  We introduce a new invariant for subcategories X of finitely generated
modules over a local ring R which we call the radius of X. We show that if R is
a complete intersection and X is resolving, then finiteness of the radius
forces X to contain only maximal Cohen-Macaulay modules. We also show that the
category of maximal Cohen-Macaulay modules has finite radius when R 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.

Commutative Algebra;Category Theory;Representation Theory