Counting Closed String States in a Box

The computation of the microcanonical density of states for a string gas in a finite volume needs a one by one count because of the discrete nature of the spectrum. We present a way to do it using geometrical arguments in phase space. We take advantage of this result in order to obtain the thermodynamical magnitudes of the system. We show that the results for an open universe exactly coincide with the infinite volume limit of the expression obtained for the gas in a box. For any finite volume the Hagedorn temperature is a maximum one, and the specific heat is always positive. We also present a definition of pressure compatible with R-duality seen as an exact symmetry, which allows us to make a study on the physical phase space of the system. Besides a maximum temperature the gas presents an asymptotic pressure.Comment: 16 pages, 5 Postscript figure

Non-perturbative Thermodynamics in Matrix String Theory

A study of the thermodynamics in IIA Matrix String Theory is presented. The free string limit is calculated and seen to exactly reproduce the usual result. When energies are enough to excite non-perturbative objects like D-particles and specially membranes, the situation changes because they add a large number of degrees of freedom that do not appear at low energies. There seems to be a negative specific heat (even in the Microcanonical Ensemble) that moves the asymptotic temperature to zero. Besides, the mechanism of interaction and attachment of open strings to D-particles and D-membranes is analyzed.Comment: 30 pages, 3 figures. Several points are clarified. Final version to appear in Nucl. Phys. B. Also available at http://condmat1.ciencias.uniovi.e

Thermodynamic nonextensivity in a closed string gas

Well known results in string thermodynamics show that there is always a negative specific heat phase in the microcanonical description of a gas of closed free strings whenever there are no winding modes present. We will carefully compute the number of strings in the gas to show how this negative specific heat is related to the fact that the system does not have thermodynamic extensivity. We will also discuss the consequences for a system of having a microcanonical negative specific heat versus the exact result that such a thing cannot happen in any canonical (fixed temperature) description.Comment: Title + 13 pages, more typos correcte

Editorial: Hydroinformatics for water distribution systems analysis and management

Urban water distribution systems (WDS) analysis and management is a very complex challenge for researchers and technicians. Such a labyrinth contains numerous processes, sub-processes, states of being with their associated causative factors, feedback loops and interrelationships (Colombo & Karney 2003). This special issue is an occasion to study and analyse specific processes in the broader and stronger view of the entire labyrinth. The selected papers focus on some of the most important problems of urban WDS management, trying to help orientate researchers and planners, like Theseus and the Minotaur, in the labyrinth of the various concerns and processes involved in urban WDS planning (Figure 1). Figure 1 The labyrinth of WDS (modified by Macaulay 1976). This issue contains 10 papers that have been selected among those presented at the 16th Conference on Water Distribution System Analysis, WDSA 2014 (Bari, Italy, 14-17 July 2014), as very interesting studies and applications of Hydroinformatics techniques to WDS analysis and management. The selected papers have been fully rewritten, completed and improved and have undergone a rigorous peer-review process. The key points of the issue are

Finite Temperature Matrix Theory

We present the way the Lorentz invariant canonical partition function for Matrix Theory as a light-cone formulation of M-theory can be computed. We explicitly show how when the eleventh dimension is decompactified, the N = 1 eleven dimensional SUGRA partition function appears. We also provide a high temperature expansion which captures some structure of the canonical partition function when interactions amongst D-particles are on. The connection with the semi-classical computations thermalizing the open superstrings attached to a D-particle is also clarified through a Born-Oppenheimer approximation. Some ideas about how Matrix Theory would describe the complementary degrees of freedom of the massless content of eleven dimensional SUGRA are discussed. Comments about possible connections to black hole physics are also made.Comment: 32 pages. LaTeX, 1 epsf figure. Corrections and changes made in Section 4. One reference adde

WDNetXL: Efficient Research Transfer For Management, Planning And Design Of Water Distribution Networks

The WDNetXL system (www.hydroinformatics.it) is aimed at promoting transfer of research achievements in water distribution network (WDN) analysis, planning and management to practitioners, students and researchers. In order to facilitate the technology transfer, the WDNetXL functions are integrated into the worldwide known MS-Excel data-management environment. Advanced hydraulic modeling and topological analyses of WDN are combined with efficient optimization strategies to make readily available the latest, even customized, decision support tools for planning and management of WDNs. All these features make WDNetXL of practical support for technicians as well as a privileged platform to test innovations coming from research in WDN analysis, planning and management area. This, contribution illustrates the WDNetXL research transfer paradigm and its architecture, providing also few details about the main advancements in WDN analysis, which represents the primary support for engineers’ activities and the base component for other functions