RELATIVELY QUASIMOBIUS MAPPINGS IN BANACH SPACES

In this paper, we explore relatively quasimobius invariance of phi-uniform domains and natural domains. Firstly, we prove that the control function of relatively quasimobius mappings can be chosen in a power form. Applying this observation and a deformed cross-ratio introduced by Bonk and Kleiner, we next show that relatively quasimobius mappings are coarsely bilipschitz in the distance ratio metric. Combined with the assumption that the mapping is coarsely bilipschitz in the quasihyperbolic metric, we establish relatively quasimobius invariance of phi-uniform domains and natural domains. As a by-product, we also obtain a similar result for uniform domains which provides a new method to answer a question posed by Vaisala.