshold is. We also comment on one exception to this for a particular type of initial condition, when a specific overdamped solution reaches the equilibrium state sooner than all other solutions. We experimentally confirm some of our findings.","PeriodicalId":7589,"journal":{"name":"American Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135324539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
All objects and some questions 所有的物体和一些问题
4区 教育学
American Journal of Physics Pub Date : 2023-10-01 DOI: 10.1119/5.0150209
Charles H. Lineweaver, Vihan M. Patel
{"title":"All objects and some questions","authors":"Charles H. Lineweaver, Vihan M. Patel","doi":"10.1119/5.0150209","DOIUrl":"https://doi.org/10.1119/5.0150209","url":null,"abstract":"We present an overview of the thermal history of the Universe and the sequence of objects (e.g., protons, planets, and galaxies) that condensed out of the background as the Universe expanded and cooled. We plot (i) the density and temperature of the Universe as a function of time and (ii) the masses and sizes of all objects in the Universe. These comprehensive pedagogical plots draw attention to the triangular regions forbidden by general relativity and quantum uncertainty and help navigate the relationship between gravity and quantum mechanics. How can we interpret their intersection at the smallest possible objects: Planck-mass black holes (“instantons”)? Does their Planck density and Planck temperature make them good candidates for the initial conditions of the Universe? Our plot of all objects also seems to suggest that the Universe is a black hole. We explain how this depends on the unlikely assumption that our Universe is surrounded by zero density Minkowski space.","PeriodicalId":7589,"journal":{"name":"American Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135324246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"教育学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
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