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Bug? Polynomial variable name matters

asked 2021-06-28 13:13:57 +0200

FabianG gravatar image

updated 2023-01-09 23:59:55 +0200

tmonteil gravatar image

The following calculation of an intersection of curves over QQbar raises an error within Singular on Sage v9.2.

P.<a, y, z> = ProjectiveSpace(QQbar, 2)
f = a^3 + z^3
C = Curve(f)
g = (a + y)^3 + z^3
D = Curve(g)

It does work when replacing the variable name a by x.

I assume this is a bug but could not trace it down to the internals of rational_points and the Singular interface. The variables band d work, whereas c raises a different error. Does anyone know more about that? Is it already fixed in the newer versions? Should I post this as a ticket on

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answered 2021-06-28 18:43:07 +0200

tmonteil gravatar image

Thanks for reporting, this is clearly a bug, i can reproduce it on latest Sage version 9.4.beta3, it is know tracked at trac ticket 32077. If you want to contribute to this ticket (and others !), you can ask for a trac account or log-in via github, see

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thank you!

FabianG gravatar imageFabianG ( 2021-06-29 10:30:40 +0200 )edit

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Asked: 2021-06-28 13:13:57 +0200

Seen: 217 times

Last updated: Jun 28 '21