2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/211321We study the question of stability of the ground state of a scalar theory which is a generalization of the phi^3 theory and has some similarity to gravity with a cosmological constant. We show that the ground state of the theory at zero temperature becomes unstable above a certain critical temperature, which is evaluated in closed form at high temperature.Four pages, two figures. Revised version published in the Physical Review DHigh Energy Physics - TheoryGeneral Relativity and Quantum Cosmologytext