We present an algebraic, nondiagrammatic derivation of finite-temperature second-order many-body perturbation theory [FT-MBPT(2)], using techniques and concepts accessible to theoretical chemical physicists. We give explicit expressions not just for the grand potential but particularly for the mean energy of an interacting many-electron system. The framework presented is suitable for computing ...

The second quantized form of Rayleigh-Schrodinger perturbation theory is symbolically manipulated to derive many-body perturbation theory (MBPT) formulas for particle-hole excited states of closed shell atoms. The analytic results obtained from the symbolic code, written in Mathematica, will be presented for the lowest orders of MBPT. These results compare exactly with the results obtained by h...

2 The single-particle retarded Green function and its spectral function 4 2.1 Retarded, advanced, “greater”, and “lesser” single-particle Green functions . 4 2.2 The meaning of 〈· · ·〉 and the time dependence . . . . . . . . . . . . . . . . . 5 2.3 Some other forms of the Green functions . . . . . . . . . . . . . . . . . . . . 6 2.3.1 Transformations to other bases . . . . . . . . . . . . . . ....

2 The single-particle retarded Green function and its spectral function 4 2.1 Retarded, advanced, “greater”, and “lesser” single-particle Green functions . 4 2.2 The meaning of 〈· · ·〉 and the time dependence . . . . . . . . . . . . . . . . . 5 2.3 Some other forms of the Green functions . . . . . . . . . . . . . . . . . . . . 6 2.3.1 Transformations to other bases . . . . . . . . . . . . . . ....

A major task for theoretical chemists is the development of methods to predict energy differences with chemical accuracy. Most quantum chemists agree that accurate prediction of relative energies requires application of theories that include electron correlation effects, effects not treated in self-consistent-field (SCF) calculations [1-4]. Estimates of molecular correlation energy have been ob...