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Prog. Theor. Phys. Vol. 101 No. 2 (1999) pp. 373-384

Time Evolution of a Quantum System in a Medium and Mass Renormalization in the Projection Operator Method

Tomoi Koide, Masahiro Maruyama and Fujio Takagi

Department of Physics, Tohoku University, Sendai 980-8578, Japan

(Received August 21, 1998)

Abstract:

The time evolution of a quantum system in field theory is studied. We use the Shibata-Hashitsume projection operator method, which is a nonperturbative expansion method known in quantum mechanics. We calculate the time evolution of expectation values of creation and annihilation operators in a super-renormalizable model with unstable particles (or resonances) and study the initial temperature dependence. We carry out the renormalization of the ultraviolet divergence that appears in the time-dependent frequency shift using a mass counterterm. A harmless divergence of the lnt-type remains at the initial time t=0 after mass renormalization. It is suggested that the Shibata-Hashitsume projection operator method is applicable to quantum field theory.

URL : http://ptp.ipap.jp/link?PTP/101/373/
DOI : 10.1143/PTP.101.373

[ Full Text PDF : FREE ACCESS (214K) ] Citation: Plain Text BiBTeX EndNote(RIS) RSS

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Citing Article(s) :

1. Progress of Theoretical Physics Vol. 104 No. 3 (2000) pp. 575-594 :

   A New Expansion of the Heisenberg Equation of Motion with Projection Operator

   Tomoi Koide and Masahiro Maruyama

2. Progress of Theoretical Physics Vol. 107 No. 3 (2002) pp. 525-541 :

   Derivation of Transport Equations Using the Time-Dependent Projection Operator Method

   Tomoi Koide

3. Progress of Theoretical Physics Vol. 107 No. 5 (2002) pp. 1001-1035 :

   Projection Operator Approach to Langevin Equations in φ⁴ Theory

   Tomoi Koide, Masahiro Maruyama and Fujio Takagi

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