科研之友
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摘要
We show that Richard Thompson's group F is nonamenable if and only if the three element set A(2)={x(0)x(0)x(0), x(0)x(0)x(1), x(0)x(0)x(2)} is weakly-ruinous. We then show that no two element set is weakly-ruinous, thereby showing that A(2) is minimal in both the number of elements that a weakly-ruinous set must contain and also in the number of carets that each tree in a weakly-ruinous set must have.
- 出版日期2014-4-3
