Resumen de Brown representability does not come for free

Carles Casacuberta i Vergés , Amnon Neeman

• We exhibit a triangulated category $\ct$ having both products and coproducts, and a triangulated subcategory $\cs\subset \ct$ which is both localizing and colocalizing, for which neither a Bousfield localization nor a colocalization exists. It follows that neither the~category $\cs$ nor its dual satisfy Brown representability. Our example involves an abelian category whose derived category does not have small Hom-sets.