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numerical semigroup ring

numerical semigroup ring

algebra123 · Thu Mar 31, 2011 6:08 pm

How do I define a numerical semigroup ring in Singular. For example

k[[t^5,t^7]]

or something like

k[[t^6,t^8 + t^9,t^11]] ?

Re: numerical semigroup ring

barakat · Thu Apr 14, 2011 1:15 pm

I would simply write it as an affine ring. You can use eliminate to get the ring relations.

Mohamed

Re: numerical semigroup ring

algebra123 · Mon Apr 18, 2011 8:17 pm

Yes, this would do it. But how can we use eliminate to get the defining ideal? I am surprised that there is not a procedure that would take a map, say x to t^5 and y to t^7, and produce the defining ideal.

Re: numerical semigroup ring

greuel · Tue Apr 19, 2011 2:08 pm

A procedure for two lines would be overkill since one has to specify the map anyway.
Here is the SINGULAR input:

ring r = 0,(t,x,y),dp;
ideal i = x-t5, y-t7;
eliminate(i,t);