NVA2007: An Optimization Fest in Limoges

A conference in honour of  Professor Michel Théra

 --Joydeep Dutta

     It was a wet and windy morning in Limoges on the 20^th of June 2007. But outside the auditorium named Amphi Couty opposite to the Department of Mathematics of the University of Limoges was a large and enthusiastic crowd all excited for the commencement of the three days conference on nonsmooth and variational analysis. This conference has a special significance since it was also the celebration of the 60^th birthday of Professor Michel Théra who is not only a great researcher in the field of optimization but also a doyen of the University of Limoges who played a pivotal role in the growth of Department of Mathematics and also contributed largely to the growth of the University. He continues to shoulder that responsibility as a Vice-President of the University of Limoges who is also in-charge of International Relations.

  The participants at NVA 2007 in front of the Town Hall in Limoges on 20^th June

     The gathering had optimization researchers from a large number of countries, which includes, France, Spain, Italy, India, Iran, Burkina Faso, Argentina, USA, Romania, Japan and so forth. The crowd had a good mix of renowned and experienced researchers and as well as young researchers. This also brings forth the fascinating personality of Michel Théra who is popular both among the senior researchers and the young researchers. He has always being very kind and helpful to young researchers which endear him so much to them.

     The conference began with an opening ceremony and the guests were welcomed by Professor Samir Adly who was one of the main organizers. There were invited talks of 30 minutes each mainly by renowned and experienced researchers and the young researchers spoke on their research for 20 minutes. The conference began with Professor Bergounioux saying a few words about Michel, which focused not only on his accomplishments, but also focused on Michel, the human being. The first talk of the conference was by Jean-Paul Penot who incidentally is also the thesis supervisor of Michel Théra. He had a very interesting title for his talk. The title was: Exploring the Jungle of Nonsmooth Analysis. He tried to bring out from the jungle the most useful things. Of course he also highlighted Michel’s contribution in this area. His talk was followed by the talk of  Maitine Bergounioux who spoke on applications of optimization to tomography. Marco Lopez of Alicante, Spain who is an authority on semi-infinite programming gave the next talk. This session also had two beautiful talks by Darinka Dentcheva and Andrzej Ruszczynki related to stochastic optimization. Following a nice lunch in the cafeteria of the University, there were talks by Masao Fukushima from Japan on the relation of  quasi-variational inequality and generalized Nash equilibrium. This was followed by a talk by Professor Antonino Maugeri of Catania in Sicily who spoke on the infinite dimensional complementarity problems. The day ended with the talk of Alberto Zaffaroni from Italy who spoke on radiant and co-radiant sets.

     In the evening at 7 p.m. on the 20^th there was a welcome reception in Hotel de Ville, the town hall of Limoges. The Vice-Mayor of Limoges gave a nice welcome speech followed by snacks and drinks. The participants enjoyed the beautiful ambience of the town hall and then a gathered for a group photograph in front of the town hall.

     On 21^st of June the day continued to be cloudy and windy though it was a very important day in France.  The 21^st of June is the day when throughout France, music festivals are held and the day is known as Fête de La Musique. The day started with the talk by Gerald Beer from Los Angeles who in a very emotional moment brought out the first letter that Michel sent to him in 1984 inviting him to visit Limoges. During his talk Professor Beer also outlined the influence of Michel’s contribution in the area. His talk was followed by Jean-Pierre Crouzeix who spoke on Pseudomonotone integration and the revealed preference problem. Stephen Simons who is well known for his work on Monotone operators gave a talk titled: Hahn-Banach-Lagrange Theorem. After a short coffee break, Roberto Lucchetti from Milan spoke on the relations between linear programming and game theory while Aris Daniilidis from Barcelona spoke on tame optimization and Constantin Zalinescu from Iasi Romania spoke on linear programming duality in infinite dimensions.

     The lunch on 21^st was very delicious with great French cuisine in the same cafeteria of the University.  Following the lunch was a talk by the renowned mathematician Hedy Attouch from Montpellier on Alternating Proximal minimization algorithms with weak coupling. He also showed its applications to dynamical games and splitting methods in P.D. E. Lionel Thibault a leading name in convex analysis spoke on Prox-regular sets and then Michel Volle spoke on subdifferential calculus. The last session ended with the talks by Jean-Noel Corvellac on semilinear elliptic problem, Didier Aussel on quasiconvex minimization, Hantoute on subdifferential calculus and Joydeep Dutta on Inexact Chain rule and optimality conditions.

     The main conference dinner followed after the conference on the 21^st June evening in the fascinating environment of the fête de la musique in a fabulous restaurant beside the river Vienne which flows through Limoges. All the participants were in a cheerful mood and very nice music was being played inside and also Samir Adly volunteered to give all of us fun with beautiful Arabic music. The dinner was made of fine French cuisine and all the participants enjoyed it very much. Apart from the speakers there were renowned researchers like Juan-Enrique Martinez-Legaz and Jean-Baptiste Hiriart-Urruty who were also present in the conference. After the dinner most of the participants had a walk around Limoges enjoying the lovely atmosphere of the fête de la musique.

     It is also important to note that Michel Théra had played a very major role in bringing about the development of optimization and applied mathematics in France as a whole when he served as the President of SMAI, the French Society for Applied and Industrial Mathematics. In recognition of his contribution to SMAI, the Vice-President of SMAI, Maria Esteban along with the Treasurer Colette Picard was present during the part of the conference and also gave a small speech during the dinner on 21^st July highlighting Michel’s contribution to SMAI

    The last day of the conference did not make the weather any better but there was a series of interesting talks by Julian Revalski on Variational principles in reflexive Banach spaces and Patrick Combettes on Proximal Thresholding Algorithm, Dominikus Noll on proximal bundle method for nonsmooth and nonconvex function and Emil Ernst on recession analysis in non-convex optimization. Moreover Jean-Bernard Baillon spoke on the sum operators where he highlighted Michel’s immense contribution in this area.

    The conference ended with the talk given by Michel himself on Error Bounds for Lower-semicontinuous functions in Asplund spaces. He was very emotional at the beginning of the talk and said that it was very difficult for him to speak. He also acknowledged his co-author Van Ngai who works in quiet difficult situation in Vietnam.

    After the conference was over the participants were taken to a nearby porcelain manufacturing company called Bernardaud.  Limoges is very famous for porcelain and the participants enjoyed the detailed description given to them on how various artifacts of porcelain are manufactured.

    The major point in this conference was that there were no parallel sessions so all the participants could enjoy all the talks, which were of very good scientific level. This conference was successful due the hard work of Samir Adly and Jean Guillerme of the laboratory XLIM, the research students and the secretarial staff of the department. Overall this was a unique conference with so many leading researchers participating in a very amicable and friendly atmosphere. The memory of this conference surely will linger on the minds of all the participants. It was indeed an optimization festival.

Professor Michel Théra (center) with Professor Roberto Luchetti (right) and Professor Gerald Beer  (left) in the Town Hall in Limoges on 20^th July 2007.