Looking at the Haldane Conjecture from a Grouptheoretical Point of View

Based on the Lieb-Schultz-Mattis construction we present a five parameter family of Spin-1 Hamiltonians with degenerate groundstate. Starting from the critical $SU(3)$ symmetric Hamiltonian, we look for those perturbations of the $SU(3)$ symmetry, which leave the groundstate degenerate. We also discuss the spin-3/2 $SU(4)$-case.Comment: 9 pages RevTex 3.

Ferromagnetism in a hard-core boson model

The problem of ferromagnetism -- associated with a ground state with maximal total spin -- is discussed in the framework of a hard-core model, which forbids the occupancy at each site with more than one particle. It is shown that the emergence of ferromagnetism on finite square lattices crucially depends on the statistics of the particles. Fermions (electrons) lead to the well-known instabilities for finite hole densities, whereas for bosons (with spin) ferromagnetism appears to be stable for all hole densities.Comment: 8 pages, 7 figures, RevTex

Status of the GEO600 gravitational wave detector

The GEO600 laser interferometric gravitational wave detector is approaching the end of its commissioning phase which started in 1995.During a test run in January 2002 the detector was operated for 15 days in a power-recycled michelson configuration. The detector and environmental data which were acquired during this test run were used to test the data analysis code. This paper describes the subsystems of GEO600, the status of the detector by August 2002 and the plans towards the first science run

Historical Sources of Institutional Trajectories in Economic Development: China, Japan, and Korea Compared

This essay provides a game-theoretic, endogenous view of institutions, and then applies the idea to identify the sources of institutional trajectories of economic development in China, Japan, and Korea. It stylizes the Malthusian-phase of East Asian economies as peasant-based economies in which small families allocated their working time between farming on small plots - leased or owned - and handcrafting for personal consumption and markets. It then compares institutional arrangements across these economies that sustained otherwise similar economies. It characterizes the varied nature of the political states of Qing China, Tokugawa Japan, and Yi Korea by focusing on the way in which agricultural taxes were enforced. It also identifies different patterns of social norms of trust that were institutional complements to, or substitutes for, political states. Finally, it traces the path-dependent transformations of these state-norm combinations along subsequent transitions to post-Malthusian phases of economic growth in the respective economies

Personality Traits, Self-Employment, and Professions

We investigate the effect of broad personality traits' - the Big Five - on an individua's decision to become self-employed. In particular, we test an overall indicator of the entrepreneurial personality. Since we find that the level of self-employment varies considerably across professions, we also perform the analysis for different types of professions, namely, those classified as being in the 'creative class' as compared to the noncreative class. The analysis is based on micro data for individuals of the German Socio Economic Panel (SOEP). We find a significant association between personality traits and the propensity be become self-employed. However, the strength of this link is fairly weak and differs across professions, indicating an important effect of an individual's profession on his or her decision to run an own business

Are ICT, Workplace Organization and Human Capital Relevant for Innovation? A Comparative Study Based on Swiss and Greek Micro Data

This paper investigates the relationship between indicators for the intensity of use of ICT (examining three different types of ICT widely used in firms: internal, e-sales, e-procurement IS), several forms of workplace organization, and human capital on one hand, and several measures of innovation performance at firm level on the other hand, in an innovation equation framework, in which was also controlled for standard innovation determinants such as demand, competition and firm size. The empirical part is based on data of Swiss and Greek firms. This paper contributes to literature in three ways: first, it analyzes three important factors, i.e. information technology, workplace organization and human capital, which are considered to be drivers of innovation performance particularly in the last fifteen to twenty years, in the same setting, it uses several innovation indicators that cover both the input and the output side of the innovation process and, third, it does the analysis in a comparative setting for two countries, Greece and Switzerland, with quite different levels of technological and economic development

Did Liquidity Providers Become Liquidity Seekers?

The misalignment between corporate bond and credit default swap (CDS) spreads (i.e., CDSbond basis) during the 2007-09 financial crisis is often attributed to corporate bond dealers shedding off their inventory, right when liquidity was scarce. This paper documents evidence against this widespread perception. In the months following Lehman's collapse, dealers, including proprietary trading desks in investment banks, provided liquidity in response to the large selling by clients. Corporate bond inventory of dealers rose sharply as a result. Although providing liquidity, limits to arbitrage, possibly in the form of limited capital, obstructed the convergence of the basis. We further show that the unwinding of precrisis 'basis trades' by hedge funds is the main driver of the large negative basis. Price drops following Lehman's collapse were concentrated among bonds with available CDS contracts and high activity in basis trades. Overall, our results indicate that hedge funds that serve as alternative liquidity providers at times, not dealers, caused the disruption in the credit market