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We study the Riesz Decomposition Property types of the lexicographic product of two po-groups. Then we apply them to the study of pseudo effect algebras which can be decomposed to a comparable system of non-void slices indexed by some…

Mathematical Physics · Physics 2013-03-05 A. Dvurecenskij , M. Kolarik

Let A be a maximal abelian self-adjoint subalgebra (masa) in a type II_1 factor M acting via standard representation on L^2(M). The abelian von Neumann algebra A generated by A and JAJ has a type I commutant which contains the projection…

Operator Algebras · Mathematics 2007-05-23 Ken Dykema , Allan Sinclair , Roger Smith

Extending results of Wyser, we determine formulas for the equivariant cohomology classes of closed orbits of certain families of spherical subgroups of $GL_n$ on the flag variety $GL_n/B$. Putting this together with a slight extension of…

Algebraic Geometry · Mathematics 2017-12-12 Mahir Bilen Can , Michael Joyce , Benjamin Wyser

We prove a generalization of N. Ozawa's Kurosh-type theorem to the setting of free products of semiexact II_1 factors with respect to arbitrary (non-tracial) faithful normal states. We are thus able to distinguish certain resulting type III…

Operator Algebras · Mathematics 2008-09-23 Jason Asher

In the late 1980s, A. Premet conjectured that the variety of nilpotent elements of any finite dimensional restricted Lie algebra over an algebraically closed field of characteristic $p>0$ is irreducible. This conjecture remains open, but it…

Rings and Algebras · Mathematics 2019-10-03 Cong Chen

In this study, we define a new triangle matrix $\hat{W}=\{w_{nk}^{\lambda}(r,s,t)\}$ which derived by using multiplication of $\lambda=(\lambda_{nk})$ triangle matrix with $B(r,s,t)$ triple band matrix. Also, we introduce the sequence…

Functional Analysis · Mathematics 2013-09-17 Serkan Demiriz , Osman Ozdemir , Osman Duyar

All the $F:$N$\rightarrow $C having Ramanujan expansion $F(a)=\sum_{q=1}^{\infty}G(q)c_q(a)$ (here $c_q(a)$ is the Ramanujan sum) pointwise converging in $a\in $N, with $G:$N$\rightarrow $C a multiplicative function, may be factored into…

Number Theory · Mathematics 2019-11-12 Giovanni Coppola

Homogeneous countably compact spaces $X$ and $Y$ whose product $X\times Y$ is not pseudocompact are constructed. It is proved that all compact subsets of homogeneous subspaces of the third power of an extremally disconnected space are…

General Topology · Mathematics 2023-06-13 Evgenii Reznichenko

We examine the ranks of operators in semi-finite C*-algebras as measured by their densely defined lower semicontinuous traces. We first prove that a unital simple C*-algebra whose extreme tracial boundary is nonempty and finite contains…

Operator Algebras · Mathematics 2015-06-01 Aaron Tikuisis , Andrew Toms

Our motivating question was whether all traces on a U-ultrapower of a C*-algebra A, where U is a non-principal ultrafilter on N, are necessarily U-limits of traces on A. We show that this is false so long as A has infinitely many extremal…

Operator Algebras · Mathematics 2017-02-10 Tristan Bice , Ilijas Farah

It is known that the eigenvalues of selfadjoint elements a,b,c with a+b+c=0 in the factor R^omega (ultrapower of the hyperfinite II1 factor) are characterized by a system of inequalities analogous to the classical Horn inequalities of…

Operator Algebras · Mathematics 2019-02-27 H. Bercovici , B. Collins , K. Dykema , W. S. Li , D. Timotin

This text is a detailed overview of the theories of W*-algebras and noncommutative integration, up to the Falcone-Takesaki theory of noncommutative Lp spaces over arbitrary W*-algebras, and its extension to noncommutative Orlicz spaces. The…

Operator Algebras · Mathematics 2014-10-28 Ryszard Paweł Kostecki

We extend the definition of quasi-finite complexes by considering not necessarily countable complexes. We provide a characterization of quasi-finite complexes in terms of L-invertible maps and dimensional properties of compactifications.…

General Topology · Mathematics 2007-05-23 Alex Karasev , Vesko Valov

We establish a non-commutative version of the Intermediate Factor Theorem for crossed products associated with product lattices. Given an irreducible lattice $\Gamma < G= G_1 \times \dots \times G_d$ in higher rank semisimple algebraic…

Operator Algebras · Mathematics 2026-01-16 Tattwamasi Amrutam , Yongle Jiang , Shuoxing Zhou

Finite quantum groupoids can be described in many equivalent ways: In terms of the weak Hopf C*-algebras of B\"ohm, Nill, and Szlach\'anyi or the finite-dimensional Hopf-von Neumann bimodules of Vallin, and in terms of finite-dimensional…

Operator Algebras · Mathematics 2007-11-12 Thomas Timmermann

We study the complexity of the classification problem for Cartan subalgebras in von Neumann algebras. We construct a large family of II$_1$ factors whose Cartan subalgebras up to unitary conjugacy are not classifiable by countable…

Operator Algebras · Mathematics 2018-05-28 Pieter Spaas

In this work it is shown that certain interesting types of quasi-orthogonal system of subalgebras (whose existence cannot be ruled out by the trivial necessary conditions) cannot exist. In particular, it is proved that there is no…

Mathematical Physics · Physics 2010-02-02 Mihály Weiner

Let $\Gamma$ be a countable group and $(X, \Gamma)$ a compact topological dynamical system. We study the question of the existence of an intermediate $C^*$-subalgebra $\mathcal{A}$ $$C^{*}_{r}(\Gamma)<\mathcal{A}<C(X)\rtimes_r\Gamma,$$…

Operator Algebras · Mathematics 2024-04-16 Tattwamasi Amrutam , Eli Glasner , Yair Glasner

We extend the usual theory of universal C*-algebras from generators and relations in order to allow some relations to be described using the strong operator topology. In particular, we can allow some infinite sum relations. We prove a…

Operator Algebras · Mathematics 2020-08-13 Giuliano Boava , Gilles G. de Castro

We give sufficient conditions, in terms of the existence of unbounded derivations satisfying certain properties, which ensure that a II$_1$ factor $M$ is prime or has at most one Cartan subalgebra. For instance, we prove that if there…

Operator Algebras · Mathematics 2013-01-01 Yoann Dabrowski , Adrian Ioana