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| Strange results of ncExt_R https://www.singular.uni-kl.de/forum/viewtopic.php?f=10&t=2635 |
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| Author: | caramdir [ Fri Jul 21, 2017 10:34 pm ] |
| Post subject: | Strange results of ncExt_R |
I was trying to do some noncommutative Ext-computations and got unexpected results. The following is a minimal example (where everything is actually commutative): Code: LIB "nchomolog.lib"; ring base = 0,(x,y),dp; def A = nc_algebra(1,0); setring A; ideal i = (x,y); ncExt_R(0,i); => _[1,1]=1 ncExt_R(1,i); => _[1]=x*gen(1) ncExt_R(2,i); => _[1]=gen(1) I'm reading this as Ext^i_{k[x,y]}(k, k[x,y]) = 0 for i != 1 and Ext^1 = k[y]. But this is clearly no the correct result. Am I misunderstanding something? Ext_R from homolog.lib gives me the correct Ext's (i.e. Ext^2 = k, everything else vanishes). |
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