Property (T) was introduced by Kazhdan in 1967 in terms of unitary representations. Its most striking application is that this property is inherited by lattices, and implies compact generation and compact abelianization. Property (T) has very early on been linked to fixed point properties of group actions and the work of Guichardet and Delorme showed that a locally compact second countable group has property (T) if and only if any isometric action on a Hilbert space has a fixed point. It follows that a group with property (T) also has Serre's property FA that any action on a tree has a fixed point. It has been an active field of research to find objects on which an effective action gives an obstruction to property (T) (see for instance the work of Niblo-Reeves, Haglund-Paulin, Cherix-Martin-Valette or Chatterji-Drutu-Haglund) and of course, given Delorme and Guichardet's result on fixed point property for actions on a Hilbert space, Lp-spaces are natural objects to look at. (The class of all Banach space is too large as any group acts by isometries and without a fix point on some Banach space.) Fixed point properties for a group action on a class of objects is a measure of complication for the group as it prevents the use of the geometry of that class of objects to fit in the geometry of the group. For instance, the Baum-Connes conjecture for groups with property (T) was open until a few years ago when V. Lafforgue gave the first examples of property (T) groups satisfying that conjecture. Recently, several stronger versions of property (T) have been given, notably by V. Lafforgue to explain the limitations of his techniques to prove the Baum-Connes conjecture, but also by Gomez or by Fisher and Hitchman who twist definitions of property (T) to obtain stronger versions. This project has several parts, all of them of independent interest but part of a whole. 1. Introducing and studying, for a property (T) group G, a constant tau(G) indicating the class of Lp-spaces the group G cannot act on isometrically without a fix point; 2. Understand the relationship between the lack of action on any Lp-space with other existing stronger or weaker notions of property (T); 3. For a group G with property (T) and such that tau(G) is finite, to which extent do we recover some non-property (T) behaviour (like a proof to the Baum-Connes conjecture, or an action on a geometric object resembling a median space).

Energy transfer from a plasma to a substrate is a real issue in plasma processing. The understanding of the mechanisms responsible for the heat transfer is relevant and can help optimizing processes. - At GREMI, young researchers (Anne-Lise THOMANN and Rémi DUSSART) working on low pressure plasma processes (sputtering deposition, cryogenic etching of silicon ...) had an interest on the energy transfer from the plasma to the substrate during processes: A.L. Thomann used to study the growth regime of metal thin films synthesized by plasma sputtering. It has been shown that the film formation depends on the flux and energy of plasma ions incoming onto the surface during the growth, and on the kinetic energy of the condensing metal atoms. However quantification of the observed effects was missing. R. Dussart and its colleagues have evidenced the building of a passivation layer on etched silicon surface. This layer is destroyed during the etching process by thermal effects. - At the time that such questions arise, a researcher (Nadjib SEMMAR), specialist of thermal mechanisms joined the GREMI lab. After many discussions and brainstorming, we decided to initiate a new team in the lab to study and to measure the energy flux involved in the plasma/surface interaction. - - New ideas of diagnostics and measurements are born partly because the team is composed of researchers coming from different disciplines. - - Anne-Lise THOMANN (CNRS) is a specialist of materials science: she works on the elaboration and characterization of thin films deposited by low pressure plasmas. - - Remi DUSSART (Associate professor at the University of Orleans) used to work on capillary discharges for high energy photon production. He now works on cryogenic etching in low pressure plasmas. - - Nadjib SEMMAR (Associate professor at the University of Orleans) is a physicist specialized on thermal transfers. He used to work at the Lermab Laboratory at Nancy during eight years on the energetic of systems. He now works on the modelization of the laser-materials interaction and on the experimental characterization of the energy transfer. - To help us mounting and testing the experiments, Jacky MATHIAS, engineer (CNRS) joined the team. He is engineer specialized in Optical devices and works on the development of new diagnostics and reactors. - An engineer assistant, Yves Tessier, specialist in Electronics will also work on this project especially to install the data acquisition of the new diagnostic recently developed. - - The experience and the different origin of each of us is a real benefit for this project. Because we have complementary capabilities in plasma and materials science and energetics we were able to propose a new approach of plasma/surface interaction study involving the direct measurement of the energy transfers. Two ATIP proposals (CNRS) have already been proposed in the 3 last years. Although the subject was qualified as a very interesting and relevant, it was not selected. But we think that the project did not have the maturity of today. The team is now clearly identified in the lab and a plasma reactor is dedicated to this experiment. Its autonomy is now total, but the team needs the recognition of the ANR to really expand its activities. A post doc will be appreciated on this new subject to participate to the experiments. - - The role of each member of the team is clearly identified: - Jacky MATHIAS and Yves TESSIER will take part to the experiment installation and to the diagnostic construction. - Nadjib SEMMAR will take part to the design of the proposed new diagnostic to make some direct estimation of the energy flux. He has a good background on calibration methods using black bodies. One of them has been made in the lab and is dedicated to this project. He will also participate to the modelisation of heat flux transfer when a sample is mounted on the diagnostic. - Rémi DUSSART will be involved in the plasma characterization b

The aim of this project is the fabrication and the characterization of integrated plasma microreactors in silicon. These microdevices can be utilized in the near future either in MEMS technology (e.g. microsensors, lab on chip, micro Total Analysis Systems'), if they are associated to the microfluidic and microelectronics components, or in plasma processing at the macroscopic scale if we are able to operate hundreds of microplasmas in parallel. Two types of demontrators (prototype A and B) are proposed within this project. They will be fabricated using the equipment of the clean room of the RTB network (mainly the Minerve/IEF facility in Orsay and/or LPN facility in Marcoussis). The two prototypes both correspond to MHCD (Micro Hollow Cathode Discharges) type microplasmas. MHCDs are non thermal and non equilibrium plasmas, which has the exceptional ability to work at atmospheric pressure or beyond in DC regime. The first of the two prototypes, which we want to make, will not be emerging. Hence, it will not be possible to flow a gaz through it. For this prototype, different chips containing microreactors of different diameters and having different geometric configurations will be realized on a same wafer. In this manner, we will be able to investigate the limit of the micro devices in terms of maximal injected power, number of microreactors working in parallel and microreactor diameter. The second prototype will consist of emerging holes, so that it will possible to work in gas flow regime. The deep silicon etching part, which will form the emerging microcavities, will be made at GREMI laboratory using a recently patented plasma cryogenic etching process, developed at GREMI. The optical and electrical characterization of these prototypes will be carried out at GREMI. An experimental setup is already partially installed at GREMI will be available to test the operation and the efficiency of the microreactors. Different diagnostics (optical spectroscopy, space and time resolved imaging, electrical diagnostics, ') will be used for the characterization. The maximum injected power and the maximum number of microplasmas functioning simultaneaously without individual ballast will be tested using this experimental setup. The aging of the miocroreactors will be studied using observation instruments such as SEM or optical microscope available in the lab. Several different gas will tested (noble gas and molecular gas). One part of the project will consist to test the two prototypes to convert volatile organic compounds. This research activity is already running in the laboratory, but using only Dielectric Barrier Discharge reactors or gliding arcs. MHCDs able to workin DC offer an interesting perspective in gas processing if we are able to operate hundreds of them in parallel to treat gas in the macroscopic scale. In parallel with the experimental part of this project, a modelization work will carried out to simulate MHCDs in collaboration with the LAPLACE lab in Toulouse, which owns an efficient code to simulate this kind of microplasmas. This project will be conducted by a team composed of four persons having a permanent position (two associate professors, one research engineer and one engineer assistant) whose complementary competences will make this project succeed. Two post docs (one year each) and one PhD student will reinforce the research team. The ambition of this project is to create and develop a new thematic at the boundary between MEMS microtechnology and plasma processes.