Difference between revisions of "Schonemann's criterion"

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Suppose the following conditions hold:
 
Suppose the following conditions hold:
 
* <math>k=f^n+pg</math> with <math>n\geq 1</math>, <math>p</math> prime, and <math>f,g\in \mathbb{Z}[X]</math>.
 
* <math>k=f^n+pg</math> with <math>n\geq 1</math>, <math>p</math> prime, and <math>f,g\in \mathbb{Z}[X]</math>.
* <math>\text{deg}(f^n)>\text{deg}(g)</math>
+
* <math>\text{deg}(f^n)>\text{deg}(g)</math>.
* <math>k</math> is primitive
+
* <math>k</math> is primitive.
 
* <math>f^*</math> is irreducible in <math>\mathbb{F}_p[X]</math>.
 
* <math>f^*</math> is irreducible in <math>\mathbb{F}_p[X]</math>.
 
* <math>f^*</math> does not divide <math>g^*</math>.
 
* <math>f^*</math> does not divide <math>g^*</math>.

Revision as of 10:44, 18 December 2009

For a polynomial q denote by $q^*$ the residue of $q$ modulo $p$. Suppose the following conditions hold:

  • $k=f^n+pg$ with $n\geq 1$, $p$ prime, and $f,g\in \mathbb{Z}[X]$.
  • $\text{deg}(f^n)>\text{deg}(g)$.
  • $k$ is primitive.
  • $f^*$ is irreducible in $\mathbb{F}_p[X]$.
  • $f^*$ does not divide $g^*$.

Then $k$ is irreducible in $\mathbb{Q}[X]$.

See also Eisenstein's criterion.