The radius of a subcategory of modules

We introduce a new invariant for subcategories [math] of finitely generated modules over a local ring [math] which we call the radius of [math] . We show that if [math] is a complete intersection and [math] is resolving, then finiteness of the radius forces [math] to contain only maximal Cohen–Macaulay modules. We also show that the category of maximal Cohen–Macaulay modules has finite radius when [math] is a Cohen–Macaulay complete local ring with perfect coefficient field. We link the radius to many well-studied notions such as the dimension of the stable category of maximal Cohen–Macaulay modules, finite/countable Cohen–Macaulay representation type and the uniform Auslander condition.