Terence TaoのABC予想解説
（数式が沢山出てきて制約上乗らないものが多い）
http://terrytao.wordpress.com/2012/09/18/the-probabilistic-heuristic-justification-of-the-abc-conjecture/#more-6159
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Updates on my research and expository papers, discussion of open problems, and other maths-related topics. By Terence Tao

The probabilistic heuristic justification of the ABC conjecture
18 September, 2012 in math.NT, math.PR | Tags: abc conjecture, probabilistic heuristic
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There has been a lot of recent interest in the abc conjecture, since the release a few weeks ago of the last of a series of papers by Shinichi Mochizuki which, as one of its major applications, claims to establish this conjecture.
It’s still far too early to judge whether this proof is likely to be correct or not (the entire argument encompasses several hundred pages of argument, mostly in the area of anabelian geometry,
which very few mathematicians are expert in, to the extent that we still do not even have a full outline of the proof strategy yet),
and I don’t have anything substantial to add to the existing discussion around that conjecture.
(But, for those that are interested, the Polymath wiki page on the ABC conjecture has collected most of the links to that discussion, and to various background materials.)

In the meantime, though, I thought I might give the standard probabilistic heuristic argument that explains why we expect the ABC conjecture to be true.
The underlying heuristic is a common one, used throughout number theory, and it can be summarised as follows:
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Below the fold, we apply similar heuristics to suggest the truth of the ABC conjecture.
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