Universal graphs at the successor of a singular cardinal

Abstract

The paper is concerned with the existence of a universal graph at the successor of a strong limit singular μ of cofinality \aleph₀. Starting from the assumption of the existence of a supercompact cardinal, a model is built in which for some such μ there are μ⁺⁺ graphs on μ⁺ that taken jointly are universal for the graphs on μ⁺, while $2^μ+ \gg μ⁺⁺$. The paper also addresses the general problem of obtaining a framework for consistency results at the successor of a singular strong limit starting from the assumption that a supercompact cardinal κ exists. The result on the existence of universal graphs is obtained as a specific application of a more general method.