“…Given our limited knowledge as how to quantize string theory in flux backgrounds [39,40,41,42], one can use the non geometric world-sheet construction as an equivalent 'dual' definition of the latter. Indeed duality between geometric fluxes (H ijk 3-form and T ij k torsion) and non geometric ones (Q i jk and R ijk ) has been proposed and supported by some evidence [43,44,45,46,47,48,49,50,51,52,55,54,55,56,57].…”