G2 gauge theories

QCD can be formulated using any gauge group. One particular interesting choice is to replace SU(3) by the exceptional group G2. Conceptually, this group is the simplest group with a trivial center. It thus permits to study the conjectured relevance of center degrees of freedom for QCD. Practically, since all its representation are real, it is possible to perform lattice simulations for this theory also at finite baryon densities. It is thus an excellent environment to test methods and to investigate general properties of gauge theories at finite densities. We review the status of our understanding of gauge theories with the gauge group G2, including Yang-Mills theory, Yang-Mills-Higgs theory, and QCD both in the vacuum and in the phase diagram.Comment: 13 pages, 11 figures, combined proceedings of the talks of both authors given at the "XXX International Symposium on Lattice Field Theory", Cairns, Australia, June 2012. Submitted to the proceeding

The impact of demographic change on U. S. labor markets: discussion

I enjoyed reading this paper, particularly so because I was writing a paper on aging and its impacts on the German labor market at the very same time that Jane Little and Robert Triest were developing their paper. Their interesting, broad-based, and thoughtful analysis has a decidedly American point of view. My main duty as a discussant, therefore, is to compare their analysis and their projections with a European perspective.Demography ; Economic conditions ; Labor market

International Stock-Bond Correlations in a Simple Affine Asset Pricing Model

In this paper we use an affine asset pricing model to jointly value stocks and bonds. This enables us to derive endogenous correlations and to explain how economic fundamentals influence the correlation between stock and bond returns. The presented model is implemented for G7 post- war economies and its in-sample and out-of-sample performance is assessed by comparing the correlations generated by the model with conventional statistical measures. The affine framework developed in this paper is found to generate stock-bond correlations that are in line with empirically observed figuresAffine Pricing Models, Stock-Bond Correlations, G-7 Countries

A two species trap for chromium and rubidium atoms

We realize a combined trap for bosonic chromium 52Cr and rubidium 87Rb atoms. First experiments focus on exploring a suitable loading scheme for the combined trap and on studies of new trap loss mechanisms originating from simultaneous trapping of two species. By comparing the trap loss from the 87Rb magneto-optical trap (MOT) in absence and presence of magnetically trapped ground state 52Cr atoms we determine the scattering cross section of sigma_{inelRbCr}=(5.0+-4.0)*10^{-18}m^2 for light induced inelastic collisions between the two species. Studying the trap loss from the Rb magneto-optical trap induced by the Cr cooling-laser light, the photoionization cross section of the excited 5P_{3/2} state at an ionizing wavelength of 426nm is measured to be sigma_{p}=(1.1+-0.3)*10^{-21}m^2

Hybrid deterministic and stochastic approach for efficient atomistic simulations at long time scales

We propose a hybrid deterministic and stochastic approach to achieve extended time scales in atomistic simulations that combines the strengths of molecular dynamics (MD) and Monte Carlo (MC) simulations in an easy-to-implement way. The method exploits the rare event nature of the dynamics similar to most current accelerated MD approaches but goes beyond them by providing, without any further computational overhead, (a) rapid thermalization between infrequent events, thereby minimizing spurious correlations, and (b) control over accuracy of time-scale correction, while still providing similar or higher boosts in computational efficiency. We present two applications of the method: (a) Vacancy-mediated diffusion in Fe yields correct diffusivities over a wide range of temperatures and (b) source-controlled plasticity and deformation behavior in Au nanopillars at realistic strain rates (10^4/s and lower), with excellent agreement with previous theoretical predictions and in situ high-resolution transmission electron microscopy observations. The method gives several orders-of-magnitude improvements in computational efficiency relative to standard MD and good scalability with the size of the system.Comment: 4 pages, 2 figures. Corrected logarithm base in figures 2 and

Convergence of a discontinuous Galerkin multiscale method

A convergence result for a discontinuous Galerkin multiscale method for a second order elliptic problem is presented. We consider a heterogeneous and highly varying diffusion coefficient in $L^\infty(\Omega,\mathbb{R}^{d\times d}_{sym})$ with uniform spectral bounds and without any assumption on scale separation or periodicity. The multiscale method uses a corrected basis that is computed on patches/subdomains. The error, due to truncation of corrected basis, decreases exponentially with the size of the patches. Hence, to achieve an algebraic convergence rate of the multiscale solution on a uniform mesh with mesh size $H$ to a reference solution, it is sufficient to choose the patch sizes as $\mathcal{O}(H|\log(H^{-1})|)$. We also discuss a way to further localize the corrected basis to element-wise support leading to a slight increase of the dimension of the space. Improved convergence rate can be achieved depending on the piecewise regularity of the forcing function. Linear convergence in energy norm and quadratic convergence in $L^2$-norm is obtained independently of the forcing function. A series of numerical experiments confirms the theoretical rates of convergence

Reforming the German Public Pension System

Chancellor Bismarck introduced public pensions in Germany more than 120 years ago. That system has expanded into one of the most generous pension systems in the world. Most workers receive virtually all of their retirement income from it. Costs are almost 12 percent of GDP, more than 2.5 times as much as the U.S. Social Security System. The pressures exerted by population aging, amplified by negative incentive effects, have induced a reform process that began in 1992 and reached its peak in the 2001 and 2004 reforms. The 2001 reform converted the exemplary monolithic Bismarckian public insurance system into a complex multipillar system. The 2004 reform converted the pay-as-you-go pillar into a quasi notional defined contribution (NDC) system. This paper delivers an assessment in how far these reform steps will solve the pressing pension problems in Germany.

Population Aging, Savings Behavior and Capital Markets

Population aging is just beginning to hit the industrialized countries in full force, and it will have a tremendous impact on capital markets. In this paper, we argue that the capital market effects of population aging are particularly strong in continental European economies such as Germany, France, and Italy, with their large and ailing pay-as-you-go public pension systems, relatively thin capital markets, and poor capital performance. The younger generations in these countries are quite aware of the need to provide for more retirement income through own private saving, and these effects will be accentuated by fundamental pension reforms that aim at more pre-funding. Population aging changes households' savings behavior and portfolio composition, and much more assets will be invested on the stock market. Capital markets will grow in size, and active institutional investors such as pension funds will become more important in continental European countries. These changes are likely to have beneficial side effects in terms of improved capital efficiency, total factor productivity, and growth. Looking at the effects of population aging on savings behavior and capital markets therefore adds a new dimension to the continuing debate about advantages and disadvantages of pay-as-you-go and fully funded pension systems.