في الورقة السابقة (J. Combin. Theory Ser. A، 120، 2013، 1263--1284)، قام H. Tagawa والمؤلفين الاثنين باقتراح طريقة جبرية لحساب بعض البفافيان الذين يشبهون التحديدات الهانكل المرتبطة بتسلسلات اللحظات للخطط الهندسية التقليدية. في نهاية الورقة، قدموا عدة افتراضات. في هذا العمل، نستخدم طريقة مختلفة تمامًا لتقدير هذا النوع من البفافيان. فكرة الأمر هي تطبيق صيغة نوع دي بروين وتحويل تقدير البفافيان إلى بعض الأحاديث النوع سيلبرغ. يعمل هذا النهج ليس فقط على البفافيان بل أيضًا على الهايبربفافيان. وبالتالي، يمكنها تأسيس هويات أكثر تطبيقًا بكثير من الأفتراضات التي قدمت في الورقة السابقة. نحاول أيضًا التطبيقات الكوانتومية.
In the previous paper (J. Combin. Theory Ser. A, 120, 2013, 1263--1284) H. Tagawa and the two authors proposed an algebraic method to compute certain Pfaffians whose form resemble to Hankel determinants associated with moment sequences of the classical orthogonal polynomials. At the end of the paper they offered several conjectures. In this work we employ a completely different method to evaluate this type of Pfaffians. The idea is to apply certain de Bruijn type formula and convert the evaluation of the Pfaffians to the certain Selberg type integrals. This approach works not only for Pfaffians but also for hyperpfaffians. Hence it enables us to establish much more generalized identities than those conjectured in the previous paper. We also attempt q-analogues.
We study the asymptotics in n for n-dimensional Toeplitz determinants whose symbols possess Fisher-Hartwig singularities on a smooth background. We prove the general non-degenerate asymptotic behavior as conjectured by Basor and Tracy. We also obtain asymptotics of Hankel determinants on a finite interval as well as determinants of Toeplitz+Hankel type. Our analysis is based on a study of the related system of orthogonal polynomials on the unit circle using the Riemann-Hilbert approach.
We present an elliptic version of Selbergs integral formula.
We present $text{Fuchsia}$ $-$ an implementation of the Lee algorithm, which for a given system of ordinary differential equations with rational coefficients $partial_x,mathbf{f}(x,epsilon) = mathbb{A}(x,epsilon),mathbf{f}(x,epsilon)$ finds a basis transformation $mathbb{T}(x,epsilon)$, i.e., $mathbf{f}(x,epsilon) = mathbb{T}(x,epsilon),mathbf{g}(x,epsilon)$, such that the system turns into the epsilon form: $partial_x, mathbf{g}(x,epsilon) = epsilon,mathbb{S}(x),mathbf{g}(x,epsilon)$, where $mathbb{S}(x)$ is a Fuchsian matrix. A system of this form can be trivially solved in terms of polylogarithms as a Laurent series in the dimensional regulator $epsilon$. That makes the construction of the transformation $mathbb{T}(x,epsilon)$ crucial for obtaining solutions of the initial equations. In principle, $text{Fuchsia}$ can deal with any regular systems, however its primary task is to reduce differential equations for Feynman master integrals. It ensures that solutions contain only regular singularities due to the properties of Feynman integrals.
The Euler numbers occur in the Taylor expansion of $tan(x)+sec(x)$. Since Stieltjes, continued fractions and Hankel determinants of the even Euler numbers, on the one hand, of the odd Euler numbers, on the other hand, have been widely studied separately. However, no Hankel determinants of the (mixed) Euler numbers have been obtained and explicitly calculated. The reason for that is that some Hankel determinants of the Euler numbers are null. This implies that the Jacobi continued fraction of the Euler numbers does not exist. In the present paper, this obstacle is bypassed by using the Hankel continued fraction, instead of the $J$-fraction. Consequently, an explicit formula for the Hankel determinants of the Euler numbers is being derived, as well as a full list of Hankel continued fractions and Hankel determinants involving Euler numbers. Finally, a new $q$-analog of the Euler numbers $E_n(q)$ based on our continued fraction is proposed. We obtain an explicit formula for $E_n(-1)$ and prove a conjecture by R. J. Mathar on these numbers.
Soliton theory and the theory of Hankel (and Toeplitz) operators have stayed essentially hermetic to each other. This paper is concerned with linking together these two very active and extremely large theories. On the prototypical example of the Cauchy problem for the Korteweg-de Vries (KdV) equation we demonstrate the power of the language of Hankel operators in which symbols are conveniently represented in terms of the scattering data for the Schrodinger operator associated with the initial data for the KdV equation. This approach yields short-cuts to already known results as well as to a variety of new ones (e.g. wellposedness beyond standard assumptions on the initial data) which are achieved by employing some subtle results for Hankel operators.