The quantity in parentheses on the right hand side is in fact (twice) the mean curvature of the surface (depending on normalization).
ð ə WORD_BOUNDARY k w ɔ n t ɪ t i WORD_BOUNDARY ɪ n WORD_BOUNDARY p ə ɹ ɹ ɛ n θ ə s iː z WORD_BOUNDARY ɔ n ð ə WORD_BOUNDARY ɹ aɪ t WORD_BOUNDARY h æ n d WORD_BOUNDARY s aɪ d WORD_BOUNDARY ɪ z WORD_BOUNDARY ɪ n WORD_BOUNDARY f æ k t WORD_BOUNDARY t w aɪ s WORD_BOUNDARY ð ə WORD_BOUNDARY m iː n WORD_BOUNDARY k ɜː v ə t̠ʃ ə ɹ ɹ WORD_BOUNDARY ʌ v ð ə WORD_BOUNDARY s ɜː f ɪ s WORD_BOUNDARY d ɪ p ɛ n d ɪ ŋ WORD_BOUNDARY ɔ n WORD_BOUNDARY n ɔ ɹ m ə l ɪ z eɪ ʃ ə n WORD_BOUNDARY