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Questions in which polynomials (single or several variables) play a key role. It is typically important that this tag is combined with other tags; polynomials appear in very different contexts. Please, use at least one of the top-level tags, such as nt.number-theory, co.combinatorics, ac.commutative-algebra, in addition to it. Also, note the more specific tags for some special types of polynomials, e.g., orthogonal-polynomials, symmetric-polynomials.

12 votes

About irreducible trinomials

manifestly additive ($m(PQ) = m(P) + m(Q)$), the proof that the trinomial has not more than a single non-cyclotomic factor is an almost immediate consequence of two general, if not easy, facts about polynomials
Vesselin Dimitrov's user avatar
13 votes
Accepted

Is the set of certain polynomials finite or infinite?

For the proof of this, write $p = \prod_{i=1}^d (x - 2\cos(2\pi \, t_i))$ and observe that the sequence of degree $d$ monic polynomials $p_n := \prod_{i=1}^d(x - 2\cos(2\pi n t_i))$ is also in $\mathbb … Combining these two statements, you can see that your set consists precisely of the products of pairwise different minimal polynomials of those $2\cos(2\pi / d)$ that do not exceed $1.99$. …
Vesselin Dimitrov's user avatar
39 votes

$f(x)$ is irreducible but $f(x^n)$ is reducible

There is no such polynomial. It is clear that $f$ cannot be a cyclotomic polynomial (your condition $\deg{f} > 1$ excludes $x-1$). So suppose $f$ is non-cyclotomic and irreducible, of degree $d$, an …
Vesselin Dimitrov's user avatar
4 votes

Old question of Serre on discriminants of a sequence of polynomials

(Another reference is Prasolov's book Polynomials, which reproduces the same calculation). … However, one may wish to restrict to reciprocal polynomials; for Lehmer's problem this would be sufficient. …
Vesselin Dimitrov's user avatar
4 votes
1 answer
162 views

If the sequence of degrees of the iterates of a self-map of $\mathbb{A}^2$ is bounded, is it...

Let $f : \mathbb{A}_k^2 \to \mathbb{A}_k^2$ be a regular self-map of the affine plane over a field $k$ of characteristic zero. Assume that the sequence $(\deg{f^n})_{n \in \mathbb{N}}$ is bounded. Is …
Vesselin Dimitrov's user avatar
13 votes
1 answer
526 views

Are the logarithms of the integer polynomials discrete in $L^1$ of the unit circle?

Tautologically, the integer polynomials form a discrete set in $L^1$ of the unit circle. On the other hand, a set of logarithms ordered by norm becomes generally rather denser than the original set. …
Vesselin Dimitrov's user avatar
6 votes

Coefficients of shifted Bernoulli polynomials

Let me address (1). First, you need a correction: I suppose you intended $\frac{1}{n}B_n(x+k)$ in the empirical calculations, and not $\frac{1}{n-1}B_n(x+k)$. For instance, the $x^2$ coefficient of $B …
Vesselin Dimitrov's user avatar
8 votes
1 answer
326 views

Angular distribution of zero sets of sparse polynomials

Consider a sequence of complex polynomials $f \in \mathbb{C}[z]$, $f(0) \neq 0$, that are composed of a negligible fraction $o(\deg{f})$ of monomials. … Are the zeros of such polynomials necessarily equidistributed in angle, for the uniform measure $d\theta/2\pi$ on $S^1 = \mathbb{C}^{\times} / \mathbb{R}^{> 0}$? …
Vesselin Dimitrov's user avatar
6 votes
0 answers
218 views

Extremal polynomial majorants of $\log{|f|}$: a multivariate extension of a theorem of Carne...

(The first two of those extremal polynomials are $P_0(z) = \log{2}$ and $P_1(z) = \frac{1}{2}( \log{2} - (z + z^{-1})/2 )$.) … arbitrary $f$ gets straightforwardly reduced to the $f(z) = 1 - z$ case, but this way of phrasing the result suggests an immediate generalization: I would like to raise the following for multivariate polynomials
Vesselin Dimitrov's user avatar
8 votes
0 answers
220 views

Is there an approximate formula for the discriminant of a sparse polynomial?

Consider integer polynomials $P \in \mathbb{Z}[X] \setminus \{0\}$ of a degree $D \geq 1$ and without multiple complex roots. … An outstanding open problem is to prove (or disprove) that $d(P) \to \infty$ under any sequence of polynomials with degrees $D \to \infty$. …
Vesselin Dimitrov's user avatar
9 votes
0 answers
333 views

Is this a possible strengthening of the Lehmer conjecture?

Here is another possible refinement of the Lehmer conjecture. For $\alpha \in \overline{\mathbb{Q}}^{\times}$, let $C_{\alpha} \subseteq \mathbb{Q}(\alpha)$ be the maximal cyclotomic field contained …
Vesselin Dimitrov's user avatar
3 votes
0 answers
100 views

Independence of number fields generated by roots of Littlewood polynomials

Let $\mathcal{R}_d \subset \bar{\mathbb{Q}}$ be the set of all roots of degree $d$ polynomials with $\{-1,0,1\}$ coefficients and $$ c(d) := \min_{\substack{ \alpha, \beta \in \mathcal{R}_d \\ \alpha^k … Thus, in particular, it follows easily that there are only finitely many irreducible and non-cyclotomic $\{-1,0,1\}$-polynomials $f(X)$ for which the number field $\mathbb{Q}[X] / (f(X))$ is Galois over …
Vesselin Dimitrov's user avatar
2 votes
0 answers
160 views

Must the coordinates of a polynomial iteration have about the same size?

Let us say that a polynomial mapping of $\mathbb{C}^2$ is reducible if either it takes the shape $(x,y) \mapsto (f(x),B(x,y))$ or the shape $(x,y) \mapsto (A(x,y),g(y))$, where $f,g$ are univariate polynomials
Vesselin Dimitrov's user avatar
11 votes

About the prime divisors of values of polynomials

Assume without loss of generality that $P$ is irreducible, and denote by $S_P(X)$ the set of primes $p < X$ that divide some value $P(n)$. Let $G$ be the Galois group of $P$ and $n_1 > 0$ the number o …
Vesselin Dimitrov's user avatar
29 votes
Accepted

Is $x^{n}-x-1$ irreducible?

To this I may add Prasolov's monograph Polynomials as a (probably) more accessible reference; there, you will find a complete treatment of Ljunggren's result. Added. … Osada's paper to which he refers is The Galois groups of the polynomials $X^n + aX^l+b$ (J. Number Theory 25, pp. 230-238, 1987), although the result already appears in an earlier paper by E. …
Vesselin Dimitrov's user avatar

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