Solving the incompressible surface Navier-Stokes equation by surface finite elements

We consider a numerical approach for the incompressible surface Navier-Stokes equation on surfaces with arbitrary genus $g(\mathcal{S})$. The approach is based on a reformulation of the equation in Cartesian coordinates of the embedding $\mathbb{R}^3$, penalization of the normal component, a Chorin projection method and discretization in space by surface finite elements for each component. The approach thus requires only standard ingredients which most finite element implementations can offer. We compare computational results with discrete exterior calculus (DEC) simulations on a torus and demonstrate the interplay of the flow field with the topology by showing realizations of the Poincar\'e-Hopf theorem on $n$-tori

Does Membership in International Organizations Increase Governments’ Credibility? Testing the Effects of Delegating Powers

This paper analyzes whether nation-state governments can increase their credibility by becoming members of international organizations. Credibility is an important asset because it determines the real interest rate and is expected to have an important impact on investment and growth. It is hypothesized that the degree of delegation to international organizations can improve the credibility of nation-state governments. This hypothesis is tested by introducing three new indicators for international delegation. On the basis of panel data for up to 136 countries and the time period from 1984 to 2004, membership in international organizations is significantly and robustly linked with better credibility, here proxied for by country risk ratings. Two more results stand out: the longer a country has had a high level of membership, the higher its credibility, ceteris paribus; and: the credibility-enhancing effect is strongest in countries whose domestic institutions are weak.Delegation of Competence, Credibility, Dilemma of the Strong State, International Organizations

Does Membership in International Organizations Increase Governments’ Credibility? Testing the Effects of Delegating Powers

This paper analyzes whether nation-state governments can increase their credibility by becoming members of international organizations. Credibility is an important asset because it determines the real interest rate and is expected to have an important impact on investment and growth. It is hypothesized that the degree of delegation to international organizations can improve the credibility of nation-state governments. This hypothesis is tested by introducing three new indicators for international delegation. On the basis of panel data for up to 136 countries and the time period from 1984 to 2004, membership in international organizations is significantly and robustly linked with better credibility, here proxied for by country risk ratings. Two more results stand out: the longer a country has had a high level of membership, the higher its credibility, ceteris paribus; and: the credibility-enhancing effect is strongest in countries whose domestic institutions are weak.delegation of competence, credibility, dilemma of the strong state, international organizations

A finite element approach for vector- and tensor-valued surface PDEs

We derive a Cartesian componentwise description of the covariant derivative of tangential tensor fields of any degree on general manifolds. This allows to reformulate any vector- and tensor-valued surface PDE in a form suitable to be solved by established tools for scalar-valued surface PDEs. We consider piecewise linear Lagrange surface finite elements on triangulated surfaces and validate the approach by a vector- and a tensor-valued surface Helmholtz problem on an ellipsoid. We experimentally show optimal (linear) order of convergence for these problems. The full functionality is demonstrated by solving a surface Landau-de Gennes problem on the Stanford bunny. All tools required to apply this approach to other vector- and tensor-valued surface PDEs are provided

Hydrodynamic interactions in polar liquid crystals on evolving surfaces

We consider the derivation and numerical solution of the flow of passive and active polar liquid crystals, whose molecular orientation is subjected to a tangential anchoring on an evolving curved surface. The underlying passive model is a simplified surface Ericksen-Leslie model, which is derived as a thin-film limit of the corresponding three-dimensional equations with appropriate boundary conditions. A finite element discretization is considered and the effect of hydrodynamics on the interplay of topology, geometric properties and defect dynamics is studied for this model on various stationary and evolving surfaces. Additionally, we consider an active model. We propose a surface formulation for an active polar viscous gel and exemplarily demonstrate the effect of the underlying curvature on the location of topological defects on a torus

A Navier Stokes Phase Field Crystal Model for Colloidal Suspensions

We develop a fully continuous model for colloidal suspensions with hydrodynamic interactions. The Navier Stokes Phase Field Crystal (NS-PFC) model combines ideas of dynamic density functional theory with particulate flow approaches and is derived in detail and related to other dynamic density functional theory approaches with hydrodynamic interactions. The derived system is numerically solved using adaptive finite elements and used to analyse colloidal crystallization in flowing environments demonstrating a strong coupling in both directions between the crystal shape and the flow field. We further validate the model against other computational approaches for particulate flow systems for various colloidal sedimentation problems

Membership has its Privileges - The Effect of Membership in International Organizations on FDI

We argue that membership in International Organizations (IOs) is an important determinant of FDI inflows. To the extent that membership restricts a country from pursuing policies that are harmful to investors, it can signal low political risk. Using data over the 1971-2005 period, we find that membership in IOs does indeed increase inflows of FDI. Controlling for the endogeneity of membership, we find this effect to be substantively important and robust to the method of estimation.membership in international organizations, FDI, investment climate, political risk, signaling, separating equilibrium