  Selfadhesivity is a property of entropic polymatroids which guarantees that
the polymatroid can be glued to an identical copy of itself along arbitrary
restrictions such that the two pieces are independent given the common
restriction. We show that positive definite matrices satisfy this condition as
well and examine consequences for Gaussian conditional independence structures.
New axioms of Gaussian CI are obtained by applying selfadhesivity to the
previously known axioms of structural semigraphoids and orientable gaussoids.
