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 H_0 leading to eigenstates of H_0 + V for degenerate systems. These initial states are eigenstates of P_0 V P_0, where P_0 is the projection onto a degenerate eigenspace of H_0. This result is used to give the proper definition of the Green function, the statistical Green function and the nonequilibrium Green function of degenerate systems. The convergence of these Green functions is established.
Many-body Green function of degenerate systems / Brouder, Ch; Stoltz, G; Panati, Gianluca. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 103:(2009), pp. 230401-230404. [10.1103/PhysRevLett.103.230401]
Many-body Green function of degenerate systems
PANATI, GIANLUCA
2009
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 H_0 leading to eigenstates of H_0 + V for degenerate systems. These initial states are eigenstates of P_0 V P_0, where P_0 is the projection onto a degenerate eigenspace of H_0. This result is used to give the proper definition of the Green function, the statistical Green function and the nonequilibrium Green function of degenerate systems. The convergence of these Green functions is established.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
