The irreducible_components gives an answer that is consistent with magma: C is a complete intersection of two hypersurfaces in A4 and hence of dimension 2 itself. Looks like "Curve" over QQ doesn't check dimension or delegates to a routine that doesn't check properly.
On Tuesday 23 July 2024 at 05:26:20 UTC-7 Georgi Guninski wrote: > #Author Georgi Guninski > > K.<x,y,z,t>=QQ[] > t1=x^2*z^2 + y*t; > t2= y*z^2 + x^2*t; > C=Curve([x^4-y^2-19,z^4-t^2-23,t1^2-t2^2-19*23]); > C.genus() > #93 #Wrong > > C.irreducible_components() > [ > Closed subscheme of Affine Space of dimension 4 over Rational Field > defined by: > z^4 - t^2 - 23, > x^4 - y^2 - 19 > ] > > Magma raises error when trying to construct Curve() > > When I work over GF(113) instead of QQ, I get error: > > RuntimeError: error in Singular function call 'genus': > This is not a curve > leaving normal.lib::genus (0) > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/fc53331a-4ea9-47fe-bc9b-393983270ba8n%40googlegroups.com.
