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Groebner basis computation with symbolic constants

asked 9 years ago

jooyous gravatar image

updated 9 years ago

Hello! If I have a system of polynomials in CC[x,y,z] or any other field, is there a way to create constants that are in that field in a way that makes Groebner basis computation still work? For example, if I want to compute the Groebner basis for the ideal generated by

y^2 + z - c1
x*y^2 - c2 - 2

Is there a way to indicate that the c1 and c2 are in CC or whatever field I'm in? I've figured out how to get them to not be indeterminates (over the symbolic ring),

Ideal (y^2 + z - c1, x*y^2 - c2 - 2) of Multivariate Polynomial Ring in x, y, z over Symbolic Ring

but then the polynomials containing them don't have division.

AttributeError: 'MPolynomialRing_polydict_with_category' object has no attribute 'monomial_divides'

Thank you!

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answered 9 years ago

tmonteil gravatar image

updated 9 years ago

I am not sure this trick is formally correct (please tell us!), but you can try to make c1 and c2 transcendental, by creating a fraction field around them:

sage: R.<c1,c2> = PolynomialRing(QQ)
sage: F = R.fraction_field()
sage: S.<x,y,z> = PolynomialRing(F)
sage: I = ideal(y^2 + z - c1, x*y^2 - c2 - 2)
sage: I.groebner_basis()
[y^2 + z - c1, x*z + (-c1)*x + c2 + 2]
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Seems to be working so far!

jooyous gravatar imagejooyous ( 9 years ago )

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Asked: 9 years ago

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Last updated: May 07 '15