#11930: function to check if hyperelliptic curve is singular in the sense of
hyperelliptic curves
------------------------------------------------------------+---------------
   Reporter:  dkrenn                                        |          Owner:  
cremona                                  
       Type:  enhancement                                   |         Status:  
needs_work                               
   Priority:  minor                                         |      Milestone:  
sage-4.8                                 
  Component:  elliptic curves                               |       Keywords:  
hyperelliptic curve, singular, sd35      
Work_issues:  make resultants work for more general fields  |       Upstream:  
N/A                                      
   Reviewer:  Marco Streng, Damiano Testa                   |         Author:  
Daniel Krenn, Marco Streng, Damiano Testa
     Merged:                                                |   Dependencies:   
                                        
------------------------------------------------------------+---------------
Changes (by mstreng):

  * work_issues:  add singular examples to the documentation of the
                  constructor, do some tests => make
                  resultants work for more general fields


Old description:

> We have
> {{{
> sage: R.<x> = PolynomialRing(GF(3))
> sage: H=HyperellipticCurve(x^5+1)
> sage: H.is_singular()
> True
> }}}
> but `H` is a non-singular hyperelliptic curve.
>
> Hyperelliptic curves are smooth curves mathematically. In Sage, they are
> implemented as plane curves with a singularity at infinity, but that
> singularity can always be resolved.
>
> Apply
>
>  * [attachment:11930_singular_hyperelliptic.patch]
>  * [attachment:11930_is_singular.patch]

New description:

 We have
 {{{
 sage: R.<x> = PolynomialRing(GF(3))
 sage: H=HyperellipticCurve(x^5+1)
 sage: H.is_singular()
 True
 }}}
 but `H` is a non-singular hyperelliptic curve.

 Hyperelliptic curves are smooth curves mathematically. In Sage, they are
 implemented as plane curves with a singularity at infinity, but that
 singularity can always be resolved.

 Apply

  * [attachment:11930b.patch]
  * [attachment:11930_is_singular.patch]

--

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11930#comment:10>
Sage <http://www.sagemath.org>
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