Condensed-Matter Physics & Materials Science Seminar

Feynman diagrams are the most celebrated and powerful tool of theoretical physics usually associated with the analytic approach. I will argue that diagrammatic expansions are also an ideal numerical tool with enormous and yet to be explored potential for solving interacting many-body systems by direct simulation of Feynman diagrams (bare or skeleton) for the proper self-energies and polarization operators up to high order. Though the original series based on are propagators are sign-alternating and often divergent one can determine the answer behind them by using proper series re-summation techniques and working with skeleton diagrams,
i.e. by making the entire scheme self-consistent. The bottom line is that the diagrammatic Monte Carlo approach generically solves the computational complexity for interacting fermionic systems.
In terms of physical applications, I will disucss results for the Hubbard model, resonant fermi gas at unitarity, and stability of Dirac liquid against strong Coulomb interaction in graphene.