In this paper, we make some observations on the work of Di Fazio concerning $W^{1,p}$ estimates, $1<p<\mathrm{\infty }$, for solutions of elliptic equations $\text{div}A\nabla u=\text{div}f$ , on a domain $\mathrm{\Omega }$ with Dirichlet data $0$ whenever $A\in VMO\left(\mathrm{\Omega }\right)$ and $f\in L^p\left(\mathrm{\Omega }\right)$. We weaken the assumptions allowing real and complex non-symmetric operators and $C^1$ boundary. We also consider the corresponding inhomogeneous Neumann problem for which we prove the similar result. The main tool is an appropriate representation for the Green (and Neumann) function on the upper half space. We propose...

In the present paper we study some basic qualitative properties of solutions of a nonlinear parabolic integrodifferential equation of Barbashin type which occurs frequently in applications. The fundamental integral inequality with explicit estimate is used to establish the results.

We prove an existence theorem of Cauchy-Kovalevskaya type for the equation $D_{t}u(t,z)=f(t,z,u\left({\alpha }^{\left(0\right)}(t,z)\right),D_{z}u\left({\alpha }^{\left(1\right)}(t,z)\right),...,D_z^{k}u\left({\alpha }^{\left(k\right)}(t,z)\right))$ where f is a polynomial with respect to the last k variables.

We seek for classical solutions to hyperbolic nonlinear partial differential-functional equations of the second order. We give two theorems on existence and uniqueness for problems with nonlocal conditions in bounded and unbounded domains.

In this paper the Leray-Schauder nonlinear alternative for multivalued maps combined with the semigroup theory is used to investigate the existence of mild solutions for first order impulsive semilinear functional differential inclusions in Banach spaces.

We investigate existence and unicity of global sectorial holomorphic solutions of functional linear partial differential equations in some Gevrey spaces. A version of the Cauchy-Kowalevskaya theorem for some linear partial $q$-difference-differential equations is also presented.

Qualitative comparison of the nonoscillatory behavior of the equations $$L_{n}y\left(t\right)+H(t,y\left(t\right))=0$$ and $$L_{n}y\left(t\right)+H(t,y\left(g\left(t\right)\right))=0$$ is sought by way of finding different nonoscillation criteria for the above equations. $L_n$ is a disconjugate operator of the form $$L_n=\frac{1}{p_n\left(t\right)}\frac{\mathrm{d}}{\mathrm{d}t}\frac{1}{p_{n-1}\left(t\right)}\frac{\mathrm{d}}{\mathrm{d}t}...\frac{\mathrm{d}}{\mathrm{d}t}\frac{·}{p_0\left(t\right)}.$$ Both canonical and noncanonical forms of $L_n$ have been studied.

We will prove existence of weak solutions of a system, containing non-local terms $u$, $w$.

We consider the Cauchy problem for a nonlocal wave equation in one dimension. We study the existence of solutions by means of bicharacteristics. The existence and uniqueness is obtained in $W_{loc}^{1,\infty }$ topology. The existence theorem is proved in a subset generated by certain continuity conditions for the derivatives.

We present an existence theorem for the Cauchy problem related to linear partial differential-functional equations of an arbitrary order. The equations considered include the cases of retarded and deviated arguments at the derivatives of the unknown function. In the proof we use Tonelli's constructive method. We also give uniqueness criteria valid in a wide class of admissible functions. We present a set of examples to illustrate the theory.