ABSTRACT:
Through string theory, people found interesting relations in particle theory. For example, KawaiLewellenTye (KLT) relation relates the scattering amplitudes of QCD and gravity. However, these kinds of relation are completely mysterious from the point view of Quantum Field Theory since the gravity Lagrangian seems totally unrelated to the YangMills Lagrangian. On the other hand, these kinds of relations are nevertheless true and can be checked by computing the amplitudes using Feynman diagrams order by order. Thus the Feynman diagrammatic expansion does not capture everything of interest, there are still hidden relations between different field theories. Worldline approach, born as a first quantized approach to calculate amplitudes, shares a lot of similarities to string theory. In this talk, I will show how worldline approach works and how it helps shed some light on the problems we are interested in. I will also discuss the subtlety and limitation of the approach and the possibility of generalizing it to "worldgraph approach".

Condensed Matter Seminar Thursday, May 2, 2019 3:30 PM Physics Building, Room 313 Note special room. 
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