renormalisation
http://plus.maths.org/content/category/tags/renormalisation
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>).<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?<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/content