3 papers
math.LO2015
Borel Complexity and Potential Canonical Scott Sentences
Douglas Ulrich, Richard Rast, Michael C. Laskowski
We define and investigate HC-forcing invariant formulas of set theory, whose interpretations in the hereditarily countable sets are well behaved under forcing extensions. This lead…
math.LO2015
The Borel Complexity of Isomorphism for Complete Theories of Linear Orders With Unary Predicates
Richard Rast
We show that if A is a linear order then Th(A) is either -categorical or Borel complete (in the sense of Friedman and Stanley). We generalize this; if A has countably man…
math.LO2014
The Borel Complexity of Isomorphism for O-Minimal Theories
Richard Rast, Davender Singh Sahota
Given a countable o-minimal theory T, we characterize the Borel complexity of isomorphism for countable models of T up to two model-theoretic invariants. If T admits a nonsimple ty…