Schematic models for dynamic yielding of sheared colloidal glasses

The nonlinear rheological properties of dense suspensions are discussed within simplified models, suggested by a recent first principles approach to the model of Brownian particles in a constant-velocity-gradient solvent flow. Shear thinning of colloidal fluids and dynamical yielding of colloidal glasses arise from a competition between a slowing down of structural relaxation, because of particle interactions, and enhanced decorrelation of fluctuations, caused by the shear advection of density fluctuations. A mode coupling approach is developed to explore the shear-induced suppression of particle caging and the resulting speed-up of the structural relaxation.Comment: 33 pages, 10 figures; accepted for publication in Faraday Disc. 123 (2002); small numerical correction

Structural issues in the Kenyan financial system: improving competition and access

Although by regional standards, Kenya's financial system is relatively well developed and diversified, major structural impediments prevent it from reaching its full potential. Crosscountry comparisons, however, show the importance of a well-developed financial sector for long-term economic growth and poverty alleviation. Experience from other developing economies has shown the detrimental effect of government ownership and the positive impact that foreign bank ownership can have on the development of a market-based financial system. Analyzing and decomposing the high interest rate spreads and margins in Kenya helps identify structural impediments that drive the high cost of and low access to financial services. The limited information sharing on debtors, deficiencies in the legal and judicial system, the limited number of strong and reputable banks and non-transparency and uncertainty in the banking market are major impediments to the development of Kenya's financial system, to reducing spreads and to widening access.Financial Intermediation,Payment Systems&Infrastructure,Financial Crisis Management&Restructuring,Banks&Banking Reform,Economic Theory&Research,Financial Intermediation,Financial Crisis Management&Restructuring,Environmental Economics&Policies,Banks&Banking Reform,Economic Theory&Research

W{\cal W} algebras are L∞_\infty algebras

It is shown that the closure of the infinitesimal symmetry transformations underlying classical ${\cal W}$ algebras give rise to L$_\infty$ algebras with in general field dependent gauge parameters. Therefore, the class of well understood ${\cal W}$ algebras provides highly non-trivial examples of such strong homotopy Lie-algebras. We develop the general formalism for this correspondence and apply it explicitly to the classical ${\cal W}_3$ algebra.Comment: 15 pages; v2: typos corrected, minor change