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- Greg Hjorth, Alexander S. Kechris
- Ann. Pure Appl. Logic
- 1996

- Greg Hjorth, Alexander S. Kechris
- J. Symb. Log.
- 1995

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Association for… (More)

- GREG HJORTH
- 2005

Every non-amenable countable group induces orbit inequivalent ergodic equivalence relations on standard Borel probability spaces. Not every free, ergodic, measure preserving action of F2 on a standard Borel probability space is orbit equivalent to an action of a countable group on an inverse limit of finite spaces. There is a treeable non-hyperfinite Borel… (More)

An analog of ML-randomness in the effective descriptive set theory setting is studied, where the r.e. objects are replaced by their Π 1 1 counterparts. We prove the analogs of the Kraft-Chaitin Theorem and Schnorr's Theorem. In the new setting, while K-trivial sets exist that are not hyper-arithmetical, each low for random set is. Finally we study a very… (More)

- GREG HJORTH, ANDRÉ NIES
- 2007

An analog of ML-randomness in the effective descriptive set theory setting is studied, where the r.e. objects are replaced by their Π 1 1 counterparts. We prove the analogs of the Kraft-Chaitin Theorem and Schnorr's Theorem. In the new setting, while K-trivial sets exist that are not hyperarithmetical, each low for random set is. Finally, we begin to study… (More)

- Greg Hjorth
- J. Symb. Log.
- 1995

- Greg Hjorth
- 2012

Using recent work on the algebraic structure of topological full groups of minimal subshifts, we prove that the isomorphism relation on the space of infinite finitely generated simple amenable groups is not smooth. As an application, we deduce that there does not exist an isomorphism-invariant Borel map which selects a just-infinite quotient of each… (More)

Assuming AD + DC(R), we characterize the self-dual boldface point-classes which are strictly larger (in terms of cardinality) than the pointclasses contained in them: these are exactly the clopen sets, the collections of all sets of Wadge rank ≤ ω ξ 1 , and those of Wadge rank < ω ξ 1 when ξ is limit.

- Greg Hjorth
- 2008

For any countable Borel equivalence relation E on a standard Borel space X, there is a Borel function θ from X to the 2-generated groups such that xEy ⇔ θ(x) ∼ = θ(y) .