“…It was realized consequently that the leading term of the fidelity, called the FS [9] or the Riemannian metric tensor [10], should play a key role in such a new approach to QPTs. After that, various issues based on the fidelity or its leading term [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] , including scaling and universality class [13,14], and its role in topological QPTs [23][24][25][26] etc, were raised and addressed. However, it seems to us that all relevant studies took it for granted that the FS, in general quantum phases, has dimension d, i.e.,χ F ∝ L d where d(L) is the dimension (length) of the system.…”