Additive Functional Equation Research Articles

Generalised Ulam-Hyers Stability Analysis for System of Additive Functional Equation in Fuzzy and Random Normed Spaces: Direct and Fixed Point Approach

In this article, a new system of Functional Equations is proposed. The Ulam-Hyers stability of this class of equations is investigated using the product, sum, and mixed product-sum of powers of norms, as well as the general control function. The stability analysis is carried out in random and fuzzy normed spaces using fixed point and direct methods. One of the unique and interesting aspects of this study is that, three new and different kinds of FEs have been introduced and the stability analysis is derived for all three equations simultaneously.

Stability and Instability of an Apollonius-Type Functional Equation

For the inner product space, we have Appolonius’ identity. From this identity, Park and Th. M. Rassias induced and investigated the quadratic functional equation of the Apollonius type. And Park and Th. M. Rassias first introduced an Apollonius-type additive functional equation. In this work, we investigate an Apollonius-type additive functional equation in 2-normed spaces. We first investigate the stability of an Apollonius-type additive functional equation in 2-Banach spaces by using Hyers’ direct method. Then, we consider the instability of an Apollonius-type additive functional equation in 2-Banach spaces.

Hyers-Ulam stability of a-type additive functional equations in Banach space using direct method

Hyers-Ulam stability of a-type additive functional equations in Banach space using direct method

Isometries to Analyze the Stability of Norm-Based Functional Equations in p-Uniformly Convex Spaces

Over the past two decades, significant advancements have been made in understanding the stability according to Hyers–Ulam involving different functional equations (FEs). This study investigates the generalized stability of norm-based (norm-additive) FEs within the framework of arbitrary (noncommutative) groups and p-uniformly convex spaces. Specifically, we analyze two key functional equations, ∥η(gh)∥=∥η(g)+η(h)∥ and ∥η(gh−1)∥=∥η(g)−η(h)∥foreveryg,h∈G, where (G,·) denotes an arbitrary group and B is considered to be a p-uniformly convex space. The surjectivity of the function η:G→B is a critical assumption in our analysis. Drawing upon the foundational works of L. Cheng and M. Sarfraz, this paper applies the large perturbation method tailored for p-uniformly convex spaces, where p≥1. This study extends previous research by offering a deeper exploration of the conditions under which these functional equations demonstrate Hyers–Ulam stability. In this study, the additive functional equation demonstrates a fundamental form of symmetry, where the order of operands does not affect the results. This symmetry under permutation of arguments is crucial for the analysis of stability. In the context of norm-additive FEs, this stability criterion investigates how small changes in the inputs of a functional equation affect the outputs, especially when the function is expected to follow an additive form.

Stability Of 4D alternate additive functional equation

In this paper, we confer the generalized Ulam-Hyers stability of a 4D alternate additive functional equation in Banach and Random Banach space via direct and fixed point methods.

Combined system of additive functional equations in Banach algebras

Abstract In this study, we solve the system of additive functional equations: h ( x + y ) = h ( x ) + h ( y ) , g ( x + y ) = f ( x ) + f ( y ) , 2 f x + y 2 = g ( x ) + g ( y ) , \left\{\begin{array}{l}h\left(x+y)=h\left(x)+h(y),\\ g\left(x+y)=f\left(x)+f(y),\\ 2f\left(\frac{x+y}{2}\right)=g\left(x)+g(y),\end{array}\right. and we investigate the stability of (homomorphism, derivation)-systems in Banach algebras.

A Pexider system of additive functional equations in Banach algebras

AbstractIn this paper, we solve the system of functional equations $$\begin{aligned} \textstyle\begin{cases} f(x+y)+g(y-x)=2f(x), \\ g(x+y)-f(y-x)=2g(y) \end{cases}\displaystyle \end{aligned}$$ { f ( x + y ) + g ( y − x ) = 2 f ( x ) , g ( x + y ) − f ( y − x ) = 2 g ( y ) and we investigate the stability of g-derivations in Banach algebras.

Characterization and stability of multi-additive-quadratic-cubic mappings

In this work, we introduce a system of additive, quadratic and cubic functional equations (somewhat different from what has been defined by Bodaghi and Rassias) which defines the multi-additive-quadratic-cubic mappings and then unify and characterize such mappings as a single equation without the quadratic condition. Moreover, by using a fixed point theorem, we establish the Găvruţa stability of the multi-additive-quadratic-cubic mappings in the setting of Banach spaces. As few known results, we prove the Hyers stability for multi-additive, multi-quadratic and multi-cubic mappings.

Instabilities and Stabilities of Additive Functional Equation in Paranormed Spaces

In this paper, we solve the general solution in vector space and prove the Hyers-Ulam stability of the following additive functional equationin paranormed spaces by using the direct and fixed point methods. Also we present its pertinent counter examples for instabilities.

Generalized Additive Functional Equation: General Solution and Hyers-Ulam Stability in Banach Spaces via Alternative Fixed Point Theorem

In this paper, we secure the general solution of the generalized additive functional equation
 [Equation presented]
 where r is a positive integer with N−{0,1,2,3,4}, and also examine Hyers-Ulam stability results by utilizing alternative fixed point for a generalized additive functional equation in Banach spaces.

Stability results of mixed type functional equations in modular spaces and 2-Banach spaces ∗

In this paper, we investigate the generalized Hyers-Ulam-Stability of additive and quartic functional equations in modular spaces with and without the △2-condition using the direct method and also in 2-Banach Spaces.

On pexider additive functional equations

Let Y(+) egy Abelian group, D in Z2 ( Z(+,≤) denotes the ordered group of the integers).Dx:={uϵZ | exists vϵ X; (u,v)ϵ D}, Dy:={vϵZ | exists uϵ X; (u,v)ϵ D}, Dx+y:={zϵZ | exists (u,v)ϵ D; z=u+v}.The aim of the article is to find sets D in Z2 that the general solution of the functional equation f(x+y) = g(x) + h(y) ((x,y ϵ D) with unknown functions f, g and h is in the form of f(u)=a(u)+C1+C2 (uϵDx+y), g(v)=a(v)+C1 (vϵDx); h(z)=a(z)+C2 (zϵDy) where a is an additive function, C1, C2 ϵ Y are constants).

Stability Results of the Additive and Quartic Functional Equations in Random p-Normed Spaces

Stability Results of the Additive and Quartic Functional Equations in Random p-Normed Spaces

A system of additive functional equations in complex Banach algebras

Abstract In this article, we solve the system of additive functional equations: 2 f ( x + y ) − g ( x ) = g ( y ) , g ( x + y ) − 2 f ( y − x ) = 4 f ( x ) \left\{\phantom{\rule[-1.25em]{}{0ex}}\begin{array}{l}2f\left(x+y)-g\left(x)=g(y),\\ g\left(x+y)-2f(y-x)=4f\left(x)\end{array}\right. and prove the Hyers-Ulam stability of the system of additive functional equations in complex Banach spaces. Furthermore, we prove the Hyers-Ulam stability of f f -hom-ders in Banach algebras.

Stability Analysis of a New Class of Series Type Additive Functional Equation in Banach Spaces: Direct and Fixed Point Techniques

In this paper, the authors introduce two new classes of series type additive functional Equations (FEs). The first class of equations is derived from the sum of the squares of the alternative series and the second one is obtained from the sum of the cubes of the series. The solution of the FE is investigated using the principle of mathematical induction. The beauty of this method lies in the fact that it satisfies the property of the additive FE as well as the series. Banach spaces are one of the widely-used spaces that are very helpful to analyse the stability results of various FEs. The Banach space conditions have been applied and the stability results are established for both of the equations. Furthermore, the Banach Contraction principle and alternative of fixed point theorem are used to derive the stability results in a fixed point technique (FPT). The relationship between the FEs and both the series is established through the principle of mathematical induction in the Application section, which adds novelty to the derived results.

Classical and Fixed Point Approach to the Stability Analysis of a Bilateral Symmetric Additive Functional Equation in Fuzzy and Random Normed Spaces

In this article, a new kind of bilateral symmetric additive type functional equation is introduced. One of the interesting characteristics of the equation is the fact that it is ideal for investigating the Ulam–Hyers stabilities in two prominent normed spaces, namely fuzzy and random normed spaces simultaneously. This article analyzes the proposed equation in both spaces. The solution of this equation exhibits the property of symmetry, that is, the left of the object becomes the right of the image, and vice versa. Additionally, the stability results of this functional equation are determined in fuzzy and random normed spaces using direct and fixed point methods.

Ulam Stability Results of Functional Equations in Modular Spaces and 2-Banach Spaces

In this work, we investigate the refined stability of the additive, quartic, and quintic functional equations in modular spaces with and without the Δ2-condition using the direct method (Hyers method). We also examine Ulam stability in 2-Banach space using the direct method. Additionally, using a suitable counterexample, we eventually demonstrate that the stability of these equations fails in a certain case.

Refined stability of the additive, quartic and sextic functional equations with counter-examples

<abstract><p>In this study, we utilize the direct method (Hyers approach) to examine the refined stability of the additive, quartic, and sextic functional equations in modular spaces with and without the $ \Delta _{2} $-condition. We also use the direct approach to discuss the Ulam stability in $ 2 $-Banach spaces. Ultimately, we ensure that stability of above equations does not hold in a particular scenario by utilizing appropriate counter-examples.</p></abstract>

Generalized Stability of Functional Inequalities with 3k-Variables Associated for Jordan-von Neumann-Type Additive Functional Equation

Generalized Stability of Functional Inequalities with 3k-Variables Associated for Jordan-von Neumann-Type Additive Functional Equation

Functional inequalities associated with additive, quadratic and Drygas functional equations

Functional inequalities associated with additive, quadratic and Drygas functional equations