## Zeros of polynomials with $$0, 1$$ coefficients.(English)Zbl 0814.30006

Let us consider the $$P= \{f(z): f(z)= 1+ \sum_{j=1}^d a_j z^j$$, $$a_j=0$$ or $$1\}$$ and define $$W= \{z\in \mathbb C: f(z)=0$$ for some $$f\in P\}$$. The authors have obtained several interesting results about the set $$\overline {W}$$. The set $$\overline {W}\cap \{z: | z|<1\}$$ is the set of zeros of power series $$f(z)= \sum_{k=1}^ \infty a_k z^k$$, $$a_k=0$$ or $$1$$. Since $$1/z\in W$$ for all $$z\in W$$, it is sufficient to study $$z\in W$$, $$| z|\leq 1$$, and in some ways it is more natural to deal with the above power series.
Applying Jensen’s theorem, the authors prove that for any $$0<r<1$$, the power series $$f(z)$$ has $$\leq 2(\log (1- \sqrt{r} ))/( -\log r)$$ zeros in $$| z|\leq r$$. Also the bounds on the size of $$z\in W$$ were obtained. The set $$\overline {W}$$ is connected and path connected and there is an open neighborhood of $$\{z: | z|=1,\ z\neq 1\}$$ contained in $$\overline {W}$$. These results are based on several interesting topological lemmas.
The paper contains remarkable pictures which illustrate the theoretical results and as well as the description of the computational algorithms needful for plotting of these pictures.
Reviewer: A.Klíč (Praha)

### MSC:

 11C08 Polynomials in number theory 11Y35 Analytic computations 12D10 Polynomials in real and complex fields: location of zeros (algebraic theorems) 30C15 Zeros of polynomials, rational functions, and other analytic functions of one complex variable (e.g., zeros of functions with bounded Dirichlet integral)