Symmetric ring spectra and topological Hochschild homology
  Symmetric spectra were introduced by Jeff Smith as a symmetric monoidal category of spectra. In this paper, a detection functor is defined which detects stable equivalences of symmetric spectra. This detection functor is useful because the classic stable homotopy groups do not detect stable equivalences in symmetric spectra.   One of the advantages of a symmetric monoidal category of spectra is that one can define topological Hochschild homology on ring spectra simply by mimicking the Hochschild complex from algebra. Using the detection functor mentioned above, this definition of topological Hochschild homology is shown to agree with Bokstedt's original definition. In particular, this shows that Bokstedt's definition is correct even for non-connective non-convergent symmetric ring spectra. 
Brooke Shipley (University of Chicago)