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The many-body Green function of degenerate systems

Abstract : A rigorous non perturbative adiabatic approximation of the evolution operator in the many-body physics of degenerate systems is derived. This approximation is used to solve the long-standing problem of the choice of the initial states of H0 leading to eigenstates of H0+V for degenerate systems. These initial states are eigenstates of P0 V P0, where P0 is the projection onto a degenerate eigenspace of H0. This result is used to give the proper definition of the Green function, the statistical Green function and the non-equilibrium Green function of degenerate systems. The convergence of these Green functions is established.
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Contributor : Christian Brouder <>
Submitted on : Friday, October 30, 2009 - 10:50:42 PM
Last modification on : Friday, March 27, 2020 - 2:57:21 AM
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Christian Brouder, Gianluca Panati, Gabriel Stoltz. The many-body Green function of degenerate systems. Physical Review Letters, American Physical Society, 2009, 103 (23), pp.230401. ⟨10.1103/PhysRevLett.103.230401⟩. ⟨hal-00394238v2⟩



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