{"id":743,"date":"2019-06-05T18:04:21","date_gmt":"2019-06-05T17:04:21","guid":{"rendered":"https:\/\/research.kent.ac.uk\/upgrade-theoryandsimulation\/?page_id=743"},"modified":"2020-07-27T10:35:29","modified_gmt":"2020-07-27T09:35:29","slug":"johannes-hofmann-high-temperature-expansion-of-the-viscosity-in-interacting-quantum-gases","status":"publish","type":"page","link":"https:\/\/research.kent.ac.uk\/theoryandsimulation\/theory-discussion-group\/johannes-hofmann-high-temperature-expansion-of-the-viscosity-in-interacting-quantum-gases\/","title":{"rendered":"Johannes Hofmann \/ High-temperature expansion of the viscosity in interacting quantum gases"},"content":{"rendered":"<p>Discussion group on 6 June 2019, Ingram Building, Rm. 110<\/p>\n<p>I will talk about new methods to compute the shear and the bulk viscosity in strongly interacting quantum gases. These quantities determine the damping and dissipation of the collective dynamics of a quantum gas (such as the collective oscillations or the expansion from a trap). There is a significant effort to measure the viscosities since quantum gases are said to form a &#8220;perfect fluid\u2019\u2019, in which the viscosities are anomalously small (the only other example of such a fluid is the quark-gluon plasma at a vastly different energy scale). In particular, the shear viscosity comes close to saturating a shear viscosity-to-entropy bound from string theory. I will discuss why the theoretical calculations of the viscosity is very intricate and present a way to overcome this at high temperatures by means of a cluster expansion that is represented in terms of Feynman diagrams. For the shear viscosity, I outline how a connection to results from a Boltzmann kinetic transport equation is made, and I comment on a new result for the bulk viscosity that differs from kinetic theory.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Discussion group on 6 June 2019, Ingram Building, Rm. 110 I will talk about new methods to compute the shear and the bulk viscosity in strongly interacting quantum gases. These quantities determine the damping and dissipation of the collective dynamics of a quantum gas (such as the collective oscillations or the expansion from a trap). [&hellip;]<\/p>\n","protected":false},"author":140,"featured_media":0,"parent":190,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-743","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/research.kent.ac.uk\/theoryandsimulation\/wp-json\/wp\/v2\/pages\/743","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/research.kent.ac.uk\/theoryandsimulation\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/research.kent.ac.uk\/theoryandsimulation\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/research.kent.ac.uk\/theoryandsimulation\/wp-json\/wp\/v2\/users\/140"}],"replies":[{"embeddable":true,"href":"https:\/\/research.kent.ac.uk\/theoryandsimulation\/wp-json\/wp\/v2\/comments?post=743"}],"version-history":[{"count":2,"href":"https:\/\/research.kent.ac.uk\/theoryandsimulation\/wp-json\/wp\/v2\/pages\/743\/revisions"}],"predecessor-version":[{"id":981,"href":"https:\/\/research.kent.ac.uk\/theoryandsimulation\/wp-json\/wp\/v2\/pages\/743\/revisions\/981"}],"up":[{"embeddable":true,"href":"https:\/\/research.kent.ac.uk\/theoryandsimulation\/wp-json\/wp\/v2\/pages\/190"}],"wp:attachment":[{"href":"https:\/\/research.kent.ac.uk\/theoryandsimulation\/wp-json\/wp\/v2\/media?parent=743"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}