Generalized Stochastic Gradient Learning

We study the properties of generalized stochastic gradient (GSG) learning in forwardlooking models. We examine how the conditions for stability of standard stochastic gradient (SG) learning both di1er from and are related to E-stability, which governs stability under least squares learning. SG algorithms are sensitive to units of measurement and we show that there is a transformation of variables for which E-stability governs SG stability. GSG algorithms with constant gain have a deeper justification in terms of parameter drift, robustness and risk sensitivity

A First Step Towards Automatically Building Network Representations

To fully harness Grids, users or middlewares must have some knowledge on the topology of the platform interconnection network. As such knowledge is usually not available, one must uses tools which automatically build a topological network model through some measurements. In this article, we define a methodology to assess the quality of these network model building tools, and we apply this methodology to representatives of the main classes of model builders and to two new algorithms. We show that none of the main existing techniques build models that enable to accurately predict the running time of simple application kernels for actual platforms. However some of the new algorithms we propose give excellent results in a wide range of situations

Multi-Lepton Events at H1 and Search for Doubly-Charged Higgs Bosons

Events with two or more leptons (electrons or muons) with high transverse momentum are measured in electron-proton collisions at HERA using the data sample collected in the period 1994-2005. Multi-lepton events at high transverse momenta are of special interest as these signature might reveal new physics beyond the Standard Model. An example is the single production of doubly-charged Higgs bosons $H^{\pm \pm}_{L,R}$, which couple to leptons of the $i^\prime$th and $j^\prime$th generation via Yukawa couplings $h^{L,R}_{ij}$. Results from a search for doubly-charged Higgs bosons in the decays into electrons, muons and taus are presented using data taken in the period 1994-2000. No evidence for doubly-charged Higgs production is found and we derive limits on the $h_{ee}^{L,R}$ and $h_{e \mu}^{L,R}$ Yukawa couplings as a function of the $H^{\pm\pm}_{L,R}$ mass.Comment: 4 pages, 3 figures, proceedings of the XIII International Workshop on Deep Inelastic Scattering - DIS 2005, Madison, Wisconsin, 200

Robustness of adaptive expectations as an equilibrium selection device

Equilibrium Theory;Rational Expectations

Labor market search and interest rate policy

We investigate implications of search and matching frictions in the labor market for in ation targeting interest rate policy in terms of equilibrium stability. When the interest rate is set in response to past or present in ation, determinacy of equilibrium is ensured similarly to comparable previous studies with frictionless labor markets. In stark contrast to these studies, indeterminacy is very likely if the interest rate is adjusted in response solely to expected future in ation. This is due to a vacancy channel of monetary policy that stems from the labor market frictions and renders in ation expectations self-ful lling. The indeterminacy can be overcome once the interest rate is adjusted in response also to output or the unemployment rate or if the policy contains interest rate smoothing. When E-stability is adopted as an equilibrium selection criterion, a unique E-stable fundamental rational expectations equilibrium is generated under active, but not too strong, policy responses only to expected future in ation. This suggests that the problem is not critical from the perspective of learnability of the fundamental equilibrium.