arXiv subjects

Gal Binyamini

Publications and source records attributed to Gal Binyamini.

43 records · Page 3Linked to original sources

arXiv2014

Multiplicity Operators

For functions of a single complex variable, points of multiplicity greater than $k$ are characterized by the vanishing of the first $k$ derivatives. There are various quantitative generalizations of this statement, showing that for functions that are in some sense close to having multiplicity greater than $k$, the first $k$ derivatives must be small. In this paper we aim to generalize this situation to the multi-dimensional setting. We define a class of differential operators, the \emph{multiplicity operators}, which act on maps from $\C^n$ to $\C^n$ and satisfy properties analogous to those described above. We demonstrate the usefulness of the construction by applying it to some problems in the theory of Noetherian functions.

math.CV↗

arXiv2013

Moment vanishing of piecewise solutions of linear ODEs

We consider the "moment vanishing problem" for a general class of piecewise-analytic functions which satisfy on each continuity interval a linear ODE with polynomial coefficients. This problem, which essentially asks how many zero first moments can such a (nonzero) function have, turns out to be related to several difficult questions in analytic theory of ODEs (Poincare's Center-Focus problem) as well as in Approximation Theory and Signal Processing ("Algebraic Sampling"). While the solution space of any particular ODE admits such a bound, it will in the most general situation depend on the coefficients of this ODE. We believe that a good understanding of this dependence may provide a clue for attacking the problems mentioned above. In this paper we undertake an approach to the moment vanishing problem which utilizes the fact that the moment sequences under consideration satisfy a recurrence relation of fixed length, whose coefficients are polynomials in the index. For any given operator, we prove a general bound for its moment vanishing index. We also provide uniform bounds for several operator families.

math.CA↗

arXiv2011

Quasialgebraic Functions

We introduce and discuss a new class of (multivalued analytic) transcendental functions which still share with algebraic functions the property that the number of their isolated zeros can be explicitly counted. On the other hand, this class is sufficiently rich to include all periods (integral of rational forms over algebraic cycles).

math.CA↗

arXiv2011

A Uniform Version of the Petrov-Khovanskii Theorem

An Abelian integral is the integral over the level curves of a Hamiltonian $H$ of an algebraic form $ω$. The infinitesimal Hilbert sixteenth problem calls for the study of the number of zeros of Abelian integrals in terms of the degrees $H$ and $ω$. Petrov and Khovanskii have shown that this number grows at most linearly with the degree of $ω$, but gave a purely existential bound. Binyamini, Novikov and Yakovenko have given an \emph{explicit} bound growing doubly-exponentially with the degree. We combine the techniques used in the proofs of these two results, to obtain an explicit bound on the number of zeros of Abelian integrals growing linearly with $\degω$.

math.CA↗

arXiv2011

Intersection multiplicities of Noetherian functions

We provide a partial answer to the following problem: \emph{give an effective upper bound on the multiplicity of non-isolated common zero of a tuple of Noetherian functions}. More precisely, consider a foliation defined by two commuting polynomial vector fields $V_1,V_2$ in $\C^n$, and $p$ a nonsingular point of the foliation. Denote by $\cL$ the leaf passing through $p$, and let $F,G\in\C[X]$ be two polynomials. Assume that $F\onL=0,G\onL=0$ have several common branches. We provide an effective procedure which allows to bound from above multipllicity of intersection of remaining branches of $F\onL=0$ with $G\onL=0$ in terms of the degrees and dimensions only.

math.CV↗

arXiv2009

On the Number of Zeros of Abelian Integrals: A Constructive Solution of the Infinitesimal Hilbert Sixteenth Problem

We prove that the number of limit cycles generated by a small non-conservative perturbation of a Hamiltonian polynomial vector field on the plane, is bounded by a double exponential of the degree of the fields. This solves the long-standing tangential Hilbert 16th problem. The proof uses only the fact that Abelian integrals of a given degree are horizontal sections of a regular flat meromorphic connection (Gauss-Manin connection) with a quasiunipotent monodromy group.

math.DS↗

arXiv2009

Polynomial Bounds for Oscillation of Solutions of Fuchsian Systems

We study the problem of placing effective upper bounds for the number of zeros of solutions of Fuchsian systems on the Riemann sphere. The principal result is an explicit (non-uniform) upper bound, polynomially growing on the frontier of the class of Fuchsian systems of given dimension n having m singular points. As a function of n,m, this bound turns out to be double exponential in the precise sense explained in the paper. As a corollary, we obtain a solution of the so called restricted infinitesimal Hilbert 16th problem, an explicit upper bound for the number of isolated zeros of Abelian integrals which is polynomially growing as the Hamiltonian tends to the degeneracy locus. This improves the exponential bounds recently established by A. Glutsyuk and Yu. Ilyashenko.

math.DS↗