  We study a simple chemical reaction system and effects of the internal noise.
The chemical reaction system causes the same transition phenomenon discussed by
Togashi and Kaneko [Phys. Rev. Lett. 86 (2001) 2459; J. Phys. Soc. Jpn. 72
(2003) 62]. By using the simpler model than Togashi-Kaneko's one, we discuss
the transition phenomenon by means of a random walk model and an effective
model. The discussion makes it clear that quasi-absorbing states, which are
produced by the change of the strength of the internal noise, play an important
role in the transition phenomenon. Stabilizing the quasi-absorbing states
causes bifurcation of the peaks in the stationary probability distribution
discontinuously.
