quantum electrodynamics
https://plus.maths.org/content/category/tags/quantum-electrodynamics
enGoing with the flow — part II
https://plus.maths.org/content/going-flow-part-ii
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Marianne Freiberger and Rachel Thomas </div>
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<p>In the <a href="https://plus.maths.org/content/going-flow-0">first part of this article</a> we saw how statistical physics provided a way of zooming in and out of a system to examine it on many scales. Kadanoff's block spin method is an example of a powerful general idea called the <em>renormalisation group</em>. Ironically, this isn't actually a group in the usual, strict mathematical sense (you can read more about mathematical groups in <a href="https://plus.maths.org/content/os/issue39/features/colva/index">The power of groups</a>).<p><a href="https://plus.maths.org/content/going-flow-part-ii" target="_blank">read more</a></p>https://plus.maths.org/content/going-flow-part-ii#commentsasymptotic freedomfundamental forcesparticle physicsquantum electrodynamicsquantum field theoryrenormalisationstrong nuclear forceThu, 27 Mar 2014 17:48:54 +0000mf3446038 at https://plus.maths.org/contentGoing with the flow
https://plus.maths.org/content/going-flow-0
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Marianne Freiberger and Rachel Thomas </div>
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<p>By the 1970s physicists had successfully tamed three of the fundamental forces using a sophisticated construct called quantum field theory. The trouble was that the framework seemed to fall apart when you looked at very high or very low energy scales. So how could these be thought of as valid theories? It's a question physicists are still grappling with today.</p>
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<p><em>In the <a href="https://plus.maths.org/content/strong-free">last article</a> we saw that asymptotic freedom allowed the strong force that binds nuclei together to be described by a quantum field theory. But the perturbative calculations only worked at high energies when the strong coupling constant becomes small. Similarly, it seemed that quantum electrodynamics, the theory that described the interaction of light and matter, only worked at sufficiently low energies. If they did not work at all energy scales, how could these be thought of as valid theories? What is a valid theory, anyway?<p><a href="https://plus.maths.org/content/going-flow-0" target="_blank">read more</a></p>https://plus.maths.org/content/going-flow-0#commentsasymptotic freedomfundamental forcesparticle physicsquantum electrodynamicsquantum field theoryrenormalisationstrong nuclear forceThu, 27 Mar 2014 17:25:51 +0000mf3446037 at https://plus.maths.org/contentStrong but free — part II
https://plus.maths.org/content/strong-free-part-ii
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Marianne Freiberger and Rachel Thomas </div>
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<p>As we saw in the <a href="https://plus.maths.org/content/strong-free">first part of this article</a>, the early 1950s were an experimental gold mine for particle physics, with new particles being discovered almost every week. What was missing, though, was a theory to describe the new discoveries. It took another decade and two Nobel Prizes before the particle zoo was finally tamed. </p><p><a href="https://plus.maths.org/content/strong-free-part-ii" target="_blank">read more</a></p>https://plus.maths.org/content/strong-free-part-ii#commentsasymptotic freedomfundamental forcesparticle physicsquantum electrodynamicsquantum field theorystrong nuclear forceThu, 27 Mar 2014 16:58:13 +0000mf3446036 at https://plus.maths.org/contentStrong but free
https://plus.maths.org/content/strong-free
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Marianne Freiberger and Rachel Thomas </div>
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<p>The early 1950s were an experimental gold mine for physicists, with new particles produced in accelerators almost every week. Yet the strong nuclear force that acted between them defied theoretical description, sending physicists on a long and arduous journey that culminated in several Nobel prizes and the exotic concept of "asymptotic freedom".</p>
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<p>One day in the early 1950s two great physicists met in an office in Chicago. The first, <a href="http://www-history.mcs.st-and.ac.uk/Biographies/Fermi.html">Enrico Fermi</a>, had conducted an unprecedented experiment observing the interaction of tiny particles that had only just been discovered. The second, <a href="http://www-history.mcs.st-andrews.ac.uk/Biographies/Dyson.html">Freeman Dyson</a>, had found a theory that explained the observations. Having glanced at Dyson's results, Fermi put them down and said,"You know, there are two ways of doing theoretical physics.<p><a href="https://plus.maths.org/content/strong-free" target="_blank">read more</a></p>https://plus.maths.org/content/strong-free#commentsasymptotic freedomfundamental forcesparticle physicsquantum electrodynamicsquantum field theorystrong nuclear forceThu, 27 Mar 2014 09:35:53 +0000mf3446035 at https://plus.maths.org/contentThe problem with infinity
https://plus.maths.org/content/problem-infinity
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Marianne Freiberger and Rachel Thomas </div>
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<p>This is the second article in our four-part series exploring quantum electrodynamics. After successfully applying quantum mechanics to the electromagnetic field, physicists faced a problem of boundless proportions: every calculation they made returned infinity as the answer.</p>
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<p><em>This article is the second in a four-part series on quantum electrodynamics. You can read the previous article <a href="https://plus.maths.org/content/let-me-take-you-down-cos-were-going-quantum-fields">here</a> and the next one <a href="https://plus.maths.org/content/rise-qed">here</a>.</em></p>
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<p>Paul Dirac (1902-1984). </p><p><a href="https://plus.maths.org/content/problem-infinity" target="_blank">read more</a></p>https://plus.maths.org/content/problem-infinity#commentsmathematical realityEinsteinelectromagnetismphotonquantum electrodynamicsquantum physicsvirtual particleMon, 22 Jul 2013 07:57:33 +0000mf3445917 at https://plus.maths.org/contentLet me take you down, cos we're going to ... quantum fields
https://plus.maths.org/content/let-me-take-you-down-cos-were-going-quantum-fields
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Marianne Freiberger and Rachel Thomas </div>
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<p>You may have heard of quantum theory and you probably know what a field is. But what is quantum field theory? This article traces the development of quantum electrodynamics in the first half of the 20th century. Hair raising difficulties, heroic struggle and illustrious characters — this story has it all!</p>
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<p><em>You may have heard of quantum theory before and you probably know what a field is. But what is quantum field theory? This four-part article traces the development of an example of a quantum field theory, quantum electrodynamics, in the first half of the 20th century. You can read the next article in the series <a href="https://plus.maths.org/content/problem-infinity">here</a>.</em></p><p><a href="https://plus.maths.org/content/let-me-take-you-down-cos-were-going-quantum-fields" target="_blank">read more</a></p>https://plus.maths.org/content/let-me-take-you-down-cos-were-going-quantum-fields#commentsmathematical realityDirac's equationEinsteinelectromagnetismMaxwell's equations of electromagnetismquantum electrodynamicsquantum mechanicsquantum physicsSchrödinger equationMon, 22 Jul 2013 07:42:44 +0000mf3445916 at https://plus.maths.org/contentTaming QED
https://plus.maths.org/content/rise-qed
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Marianne Freiberger and Rachel Thomas </div>
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<p>This is the third article in our four-part series exploring quantum electrodynamics. After struggling with a theory plagued by unwieldy infinities an ingenious trick put QED back on track.</p>
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<p><em>This article is the third in a four-part series on quantum electrodynamics. You can read the previous article <a href="https://plus.maths.org/content/problem-infinity">here</a> and the next one <a href="https://plus.maths.org/content/quantum-pictures">here</a>. You might also want to read our <a href="https://plus.maths.org/content/another-conversation-freeman-dyson-revise-title">interview with Freeman Dyson</a>.</em></p><p><a href="https://plus.maths.org/content/rise-qed" target="_blank">read more</a></p>https://plus.maths.org/content/rise-qed#commentsmathematical realityelectromagnetismquantum electrodynamicsquantum mechanicsquantum physicsMon, 22 Jul 2013 07:06:30 +0000mf3445918 at https://plus.maths.org/contentQuantum pictures
https://plus.maths.org/content/quantum-pictures
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Marianne Freiberger and Rachel Thomas </div>
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<p>This is the last article in a four-part series exploring quantum electrodynamics. After a breakthrough that tamed QED in theory, the stick-like drawings known as Feynman diagrams, policed by a young Freeman Dyson, made the theory useable.</p>
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<p><em>This article is the last in a four-part series on quantum electrodynamics. You can read the previous article <a href="https://plus.maths.org/content/rise-qed">here.</a> You might also want to read our <a href="https://plus.maths.org/content/another-conversation-freeman-dyson-revise-title">interview with Freeman Dyson</a>.</em></p><p><a href="https://plus.maths.org/content/quantum-pictures" target="_blank">read more</a></p>https://plus.maths.org/content/quantum-pictures#commentsmathematical realityelectromagnetismFeynman diagramquantum electrodynamicsquantum mechanicsquantum physicsMon, 22 Jul 2013 07:05:01 +0000mf3445920 at https://plus.maths.org/content