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Normal conditional expectations E: M --> N in M of finite index on von Neumann algebras M with discrete center are investigated to find an estimate for the minimal number of generators of M as a Hilbert N-module. Analyzing the case of M…

Operator Algebras · Mathematics 2007-05-23 Michael Frank

We prove that an inclusion $\mathcal{B} \subset \mathcal{A}$ of simple unital $C^*$-algebras with a finite-index conditional expectation is regular if and only if there exists a finite group $G$ that admits a cocycle action…

Operator Algebras · Mathematics 2026-01-01 Keshab Chandra Bakshi , Ved Prakash Gupta

Let N \subseteq M be von Neumann algebras and E:M\to N a faithful normal conditional expectation. In this work it is shown that the similarity orbit S(E) of E by the natural action of the invertible group of G_M of M has a natural complex…

Operator Algebras · Mathematics 2007-05-23 M. Argerami , D. Stojanoff

We shall introduce the notions of the strong Morita equivalence for unital inclusions of unital $C^*$-algebras and conditional expectations from an equivalence bimodule onto its closed subspace with respect to conditional expectations from…

Operator Algebras · Mathematics 2016-09-28 Kazunori Kodaka , Tamotsu Teruya

For a conditional expectation E on a (unital) C*-algebra A there exists a real number K>=1 such that the mapping (K.E-id_A) is positive if and only if there exists a real number L>=1 such that the mapping (L.E-id_A) is completely positive,…

Operator Algebras · Mathematics 2025-05-08 M. Frank , E. Kirchberg

In the first part of this paper, we give a new look at inclusions of von Neumann algebras with finite-dimensional centers and finite Jones' index. The minimal conditional expectation is characterized by means of a canonical state on the…

Operator Algebras · Mathematics 2021-01-26 Luca Giorgetti , Roberto Longo

Let $D \subseteq A$ be an inclusion of unital abelian $C^*$-algebras. In this note we characterize (in topological terms) when there is a unique conditional expectation $E:A \to D$, at least when $A$ is separable. As an application, we…

Operator Algebras · Mathematics 2016-09-21 Vrej Zarikian

Analogous to subfactor theory, employing Watatani's notions of index and $C^*$-basic construction of certain inclusions of $C^*$-algebras, (a) we develop a Fourier theory (consisting of Fourier transforms, rotation maps and shift operators)…

Operator Algebras · Mathematics 2026-01-01 Keshab Chandra Bakshi , Ved Prakash Gupta

For any injective von Neumann algebra R and any discrete, countable group G, which acts by *-automorphisms on R, we construct an idempotent mapping of an ultra-weakly dense subspace of B(H) onto the reducerd crossed product von Neumann…

Operator Algebras · Mathematics 2020-06-15 Erik Christensen

We initiate the effective study of conditional expectations onto subfactors. Our main result is that if $M$ is an existentially closed II$_1$ factor with a w-spectral gap subfactor $N$, then the conditional expectation function onto $N$ can…

Operator Algebras · Mathematics 2020-02-10 Isaac Goldbring

We determine when there is a unique conditional expectation from a semifinite von Neumann algebra onto a singly-generated maximal abelian *-subalgebra. Our work extends the results of Kadison and Singer via new methods, notably the…

Operator Algebras · Mathematics 2009-06-11 Charles A. Akemann , David Sherman

We define a canonical relative commutant planar algebra from a strongly Markov inclusion of finite von Neumann algebras. In the case of a connected unital inclusion of finite dimensional C*-algebras with the Markov trace, we show this…

Operator Algebras · Mathematics 2010-07-20 Vaughan F. R. Jones , David Penneys

We show that the existence of a continuous conditional expectation from a Fell bundle to a Fell subbundle implies that the full cross-sectional C*-algebra of the subbundle is contained in the full cross-sectional C*-algebra of the bundle,…

Operator Algebras · Mathematics 2024-12-18 Fernando Abadie

Motivated by [2] and [5], the notions of interior and exterior angles between a pair of compatible intermediate W*-subalgebras of an inclusion of W*-algebras with a normal conditional expectation with finite probabilistic index are…

Operator Algebras · Mathematics 2026-02-04 Ved Prakash Gupta , Deepika Sharma

We show that any finite dimensional von Neumann algebra admits an orthonormal unitary basis with respect to its standard trace. We also show that a finite dimensional von Neumann subalgebra of $M_n(\mathbb{C})$ admits an orthonormal unitary…

Operator Algebras · Mathematics 2022-11-22 Jason Crann , David W. Kribs , Rajesh Pereira

Let $(M, \varphi) = (M_1, \varphi_1) \ast (M_2, \varphi_2)$ be the free product of any $\sigma$-finite von Neumann algebras endowed with any faithful normal states. We show that whenever $Q \subset M$ is a von Neumann subalgebra with…

Operator Algebras · Mathematics 2016-10-05 Cyril Houdayer , Yoshimichi Ueda

A notion of partial ideal for an operator algebra is a weakening the notion of ideal where the defining algebraic conditions are enforced only in the commutative subalgebras. We show that, in a von Neumann algebra, the ultraweakly closed…

Operator Algebras · Mathematics 2014-08-07 Nadish de Silva , Rui Soares Barbosa

Let M be a factor of type III with separable predual and with normal states phi_1,...,phi_k, omega with omega faithful. Let A be a finite dimensional C*-subalgebra of M. Then it is shown that there is a unitary operator u in M such that…

Operator Algebras · Mathematics 2014-02-26 Yasuyuki Kawahigashi , Yoshiko Ogata , Erling Størmer

In operator algebra theory, a conditional expectation is usually assumed to be a projection map onto a sub-algebra. In the paper, a further type of conditional expectation and an extension of the Lueders - von Neumann measurement to…

Mathematical Physics · Physics 2010-01-22 Gerd Niestegge

Given an irreducible inclusion of infinite von-Neumann-algebras $\cn \subset \cm$ together with a conditional expectation $ E : \cm \rightarrow \cm $ such that the inclusion has depth 2, we show quite explicitely how $\cn $ can be viewed as…

High Energy Physics - Theory · Physics 2009-10-28 Florian Nill , Hans-Werner Wiesbrock
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