This equilibrium is the equilibrium of the ``naked'' planet. Let us consider it in detail.
If , i.e. the equilibrium temperature lies outside
the tolerance interval for photosynthesis, then this equilibrium is always
stable. If then the equilibrium is stable, if
or
Suppose the reciprocal operator exists, so
that
Since
then the left part of (42) depends only on the characteristics and total
amount of carbon in the system. The right part of (42) depends only
on the biotic characteristics of the planetary vegetation and also the total
carbon. If we assume that the equilibrium temperature for the ``naked'' planet is
fixed -- the total carbon is fixed also -- but we can change (e.g. in an evolutionary
way) the vegetation characteristics, then we can pass from a stable ``naked''
equilibrium to an unstable one.
Figure 9: To the problem of stability for "naked" equilibrium: in the interval with it is unstable ( for ). For
this interval is reduced to a point, above 1 the equilibrium
is stable for any T.
Let us consider Fig. 9: from this picture we can see that the condition , i.e. the condition that the equilibrium temperature belongs to the photosynthesis tolerance interval, is not sufficient in order to pass to the instability of a ``naked'' equilibrium, i.e. for the ``origin of life'' It is necessary that the temperature , then the ``naked'' equilibrium becomes unstable and ``life'' can occur. This interval depends on such biotic characteristics as the residence time of carbon in the biota () and its maximum productivity . We call the interval the ``vegetation tolerance interval''
Let us consider the change of the product . Its increase, which corresponds either to the decrease of carbon residence time in the biota or to a decrease of the maximal productivity of photosynthesis, leads to a reduction of the vegetation interval. And, vice versa, the decrease of , because of the increase of residence time or increase of maximal productivity, increases the vegetation interval.
It is obvious that if , then the ``naked'' equilibrium
is stable for any , and ``life'' cannot arise in the vicinity
of this equilibrium. In other words, there is some critical combination from
, m (or ), and A:
or
On the other hand
is the monotonous increasing function of A, since monotonously
decreases with the growth of A. Since
,
then , if
.
In fact there are two bifurcation parameters: and A. Note that
, if , where
since .
Let us assume that , and , then
we have the stability diagram as in Fig. 10. The border in the domain is determined by
the function
whereat for the ``naked'' equilibrium is unstable.
Figure 10: Stability border for in the domain: , . The shaded area indicates the area of instability of
where ``life'' can arise in the vicinity of the ``naked'' equilibrium.