For a class of hyperbolic partial integrodifferential equations of the form $u_{tt} - u_{xx} + a*u_{xx} = 0$, fundamental solutions are found that depend on the similarity variable $\xi =x(t-|x|)^{-\alpha}$, where $\alpha \in (0,1)$ and the integral kernel $a$ behaves like $t^{-\alpha}$ near $t=0$. The asymptotic behavior of these solutions in various scaling limits and their regularity is discussed. Applications to solutions of general initial-value problems of such equations are given.

Necessary and sufficient conditions are given for the stability and asymptotic stability of nonantonomous linear delay differential systems under the assumption that the coefficient matrix or the delay is an $L^p$-function.

A quite general abstract system of an integral and an integrodifferential equation is studied. Necessary conditions and sufficient conditions for its well posedness are given in many functional spaces. Examples and applications are considered.

The aim of this paper is to study a class of eigenvalue problems of variational-hemivariational type.

In this paper we investigate the existence of positive solutions to a system of differential equations which model a competitive system. Instead of assuming the usual logistic growth model for each population we allow the growth rate to increase for positive populations. This leads to models which exhibit the Allee effect.

The existence and uniqueness of solutions to the Cauchy problem for a first-order quasi-linear partial differential equation is studied in this paper using the Henstock-Kurzweil integral. The classical theory requires certain differentiability and continuity conditions on the coefficients of the derivatives in the equation. It is shown here that in the Henstock-Kurzweil integral setting these conditions can be relaxed and that the resulting solution is differentiable though the derivatives need not be continuous. This sharpens the classical result and provides a bridge between classical and weak solutions in the linear case.

We prove the existence and uniqueness of smooth solutions of the vector Burgers equation in arbitrary two- and three-dimensional domains. The only assumption about the spatial domain is that it should be an open set. The underlying estimates for these results are proved using new "elliptic-Sobolev" inequalities of Xie ([13], [15]) for the Laplacian. Our purpose in giving these results is to develop methods that we think can be eventually transferred to the Navier-Stokes equations. Indeed, the only missing point is the proof of analogous "elliptic-Sobolev" inequalities for the Stokes operator, which we conjecture to be valid.

An annulus argument is a method of proof which can detect that a curve in $\mathbb{R}^n$ crosses an annulus around the origin infinitely many times. In this paper we give annulus arguments not requiring the boundedness of the derivatives of the functions involved. Using these results we establish Lyapunov type theorems for the attractivity, asymptotic stability, and partial stability properties of the zero solution of nonautonomous functional differential equations whose right hand sides are not bounded with respect to the time. We apply these results to the scalar equation $$ x'(t) = -c(t)x(t) + b(t)x(t-h)\qquad(c(t) \ge 0), $$ the scalar equation with several delays $$ x'(t) = -c(t)x(t) + \sum^n_{i=1} b_i(t)x(t - h_i)\qquad(c(t) \ge 0), $$ as well as to the system $$ x'(t) = B(t)x(t-h)-C(t)x(t), $$ where $B (t)$ and $C(t)$ are continuous matrix functions.

We describe all the rotationally symmetric spacelike graphs $G_u=\bigl( x,u(\vert x\vert)\bigr)$ in Minkowsky's space whose mean curvature is a prescribed function $f$ of $u$. In particular, we prove the existence of regular and singular solutions by means of a fixed-point theorem, and we study the global behaviour of solutions in the case $f(u)\cdot u$ does not change sign.