We argue that in strongly correlated electron system collective instanton
excitations of the phase field (dual to the charge) arise with a great degree
of stability, governed by gauge flux changes by an integer multiple of 2π.
By unraveling consequences of the non-trivial topology of the charge gauge U(1)
group, we found that the pinning of μ and the zero-temperature divergence
of charge compressibility κ∼∂ne/∂μ defines novel
"hidden" quantum criticality on verge of the Mott transition governed by the
protectorate of stable topological numbers rather than Landau paradigm of the
symmetry breaking.Comment: 2 pages, SCES '05, Vienn