On the Stability of J*-Homomorphisms

Approximate $C^*$-Ternary Ring Homomorphisms

In this paper, we establish the generalized Hyers--Ulam--Rassias stability of $C^*$-ternary ring homomorphisms associated to the Trif functional equation \begin{eqnarray*} d \cdot C_{d-2}^{l-2} f(\frac{x_1+... +x_d}{d})+ C_{d-2}^{l-1}\sum_{j=1}^d f(x_j) = l \cdot \sum_{1\leq j_1< ... < j_l\leq d} f(\frac{x_{j_1} + ... + x_{j_l}}{l}). \end{eqnarray*}

Approximation of a Cauchy-Jensen additive mapping in various normed spaces

In this paper, using the fixed point and direct methods, we prove the generalized Hyers-Ulam-Rassias stability of a Cauchy-Jensen additive functional equation in various normed spaces. The concept of Hyers-Ulam-Rassias stability originated from Th. M. Rassias stability theorem that appeared in his paper: On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc. 72 (1978), 297-300.

Fixed points and the stability of the linear functional equations in a single variable

We prove that an interesting result concerning generalized Hyers-Ulam-Rassias stability of a linear functional equation obtained in 2014 by S.M. Jung, D. Popa and M.T. Rassias in Journal of Global Optimization is a particular case of a fixed point theorem given by us in 2012. Moreover, we give a characterization of functions that can be approximated with a given error, by the solution of the previously mention linear equation.

Stability of the Jensen--type functional equation in ternary Banach algebras: An alternative fixed point approach

Using fixed point methods, we prove the generalized Hyers--Ulam--Rassias stability of ternary homomorphisms, and ternary multipliers in ternary Banach algebras for the Jensen--type functional equation $$f(\frac{x+y+z}{3})+f(\frac{x-2y+z}{3})+f(\frac{x+y-2z}{3})= f(x).$$

Stability of a functional equation deriving from quartic and additive functions

In this paper, we obtain the general solution and the generalized Hyers-Ulam Rassias stability of the functional equation $$f(2x+y)+f(2x-y)=4(f(x+y)+f(x-y))-{3/7}(f(2y)-2f(y))+2f(2x)-8f(x).$$

Stability of a mixed type quadratic, cubic and quartic functional equation

In this paper, we obtain the general solution and the generalized Hyers-Ulam Rassias stability of the functional equation $$3(f(x+2y)+f(x-2y))=12(f(x+y)+f(x-y))+4f(3y)-18f(2y)+36f(y)-18f(x).$$

Hilbert C*-模上同态与*-同态的Hyers-Ulam稳定性

Hyers-Ulam stability of homomorphisms and *-homomorphisms on Hilbert C*-modules

该研究提出Hilbert C*-模上*-同态的概念，并采用不动点方法证明了此类模上同态与*-同态的Hyers-Ulam稳定性。

Stability of generalized mixed type additive-quadratic-cubic functional equation in non-Archimedean spaces

In this paper, we prove generalized Hyres--Ulam--Rassias stability of the mixed type additive, quadratic and cubic functional equation $$f(x+ky)+f(x-ky)=k^2f(x+y)+k^2f(x-y)+2(1-k^2)f(x)$$ for fixed integers $k$ with $k\neq0,\pm1$ in non-Archimedean spaces.

Solution and stability of generalized mixed type cubic, quadratic and additive functional equation in quasi-Banach spaces

In this paper, we achieve the general solution and the generalized Hyers-Ulam-Rassias stability of the following functional equation $$f(x+ky)+f(x-ky)=k^2f(x+y)+k^2f(x-y)+2(1-k^2)f(x)\eqno {2 cm}$$for fixed integers $k$ with $k\neq0,\pm1$ in the quasi-Banach spaces.

On the stability of generalized mixed type quadratic and quartic functional equation in quasi-Banach spaces

In this paper, we establish the general solution of the functional equation $$f(nx+y)+f(nx-y)=n^2f(x+y)+n^2f(x-y)+2(f(nx)-n^2f(x))-2(n^2-1)f(y)\eqno {0 cm}$$for fixed integers $n$ with $n\neq0,\pm1$ and investigate the generalized Hyers-Ulam-Rassias stability of this equation in quasi-Banach spaces.

Solution and Stability of a Mixed Type Functional Equation

In this paper, we obtain the general solution and investigate the generalized Hyers-Ulam-Rassias stability for the new mixed type additive and cubic functional equation $$3f(x+3y) - f(3x + y)=12[f(x+y)+f(x-y)]-16[f(x)+f(y)] + 12f(2y) - 4f(2x).$$ As some corollaries, we show that the stability of this equation can be controlled by the sum and product of powers of norms.

Stability of Generalized Jensen Equation on Restricted Domains

In this paper, we establish the conditional Hyers-Ulam-Rassias stability of the generalized Jensen functional equation $r f \left (\frac{sx+ty}{r}) = s g(x) + t h(y)$ on various restricted domains such as inside balls, outside balls, and punctured spaces. In addition, we prove the orthogonal stability of this equation and study orthogonally generalized Jensen mappings on Balls in inner product spaces.

The stability of a quadratic type functional equation with the fixed point alternative

In this paper, we achieve the general solution and the generalized Hyers-Ulam-Rassias stability for the quadratic type functional equation &f(x+y+2cz)+f(x+y-2cz)+c^2f(2x)+c^2f(2y) &=2[f(x+y)+c^2f(x+z)+c^2f(x-z)+c^2f(y+z)+c^2f(y-z)] {2.6 cm} for fixed integers $c$ with $c\neq0,\pm1$, by using the fixed point alternative.

Hyers-Ulam Stability of Bessel Equations

We analyse different kinds of stabilities for the Bessel equation and for the modified Bessel equation with initial conditions. Sufficient conditions are obtained in order to guarantee Hyers-Ulam-Rassias, $σ$-semi-Hyers-Ulam and Hyers-Ulam stabilities for those equations. Those sufficient conditions are obtained based on the use of integral techniques and majorations.

Stability of cubic and quartic functional equations in non-Archimedean spaces

We prove generalized Hyres-Ulam-Rassias stability of the cubic functional equation $f(kx+y)+f(kx-y)=k[f(x+y)+f(x-y)]+2(k^3-k)f(x)$ for all $k\in \Bbb N$ and the quartic functional equation $f(kx+y)+f(kx-y)=k^2[f(x+y)+f(x-y)]+2k^2(k^2-1)f(x)-2(k^2-1)f(y)$ for all $k\in \Bbb N$ in non-Archimedean normed spaces.

$θ$-derivations on $JB^*$-triples

We introduce the concept of $θ$-derivations on $JB^*$-triples, and prove the Hyers--Ulam--Rassias stability of $θ$-derivations on $JB^*$-triples.

Approximate $(σ-τ)$-Contractibility

In this paper, the generalized Hyers--Ulam--Rassias stability of $(σ-τ)$-derivations on normed algebras into Banach bimodules is established. We introduce the notion of approximate $(σ-τ)$-contractibility and prove that a Banach algebra is $(σ-τ)$-contractible if and only if it is approximately $(σ-τ)$-Contractible.

Stability of ternary Jordan homomorphisms and derivations associated to the generalized Jensen equation

In this paper, we establish the generalized Hyers-Ulam stability of Jordan homomorphisms and Jordan derivations between ternary algebras via the generalized Jensen equation $rf(\frac{sx+ty}{r})=sf(x)+tf(y)$.

On approximate ternary m-derivations and $σ$-homomorphisms

In this paper we introduce ternary modules over ternary algebras and using fixed point methods, we prove the stability and super-stability of ternary additive, quadratic, cubic and quartic derivations and $σ$-homomorphisms in such structures for the functional equation \begin{equation*} \begin{split} &\quad f(ax+y)+f(ax-y)= a^{m-2}[f(x+y)+f(x-y)]\\&+2(a^2-1)[a^{m-2}f(x)+\frac{(m-2)(1-(m-2)^2)}{6}f(y)]. \end{split} \end{equation*} for each $m=1,2,3,4$.

Hyperstability of orthogonally 3-Lie homomorphism: an orthogonally fixed point approach

In this paper, by using the orthogonally fixed point method, we prove the Hyers-Ulam stability and the hyperstability of orthogonally 3-Lie homomorphisms for additive $ρ$-functional equation in 3-Lie algebras.\\ Indeed, we investigate the Hyers-Ulam stability and the hyperstability of the system of functional equations \begin{eqnarray*} \left\{ \begin{array}{ll} f(x+y)-f(x)-f(y)= ρ(2f(\frac{x+y}{2})+ f(x)+ f(y)),\\ f([[x,y],z])=[[f(x),f(y)],f(z)] \end{array} \right. \end{eqnarray*} in 3-Lie algebras (where $ρ$ is a fixed real number with $ρ\ne 1$).

Stability, cohomology vanishing, and non-approximable groups

Several well-known open questions (such as: are all groups sofic/hyperlinear?) have a common form: can all groups be approximated by asymptotic homomorphisms into the symmetric groups $\mathrm{Sym}(n)$ (in the sofic case) or the finite dimensional unitary groups ${\rm U}(n)$ (in the hyperlinear case)? In the case of ${\rm U}(n)$, the question can be asked with respect to different metrics and norms. This paper answers, for the first time, one of these versions, showing that there exist fintely presented groups which are not approximated by ${\rm U}(n)$ with respect to the Frobenius norm $\|T\|…