  Understanding the pseudo-gap phase which opens in the under-doped regime of
cuprate superconductors is one of the most enduring challenges of the physics
of these compounds. A depletion in the electronic density of states is
observed, which is gapping out part of the Fermi surface, leading to the
formation of mysterious lines of massless excitations- the Fermi arcs. Here we
give a new theoretical account of the physics of the pseudo-gap phase in terms
of the emergence of local patches of particle-hole pairs generated by SU(2)
symmetry fluctuations. The proliferation of these local patches accounts
naturally for the robustness of the pseudo-gap phase to disturbances like
disorder or magnetic field and is shown to gap out part fo the Fermi surface,
leading to the formation of the Fermi arcs. Most noticeably, we show that these
patches induce a modulated charge distribution on the Oxygen atoms, in
remarkable agreement with recent X-ray and STM observations.
