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We construct finitely generated simple torsion-free groups with strong homological control. Our main result is that every subset of $\mathbb{N} \cup \{\infty\}$, with some obvious exceptions, can be realized as the set of dimensions of…

Group Theory · Mathematics 2025-04-14 Francesco Fournier-Facio , Bin Sun

We give an expression for the Garsia entropy of Bernoulli convolutions in terms of products of matrices. This gives an explicit rate of convergence of the Garsia entropy and shows that one can calculate the Hausdorff dimension of the…

Classical Analysis and ODEs · Mathematics 2018-01-23 Shigeki Akiyama , De-Jun Feng , Tom Kempton , Tomas Persson

We give a description of the Linnell division ring of a countable residually (poly-$\mathbb Z$ virtually nilpotent) (RPVN) group in terms of a generalised Novikov ring, and show that vanishing top-degree cohomology of a finite type group…

Group Theory · Mathematics 2024-10-11 Sam P Fisher , Kevin Klinge

Voiculescu's random matrix model for freeness is extended to the non-Gaussian case and also the case of constant block diagonal matrices. Thus we are able to investigate free products of free group factors with matrix algebras and with the…

funct-an · Mathematics 2016-08-31 Ken Dykema

We continue previous work on Voiculescu's topological free entropy dimension {\delta}_{top}. We introduce the notions of MF-trace, MF-ideal, and MF-nuclearity and use these concepts to obtain upper and lower bounds for {\delta}_{top}, and…

Operator Algebras · Mathematics 2011-09-06 Don Hadwin , Qihui Li , Weihua Li , Junhao Shen

We construct a continuum sized family $\{G_x\}_{x\in\{0,1\}^{\mathbb N}}$ of pairwise non-measure equivalent countable groups which have property (T) (hence are finitely generated), have zero $\ell^2$-Betti numbers of all orders, and are…

Group Theory · Mathematics 2025-12-05 Adrian Ioana , Robin Tucker-Drob

Suppose that a finitely generated group $G$ is hyperbolic relative to a collection of subgroups $\{H_1, ..., H_m\} $. We prove that if each of the subgroups $H_1, ..., H_m$ has finite asymptotic dimension, then asymptotic dimension of $G$…

Group Theory · Mathematics 2007-05-23 D. V. Osin

We show that in a tracial and finitely generated $W^\ast$-probability space existence of conjugate variables excludes algebraic relations for the generators. Moreover, under the assumption of maximal non-microstates free entropy dimension,…

Operator Algebras · Mathematics 2015-09-03 Tobias Mai , Roland Speicher , Moritz Weber

A group G has homological dimension less or equal to 1 if it is locally free. We prove the converse provided that G satisfies the Atiyah Conjecture about L^2-Betti numbers. We also show that a finitely generated elementary amenable group G…

Group Theory · Mathematics 2007-05-23 Peter Kropholler , Peter Linnell , Wolfgang Lueck

We show that a finitely generated abelian group $G$ of torsion-free rank $n\geq 1$ admits a $n+r$ dimensional model for the classifying space with isotropy in the family of subgroups of torsion-free rank less than or equal to $r\geq 0$.

Group Theory · Mathematics 2016-04-21 Ged Corob Cook , Victor Moreno , Brita Nucinkis , Federico Pasini

We compute the ${\mathbb F}_p$-dimension of an $n$-th graded piece $G_{(n)}/G_{(n+1)}$ of the Zassenhaus filtration for various finitely generated pro-$p$-groups $G$. These groups include finitely generated free pro-$p$-groups, Demushkin…

Group Theory · Mathematics 2015-07-08 Jan Minac , Michael Rogelstad , Nguyen Duy Tan

Using Voiculsecu's free entropy, it is shown that the free group factors L(F_n) lack property C of Popa and that they lack finite multiplicity abelian subalgebras. Property C is an assymptotic commutivity property.

funct-an · Mathematics 2008-02-03 Ken Dykema

It is demonstrated how to use certain family of commutative hypergroups to provide a universal construction of Biane's quantum Bessel processes of all dimensions not smaller than 1. The classical Bessel processes BES$(\delta)$ are…

Probability · Mathematics 2016-11-16 Wojciech Matysiak

In the process of developing the theory of free probability and free entropy, Voiculescu introduced in 1991 a random matrix model for a free semicircular system. Since then, random matrices have played a key role in von Neumann algebra…

Operator Algebras · Mathematics 2007-06-21 Uffe Haagerup , Steen Thorbjornsen

Using an analogy with the rank theorem in differential geometry, it is shown that for a finite $n$-tuple $X$ in a tracial von Neumann algebra and any finite $m$-tuple $F$ of $*$-polynomials in $n$ noncommuting indeterminates,…

Operator Algebras · Mathematics 2016-02-16 Kenley Jung

In this paper we introduce the concept of the upper free orbit-dimension of a finite von Neumann algebra, and we derive some of its basic properties. Using this concept, we are able to improve most of the applications of free entropy to…

Operator Algebras · Mathematics 2007-05-23 Don Hadwin , Junhao Shen

S. Artstein, K. Ball, F. Barthe, and A. Naor have shown that if (X_j) are i.i.d. random variables, then the entropy of n^{-1/2}(X_1+....+X_n) increases as n increases. The free analogue was recently proven by D. Shlyakhtenko. That is, if…

Operator Algebras · Mathematics 2007-05-23 Hanne Schultz

We investigate an analogue of the L^2-Betti numbers for amenable linear subshifts. The role of the von Neumann dimension shall be played by the topological entropy.

Dynamical Systems · Mathematics 2007-05-23 Gabor Elek

A non-commutative non-selfadjoint random variable z is called R-diagonal, if its *-distribution is invariant under multiplication by free unitaries: if a unitary w is *-free from z, then the *-distribution of z is the same as that of wz.…

Operator Algebras · Mathematics 2007-05-23 A. Nica , D. Shlyakhtenko , R. Speicher

Let $\Delta=\Delta(a,b,c)$ be a hyperbolic triangle group, a Fuchsian group obtained from reflections in the sides of a triangle with angles $\pi/a,\pi/b,\pi/c$ drawn on the hyperbolic plane. We define the arithmetic dimension of $\Delta$…

Number Theory · Mathematics 2016-01-27 Steve Nugent , John Voight