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Largest Capture That Still Cannot Live
There are a number of life-and-death problems with the following theme: despite capturing a large chain of stones, the group still cannot live. A challenge here is to construct such life-and-death problems involving a capture of a chain as large as possible. What is the largest such capture that is possible in such problems?
This is currently an open problem. About three hundred years ago, the Igo Hatsuyoron contained a problem that involves the sacrifice of a 16-stone chain. This record was only broken a few years ago, on 2004 May 1, when Robert Pauli posted a slightly modified form of the Igo Hatsuyoron problem involving a 17-stone capture. The current record is 18 stones, posted on 2009 September 10 by "asmobia", which is also a slight modification of Robert's problem.
Inspired by these record breaking attempts, I constructed another life-and-death problem involving killing a group after sacrificing a 18-stone chain, and posted it on Sensei's Library one day later. While not a record breaking event, my problem is very different from the others, and currently shares the top spot. My problem is shown below.
Black to kill all White stones.
Black 1 is necessary to prevent White from making two eyes here. White 2 captures 18 Black stones.
Black 3 is the next key point, making miai of White 4 and Black 5 are miai, giving White no eye at the top edge. Despite White 6, the large White group has only one eye in the center.
This is one line of resistance.
The second line of resistance reverts to the previous diagram.
Connecting at White 8 here does not make two eyes either.
For a list of the largest capture problem constructions, please go to this page on Sensei's Library.