Accounting for risk of non linear portfolios - A novel Fourier approach G. Bormetti, V. Cazzola, D. Delpini and G. Livan Eur. Phys. J. B, 76 1 (2010) 157-165 Published online: 29 June 2010 DOI: 10.1140/epjb/e2010-00199-9