We believe that confusion has been generated by the way we discussed our concepts of criticality and ignition. The cause of this confusion is the paragraph in our paper [1] that contains Eq. ( ). The word "ignition" was used just before the equation, whereas we should have used instead the word "criticality." (Similarly, we should not have used the word "extinction" three lines later.) The inadvertent use of the wrong word is all the more regrettable because in this instance it leads to the confusion and misunderstanding that we wanted to avoid in the first place.
Our concepts of criticality and ignition are based on a jump in the steady-state temperature and an inflection point in the time variation, respectively. Except in the above-mentioned paragraph, we have been consistent in keeping them distinct. The criterion for criticality and that for ignition can be the same, but they also can be different. Figure of our paper shows clearly how both situations are possible. When one goes from region c to region b by crossing boundary A, the steady-state temperature will jump from ui to u3, and two inflections appear, whereas there were none in region c. In this case the criterion for criticality and that for ignition are both satisfied. But if the crossing is made