Thermal averaging in quantum many-body systems: a non-perturbative thermal cluster cumulant approach

Sanyal, Goutam ; Mandal, Seikh Hannan ; Mukherjee, Debashis (1992) Thermal averaging in quantum many-body systems: a non-perturbative thermal cluster cumulant approach Chemical Physics Letters, 192 (1). pp. 55-61. ISSN 0009-2614

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/000926...

Related URL: http://dx.doi.org/10.1016/0009-2614(92)85427-C

Abstract

We present here a non-perturbative cluster cumulant approach for effecting thermal averaging in quantum-mechanical observables. We introduce a new representation of thermo field dynamics (TFD), with the associated thermal normal order and Wick expansion, and replace the thermal averaging by a quantum mechanical one involving a thermal "base state" |0β. Unlike the traditional TFD, only the physical variables appear in our formulation. The imaginary time evolution of the statistical operator is treated by our recently developed time-dependent coupled cluster theory. The partition function Z is evaluated as a completely contracted quantity involving |0β. We have computed Z for an anharmonic oscillator with quartic perturbation as an illustrative application. We also demonstrate numerically the validity of the Kohn-Luttinger theorem.

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ID Code:21839
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