Generalized Weierstrass Integrability of the Abel Differential Equations

We study the Abel differential equations that admit either a generalized Weierstrass first integral or a generalized Weierstrass inverse integrating factor.     

Integrability of Solutions to Mixed Stochastic Differential Equations

We prove that the standard conditions for the unique solvability of a mixed stochastic differential equation guarantee that its solution possesses finite moments. We also give conditions supplying the existence of exponential moments. For a special equation whose coefficients do not satisfy the linear growth condition, we prove the integrability of its solution.     

Integrability of (Non-)Linear Rough Differential Equations and Integrals

Integrability properties of (classical, linear, linear growth) rough differential equations (RDEs) are considered, the Jacobian of the RDE flow driven by Gaussian signals being a motivating example. We revisit and extend some recent ground-breaking work of Cass-Litterer-Lyons in this regard; as by-product, we obtain a user-friendly “transitivity property” of such integrability estimates. We also consider rough integrals; as a novel application, uniform Weibull tail estimates for a class of (random) rough integrals are obtained. A concrete example arises from the stochastic heat-equation, spatially mollified by hyper-viscosity, and we can recover (in fact, sharpen) a technical key result of Hairer [11 Hairer , M. 2011 . Rough stochastic PDEs . Comm. Pure Appl. Math. 64 : 1547 – 1585 . [Google Scholar]].     

复高阶微分方程的解

利用亚纯函数的Nevanlinna值分布理论以及最大模原理,讨论了一类复高阶微分方程的代数体解以及一类复高阶微分方程组的超越亚纯解的存在性问题,得到了两个结论.还推广了一些文献的结论,例子表明该文的结论是精确的.     

Some Geometric Aspects of Integrability of Differential Equations in Two Independent Variables

The relation between scalar evolution equations which are the integrability condition of sl(2,R)-valued linear problems with parameter (kinematic integrability) and those which possess recursion operators (formal integrability) is studied: using that kinematically integrable equations describe one-parameter families of pseudo-spherical surfaces and vice versa, it is shown that every second order formally integrable evolution equation is kinematically integrable, and that this result cannot be extended as proven to the third-order case.Conservation laws of kinematically integrable equations obtained from their underlying pseudo-spherical structure are compared with the ones one finds from the Riccati equation version of their associated linear problems. Symmetries (generalized/nonlocal) for these equations are also studied, by considering infinitesimal deformations of the associated pseudo-spherical surfaces.Finally, conservation laws for equations describing pseudo-spherical surfaces immersed in a flat three-space are found, and the class of equations describing Calapso–Guichard surfaces is introduced.     

Functional Equations and Weierstrass Transforms

The purpose of this article is to illustrate the utility of the Weierstrass transform in the study of functional equations (and systems) of the form 1 $${\mathop \sum^N\limits_{k=0}}\alpha_{k}f(x+r_{k})=f_{0}(x)\ \ \ \, x\in\ {\rm R}.$$ One may think of α₀, α₁,…, α_N as given complex numbers, r₀, r₁,…, r_N as given real numbers, ?₀: ? → C as a given function and ? as the unknown.     

On the Integrability Conditions for Some Structures Related to Evolution Differential Equations

Using the result by D. Gessler, we show that any invariant variational bivector (resp., variational 2-form) on an evolution equation with nondegenerate right-hand side is Hamiltonian (resp., symplectic).     

复微分方程组的超越解

利用最大模原理,讨论了复代数微分方程组的超越亚纯解存在性问题,得到了在一定条件下,该方程组的超越解为代数解的一个结果.例子表明这个结果是精确的.     

Functional Equations and Weierstrass Transforms II

The Weierstrass transform is examined on the space of Lebesgue measurable function on Rⁿ having at most exponential growth, thereby extending to higher dimensions the one-dimensional consideration of [4]. The resulting theory has utility in the study of certain functional equations of “translation” type; two such applications are presented.     

On Meromorphic Solutions of Nonlinear Complex Differential Equations

Applying the Nevanlinna theory of meromorphic function,we investigate the non-admissible meromorphic solutions of nonlinear complex algebraic differential equation and gain a general result.Meanwhile,we prove that the meromorphic solutions of some types of the systems of nonlinear complex differential equations are non-admissible.Moreover,the form of the systems of equations with admissible solutions is discussed.     

关于一般复微分方程的代数体函数解

利用亚纯函数的Nevanlinna值分布理论,我们研究了一般复微分方程式代数体允许解的存在性问题,得到了一些结要。     

复微分方程组及复微分-差分方程解的级

利用Zalcman关于正规族的方法,研究了两类复高阶微分方程组的亚纯解的增长级问题;同时,利用Nevanlinna值分布理论,讨论了两类复微分-差分方程的超越整函数解的增长级.所得结论推广和改进了一些文献的结果,并举例说明本文的结论精确.     

The Integrability Conditions in the Inverse Problem of the Calculus of Variations for Second-Order Ordinary Differential Equations

A novel approach to a coordinate-free analysis of the multiplier question in the inverseproblem of the calculus of variations, initiated in a previous publication, is completed in thefollowing sense: under quite general circumstances, the complete set of passivity or integrabilityconditions is computed for systems with arbitrary dimension n. The results are appliedto prove that the problem is always solvable in the case that the Jacobi endomorphism of thesystem is a multiple of the identity. This generalizes to arbitrary n a result derived byDouglas for n=2.     

Formal Integrability Criteria for Nonlinear Partial Difference Equations

In recent years, there has been a substantial growth of interest in discrete differential geometry. Can results in formal differential geometry also be discretized for nonlinear partial difference equations? Using some techniques in exterior difference calculus, we investigate the geometric property of discrete Jet bundles. Further, we define the formal integrability and discrete Spencer cohomology for nonlinear partial difference equations, and give the formal integrability criteria.     

二阶复微分方程的亚纯元素解及代数元素解

研究了一类二阶亚纯系数复微分方程的亚纯元素解及代数元素解的存在性问题,得到了几个有关解的存在性定理.     

Higher Integrability of the Gradient in Degenerate Elliptic Equations

We prove that under some global conditions on the maximum and the minimum eigenvalue of the matrix of the coefficients, the gradient of the (weak) solution of some degenerate elliptic equations has higher integrability than expected. Technically we adapt the Giaquinta–Modica regularity method in some degenerate cases. When the dimension is two, a consequence of our result is a new Hölder continuity result for the weak solution.     

复高阶代数微分方程组的亚纯解

利用亚纯函数的Nevanlinna值分布理论,研究了一类高阶代数微分方程组亚纯允许解的存在性问题,得到了一个主要结果.