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Topic Review
Sakurai's Bell Inequality
The intention of a Bell inequality is to serve as a test of local realism or local hidden variable theories as against quantum mechanics, applying Bell's theorem, which shows them to be incompatible. Not all the Bell's inequalities that appear in the literature are in fact fit for this purpose. The one discussed here holds only for a very limited class of local hidden variable theories and has never been used in practical experiments. It is, however, discussed by John Bell in his "Bertlmann's socks" paper (Bell, 1981), where it is referred to as the "Wigner–d'Espagnat inequality" (d'Espagnat, 1979; Wigner, 1970). It is also variously attributed to Bohm (1951?) and Belinfante (1973). Note that the inequality is not really applicable either to electrons or photons, since it builds in no probabilistic properties in the measurement process. Much more realistic hidden variable theories can be devised, modelling spin (or polarisation, in optical Bell tests) as a vector and allowing for the fact that not all emitted particles will be detected.
  • 638
  • 17 Oct 2022
Topic Review
Sagittarius
Sagittarius, often referred to as "the Archer," is a prominent constellation in the southern celestial hemisphere, renowned for its association with Greek mythology and the mythical centaur Chiron. Positioned along the Milky Way, Sagittarius hosts a wealth of celestial wonders, including the galactic center and numerous star clusters.
  • 281
  • 15 Mar 2024
Topic Review
Ryu-Takayanagi Conjecture
The Ryu-Takayanagi conjecture is a conjecture within holography that posits a quantitative relationship between the entanglement entropy of a conformal field theory and the geometry of an associated Anti-de Sitter spacetime . The formula characterizes "holographic screens" in the bulk; that is, it specifies which regions of the bulk geometry are "responsible to particular information in the dual CFT". The conjecture is named after Shinsei Ryu and Tadashi Takayanagi, who jointly published the result in 2006. As a result, the authors were awarded the 2015 New Horizons in Physics Prize for "fundamental ideas about entropy in quantum field theory and quantum gravity". The formula was generalized to a covariant form in 2007.
  • 735
  • 12 Oct 2022
Biography
Rudolph Koenig
Karl Rudolph Koenig (26 November 1832 – 2 October 1901) was born in Königsberg of Prussia. Koenig was a businessman, instrument maker, and Germany physicist, chiefly concerned with acoustic phenomena. He was best known for designing and building acoustical instruments such as the tuning fork and sound analyser. Karl Rudolph Koening was born on 26 November 1832, a descendant of a prominent
  • 381
  • 23 Nov 2022
Biography
Rudolf Haag
Rudolf Haag (17 August 1922 – 5 January 2016) was a German theoretical physicist, who mainly dealt with fundamental questions of quantum field theory. He was one of the founders of the modern formulation of quantum field theory and he identified the formal structure in terms of the principle of locality and local observables. He also made important advances in the foundations of quantum statis
  • 713
  • 30 Nov 2022
Topic Review
Rubens' Tube
A Rubens' tube, also known as a standing wave flame tube, or simply flame tube, is an antique physics apparatus for demonstrating acoustic standing waves in a tube. Invented by German physicist Heinrich Rubens in 1905, it graphically shows the relationship between sound waves and sound pressure, as a primitive oscilloscope. Today, it is used only occasionally, typically as a demonstration in physics education.
  • 570
  • 29 Nov 2022
Topic Review
Royal Society Bakerian Medal
The Bakerian Medal is one of the premier medals of the Royal Society that recognizes exceptional and outstanding science. It comes with a medal award and a prize lecture. The medalist is required to give a lecture on any topic related to physical sciences. It is awarded annually to individuals in the field of physical sciences, including computer science.
  • 415
  • 07 Nov 2022
Topic Review
Rotating Triboelectric Nanogenerators for Energy Harvesting Applications
Addressing the increasing development of IoT networks and the associated energy requirements, rotating triboelectric nanogenerators (R-TENGs) are proving to be strong candidates in the field of energy harvesting, as well as to that of self-powered devices and autonomous sensors.
  • 537
  • 13 Jul 2023
Topic Review
Rooftop Photovoltaic Power Station
A rooftop photovoltaic power station, or rooftop PV system, is a photovoltaic (PV) system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure. The various components of such a system include photovoltaic modules, mounting systems, cables, solar inverters and other electrical accessories. Rooftop mounted systems are small compared to ground-mounted photovoltaic power stations with capacities in the megawatt range, hence being a form of distributed generation. Most rooftop PV stations in developed countries are Grid-connected photovoltaic power systems. Rooftop PV systems on residential buildings typically feature a capacity of about 5 to 20 kilowatts (kW), while those mounted on commercial buildings often reach 100 kilowatts to 1 Megawatt (MW). Very large roofs can house industrial scale PV systems in the range of 1-10 Megawatts.
  • 1.7K
  • 17 Nov 2022
Topic Review
Role of Uranium in the Nuclear Fuel Cycle
Uranium was discovered in 1789 by the German chemist Martin Heinrich Klaproth. It is the most known and used actinide element mainly because of its usage in nuclear fuel processing; however, the application potential of uranium compounds is much broader, stretching, e.g., into the field of organometallic synthesis, catalysis and beyond. Moreover, uranium is one of the few naturally occurring actinides, whereas the other members, with the exception of thorium, are considered to be human-made, despite their natural occurrence in traces as a result of uranium and thorium spontaneous fissions. In nature, uranium occurs as three main isotopes, where the non-fissile 238U is the most abundant, encompassing over 99% of the available uranium resources.
  • 616
  • 23 May 2022
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