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In a recent paper ͓Phys. Rev. B 52, R17 005 ͑1995͔͒ Tsukada, Gotoda, Nunoshita, and Nishino have investigated the effect of the Coulomb charging energy on the time evolution of the electron occupation probability in a coupled-dot system. At a small initial fluctuation around the equal distribution of the electron occupation probability to two quantum dots, they reported that the symmetry-breaking instabilities are induced for Coulomb charging energy larger than a certain threshold value. We claim that the symmetry-breaking instabilities are invalid for a negative coupling coefficient, which is the normal case for conduction band electrons. Numerical results for various initial conditions and the Coulomb charging energies are presented.

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