Operator theory
1. Coupled fixed point results for $T$-contractions on $\mathcal{F}$-metric spaces and an application

H. Majani; R. Zaer Soleimani; J. Izadi

Volume 10, Issue 01 , Winter 2021, , Pages 1-10

Abstract
  The main purpose of this article is to introduce the concept of $T$-contraction type mappings in the function weighed metric spaces and to obtain some coupled fixed points theorems in this framework. Also, an example and an application of the existence of a solution of a system of nonlinear integral ...  Read More

Functional analysis
2. A new implicit iteration process for approximating common fixed points of $\alpha$-demicontraction semigroup

A. E. Ofem; D. I. Igbokwe

Volume 10, Issue 01 , Winter 2021, , Pages 19-34

Abstract
  It is our purpose in this paper to introduce the concept of $\alpha$-demicontractive semigroup. Also, we construct a new implicit iterative scheme for approximating the common fixed points of $\alpha$-demicontractive semigroup. We prove strong convergence of our new iterative scheme to the common fixed ...  Read More

Operator theory
3. Integral type contraction and coupled fixed point theorems in ordered G-metric spaces

E. Lotfali Ghasab; H. Majani; G. Soleimani Rad

Volume 09, Issue 02 , Spring 2020, , Pages 113-120

Abstract
  In this paper, we apply the idea of integral type contraction and prove some coupled fixed point theorems for such contractions in ordered $G$-metric space. Also, we support the main results by an illustrative example.  Read More

Operator theory
4. $C$-class functions on common fixed point theorems for weak‎ ‎contraction mapping of integral type in modular spaces

H. A. Hammad; R. A. Rashwan; A. H. Ansari

Volume 08, Issue 04 , Autumn 2019, , Pages 265-285

Abstract
  ‎In this paper‎, ‎we use the concept of $C$-class functions introduced‎ ‎by Ansari [4] to prove the existence and uniqueness of‎ ‎common fixed point for self-mappings in modular spaces of integral‎ ‎inequality‎. ‎Our results extended and generalized ...  Read More

Linear and multilinear algebra; matrix theory
5. *-frames in Hilbert modules over pro-C*-algebras

M. Naroei Irani; A. Nazari

Volume 08, Issue 01 , Winter 2019, , Pages 1-10

Abstract
  ‎In this paper‎, ‎by using the sequence of multipliers‎, ‎we introduce frames with algebraic bounds in Hilbert pro-$ C^* $-modules‎. ‎We investigate the relations between frames and $ \ast $-frames‎. ‎Some properties of $ \ast $-frames in Hilbert pro-$ C^* $-modules ...  Read More

Functional analysis
6. System of AQC functional equations in non-Archimedean normed spaces

H. Majani

Volume 08, Issue 01 , Winter 2019, , Pages 41-52

Abstract
  ‎In 1897‎, ‎Hensel introduced a normed space which does‎ ‎not have the Archimedean property‎. ‎During the last three decades‎ ‎theory of non--Archimedean spaces has gained the interest of‎ ‎physicists for their research in particular in problems ...  Read More

Operator theory
7. Algebraic distance in algebraic cone metric spaces and its properties

K. Fallahi; G. Soleimani Rad

Volume 07, Issue 04 , Autumn 2018, , Pages 273-280

Abstract
  In this paper, we prove some properties of algebraic cone metric spaces and introduce the notion of algebraic distance in an algebraic cone metric space. As an application, we obtain some famous fixed point results in the framework of this algebraic distance.  Read More

Difference and functional equations
8. Stability and hyperstability of orthogonally ring $*$-$n$-derivations and orthogonally ring $*$-$n$-homomorphisms on $C^*$-algebras

R. Gholami; Gh. Askari; M. Eshaghi Gordji

Volume 07, Issue 02 , Spring 2018, , Pages 109-119

Abstract
  In this paper, we investigate the generalized Hyers-Ulam-Rassias and the Isac and Rassias-type stability of the conditional of orthogonally ring $*$-$n$-derivation and orthogonally ring $*$-$n$-homomorphism on $C^*$-algebras. As a consequence of this, we prove the hyperstability of orthogonally ring ...  Read More

Operator theory
9. Characterization of $(\delta‎, ‎\varepsilon)$-double derivation on rings ‎and ‎algebras

Z. Jokar; A. Niknam

Volume 06, Issue 03 , Summer 2017, , Pages 191-198

Abstract
  This paper is an attempt to prove the following result:Let $n>1$ be an integer and let $\mathcal{R}$ be a $n!$-torsion-free ring with the identity element. Suppose that $d, \delta, \varepsilon$ are additive mappings satisfying\begin{equation}d(x^n) = \sum^{n}_{j=1}x^{n-j}d(x)x^{j-1}+\sum^{n-1}_{j=1}\sum^{j}_{i=1}x^{n-1-j}\Big(\delta(x)x^{j-i}\varepsilon(x)+\varepsilon(x)x^{j-i}\delta(x)\Big)x^{i-1}\quad\end{equation}for ...  Read More

Functional analysis
10. Duals and approximate duals of g-frames in Hilbert spaces

M. Mirzaee Azandaryani; A. Khosravi

Volume 04, Issue 04 , Autumn 2015, , Pages 259-265

Abstract
  In this paper we get some results and applications for duals and approximate duals of g-frames in Hilbert spaces. In particular, we consider the stability of duals and approximate duals under bounded operators and we study duals and approximate duals of g-frames in the direct sum of Hilbert spaces. We ...  Read More

Functional analysis
11. New characterizations of fusion bases and Riesz fusion bases in Hilbert spaces

F. Aboutorabi Goudarzi; M. S. Asgari

Volume 04, Issue 02 , Spring 2015, , Pages 131-142

Abstract
  In this paper we investigate a new notion of bases in Hilbert spaces and similar to fusion frame theory we introduce fusion bases theory in Hilbert spaces. We also introduce a new de nition of fusion dual sequence associated with a fusion basis and show that the operators of a fusion dual ...  Read More

Operator theory
12. On the boundedness of almost multipliers on certain Banach algebras

E. Ansari-Piri; M. Shams Youse fi; S. Nouri

Volume 04, Issue 02 , Spring 2015, , Pages 143-152

Abstract
  Almost multiplier is rather a new concept in the theory of almost functions. In this paper we discussion the boundedness of almost multipliers on some special Banach algebras, namely stable algebras. We also defi ne an adjoint and extension for almost multiplier.  Read More

Operator theory
13. On dual shearlet frames

M. Amin khah; A. Askari Hemmat; R. Raisi Tousi

Volume 04, Issue 02 , Spring 2015, , Pages 159-163

Abstract
  In This paper, we give a necessary condition for function in $L^2$ with its dual to generate a dual shearlet tight frame with respect to admissibility.  Read More

Functional analysis
14. Frames for compressed sensing using coherence

L. Gavruta; G. Zamani Eskandani; P. Gavruta

Volume 04, Issue 01 , Winter 2015, , Pages 25-34

Abstract
  We give some new results on sparse signal recovery in the presence of noise, for weighted spaces. Traditionally, were used dictionaries that have the norm equal to 1, but, for random dictionaries this condition is rarely satis ed. Moreover, we give better estimations then the ones given ...  Read More

Functional analysis
15. The solutions to some operator equations in Hilbert $C^*$-module

M. Mohammadzadeh Karizaki; M. Hassani

Volume 04, Issue 01 , Winter 2015, , Pages 35-42

Abstract
  In this paper, we state some results on product of operators with closed ranges and we solve the operator equation $TXS^*-SX^*T^*= A$ in the general setting of the adjointable operators between Hilbert $C^*$-modules, when $TS = 1$. Furthermore, by using some block operator matrix techniques, ...  Read More

Functional analysis
16. On duality of modular G-Riesz bases and G-Riesz bases in Hilbert C*-modules

M. Rashidi-Kouchi

Volume 04, Issue 01 , Winter 2015, , Pages 53-63

Abstract
  In this paper, we investigate duality of modular g-Riesz bases and g-Riesz bases in Hilbert C*-modules. First we give some characterization of g-Riesz bases in Hilbert C*-modules, by using properties of operator theory. Next, we characterize the duals of a given g-Riesz basis in Hilbert C*-module. ...  Read More

Group theory and generalizations
17. Module amenability and module biprojectivity of θ-Lau product of Banach algebras

D. Ebrahimi Bagha; H. Azaraien

Volume 03, Issue 03 , Summer 2014, , Pages 185-196

Abstract
  In this paper we study the relation between module amenability of $\theta$-Lau product $A×_\theta B$ and that of Banach algebras $A, B$. We also discuss module biprojectivity of $A×\theta B$. As a consequent we will see that for an inverse semigroup $S$, $l^1(S)×_\theta l^1(S)$ is module ...  Read More

Functional analysis
18. Operator-valued bases on Hilbert spaces

M. S. Asgari

Volume 02, Issue 04 , Autumn 2013, , Pages 201-218

Abstract
  In this paper we develop a natural generalization of Schauder basis theory, we term operator-valued basis or simply ov-basis theory, using operator-algebraic methods. We prove several results for ov-basis concerning duality, orthogonality, biorthogonality and minimality. We prove that ...  Read More

Functional analysis
19. On the Finsler modules over H-algebras

F. Hasanvand; M. Khanehgir; M. Hassani

Volume 02, Issue 04 , Autumn 2013, , Pages 219-227

Abstract
  In this paper, applying the concept of generalized A-valued norm on a right $H^*$-module and also the notion of ϕ-homomorphism of Finsler modules over $C^*$-algebras we first improve the definition of the Finsler module over $H^*$-algebra and then define ϕ-morphism of Finsler modules over $H^*$-algebras. ...  Read More

Operator theory
20. Some algebraic properties of Lambert Multipliers on $L^2$ spaces

A. Zohri; S. Khalil Sarbaz

Volume 02, Issue 04 , Autumn 2013, , Pages 255-261

Abstract
  In this paper, we determine the structure of the space of multipliers of the range of a composition operator $C_\varphi$ that induces by the conditional expectation between two $L^p(\Sigma)$ spaces.  Read More