Feynman Diagrams Versus Fermi-gas Feynman Emulator
Dr Félix Werner
CNRS, Laboratoire Kastler Brossel, Ecole Normale Superieure, France
3:30 pm Friday, 4 May 2012, EN101 Lecture Theatre (EN Building), Hawthorn.
Precise understanding of strongly interacting fermions, from electrons in modern materials to nuclear matter, presents a major goal in modern physics. For the first time, we sum the series of Feynman diagrams for such a many-body problem to essentially infinite order. This is made possible by a new theoretical approach, Bold Diagrammatic Monte Carlo (BDMC), which combines a Monte Carlo process capable of sampling billions of diagram topologies, bold lines representing fully dressed propagators, and divergent-series resummation techniques.
Specifically, we compute the equation of state of the unitary gas - a prototypical example of a strongly correlated fermionic system - in the normal unpolarised phase. We cross-validate the results with new precision experiments on ultra-cold
6Li atoms at the broad Feshbach resonance. Excellent agreement demonstrates that a series of Feynman diagrams can be controllably resummed in a non-perturbative regime using BDMC. This opens the door to the solution of challenging problems across many areas of physics.
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Reference:
K. Van Houcke, F. Werner, E. Kozik, N. Prokofev, B. Svistunov, M. Ku, A.Sommer, L. W. Cheuk, A. Schirotzek, M. W. Zwierlein, Nature Physics (2012), doi:10.1038/nphys2273 [http://arxiv.org/abs/1110.3747]
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