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The purpose of this work is to advance and simplify our understanding of some of the basic theory of linear dynamic equations and dynamic inequalities on time scales. Firstly, we revisit and simplify approaches to Gronwall's inequality on time scales. We provide new, simple and direct proofs that are accessible to those with only a basic understanding of calculus. Secondly, we apply the ideas to second and higher order linear dynamic equations on time scales. Part of the novelty herein involves a strategic choice of metric, notably the taxicab metric, to produce {\em a priori} bounds on solutions. This choice of metric significantly simplifies usual approaches and extends ideas from the literature. Thirdly, we examine mathematical applications of the aforementioned bounds. We form results concerning the non-multiplicity of solutions to linear problems; and error estimates on solutions to initial value problems when the initial conditions are imprecisely known. [ABSTRACT FROM AUTHOR]

This article examines the qualitative properties of solutions to systems of boundary value problems involving fractional differential equations. Our primary interest is in forming new results that involve suficient conditions for the existence of solutions. To do this, we formulate some new ideas concerning a priori bounds on solutions, which are then applied to produce the novel existence results. The main techniques of the paper involve the introduction of novel fractional differential inequalities and the application of the fixed-point theorem of Schäfer. We conclude the work with several new results that link the number of solutions to our problem with a fractional initial value problem, akin to an abstract shooting method. [ABSTRACT FROM AUTHOR]

In this paper we examine "terminal" value problems for dynamic equations on time scales -- that is, a dynamic equation whose solutions are asymptotic at infinity. We present a number of new theorems that guarantee the existence and uniqueness of solutions, as well as some comparison-type results. The methods we employ feature dynamic inequalities, weighted norms, and fixed-point theory. [ABSTRACT FROM AUTHOR]

In this work we present some new results concerning the existence and uniqueness of solutions to an impulsive first-order, nonlinear ordinary differential equation with "non-periodic" boundary conditions. These boundary conditions include, as a special case, so-called "anti-periodic" boundary conditions. Our methods to prove the existence and uniqueness of solutions involve new differential inequalities, the classical fixed-point theorem of Schaefer, and the Nonlinear Alternative. Our new results apply to systems of impulsive differential equations where the right-hand side of the equation may grow linearly, or sub- or super-linearly in its second argument. [ABSTRACT FROM AUTHOR]

We consider the generalization of two classical periodic problems to the context of time scales. On the one hand, we generalize a celebrated result by Castro for the forced pendulum equation. On the other hand, we extend a well-known result by Nirenberg to a resonant system of equations on time scales. Furthermore, the results are new even for classical difference equations. [ABSTRACT FROM AUTHOR]

We are concerned with the existence and form of positive solutions to a nonlinear third-order three-point nonlocal boundary-value problem on general time scales. Using Green's functions, we prove the existence of at least one positive solution using the Guo-Krasnoselskii fixed point theorem. Due to the fact that the nonlinearity is allowed to change sign in our formulation, and the novelty of the boundary conditions, these results are new for discrete, continuous, quantum and arbitrary time scales. [ABSTRACT FROM AUTHOR]

This article investigates the existence of solutions to first-order nonlinear boundary-value problems (BVPs) involving systems of ordinary differential equations and two-point boundary conditions. Some sufficient conditions are presented that will ensure solvability. The main tools employed are novel differential inequalities and fixed-point methods. [ABSTRACT FROM AUTHOR]

The aim of this article is to establish sufficient conditions for the approximate controllability of fractional control systems with time delay in Hilbert spaces. By the technique of sequential approach, we prove that the fractional control systems with time delay are approximately controllable. Finally, an example is provided to illustrate our main results. [ABSTRACT FROM AUTHOR]

Here, we investigate boundary-value problems (BVPs) for systems of second-order, ordinary, delay-differential equations. We introduce some differential inequalities such that all solutions (and their derivatives) to a certain family of BVPs satisfy some a priori bounds. The results are then applied, in conjunction with topological arguments, to prove the existence of solutions. We then apply earlier abstract theory of Petryshyn to formulate some constructive results under which solutions to BVPs for systems of second-order, ordinary, delay-differential equations are A-solvable and may be approximated via a Galerkin method. Finally, we provide some differential inequalities such that solutions to our equations are unique. [ABSTRACT FROM AUTHOR]