Dispersions for linear differential equations of arbitrary order

summary:For linear differential equations of the second order in the Jacobi form $$y^{\prime \prime } + p(x)y = 0$$ O. Borvka introduced a notion of dispersion. Here we generalize this notion to certain classes of linear differential equations of arbitrary order. Connection with Abel’s functional equation is derived. Relations between asymptotic behaviour of solutions of these equations and distribution of zeros of their solutions are also investigated

Critical measures, quadratic differentials, and weak limits of zeros of Stieltjes polynomials

We investigate the asymptotic zero distribution of Heine-Stieltjes polynomials - polynomial solutions of a second order differential equations with complex polynomial coefficients. In the case when all zeros of the leading coefficients are all real, zeros of the Heine-Stieltjes polynomials were interpreted by Stieltjes as discrete distributions minimizing an energy functional. In a general complex situation one deals instead with a critical point of the energy. We introduce the notion of discrete and continuous critical measures (saddle points of the weighted logarithmic energy on the plane), and prove that a weak-* limit of a sequence of discrete critical measures is a continuous critical measure. Thus, the limit zero distributions of the Heine-Stieltjes polynomials are given by continuous critical measures. We give a detailed description of such measures, showing their connections with quadratic differentials. In doing that, we obtain some results on the global structure of rational quadratic differentials on the Riemann sphere that have an independent interest.Comment: 70 pages, 14 figures. Minor corrections, to appear in Comm. Math. Physic

Oscillation Properties of Some Functional Fourth Order Ordinary Differential Equations

2010 Mathematics Subject Classification: 34A30, 34A40, 34C10.In this paper are considered oscillation properties of some classes of functional ordinary differential equations, namely equations of the type ziv(t) + mz′′(t) + g(z(t), z′(t), z′′(t), z′′′(t)) +nXi=1_i(t)z(t − i) = f(t), where m > 0 is constant, f(t) 2 C([T,1);R), T _ 0 is a large enough constant, g(z, _, _, _) 2 C(R4;R), _i(t) 2 C([0,1); [0,1)), 8 i = 1, n, n 2 N and {i}n i=1 are nonnegative constants. As a main result of this work we derive a sufficient condition for the distribution of the zeros of the above equations. Furthermore we discuss the complexity of the oscillation behavior of such equations and its relation to some properties of the corresponding solutions. Finally, we comment the oscillation behavior of a neutral fourth order ordinary differential equation, which appears in two papers of Ladas and Stavroulakis, as well as in a paper of Grammatikopoulos et al

Finite size corrections in random matrix theory and Odlyzko's data set for the Riemann zeros

Odlyzko has computed a data set listing more than $10^9$ successive Riemann zeros, starting at a zero number beyond $10^{23}$. The data set relates to random matrix theory since, according to the Montgomery-Odlyzko law, the statistical properties of the large Riemann zeros agree with the statistical properties of the eigenvalues of large random Hermitian matrices. Moreover, Keating and Snaith, and then Bogomolny and collaborators, have used $N \times N$ random unitary matrices to analyse deviations from this law. We contribute to this line of study in two ways. First, we point out that a natural process to apply to the data set is to thin it by deleting each member independently with some specified probability, and we proceed to compute empirical two-point correlation functions and nearest neighbour spacings in this setting. Second, we show how to characterise the order $1/N^2$ correction term to the spacing distribution for random unitary matrices in terms of a second order differential equation with coefficients that are Painlev\'e transcendents, and where the thinning parameter appears only in the boundary condition. This equation can be solved numerically using a power series method. Comparison with the Riemann zero data shows accurate agreement.Comment: 22 pages, 10 figures, Version 2 added some new references in bibliography, Version 3 corrected the scaling on the spacing distribution and some typo

Complex Langevin Equations and Schwinger-Dyson Equations

Stationary distributions of complex Langevin equations are shown to be the complexified path integral solutions of the Schwinger-Dyson equations of the associated quantum field theory. Specific examples in zero dimensions and on a lattice are given. Relevance to the study of quantum field theory phase space is discussed.Comment: 23 pages, 4 figures, elsart, typos fixed, includes additional conten