Photon: New Light on an Old Name
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The Five Common Particles
The Five Common Particles The world around you consists of only three particles: protons, neutrons, and electrons. Protons and neutrons form the nuclei of atoms, and electrons glue everything together and create chemicals and materials. Along with the photon and the neutrino, these particles are essentially the only ones that exist in our solar system, because all the other subatomic particles have half-lives of typically 10-9 second or less, and vanish almost the instant they are created by nuclear reactions in the Sun, etc. Particles interact via the four fundamental forces of nature. Some basic properties of these forces are summarized below. (Other aspects of the fundamental forces are also discussed in the Summary of Particle Physics document on this web site.) Force Range Common Particles It Affects Conserved Quantity gravity infinite neutron, proton, electron, neutrino, photon mass-energy electromagnetic infinite proton, electron, photon charge -14 strong nuclear force ≈ 10 m neutron, proton baryon number -15 weak nuclear force ≈ 10 m neutron, proton, electron, neutrino lepton number Every particle in nature has specific values of all four of the conserved quantities associated with each force. The values for the five common particles are: Particle Rest Mass1 Charge2 Baryon # Lepton # proton 938.3 MeV/c2 +1 e +1 0 neutron 939.6 MeV/c2 0 +1 0 electron 0.511 MeV/c2 -1 e 0 +1 neutrino ≈ 1 eV/c2 0 0 +1 photon 0 eV/c2 0 0 0 1) MeV = mega-electron-volt = 106 eV. It is customary in particle physics to measure the mass of a particle in terms of how much energy it would represent if it were converted via E = mc2. -
Philosophical Magazine Vol
Philosophical Magazine Vol. 92, Nos. 1–3, 1–21 January 2012, 353–361 Exploring models of associative memory via cavity quantum electrodynamics Sarang Gopalakrishnana, Benjamin L. Levb and Paul M. Goldbartc* aDepartment of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street Urbana, Illinois 61801, USA; bDepartments of Applied Physics and Physics and E. L. Ginzton Laboratory, Stanford University, Stanford, CA 94305, USA; cSchool of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, GA 30332, USA (Received 2 August 2011; final version received 24 October 2011) Photons in multimode optical cavities can be used to mediate tailored interactions between atoms confined in the cavities. For atoms possessing multiple internal (i.e., ‘‘spin’’) states, the spin–spin interactions mediated by the cavity are analogous in structure to the Ruderman–Kittel–Kasuya– Yosida (RKKY) interaction between localized spins in metals. Thus, in particular, it is possible to use atoms in cavities to realize models of frustrated and/or disordered spin systems, including models that can be mapped on to the Hopfield network model and related models of associative memory. We explain how this realization of models of associative memory comes about and discuss ways in which the properties of these models can be probed in a cavity-based setting. Keywords: disordered systems; magnetism; statistical physics; ultracold atoms; neural networks; spin glasses 1. Introductory remarks Since the development of laser cooling and trapping, a -
1.1. Introduction the Phenomenon of Positron Annihilation Spectroscopy
PRINCIPLES OF POSITRON ANNIHILATION Chapter-1 __________________________________________________________________________________________ 1.1. Introduction The phenomenon of positron annihilation spectroscopy (PAS) has been utilized as nuclear method to probe a variety of material properties as well as to research problems in solid state physics. The field of solid state investigation with positrons started in the early fifties, when it was recognized that information could be obtained about the properties of solids by studying the annihilation of a positron and an electron as given by Dumond et al. [1] and Bendetti and Roichings [2]. In particular, the discovery of the interaction of positrons with defects in crystal solids by Mckenize et al. [3] has given a strong impetus to a further elaboration of the PAS. Currently, PAS is amongst the best nuclear methods, and its most recent developments are documented in the proceedings of the latest positron annihilation conferences [4-8]. PAS is successfully applied for the investigation of electron characteristics and defect structures present in materials, magnetic structures of solids, plastic deformation at low and high temperature, and phase transformations in alloys, semiconductors, polymers, porous material, etc. Its applications extend from advanced problems of solid state physics and materials science to industrial use. It is also widely used in chemistry, biology, and medicine (e.g. locating tumors). As the process of measurement does not mostly influence the properties of the investigated sample, PAS is a non-destructive testing approach that allows the subsequent study of a sample by other methods. As experimental equipment for many applications, PAS is commercially produced and is relatively cheap, thus, increasingly more research laboratories are using PAS for basic research, diagnostics of machine parts working in hard conditions, and for characterization of high-tech materials. -
1 the LOCALIZED QUANTUM VACUUM FIELD D. Dragoman
1 THE LOCALIZED QUANTUM VACUUM FIELD D. Dragoman – Univ. Bucharest, Physics Dept., P.O. Box MG-11, 077125 Bucharest, Romania, e-mail: [email protected] ABSTRACT A model for the localized quantum vacuum is proposed in which the zero-point energy of the quantum electromagnetic field originates in energy- and momentum-conserving transitions of material systems from their ground state to an unstable state with negative energy. These transitions are accompanied by emissions and re-absorptions of real photons, which generate a localized quantum vacuum in the neighborhood of material systems. The model could help resolve the cosmological paradox associated to the zero-point energy of electromagnetic fields, while reclaiming quantum effects associated with quantum vacuum such as the Casimir effect and the Lamb shift; it also offers a new insight into the Zitterbewegung of material particles. 2 INTRODUCTION The zero-point energy (ZPE) of the quantum electromagnetic field is at the same time an indispensable concept of quantum field theory and a controversial issue (see [1] for an excellent review of the subject). The need of the ZPE has been recognized from the beginning of quantum theory of radiation, since only the inclusion of this term assures no first-order temperature-independent correction to the average energy of an oscillator in thermal equilibrium with blackbody radiation in the classical limit of high temperatures. A more rigorous introduction of the ZPE stems from the treatment of the electromagnetic radiation as an ensemble of harmonic quantum oscillators. Then, the total energy of the quantum electromagnetic field is given by E = åk,s hwk (nks +1/ 2) , where nks is the number of quantum oscillators (photons) in the (k,s) mode that propagate with wavevector k and frequency wk =| k | c = kc , and are characterized by the polarization index s. -
Charles Galton Darwin's 1922 Quantum Theory of Optical Dispersion
Eur. Phys. J. H https://doi.org/10.1140/epjh/e2020-80058-7 THE EUROPEAN PHYSICAL JOURNAL H Charles Galton Darwin's 1922 quantum theory of optical dispersion Benjamin Johnson1,2, a 1 Max Planck Institute for the History of Science Boltzmannstraße 22, 14195 Berlin, Germany 2 Fritz-Haber-Institut der Max-Planck-Gesellschaft Faradayweg 4, 14195 Berlin, Germany Received 13 October 2017 / Received in final form 4 February 2020 Published online 29 May 2020 c The Author(s) 2020. This article is published with open access at Springerlink.com Abstract. The quantum theory of dispersion was an important concep- tual advancement which led out of the crisis of the old quantum theory in the early 1920s and aided in the formulation of matrix mechanics in 1925. The theory of Charles Galton Darwin, often cited only for its reliance on the statistical conservation of energy, was a wave-based attempt to explain dispersion phenomena at a time between the the- ories of Ladenburg and Kramers. It contributed to future successes in quantum theory, such as the virtual oscillator, while revealing through its own shortcomings the limitations of the wave theory of light in the interaction of light and matter. After its publication, Darwin's theory was widely discussed amongst his colleagues as the competing inter- pretation to Compton's in X-ray scattering experiments. It also had a pronounced influence on John C. Slater, whose ideas formed the basis of the BKS theory. 1 Introduction Charles Galton Darwin mainly appears in the literature on the development of quantum mechanics in connection with his early and explicit opinions on the non- conservation (or statistical conservation) of energy and his correspondence with Niels Bohr. -
List of Particle Species-1
List of particle species that can be detected by Micro-Channel Plates and similar secondary electron multipliers. A Micro-Channel Plate (MCP) can detected certain particle species with decent quantum efficiency (QE). Commonly MCP are used to detect charged particles at low to intermediate energies and to register photons from VUV to X-ray energies. “Detection” means that a significant charge cloud is created in a channel (pore). Generally, a particle (or photon) can liberate an electron from channel surface atoms into the continuum if it carries sufficient momentum or if it can transfer sufficient potential energy. Therefore, fast-enough neutral atoms can also be detected by MCP and even exited atoms like He* (even when “slow”). At least about 10 eV of energy transfer is required to release an electron from the channel wall to start the avalanche. This number also determines the cut-off energy for photon detection which translates to a photon wave-length of about 200 nm (although there can be non- linear effects at extreme photon fluxes enhancing this cut-off wavelength). Not in all cases when ionization of a channel wall atom is possible, the electron will eventually be released to the continuum: the surface energy barrier has to be overcome and the electron must have the right emission direction. Also, the electron should be born close to surface because it may lose too much energy on its way out due to scattering and will be absorbed in the bulk. These effects reduce the QE at for VUV photons to about 10%. At EUV energies QE cannot improve much: although the primary electron energy increases, the ionization takes place deeper in the bulk on average and the electrons thus can hardly make it to the continuum. -
Phenomenology Lecture 6: Higgs
Phenomenology Lecture 6: Higgs Daniel Maître IPPP, Durham Phenomenology - Daniel Maître The Higgs Mechanism ● Very schematic, you have seen/will see it in SM lectures ● The SM contains spin-1 gauge bosons and spin- 1/2 fermions. ● Massless fields ensure: – gauge invariance under SU(2)L × U(1)Y – renormalisability ● We could introduce mass terms “by hand” but this violates gauge invariance ● We add a complex doublet under SU(2) L Phenomenology - Daniel Maître Higgs Mechanism ● Couple it to the SM ● Add terms allowed by symmetry → potential ● We get a potential with infinitely many minima. ● If we expend around one of them we get – Vev which will give the mass to the fermions and massive gauge bosons – One radial and 3 circular modes – Circular modes become the longitudinal modes of the gauge bosons Phenomenology - Daniel Maître Higgs Mechanism ● From the new terms in the Lagrangian we get ● There are fixed relations between the mass and couplings to the Higgs scalar (the one component of it surviving) Phenomenology - Daniel Maître What if there is no Higgs boson? ● Consider W+W− → W+W− scattering. ● In the high energy limit ● So that we have Phenomenology - Daniel Maître Higgs mechanism ● This violate unitarity, so we need to do something ● If we add a scalar particle with coupling λ to the W ● We get a contribution ● Cancels the bad high energy behaviour if , i.e. the Higgs coupling. ● Repeat the argument for the Z boson and the fermions. Phenomenology - Daniel Maître Higgs mechanism ● Even if there was no Higgs boson we are forced to introduce a scalar interaction that couples to all particles proportional to their mass. -
The Discovery of Thermodynamics
Philosophical Magazine ISSN: 1478-6435 (Print) 1478-6443 (Online) Journal homepage: https://www.tandfonline.com/loi/tphm20 The discovery of thermodynamics Peter Weinberger To cite this article: Peter Weinberger (2013) The discovery of thermodynamics, Philosophical Magazine, 93:20, 2576-2612, DOI: 10.1080/14786435.2013.784402 To link to this article: https://doi.org/10.1080/14786435.2013.784402 Published online: 09 Apr 2013. Submit your article to this journal Article views: 658 Citing articles: 2 View citing articles Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tphm20 Philosophical Magazine, 2013 Vol. 93, No. 20, 2576–2612, http://dx.doi.org/10.1080/14786435.2013.784402 COMMENTARY The discovery of thermodynamics Peter Weinberger∗ Center for Computational Nanoscience, Seilerstätte 10/21, A1010 Vienna, Austria (Received 21 December 2012; final version received 6 March 2013) Based on the idea that a scientific journal is also an “agora” (Greek: market place) for the exchange of ideas and scientific concepts, the history of thermodynamics between 1800 and 1910 as documented in the Philosophical Magazine Archives is uncovered. Famous scientists such as Joule, Thomson (Lord Kelvin), Clau- sius, Maxwell or Boltzmann shared this forum. Not always in the most friendly manner. It is interesting to find out, how difficult it was to describe in a scientific (mathematical) language a phenomenon like “heat”, to see, how long it took to arrive at one of the fundamental principles in physics: entropy. Scientific progress started from the simple rule of Boyle and Mariotte dating from the late eighteenth century and arrived in the twentieth century with the concept of probabilities. -
Philosophical Magazine Atomic-Resolution Spectroscopic
This article was downloaded by: [Cornell University Library] On: 30 April 2015, At: 08:23 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Philosophical Magazine Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tphm20 Atomic-resolution spectroscopic imaging of oxide interfaces L. Fitting Kourkoutis a , H.L. Xin b , T. Higuchi c , Y. Hotta c d , J.H. Lee e f , Y. Hikita c , D.G. Schlom e , H.Y. Hwang c g & D.A. Muller a h a School of Applied and Engineering Physics , Cornell University , Ithaca, USA b Department of Physics , Cornell University , Ithaca, USA c Department of Advanced Materials Science , University of Tokyo , Kashiwa, Japan d Correlated Electron Research Group , RIKEN , Saitama, Japan e Department of Materials Science and Engineering , Cornell University , Ithaca, USA f Department of Materials Science and Engineering , Pennsylvania State University , University Park, USA g Japan Science and Technology Agency , Kawaguchi, Japan h Kavli Institute at Cornell for Nanoscale Science , Ithaca, USA Published online: 20 Oct 2010. To cite this article: L. Fitting Kourkoutis , H.L. Xin , T. Higuchi , Y. Hotta , J.H. Lee , Y. Hikita , D.G. Schlom , H.Y. Hwang & D.A. Muller (2010) Atomic-resolution spectroscopic imaging of oxide interfaces, Philosophical Magazine, 90:35-36, 4731-4749, DOI: 10.1080/14786435.2010.518983 To link to this article: http://dx.doi.org/10.1080/14786435.2010.518983 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. -
The Value of Vague Ideas in the Development of the Periodic System of Chemical Elements
The Value of Vague Ideas in the Development of the Periodic System of Chemical Elements. Thomas Vogt Departments of Chemistry & Biochemistry and Philosophy University of South Carolina Abstract The exploration of chemical periodicity over the past 250 years led to the development of the Periodic System of Elements and demonstrates the value of vague ideas that ignored early scientific anomalies and instead allowed for extended periods of normal science where new methodologies and concepts are developed. The basic chemical element provides this exploration with direction and explanation and has shown to be a central and historically adaptable concept for a theory of matter far from the reductionist frontier. This is explored in the histories of Prout’s hypothesis, Döbereiner Triads, element inversions necessary when ordering chemical elements by atomic weights, and van den Broeck’s ad-hoc proposal to switch to nuclear charges instead. The development of more accurate methods to determine atomic weights, Rayleigh and Ramsey’s gas separation and analytical techniques, Moseley’s x-ray spectroscopy to identify chemical elements, and more recent accelerator-based cold fusion methods to create new elements at the end of the Periodic Table point to the importance of methodological development complementing conceptual advances. I propose to frame the crossover from physics to chemistry not as a loss of accuracy and precision but as an increased application of vague concepts such as similarity which permit classification. This approach provides epistemic flexibility to adapt to scientific anomalies and the continued growth of chemical compound space and rejects the Procrustean philosophy of reductionist physics. Furthermore, it establishes chemistry with its explanatory and operational autonomy epitomized by the periodic system of elements as a gateway to other experimental sciences. -
1 Humphry Davy to John Davy, 15 October [1811] Davy, Collected Letters, Vol
1 Humphry Davy: Analogy, Priority, and the “true philosopher” Sharon Ruston Lancaster University, England https://orcid.org/0000-0002-3864-7382 This essay explores how Davy fashioned himself as, what he called in his poetry, a “true philosopher.” He defined the “true philosopher” as someone who eschewed monetary gain for his scientific work, preferring instead to give knowledge freely for the public good, and as someone working at a higher level than the mere experimentalist. Specifically, Davy presented himself as using the method of analogy to reach his discoveries and emphasised that he understood the “principle” behind his findings. He portrayed himself as one who perceived analogies because he had a wider perspective on the world than many others in his society. The poem in which he describes the “true philosopher” offers us Davy’s private view of this character; the essay then demonstrates how Davy attempted to depict his own character in this way during critical moments in his career. Introduction During the safety lamp controversy of 1815–1817, Humphry Davy deliberately presented himself as a natural philosopher. For Davy this meant someone with a wider purview than others, who is alive to the metaphorical, literary, and philosophical ramifications of his scientific discoveries. He represented himself as working at a highly theoretical level in the laboratory, rather than practically in the mine, making a clear distinction between himself and George Stephenson in this regard. Davy suggested that he was working for loftier ideals and was opposed to monetary gain or profit by patent. He declared that his discoveries were the product of analogical thinking and a consequence of his understanding of scientific principle. -
Wave-Particle Duality 波粒二象性
Duality Bohr Wave-particle duality 波粒二象性 Classical Physics Object Govern Laws Phenomena Particles Newton’s Law Mechanics, Heat Fields and Waves Maxwell’s Eq. Optics, Electromagnetism Our interpretation of the experimental material rests essentially upon the classical concepts ... 我们对实验资料的诠释,是本质地建筑在经典概念之上的。 — N. Bohr, 1927. SM Hu, YJ Yan Quantum Physics Duality Bohr Wave-particle duality — Photon 电磁波 Electromagnetic wave, James Clerk Maxwell: Maxwell’s Equations, 1860; Heinrich Hertz, 1888 黑体辐射 Blackbody radiation, Max PlanckNP1918: Planck’s constant, 1900 光电效应 Photoelectric effect, Albert EinsteinNP1921: photons, 1905 All these fifty years of conscious brooding have brought me no nearer to the answer to the question, “What are light quanta?” Nowadays every Tom, Dick and Harry thinks he knows it, but he is mistaken. 这五十年来的思考,没有使我更加接近 “什么是光量子?” 这个问题的 答案。如今,每个人都以为自己知道这个答案,但其实是被误导了。 — Albert Einstein, to Michael Besso, 1954 SM Hu, YJ Yan Quantum Physics Duality Bohr Wave-particle duality — Electron Electron in an Atom Electron: Cathode rays 阴极射线 Joseph John Thomson, 1897 J. J. ThomsonNP1906 1856-1940 SM Hu, YJ Yan Quantum Physics Duality Bohr Wave-particle duality — Electron Electron in an Atom Electron: 阴极射线 Cathode rays, Joseph Thomson, 1897 Atoms: 行星模型 Planetary model, Ernest Rutherford, 1911 E. RutherfordNC1908 1871-1937 SM Hu, YJ Yan Quantum Physics Duality Bohr Spectrum of Atomic Hydrogen Spectroscopy , Fingerprints of atoms & molecules ... Atomic Hydrogen Johann Jakob Balmer, 1885 n2 λ = 364:56 n2−4 (nm), n =3,4,5,6 Johannes Rydberg, 1888 1 1 − 1 ν = λ = R( n2 n02 ) R = 109677cm−1 4 × 107/364:56 = 109721 RH = 109677.5834... SM Hu, YJ Yan Quantum Physics Duality Bohr Bohr’s Theory — Electron in Atomic Hydrogen Electron in an Atom Electron: 阴极射线 Cathode rays, Joseph Thomson, 1897 Atoms: 行星模型 Planetary model, Ernest Rutherford, 1911 Spectrum of H: Balmer series, Johann Jakob Balmer, 1885 Quantization energy to H atom, Niels Bohr, 1913 Bohr’s Assumption There are certain allowed orbits for which the electron has a fixed energy.