Relation algebras from cylindric algebras, I
Robin Hirsch and Ian Hodkinson
We characterise the class SRa CAn of subalgebras of relation algebra reducts of n-dimensional cylindric algebras (for finite n, at least 4) by the notion of a hyperbasis,analogous to the cylindric basis of Maddux, and by relativised representations. A corollary is that S Ra CAn = S Ra(CAn \cap Crsn)=S Ra(CAn \cap Gn). We give a game-theoretic approximation to the existence of a representation, and use it to obtain a recursive equational axiomatisation of S Ra CAn. We include notes on n-variable proof theory, homogeneity, and related matters, and some open problems.