Very few Banach spaces E are known for which the lattice of closed ideals in the Banach algebra B(E) of all (bounded, linear) operators on E is fully understood. Indeed, up to now the only such Banach spaces are, up to isomorphism, Hilbert spaces and the sequence spaces c0 and `p for 1 6 p < ∞. We add a new member to this family by showing that there are exactly four closed ideals in B(E) for t...

Basic relation between numerical range and Davis-Wielandt shell of an operator $A$ acting on a Hilbert space with orthonormal basis $xi={e_{i}|i in I}$ and its conjugate $bar{A}$ which is introduced in this paper are obtained. The results are used to study the relation between point spectrum, approximate spectrum and residual spectrum of $A$ and $bar{A}$. A necessary and sufficient condition fo...

In this paper we view some fundamentals of the theory of Hilbert C-modules and examine some ways in which Hilbert C-modules differ from Hilbert spaces. ∗2000 Mathematics Subject Classification. 46L08.

There are Poincare group representations on complex Hilbert spaces, like the Dirac spinor field, or real Hilbert spaces, like the electromagnetic field tensor. The Majorana spinor is an element of a 4 dimensional real vector space. The Majorana spinor field is a space-time dependent Majorana spinor, solution of the free Dirac equation. The Majorana-Fourier and Majorana-Hankel transforms of Majo...

In this paper, first, we introduce the new concept of (complex) 2–Hilbert spaces, that is, we define the concept of 2–inner product spaces with a complex valued 2–inner product by using the 2–norm. Next, we prove some theorems on Schwartz’s inequality, the polarization identity, the parallelogram laws and related important properties. Finally, we give some open problems related to 2–Hilbert spa...

We survey the recent developments concerning fixed point properties for group actions on Banach spaces. In the setting of Hilbert spaces such fixed point properties correspond to Kazhdan’s property (T). Here we focus on the general, non-Hilbert case, we discuss the methods, examples and several applications. 2010 Mathematics Subject Classification: 20J06, 18H10, 46B99

Recently fusion frame was considered as a generalization of frame in Hilbert spaces. In this paper, we establish several new inequalities for fusion frames with a scalar in Hilbert spaces. It is shown that the results we obtained can immediately lead to the existing corresponding results when we choose suitable scalars. Mathematics subject classification (2010): 42C15, 47B40.

In this paper tools for the analysis of Dirac structures on Hilbert spaces are developed. Some properties are pointed out and two natural representations of Dirac structures on Hilbert spaces are presented. The theory is illustrated on the example of the ideal transmission line. keywords: Power conserving structures, Dirac structures, Representations. AMS-Classification: 93C25, 93A30, 93B10, 70...

in this paper we introduce continuous $g$-bessel multipliers in hilbert spaces and investigate some of their properties. we provide some conditions under which a continuous $g$-bessel multiplier is a compact operator. also, we show the continuous dependency of continuous $g$-bessel multipliers on their parameters.