摘要
In this paper we apply certain results in the theory of univalent functions to investigate the time evolution of the free boundary of a viscous fluid for a planar flow problem in the Hele-Shaw cell model under injection. To this end, we prove that the property of strongly 桅-likeness of order 伪 鈭?#xA0;(0, 1] is preserved in time for both inner and outer problems, under the assumption of nonzero small surface tension.