Different algorithms for has_rational_point return different answers.

asked 2020-07-30 21:54:39 -0600

GG_2001 gravatar image

updated 2020-07-31 07:03:26 -0600

slelievre gravatar image

There seems to be an inconsistency.

Define a polynomial ring in three variables:

sage: R.<x, y, z> = QQ[]

Define a conic:

sage: C = Conic(27628*(x^2 - y^2) - 81746*x*y  - z^2)

Check whether the conic has rational points, using algorithm="local":

sage: C.has_rational_point(algorithm="local", obstruction=True)
(True, None)

Check whether the conic has rational points, using algorithm="default":

sage: C.has_rational_point(algorithm="default", obstruction=True)
(False, 17)
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