A combinatorial take on hierarchical hyperbolicity and applications to quotients of mapping class groups

We give a simple combinatorial criterion, in terms of an action on a hyperbolic simplicial complex, for a group to be hierarchically hyperbolic. We apply this to show that quotients of mapping class groups by large powers of Dehn twists are hierarchically hyperbolic (and even relatively hyperbolic in the genus 2 case). Under residual finiteness assumptions, we construct many non-elementary hyperbolic quotients of mapping class groups. Using these quotients, we reduce questions of Reid and Bridson-Reid-Wilton about finite quotients of mapping class groups to residual finiteness of specific hyperbolic groups.Comment: Revised according to comments from reader

Uncertainty quantification for personalized analyses of human proximal femurs

Computational models for the personalized analysis of human femurs contain uncertainties in bone material properties and loads, which affect the simulation results. To quantify the influence we developed a probabilistic framework based on polynomial chaos (PC) that propagates stochastic input variables through any computational model. We considered a stochastic E-ρ relationship and a stochastic hip contact force, representing realistic variability of experimental data. Their influence on the prediction of principal strains (ϵ1 and ϵ3) was quantified for one human proximal femur, including sensitivity and reliability analysis. Large variabilities in the principal strain predictions were found in the cortical shell of the femoral neck, with coefficients of variation of Math Eq. Between 60-80% of the variance in ϵ1 and ϵ3 are attributable to the uncertainty in the E-ρ relationship, while Math Eq are caused by the load magnitude and 5-30% by the load direction. Principal strain directions were unaffected by material and loading uncertainties. The antero-superior and medial inferior sides of the neck exhibited the largest probabilities for tensile and compression failure, however all were very small (Math Eq). In summary, uncertainty quantification with PC has been demonstrated to efficiently and accurately describe the influence of very different stochastic inputs, which increases the credibility and explanatory power of personalized analyses of human proximal femurs

swMATH - a new information service for mathematical software

An information service for mathematical software is presented. Publications and software are two closely connected facets of mathematical knowledge. This relation can be used to identify mathematical software and find relevant information about it. The approach and the state of the art of the information service are described here.Comment: see also: http://www.swmath.or

Synergetic use of polarimetric Doppler radars at Ka- and C- band for retrieval of water drop and ice particle size distributions

The transition from bulk to spectral bin microphysics schemes within numerical weather prediction (NWP) models promises more realistic simulations of cloud resolving processes and finally an improving of weather forecasting quality. However the needed size distributions of water drops and ice particles were parameterized from rare observations, typically from ground based rain distrometers or aircraft in-situ measurements. The current work introduces a retrieval method to derive size distributions from synergetic use of vertical pointed Ka-band and polarimetric C-band radar. The method is based on using the full height-resolved Doppler spectra instead of mean values of reflectivity and radial velocity inside the radar bin volume. Within a Mie and T-matrix based radar forward operator, Doppler spectra were simulated from assumed size distributions, taking into account the attenuation at Ka-band. In an iterative way, the parameters of distributions were varied until differences between simulated and observed radar profiles could minimized. Additional data e.g. from radiosounding and SODAR wind profilers were used to estimate and minimize the most relevant error sources expected from vertical air motion and turbulence. First results were achieved from a case study of 8th July 2007 during the Convection and Orographically Induced Precipitation Study (COPS)

Budget Processes: Theory and Experimental Evidence

This paper studies budget processes, both theoretically and experimentally. We compare the outcomes of bottom-up and top-down budget processes. It is often presumed that a top-down budget process leads to a smaller overall budget than a bottom-up budget process. Ferejohn and Krehbiel (1987) showed theoretically that this need not be the case. We test experimentally the theoretical predictions of their work. The evidence from these experiments lends strong support to their theory, both at the aggregate and the individual subject level.Budget processes; voting equilibrium; experimental economics

Budget processes: Theory and experimental evidence

This paper studies budget processes, both theoretically and experimentally. We compare the outcomes of bottom-up and top-down budget processes. It is often presumed that a top-down budget process leads to a smaller overall budget than a bottom-up budget process. We show, using structurally induced equilibrium theory, that this may but need not be the case. To test the implications for budget processes of structurally induced equilibrium theory, we conduct a series of experiments. The evidence from these experiments supports the predictions of structurally induced equilibrium theory, both at the aggregate and at the individual subject level. --

Budget Processes: Theory and Experimental Evidence

This paper studies budget processes, both theoretically and experimentally. We give a sufficient condition for top-down and bottom-up budget processes to have the same voting equilibrium. Furthermore, at a voting equilibrium, it is not always true, as often presumed, that a top-down budget process leads to a smaller overall budget than does a bottom-up budget process. To test the implications for budget processes of voting equilibrium theory, we conduct a series of 128 voting experiments using subjects in a behavior laboratory. The experimental evidence from these experiments is well organized by voting equilibrium theory, both at the aggregate level and at the individual subject level. In particular, subjects display considerable evidence of rationality in their proposals and votes. More complete information and fewer spending categories lead to greater predictive success of voting equilibrium theory, and reduce the time needed to reach a budget decision. Ce texte étudie des processus de construction budgétaire, tant d'un point de vue théorique que d'un point de vue de leur application expérimentale. Nous spécifions une condition suffisante afin que l'équilibre électoral soit le même pour les processus de construction budgétaire qu'ils soient de type top-down (par le haut) ou de type bottom-up (par le bas). D'autre part, et bien que cela soit souvent supposé, il n'est pas toujours vrai qu'à l'équilibre électoral un processus de construction budgétaire top-down conduise à un plus faible budget global que ne le ferait un processus budgétaire de type bottom-up. Pour tester les conséquences de la théorie de l'équilibre électoral sur les processus de construction budgétaire, une série de 128 expériences a été conduite en laboratoire. Les résultats de ces expériences sont largement conformes à la théorie de l'équilibre électoral, aussi bien au niveau des donnés agrégés qu'au niveau des résultats individuels. Plus particulièrement, l'étude des résultats révèle que les joueurs font preuve d'une véritable rationalité de décision tant pour formuler leur proposition que pour établir leur stratégie de vote. Enfin, une information plus complète et moins de catégories de dépenses conduisent à un plus grand succès de prévision de la théorie de l'équilibre électoral et réduisent le temps nécessaire pour atteindre une ratification budgétaire.Budget processes, voting equilibrium, experimental economics, Processus de construction budgétaire, équilibre électoral, économie expérimentale