Automorphisms of the Banach space projective tensor product of C*-algebras

For unital C*-algebras A and B, we completely characterize the isometric (*-) automorphisms of their Banach space projective tensor product A circle times(gamma) B. This leads to the characterization of inner and outer isometric *-automorphisms of A circle times(gamma) B as well. As an application, we provide a partial affirmative answer to a question posed by Kaijser and Sinclair, viz., we prove that for unital C*-algebras A and B, the set of norm-one unitaries of A circle times(gamma) B coincides with U(A). U(B), where U(A) is the unitary group of A. We also establish the fact that the relative commutant of A circle times(gamma) C1 in A circle times(gamma) B is the same as Z(A) circle times(gamma) B, where B is a subhomogenous unital C*-algebra, and A is any C*-algebra.