“…Over the past two decades, a considerable number of studies have been performed on the phase structure of the surface model of Helfrich [1], Polyakov [2], and Kleinert [3] for biological membranes [4,5,6,7,8,9,10,11,12,13,14]. The surface models can be classified into two groups, which are characterized by the curvature energy in the Hamiltonian; one is an extrinsic curvature model [15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32], and the other is an intrinsic curvature model [33,34,35,36].…”