Endomorphisms of Deligne-Lusztig varieties

This paper is a following to math.RT/0410454. For a finite group of Lie type we study the endomorphisms, commuting with the group action, of a Deligne-Lusztig variety associated to a regular element of the Weyl group. We state some general conjectures, in particular that the endomorphism algebra induced on the cohomology is a cyclotomic Hecke algebra, and prove them in some cases. On the way we also prove results on centralizers in braid groups

Quasi-semisimple elements

We study quasi-semisimple elements of disconnected reductive algebraic groups over an algebraically closed field. We describe their centralizers, define isolated and quasi-isolated quasi-semisimple elements and classify their conjugacy classes.Comment: This version: some corrections; index adde

Garside and locally Garside categories

We define and give axioms for Garside and locally Garside categories. We give an application to Coxeter and Artin groups and Deligne-Lusztig varieties.Comment: We have fixed some errors pointed to us by E. Godelle and P. Dehornoy and added new results in section

Electricity Internal Market in the European Union: What to do next?

Like in the US, the EU “internal electricity market” remains unfinished and its construction can stall, fracturing into “national blocks” separated by permanent “border effects”. This is exactly what this paper seeks to avoid in the expected life of the current European Commission (2005-2009). It identifies the critical factors: national and EU market designs, industry structure and competition policy, deeper regional cooperation between TSOs and Regulators. It suggests 8 priority actions and 12 secondary improvements to sustain the dynamics of the construction of an EU set of open r egional markets with limited “border effects”, and explains the rationale for these recommendations

H. B. Reitlinger and the origins of the Efficiency at Maximum Power formula for Heat Engines

Even if not so ancient, the history of the heat engine efficiency at maximum power expression have been yet turbulent. More than a decade after the publication of the seminal article by Curzon and Ahlborn in 1975, one's rediscovered two older works by Chambadal and Novikov, both dating from 1957. Then, some years ago, the name of Yvon arose from a textual reference to this famous relation in a conference article published in 1955. Thanks to an historical study of French written books not anymore published for a long time, and since never translated in other languages, we bring to light in this paper that this relation was actually firstly proposed by Henri B. Reitlinger in 1929.Comment: 6 pages, 3 figure

Time Segmentation Approach Allowing QoS and Energy Saving for Wireless Sensor Networks

Wireless sensor networks are conceived to monitor a certain application or physical phenomena and are supposed to function for several years without any human intervention for maintenance. Thus, the main issue in sensor networks is often to extend the lifetime of the network by reducing energy consumption. On the other hand, some applications have high priority traffic that needs to be transferred within a bounded end-to-end delay while maintaining an energy efficient behavior. We propose MaCARI, a time segmentation protocol that saves energy, improves the overall performance of the network and enables quality of service in terms of guaranteed access to the medium and end-to-end delays. This time segmentation is achieved by synchronizing the activity of nodes using a tree-based beacon propagation and allocating activity periods for each cluster of nodes. The tree-based topology is inspired from the cluster-tree proposed by the ZigBee standard. The efficiency of our protocol is proven analytically, by simulation and through real testbed measurements