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The stability of the scalar χ2ϕ interaction

Franz Gross, Cetin Savkli, John Tjon

nucl-tharXiv:nucl-th/0102041

Abstract

A scalar field theory with a χχϕ interaction is known to be unstable. Yet it has been used frequently without any sign of instability in standard text book examples and research articles. In order to reconcile these seemingly conflicting results, we show that the theory is stable if the Fock space of all intermediate states is limited to a finite number of χχ loops associated with field χ that appears quadradically in the interaction, and that instability arises only when intermediate states include these loops to all orders.

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