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Featured researches published by Toka Diagana.


Applicable Analysis | 2007

Existence of almost periodic solutions to some stochastic differential equations

Paul H. Bezandry; Toka Diagana

The article introduces and studies the concept of p-mean almost periodicity for stochastic processes. Our abstract results are, subsequently, applied to studying the existence of square-mean almost periodic solutions to some semilinear stochastic equations.


Proceedings of the American Mathematical Society | 2004

Almost automorphic solutions of evolution equations

Toka Diagana; Gaston M. N'Guérékata; Nguyen Van Minh

This paper is concerned with the existence of almost automorphic mild solutions to equations of the form (*) u(t) = Au(t) + f(t), where A generates a holomorphic semigroup and f is an almost automorphic function. Since almost automorphic functions may not be uniformly continuous, we introduce the notion of the uniform spectrum of a function. By modifying the method of sums of commuting operators used in previous works for the case of bounded uniformly continuous solutions, we obtain sufficient conditions for the existence of almost automorphic mild solutions to (*) in terms of the imaginary spectrum of A and the uniform spectrum of f.


Archive | 2013

Almost automorphic type and almost periodic type functions in abstract spaces

Toka Diagana

1. Metric, Banach, and Hilbert Spaces.- 2. Linear Operators on Banach Spaces.- 3. Almost Periodic Functions.- 4. Almost Automorphic Functions.- 5. Pseudo-Almost Periodic Functions.- 6. Pseudo-Almost Automorphic Functions.- 7. Existence Results for Some Second-Order Differential Equations.- 8. Existence Results to Some Integrodifferential Equations.- 9. Existence of C(m)-Pseudo-Almost Automorphic Solutions.- 10. Pseudo-Almost Periodic Solutions to Some Third-Order Differential Equations.- 11. Pseudo-Almost Automorphic Solutions to Some Sobolev-Type Equations.- 12. Stability Results for Some Higher-Order Difference Equations.- 13. Appendix A.- References.- Index.


Applicable Analysis | 2007

Stepanov-like almost automorphic functions and applications to some semilinear equations

Toka Diagana; Gaston M. N’Guérékata

This article is concerned with the existence and uniqueness of an almost automorphic solution to the semilinear equation where is the infinitesimal generator of an exponentially stable C 0-semigroup on a Banach space and is Sp -almost automorphic for p > 1 and jointly continuous.


Archive | 2011

Almost periodic stochastic processes

Paul H. Bezandry; Toka Diagana

Preface.-1. Banach and Hilbert Spaces.-2. Bounded and Unbounded Linear Operators.- 3.An Introduction to Stochastic Differential Equations.-4. P-th Mean Almost Periodic Random Functions.-5. Existence Results for Some Stochastic Differential Equations.-6. Existence Results for Some Partial Stochastic Differential Equations.-7.Existence Results for Some Second-Order Stochastic Differential Equations.-8. Mean Almost Periodic Random Sequences and Their Applications to Stochastic Difference Equations.-References.-Index.


Mathematical and Computer Modelling | 2007

Pseudo almost periodic solutions to some non-autonomous neutral functional differential equations with unbounded delay

Toka Diagana; Eduardo Hernández; Marcos Rabello

In this paper we give some sufficient conditions, which ensure the existence of pseudo almost periodic solutions to some classes of non-autonomous first-order partial neutral functional-differential with unbounded delay.


Applied Mathematics Letters | 2007

Almost automorphic solutions to some classes of partial evolution equations

Toka Diagana; Gaston M. N’Guérékata

We give in this work some sufficient conditions for the existence and uniqueness of almost automorphic (mild) solutions to some classes of partial evolution equations. Then we use our abstract results to discuss the existence and uniqueness of almost automorphic solutions to some partial differential equations.


Applied Mathematics and Computation | 2012

Existence of weighted pseudo anti-periodic solutions to some non-autonomous differential equations

Najja S. Al-Islam; Saud M. Alsulami; Toka Diagana

Abstract In this paper we first introduce two new concepts called respectively weighted pseudo periodicity and weighted pseudo anti-periodicity, which generalize respectively the well-known notions of periodicity and that of anti-periodicity. Basic properties of these new functions are discussed. Furthermore, the existence of weighted pseudo anti-periodic solutions to some damped non-autonomous second-order differential equations will be investigated. To illustrate our abstract results, the existence of weighted pseudo anti-periodic solutions to a plate-like equation is discussed.


Journal of Difference Equations and Applications | 2008

On the Stochastic Beverton-Holt Equation with Survival Rates

Paul H. Bezandry; Toka Diagana; Saber Elaydi

The paper studies a Beverton–Holt difference equation, in which both the recruitment function and the survival rate vary randomly. It is then shown that there is a unique invariant density, which is asymptotically stable. Moreover, a basic theory for random mean almost periodic sequence on is given. Then, some sufficient conditions for the existence of a mean almost periodic solution to the stochastic Beverton–Holt equation are given.


Journal of Difference Equations and Applications | 2007

Population Models in Almost Periodic Environments

Toka Diagana; Saber Elaydi; Abdul-Aziz Yakubu

We establish the basic theory of almost periodic sequences on ℤ+. Dichotomy techniques are then utilized to find sufficient conditions for the existence of a globally attracting almost periodic solution of a semilinear system of difference equations. These existence results are, subsequently, applied to discretely reproducing populations with and without overlapping generations. Furthermore, we access evidence for attenuance and resonance in almost periodically forced population models.

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