quantum field theory
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enGoing with the flow — part II
http://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="http://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="http://plus.maths.org/content/os/issue39/features/colva/index">The power of groups</a>).<div class="field field-type-number-integer field-field-hidden">
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<p><a href="http://plus.maths.org/content/going-flow-part-ii" target="_blank">read more</a></p>http://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 http://plus.maths.org/contentGoing with the flow
http://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="http://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?<div class="field field-type-number-integer field-field-hidden">
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<p><a href="http://plus.maths.org/content/going-flow-0" target="_blank">read more</a></p>http://plus.maths.org/content/going-flow-0#commentsasymptotic freedomfundamental forcesparticle physicsquantum electrodynamicsquantum field theoryrenormalisationstrong nuclear forceThu, 27 Mar 2014 17:25:51 +0000mf3446037 at http://plus.maths.org/contentStrong but free — part II
http://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="http://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><div class="field field-type-number-integer field-field-hidden">
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<p><a href="http://plus.maths.org/content/strong-free-part-ii" target="_blank">read more</a></p>http://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 http://plus.maths.org/contentA brief history of quantum field theory
http://plus.maths.org/content/brief-history-quantum-field-theory
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<p>Something called <em>quantum field theory</em> has been hugely successful in describing the fundamental forces and particles. But what exactly is it? This series of accessible articles traces the history of quantum field theory, from its inception at the beginning of the twentieth century to the tantalising questions that are still open today. It's a story of pain and triumph, hardship and success.</p>
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<p>The world we live in is made up of fundamental particles interacting through the fundamental forces. One of the greatest aims of theoretical physics is to describe all of these forces and particles in one all-encompassing theory. Something called <em>quantum field theory</em> has been hugely successful in this context, but what exactly is it? And does it answer all the questions?</p><p><a href="http://plus.maths.org/content/brief-history-quantum-field-theory" target="_blank">read more</a></p>http://plus.maths.org/content/brief-history-quantum-field-theory#commentsquantum field theoryThu, 27 Mar 2014 11:26:21 +0000mf3446071 at http://plus.maths.org/contentStrong but free
http://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 the 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.<div class="field field-type-number-integer field-field-hidden">
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<p><a href="http://plus.maths.org/content/strong-free" target="_blank">read more</a></p>http://plus.maths.org/content/strong-free#commentsasymptotic freedomfundamental forcesparticle physicsquantum electrodynamicsquantum field theorystrong nuclear forceThu, 27 Mar 2014 09:35:53 +0000mf3446035 at http://plus.maths.org/contentOperas, revolutions and nature's tricks: a conversation with Freeman Dyson
http://plus.maths.org/content/another-conversation-freeman-dyson-revise-title
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In February this year we were lucky enough to interview
Freeman Dyson at the Institute for Advanced Studies in
Princeton, USA. Dyson is now 89 and still does physics every day in
his first floor office at the Institute.
Here is an edited version of our interview that we hope conveys his
generous nature, wit and intellect. </div>
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<p><em>In February this year we were lucky enough to interview
Freeman Dyson at the <a href="http://www.ias.edu/">Institute for Advanced Studies</a> (IAS) in
Princeton, USA. Dyson is now 89 and still does physics every day in
his first floor office at the Institute.<div class="field field-type-number-integer field-field-hidden">
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<p><a href="http://plus.maths.org/content/another-conversation-freeman-dyson-revise-title" target="_blank">read more</a></p>http://plus.maths.org/content/another-conversation-freeman-dyson-revise-title#commentsFreeman Dysonquantum field theoryquantum mechanicsquantum physicsMon, 22 Jul 2013 07:00:58 +0000mf3445899 at http://plus.maths.org/contentStrings, particles and the early Universe
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The <em>Strong Fields, Integrability and Strings</em>
programme, which took place at the Isaac
Newton Institute in 2007, explored an area that
would have been close to Isaac Newton's heart:
how to unify Einstein's theory of gravity, a
continuation of Newton's own work on
gravitation, with quantum field theory, which
describes the atomic and sub-atomic world, but
cannot account for the force of gravity. </div>
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<p><em>This article is part of a <a href="http://plus.maths.org/content/isaac-newton-institute">series</a> celebrating the 20th birthday of the <a href="http://www.newton.ac.uk/">Isaac Newton Institute</a> in Cambridge. The Institute is a place where leading mathematicians from around the world can come together for weeks or months at a time to indulge in what they like doing best: thinking about maths and exchanging ideas without the distractions and duties that come with their normal working lives.<p><a href="http://plus.maths.org/content/strings-particles-and-early-universe" target="_blank">read more</a></p>http://plus.maths.org/content/strings-particles-and-early-universe#commentsholographic principleNewton Institutequantum field theoryquantum gravitystring theorysupersymmetryThu, 19 Jul 2012 08:55:54 +0000mf3445435 at http://plus.maths.org/contentSupergravity to the rescue?
http://plus.maths.org/content/supergravity-rescue
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<p>In the corner of the garden between the Centre of Mathematical Sciences and the Isaac Newton Institute in Cambridge, sits a reminder of our ongoing quest to understand gravity: an apple tree that was taken as a cutting from the tree at Newton's birthplace, the tree that is said to have inspired his theory of gravity. Newton's theory was extended to the cosmological scales by Einstein's theory of general relativity – but can supergravity explain how gravity works in the quantum world?</p>
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<div class="rightimage"><img src="http://plus.maths.org/content/sites/plus.maths.org/files/news/2012/hawking70/apples_pubdom_web.jpg" width="300" height="200" alt="apples"><p>Which theory will bear fruit?</p><p><a href="http://plus.maths.org/content/supergravity-rescue" target="_blank">read more</a></p>http://plus.maths.org/content/supergravity-rescue#commentsmathematical realityhawking70quantum field theoryquantum physicssupergravitysupersymmetryTue, 10 Jan 2012 16:17:49 +0000Rachel5637 at http://plus.maths.org/content