J. Rosický1
Localizing subcategories are very important in stable homotopy theory and there is not known any example of a localizing subcategory without a localization functor, which is the same thing as not being coreflective. We will confirm the suspicion of M. Hovey, J. H. Palmieri and N. P. Strickland that the answer may depend on set theory by showing that, assuming Vopěnka's principle, every localizing subcategory of the homotopy category of spectra is coreflective. Moreover, is generated by a single object and, dually, every colocalizing subcategory of is reflective and generated by a single object. The consequence is that every localizing subcategory of is a cohomological Bousfield class.