Prime values of integer polynomials

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Discussion Overview

The discussion centers around the question of whether a monic and irreducible polynomial with integer coefficients must yield a prime value for at least one integer input. The scope includes theoretical exploration of polynomial properties and conjectures related to prime values.

Discussion Character

  • Exploratory
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant proposes that if \( f \in \mathbb{Z}[x] \) is monic and irreducible over \( \mathbb{Q} \), then there exists at least one integer \( a \) such that \( f(a) \) is prime, although they cannot prove it.
  • Another participant counters this by providing the example \( f(x) = x^2 + x + 4 \), which is monic and irreducible over \( \mathbb{Q} \) but does not yield a prime number for any integer \( x \).
  • A third participant acknowledges the counterpoint without further elaboration.
  • A later reply mentions the Hardy-Littlewood conjectures, which address the topic for quadratic polynomials and some cubic ones, suggesting that there may be more extensive analysis available for higher-order polynomials.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as there are competing views regarding the original proposition, with at least one counterexample provided that challenges the claim.

Contextual Notes

The discussion highlights the limitations of the original claim, particularly in light of the counterexample, and suggests that the exploration of prime values in polynomials may depend on specific cases and conjectures.

VKint
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Hey there, physics forums!

A question occurred to me the other day: Is it true that if [tex]f \in \mathbb{Z}[x][/tex] is monic and irreducible over [tex]\mathbb{Q}[/tex], then for at least one [tex]a \in \mathbb{Z}[/tex], [tex]f(a)[/tex] is prime? I can't prove it, but I suspect it's true. Does anyone know if this problem has been solved?
 
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What about f(x) = x^2 + x + 4? That's monic and irreducible over Q but isn't prime for any x in Z.
 
Good point.
 
The Hardy-Littlewood conjectures discuss this in detail, at least for quadratic polynomials (and one cubic). I can't remember who first published the analysis of higher-order polynomials, but you could probably find it on Google.
 

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