In the study of the holomorphic automorphism groups, many researches have been carried out inside the category of bounded or hyperbolic domains. On the contrary to these cases, for unbounded non-hyperbolic cases, only a few results are known about the structure of the holomorphic automorphism groups. Main result of the present paper gives a class of unbounded non-hyperbolic Reinhardt domains with non-compact automorphism groups, Cartan's linearity theorem and explicit Bergman kernels. Moreover, a reformulation of Cartan's linearity theorem for finite volume Reinhardt domains is also given.
Introduction.In several complex variables, complex domains with properties boundedness or hyperbolicity are fundamental research objects. On the other hand, one may not expect some useful function-theoretic properties for complex domains without the two properties. Our primary motivation is to investigate some useful properties for unbounded non-hyperbolic domains.1.1. Background. One of the most important problem in several complex variables is to classify all complex domains in C n . If n = 1, then the Riemann mapping theorem tells us that every simply connected proper subdomain of C is biholomorphically equivalent to the unit disk. By showing the inequivalence of the unit ball and the polydisk in C 2 , Poincaré found that the Riemann mapping theorem does not hold even simply connected domains in C 2 . Thus the purely topological condition "simply connectedness" is not enough for the holomorphic equivalence problem in C n . Because of this background, in several complex variables, it is important to investigate biholomorphic invariant objects of complex domains.The purpose of this paper is to study two objects (the holomorphic automorphism group and the Bergman kernel) for a certain class of non-hyperbolic unbounded Reinhardt domains. The holomorphic automorphism group is a biholomorphic invariant object. Moreover, from the Bergman kernel, one can construct an invariant metric which is so-called the Bergman metric. In the theory of the automorphism groups, one important problem is to understand how the information of the holomorphic automorphism group characterizes complex domains. The next theorem is a notable result concerning this problem (cf.