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Topic review - Old rinvar examples don't work anymore
Author Message
  Post subject:  Old rinvar examples don't work anymore  Reply with quote
Hi all,

I'm trying to do some invariant theory computations with Singular, using the rinvar.lib by Thomas Bayer. I ran into some problems (I'm completely new to Singular), so I decided to try some example code that I found on his old website (link below). However, the following example from his invariant-theory examples script produces an error:
// infinite, reductive (sl2 on V+V+Sym^2V) (ub = 3)

ring S3 = 0,(s(1..4), t(1..7)), lp;
ideal G = s(1)*s(4) - s(2)*s(3) - 1;
ideal action = s(1)*t(1) + s(2)*t(2), s(3)*t(1) + s(4)*t(2), s(1)*t(3) + s(2)*t(4), s(3)*t(3) + s(4)*t(4),s(1)^2*t(5) + 2*s(1)*s(2)* t(6) + s(2)^2*t(7), s(1)*s(3)*t(5) + (s(1)*s(4) + s(2)*s(3))*t(6) + s(2)*s(4)*t(7), s(3)^2*t(5) + 2*s(3)*s(4)*t(6) + s(4)^2 * t(7);
//int time = timer; ideal inv = Invariants(G, action, 3); time = timer - time; time; //

Actually, that code doesn't produce an error, but when I replace the commented call to "Invariants" with a call to InvariantRing(std(G), action), as in the examples for the current rinvar.lib, I get the error:
def R = InvariantRing(std(G), action);
? ideal not zerodimensional
? leaving zeroset.lib::zeroSet
? leaving rinvar.lib::ReynoldsOperator
? leaving rinvar.lib::InvariantRing

Maybe his Invariants function is not the same as the InvariantRing function that is currently in Singular? I tried running his old (2002) script (link below), but could not get it to work. Any ideas what the problem is and how to fix it?


I'm not allowed to post links, so take out the spaces in the following:
old website of Thomas Bayer: www14 . in . tum . de/personen/bayert/software.html#Invariants
Old version of rinvar.lib: wwwmayr . informatik . tu-muenchen . de/personen/bayert/invariants
Post Posted: Tue May 13, 2014 9:25 am

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