  Transport experiments in twisted bilayer graphene (TBG) show a fan-like
region near integer fillings with a resistivity linear in temperature down to
the lowest temperature measured. This suggests quantum-critical points at the
boundaries to long-range ordered phases. The particular order proposed by
Blutinck et al. for twisted bi-layer graphene (TBG) is a loop-current order at
the carbon length-scale together with modulations on the moir\'e length scale.
This is shown to be the ground state of a xy model with translational symmetry
and time-reversal broken. Here, this is extended to derive a model for
quantum-critical properties. We derive the quantum xy model coupled to fermions
in this situation. The kinetic energy operator for the model and the coupling
of fermions to the fluctuations of the xy model are derived. The previously
derived universal properties in the quantum-critical region of such a model,
leading to a marginal Fermi-liquid, irrespective of the underlying microscopics
is briefly reviewed. The properties include the resistivity and various other
transport properties with and without applying a magnetic field and the
instability of the quantum fluctuating state to superconductivity in d-wave
symmetry.
