**10. Acknowledgement**

This work is dedicated to Dany my wife. With her dynamism, joie de vivre, love and trust towards me, she always supported and encouraged me to go ahead in my works and my researches, making the conditions allowing us to live with a complete peace of mind.

I am grateful to Camille Rosenthal Sabroux who gave me the opportunity to collaborate with Paris Dauphine University, and all the students whose continuous contribution and relevant questioning encouraged me to clarify and improve the models.
