From internet architecture research to standards

Many Internet architectural research initiatives have been undertaken over last twenty years. None of them actually reached their intended goal: the evolution of the Internet architecture is still driven by its protocols not by genuine architectural evolutions. As this approach becomes the main limiting factor of Internet growth and application deployment, this paper proposes an alternative research path starting from the root causes (the progressive depletion of the design principles of the Internet) and motivates the need for a common architectural foundation. For this purpose, it proposes a practical methodology to incubate architectural research results as part of the standardization process

Satellite Galaxies and Fossil Groups in the Millennium Simulation

We use a semianalytic galaxy catalogue constructed from the Millennium Simulation to study the satellites of isolated galaxies in the LCDM cosmogony. This sample (~80,000$ bright primaries, surrounded by ~178,000 satellites) allows the characterization, with minimal statistical uncertainty, of the dynamical properties of satellite/primary galaxy systems in a LCDM universe. We find that, overall, the satellite population traces the dark matter rather well: its spatial distribution and kinematics may be approximated by an NFW profile with a mildly anisotropic velocity distribution. Their spatial distribution is also mildly anisotropic, with a well-defined ``anti-Holmberg'' effect that reflects the misalignment between the major axis and angular momentum of the host halo. The isolation criteria for our primaries picks not only galaxies in sparse environments, but also a number of primaries at the centre of ''fossil'' groups. We find that the abundance and luminosity function of these unusual systems are in reasonable agreement with the few available observational constraints. We recover the expected L_{host} \sigma_{sat}^3 relation for LCDM models for truly-isolated primaries. Less strict primary selection, however, leads to substantial modification of the scaling relation. Our analysis also highlights a number of difficulties afflicting studies that rely on blind stacking of satellite systems to constrain the mean halo mass of the primary galaxies.Comment: 18 pages, 14 figures, MNRAS in press. Accepted version with minor changes. Version with high resolution figures available at: http://www.astro.uvic.ca/~lsales/SatPapers/SatPapers.htm

Anomalous Hall Effect in three ferromagnets: EuFe4Sb12, Yb14MnSb11, and Eu8Ga16Ge30

The Hall resistivity (Rho_xy), resistivity (Rho_xx), and magnetization of three metallic ferromagnets are investigated as a function of magnetic field and temperature. The three ferromagnets, EuFe4Sb12 (Tc = 84 K), Yb14MnSb11 (Tc = 53 K), and Eu8Ga16Ge30 (Tc = 36 K) are Zintl compounds with carrier concentrations between 1 x 10^21 cm^-3 and 3.5 x 10^21 cm^-3. The relative decrease in Rho_xx below Tc [Rho_xx(Tc)/Rho_xx(2 K)] is 28, 6.5, and 1.3 for EuFe4Sb12, Yb14MnSb11, and Eu8Ga16Ge30 respectively. The low carrier concentrations coupled with low magnetic anisotropies allow a relatively clean separation between the anomalous (Rho_'xy), and normal contributions to the measured Hall resistivity. For each compound the anomalous contribution in the zero field limit is fit to alpha Rho_xx + sigma_xy rho_xx^2 for temperatures T < Tc. The anomalous Hall conductivity, sigma_xy, is -220 +- 5 (Ohm^-1 cm^-1), -14.7 +- 1 (Ohm^-1 cm^-1), and 28 +- 3 (Ohm^-1 cm^-1) for EuFe4Sb12, Yb14MnSb11, and Eu8Ga16Ge30 respectively and is independent of temperature for T < Tc if the change in spontaneous magnetization (order parameter) with temperature is taken into account. These data are consistent with recent theories of the anomalous Hall effect that suggest that even for stochiometric ferromagnetic crystals, such as those studied in this article, the intrinsic Hall conductivity is finite at T = 0, and is a ground state property that can be calculated from the electronic structure.Comment: 22 pages, 13 figures Submitted to PR