Hasil untuk "math.FA"

Axel Renard

We establish an explicit criterion for determining whether a $4 \times 4$ upper-triangular matrix is a contraction with respect to the Euclidean operator norm.

Peter Semrl

We improve the Hyers-Ulam stability result for isometries of real Hilbert spaces by removing the surjectivity assumption.

A. A. Vasil'eva

Order estimates for the Kolmogorov widths of a finite-dimensional balls intersection are obtained.

Frédéric Bayart

We give a sufficient condition for a composition operator with positive characteristic to be compact on the Hardy space of Dirichlet series.

Jin Fa Cheng

Anna Kaminska

We present a direct proof of the fact that the weak-$L^1$ and weak-$\ell^1$ spaces do not have type $1$.

Li Xin Cheng, Long Fa Sun

Frédéric Bayart

We prove the existence of algebras of hypercyclic vectors in three cases: convolution operators, composition operators, and backward shift operators.

Duc-Trung Hoang

In this paper, we investigate the Hautus test for evolution equation with the operators depending on time.

Aiman Mbarek

The objective of this paper to give a formula for unitary operators that corresponds to the Heler-Sj{ö}strand formula for self-adjoint operators.

Wei-Shih Du

In this paper, we introduce and share the new concept of $\mathcal{MT}(λ)$-functions and its some characterizations.

Zafer Ercan

We give an example to show that the main result of [1] is incorrect.

Ioannis Gasparis

A proof is given of Rosenthal's \(\ell_1\) theorem.

Sajid Iqbal, Josip Pecarić

In this paper, we establish some new general Opial inequalities for Widder derivatives.

Temirkhan Sultanovich Aleroev, Mokhtar Kirane, Yi-Fa Tang

Zong-yuan Ma, Hong-jian Liao, Fa-ning Dang

Anna Skripka

This survey on approximations of perturbed operator functions addresses recent advances and some of the successful methods.

Huanxia Fa, Xiaoyan Zheng, Junbo Li

Osamu Hatori

We prove a local version of the Mazur-Ulam theorem.

Brant A De Fanti, Jock S Hamilton, Barbara A Horwitz