Is there an implemented algorithm that will take a polynomial $f(x,y)\in\mathbb Z[x,y]$ and a prime $p$, and determine whether the equation $f(x,y)=0$ has a solution over $\mathbb Q_p$?
1 Answer
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My recollection is that Nils Bruin did this is in fair generality in Magma. I do not know how efficient it is.
http://magma.maths.usyd.edu.au/magma/handbook/text/1289#13826
IsLocallySolvable(X, p) : Sch, RngIntElt -> BoolElt, Pt
Smooth: BoolElt Default: false
AssumeIrreducible: BoolElt Default: false
AssumeNonsingular: BoolElt Default: false
Given a projective scheme X defined over a number field or over the rationals, test if the scheme is locally solvable at the prime ideal p (for number fields) or prime number p (for rationals) indicated. If the scheme is found to have a local point, then true is returned together with an approximation to a point. Otherwise, false is returned.
For a description of the algorithms used, see [Bru04].