  The angle-resolved photoemission spectroscopy studies on cuprates in the
pseudogap region reveal an extraordinary topological transition in which the
ground state changes from one with a normal Fermi surface to one with four
Fermi points. Such a state is not possible without some symmetry breaking,
which allows interference between one-particle basis states that is normally
forbidden. We also show that the experimental results are quantitatively given
without any free parameters by a theory and discuss the implications of the
results.
