Considering a quasi-spherical shell subject to thermal undulations according to Langevin dynamics, one can express the time-averaged mean square amplitudes of the fluctuation modes as
where where  and  index the fluctuation mode corresponding to spherical harmonics <math>Y^m_n(\theta,\phi)
 is the reduced membrane tension,  is the spontaneous curvature and  is the bending modulus, as defined by the Helfrich hamiltonian.