Georgi Guninski on Mon, 12 May 2014 14:38:21 +0200 |
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Heuristic that might speed some thue equations with no solutions |
I am not good at theory, but this appears plausible to me. Suppose you want to solve thue(f(x),A) [1] where $f(x)$ is irreducible. Let $K$ be the number field with defining polynomial $f(x)$. Every solution to [1] $u,v$ satisfies norm(v x- u)=A. If $A$ is not an integer norm in $K$, [1] has no solution. bnfisintnorm() appears significantly faster than thue(). Is it sound first to check bnfisintnorm() and if it fails to not bother with thue(), assuming f(x) is (monic) irreducible? Example: ? a=20^30+3;K=bnfinit(x^4+1);a%4 %30 = 3 ? bnfisintnorm(K,a) %31 = [] \\ fast ? th=thueinit(K.pol); ? \g 3 debug = 3 ? thue(th,a) * Checking for small solutions <= 8095430811