Around the "Fundamental Theorem of Algebra"

Abstract: The Fundamental Theorem of Algebra (FTA) asserts that every complex polynomial has as many complex roots, counted with multiplicities, as its degree. A probabilistic analogue of this theorem for real roots of real polynomials, commonly referred to as the Kac theorem, was introduced in 1938 by J. Littlewood and A. Offord. In this paper, we present the Kac theorem and prove two more theorems that can be interpreted as analogues of the FTA: a version of FTA for real Laurent polynomials, and another version for exponential sums. In these two cases, we also provide formulations of multidimensional analogues of corresponding FTA. While these results are not new, they may appear unexpected and are therefore worth highlighting.