## Ergodic Subequivalence Relations Induced by a Bernoulli Action

- Ionut Chifan, A. Ioana
- Mathematics
- 16 February 2008

Let Γ be a countable group and denote by $${\mathcal{S}}$$ the equivalence relation induced by the Bernoulli action $${\Gamma\curvearrowright [0, 1]^{\Gamma}}$$, where [0, 1]Γ is endowed with the… Expand

## Bass-Serre rigidity results in von Neumann algebras

- Ionut Chifan, Cyril Houdayer
- Mathematics
- 11 May 2008

We obtain new Bass-Serre type rigidity results for ${\rm II_1}$ equivalence relations and their von Neumann algebras, coming from free ergodic actions of free products of groups on the standard… Expand

## II_1 factors with non-isomorphic ultrapowers

- R. Boutonnet, Ionut Chifan, A. Ioana
- Mathematics
- 22 July 2015

We prove that there exist uncountably many separable II1 factors whose ultrapowers (with respect to arbitrary ultrafilters) are non-isomorphic. In fact, we prove that the families of non-isomorphic… Expand

## On the normalizing algebra of a MASA in a II$_1$ Factor

- Ionut Chifan
- Mathematics
- 9 June 2006

Let $A$ be a maximal abelian subalgebra (MASA) in a \II1 factor $M$. Sorin Popa introduced an analytic condition that can be used to identify the normalizing algebra of $A$ in $M$ and which we call… Expand

## On the structural theory of $\rm II_1$ factors of negatively curved groups

- Ionut Chifan, Thomas Sinclair
- Mathematics
- 22 March 2011

Ozawa showed that for any i.c.c., hyperbolic group, the associated group factor is solid. Developing a new approach that combines some methods of Peterson, Ozawa and Popa, and Ozawa, we strengthen… Expand

## $$W^*$$W∗-Superrigidity for arbitrary actions of central quotients of braid groups

- Ionut Chifan, A. Ioana, Y. Kida
- Mathematics
- 19 July 2013

For any $$n\geqslant 4$$n⩾4 let $$\tilde{B}_n=B_n/Z(B_n)$$B~n=Bn/Z(Bn) be the quotient of the braid group $$B_n$$Bn through its center. We prove that any free ergodic probability measure preserving… Expand

## Amalgamated Free Product Rigidity for Group von Neumann Algebras

- Ionut Chifan, A. Ioana
- Mathematics
- 20 May 2017

## W*-rigidity for the von Neumann algebras of products of hyperbolic groups

- Ionut Chifan, Rolando de Santiago, Thomas Sinclair
- Mathematics
- 19 August 2015

We show that if $${\Gamma = \Gamma_1\times\dotsb\times \Gamma_n}$$Γ=Γ1×⋯×Γn is a product of $${{\rm n} \geq 2}$$n≥2 non-elementary ICC hyperbolic groups then any discrete group $${\Lambda}$$Λ which… Expand

## Rigidity results for von Neumann algebras arising from mixing extensions of profinite actions of groups on probability spaces

- Ionut Chifan, Sayan Das
- MathematicsMathematische Annalen
- 17 March 2019

Motivated by Popa’s seminal work Popa (Invent Math 165:409-45, 2006), in this paper, we provide a fairly large class of examples of group actions Γ↷X\documentclass[12pt]{minimal} \usepackage{amsmath}… Expand

## Some unique group-measure space decomposition results

- Ionut Chifan, J. Peterson
- Mathematics
- 25 October 2010

Using an approach emerging from the theory of closable deriva- tions on von Neumann algebras, we exhibit a class of groups CR satisfying the following property: given any groups 1, 2 2 CR , then any… Expand

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