Results 61 to 70 of about 579,350 (178)

Null projections and noncommutative function theory in operator algebras

Journal of the London Mathematical Society, Volume 114, Issue 1, July 2026.
Abstract We study projections in the bidual of a C∗$\mathrm{C}^*$‐algebra B$B$ that are null with respect to a subalgebra A$A$, that is, projections p∈B∗∗$p\in B^{**}$ satisfying |φ|(p)=0$|\varphi |(p)=0$ for every φ∈B∗$\varphi \in B^*$ annihilating A$A$. In the separable case, A$A$‐null projections are precisely the peak projections in the bidual of A$
David P. Blecher, Raphaël Clouâtre
wiley   +1 more source

Inequalities involving unitarily invariant norms and operator monotone functions [PDF]

, 2002
Let ∥·∥ be a unitarily invariant norm on matrices. For matrices A,B,X with A,B positive semidefinite and X arbitrary, we prove that the function t↦∥|AtXB1−t|r∥·∥|A1−tXBt|r∥ is convex on [0,1] for each r>0.
Hiai, FM, Zhan, Xingzhi, Zhan, XZ, Fumio Hiai, Xingzhi Zhan, Hiai, Fumio   +5 more
core   +1 more source

Shape Derivatives of the Eigenvalues of the De Rham Complex for Lipschitz Deformations and Variable Coefficients: Part I

Mathematical Methods in the Applied Sciences, Volume 49, Issue 8, Page 7975-8005, 30 May 2026.
ABSTRACT We study eigenvalue problems for the de Rham complex on varying three‐dimensional domains. Our analysis includes the Helmholtz equation as well as the Maxwell system with mixed boundary conditions and non‐constant coefficients. We provide Hadamard‐type formulas for the shape derivatives under weak regularity assumptions on the domain and its ...
Pier Domenico Lamberti, Dirk Pauly, Michele Zaccaron   +2 more
wiley   +1 more source

Norm bounds for Hadamard products and an arithmetic - geometric mean inequality for unitarily invariant norms [PDF]

, 1995
An arithmetic-geometric mean inequality for unitarily invariant norms and matrices,2∥A∗XB∥⩽∥AA∗X+XBB∗∥,is an immediate consequence of a basic inequality for singular values of Hadamard ...
Horn, Roger A.
core   +1 more source

Countable Basis for Free Electromagnetic Fields

Annalen der Physik, Volume 538, Issue 5, May 2026.
ABSTRACT Polychromatic electromagnetic fields are expanded as integrals over monochromatic fields, such as plane waves, multipolar fields, or Bessel beams. However, monochromatic fields do not belong to the Hilbert space of free Maxwell fields, since their norms diverge.
Ivan Fernandez‐Corbaton
wiley   +1 more source

Residual bounds for unitarily invariant norms on clustered eigenvalues [PDF]

, 1997
Let n × n Hermitian matrix A have eigenvalues λ1, λ2, …, λn, let k × k Hermitian matrix H have eigenvalues μ1, μ2, …, μk, and let Q be an n × k matrix having full column rank, so 1 ≤ k ≤ n. It is proved that there exist k eigenvalues λi1 ≤ λi2 … ≤ λik of
Xie, Jian-Jun, Jian-Jun Xie
core   +1 more source

Singular value inequalities for generalized anticommutators

Journal of Inequalities and Applications
We shown among other inequalities that if A 1 $A_{1}$ , B 1 $B_{1}$ , X 1 $X_{1}$ , and Y 1 $Y_{1}$ are n × n $n\times n$ complex matrices such that A 1 $A_{1}$ and B 1 $B_{1}$ are positive semidefinite, then s j ( Y 1 A 1 X 1 − X 1 B 1 Y 1 ) ≤ s j ( Z ⊕
Manal Al-Labadi, Raja’a Al-Naimi, Wasim Audeh   +2 more
doaj   +1 more source

Maximally dissipative and self‐adjoint extensions of K$K$‐invariant operators

Bulletin of the London Mathematical Society, Volume 58, Issue 5, May 2026.
Abstract We introduce the notion of K$K$‐invariant operators, S$S$, in a Hilbert space, with respect to a bounded and boundedly invertible operator K$K$ defined via K∗SK=S$K^*SK=S$. Conditions such that self‐adjoint and maximally dissipative extensions of K$K$‐invariant symmetric operators are also K$K$‐invariant are investigated.
Christoph Fischbacher, Bart Rosenzweig, Jonathan Stanfill   +2 more
wiley   +1 more source

Local Lidskii's theorems for unitarily invariant norms [PDF]

Linear Algebra and its Applications, 2018
arXiv admin note: text overlap with arXiv:1610 ...
Massey, Pedro Gustavo, Rios, Noelia Belén, Stojanoff, Demetrio   +2 more
openaire   +4 more sources

Algebraic singular functions are not always dense in the ideal of C∗$C^*$‐singular functions

Bulletin of the London Mathematical Society, Volume 58, Issue 5, May 2026.
Abstract We give the first examples of étale (non‐Hausdorff) groupoids G$\mathcal {G}$ whose C∗$C^*$‐algebras contain singular elements that cannot be approximated by singular elements in Cc(G)$\mathcal {C}_c(\mathcal {G})$. We provide two examples: one is a bundle of groups and the other a minimal and effective groupoid constructed from a self‐similar
Diego Martínez, Nóra Szakács
wiley   +1 more source