# Impulsive Periodic Boundary Value Problems for Dynamic Equations on Time Scale

- Eric R. Kaufmann
^{1}Email author

**2009**:603271

**DOI: **10.1155/2009/603271

© Eric R. Kaufmann. 2009

**Received: **31 March 2009

**Accepted: **20 May 2009

**Published: **29 June 2009

## Abstract

Let *T* be a periodic time scale with period
such that
, and
. Assume each
is dense. Using Schaeffer's theorem, we show that the impulsive dynamic equation
where
,
, and
is the
-derivative on *T*, has a solution.

## 1. Introduction

Due to their importance in numerous application, for example, physics, population dynamics, industrial robotics, optimal control, and other areas, many authors are studying dynamic equations with impulse effects; see [1 - 19] and references therein.

where and is the -derivative on .

where , and . This paper extends and generalized the above results to dynamic equations on time scales.

We assume the reader is familiar with the notation and basic results for dynamic equations on time scales. While the books [20, 21] are indispensable resources for those who study dynamic equations on time scales, these manuscripts do not explicitly cover the concept of periodicity. The following definitions are essential in our analysis.

Definition 1.1 (see [8]).

We say that a time scale
is *periodic* if there exist a
such that if
, then
. For
, the smallest positive
is called the *period* of the time scale.

Example 1.2.

- (1)
has period ,

- (2)
,

- (3)
has period ,

- (4)
, where , has period .

Remark 1.3.

All periodic time scales are unbounded above and below.

Definition 1.4.

Let be a periodic time scale with period . We say that the function is periodic with period if there exists a natural number such that , for all and is the smallest number such that .

If , we say that is periodic with period if is the smallest positive number such that for all .

Remark 1.5.

If is a periodic time scale with period , then . Consequently, the graininess function satisfies and so, is a periodic function with period .

where and . Define and note that the intervals and are defined similarly.

In Section 2 we present some preliminary ideas that will be used in the remainder of the paper. In Section 3 we give sufficient conditions for the existence of at least one solution of the nonlinear problem (1.3).

## 2. Preliminaries

In this section we present some important concepts found in [20, 21] that will be used throughout the paper. We also define the space in which we seek solutions, state Schaeffer's theorem, and invert the linearized dynamic equation.

A function
is said to be *regressive* provided
for all
. The set of all regressive rd-continuous functions
is denoted by
.

*exponential function*on , defined by

is the solution to the initial value problem . Other properties of the exponential function are given in the following lemma, [20, Theorem 2.36].

Lemma 2.1.

- (i)
and ;

- (ii)
;

- (iii)
where, ;

- (iv)
;

- (v)
;

- (vi)
.

where .

We employ Schaeffer's fixed point theorem, see [22], to prove the existence of a periodic solution.

Theorem 2.2 (Schaeffer's Theorem).

- (i)
the set is unbounded, or

- (ii)
the operator has a fixed point in .

- (A)
is periodic with period ; for all .

- (F)
and for all , .

Furthermore, to ensure that the boundary value problem is not at resonance, we assume that .

where . Our first result inverts the operator (2.6).

Lemma 2.3.

Proof.

That is, satisfies (2.7).

The converse follows trivially and the proof is complete.

## 3. The Nonlinear Problem

Then is a solution of (1.3) if and only if is a fixed point of . A standard application of the Arzelà-Ascoli theorem yields that is compact.

Our first result is an existence and uniqueness theorem.

Theorem 3.1.

and such that

Then there exists a unique solution to (1.3).

Proof.

We will show that there exists a unique solution of (3.1). By Lemma 2.3 this solution is the unique solution of (1.3).

Hence, . By the Contraction Mapping Principal, there exists a unique solution of (3.1) and the proof is complete.

Our next two results utilize Theorem 2.2 to establish the existence of solutions of (1.3).

Theorem 3.2.

Suppose that . Then there exists at least one solution of (1.3).

Proof.

which implies that We have that if , then is bounded by the constant The set is bounded and so by Schaeffer's theorem, the operator has a fixed point. This fixed point is a solution of (1.3) and the proof is complete.

In our next theorem we assume that and are sublinear at infinity with respect to the second variable.

Theorem 3.3.

Assume that

(F_{I})
, uniformly, and

(I) , uniformly.

Then there exists at least one solution of the boundary value problem (1.3).

Proof.

as , which contradicts for all . Thus the set is bounded. By Theorem 2.2, the operator has a fixed point. This fixed point is a solution of (1.3) and the proof is complete.

The following corollary is an immediate consequences of Theorem 3.3

Corollary 3.4.

Assume that and are bounded. Then there exists at least one solution of (1.3).

## Authors’ Affiliations

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