Affiliation: | a Laboratoire de Physique Théorique et Modélisation, Université de Cergy-Pontoise, CNRS, UMR 8089, 2, Avenue Adolphe Chauvin, 95302 Cergy-Pontoise Cedex, France b Institute of Physics, P.O. Box 429, Bo Ho, Hanoi 10000, Viet Nam c Asia Pacific Center for Theoretical Physics, Hogil Kim Memorial Building 5th floor, POSTECH, Hyoja-dong, Namgu, Pohang 790-784, Republic of Korea |