We argue that the spontaneous breakdown of symmetry in the chirally symmetric Nambu-JonaLasinio model which was supposed to illustrate the origin of the low mass of pions in hadron physics does not occur due to strong fluctuations in the σ -π field space. Although quarks acquire a constituent mass, σ and π turn out to have equal heavy masses of the order of the constituent quark mass.

No abstract

With the number of players of massively multiplayer online games (MMOG) going beyond the millions, there is a need for an efficient way to manage these huge digital worlds. These virtual environments are dynamic and sudden increases in player density in a part of the world have an impact on the load of the server responsible for that section of the virtual world. In this paper we propose the division of the world into several interacting microcells that can be dynamically assigned to a set of servers. We outline the architecture of such a system and describe a set of algorithms that assign the microcells to the available servers. The maximum load experienced by a server is used as a minimization criterion. The different algorithms are compared with each other and with the standard approach used in these games.

No abstract

The free energy of the Ginzburg-Landau theory satisfies a nonlinear functional differential equation which is turned into a recursion relation. The latter is solved graphically order by order in the loop expansion to find all connected vacuum diagrams, and their corresponding weights. In this way we determine the connected vacuum diagrams and their weights up to four loops.