First- and second-order phase transitions in a driven lattice gas with nearest-neighbor exclusion

A lattice gas with infinite repulsion between particles separated by $\leq 1$ lattice spacing, and nearest-neighbor hopping dynamics, is subject to a drive favoring movement along one axis of the square lattice. The equilibrium (zero drive) transition to a phase with sublattice ordering, known to be continuous, shifts to lower density, and becomes discontinuous for large bias. In the ordered nonequilibrium steady state, both the particle and order-parameter densities are nonuniform, with a large fraction of the particles occupying a jammed strip oriented along the drive. The relaxation exhibits features reminiscent of models of granular and glassy materials.Comment: 8 pages, 5 figures; results due to bad random number generator corrected; significantly revised conclusion

Slow relaxation due to optimization and restructuring: Solution on a hierarchical lattice

Motivated by the large strain shear of loose granular materials we introduced a model which consists of consecutive optimization and restructuring steps leading to a self organization of a density field. The extensive connections to other models of statistical phyics are discussed. We investigate our model on a hierarchical lattice which allows an exact asymptotic renormalization treatment. A surprisingly close analogy is observed between the simulation results on the regular and the hierarchical lattices. The dynamics is characterized by the breakdown of ergodicity, by unusual system size effects in the development of the average density as well as by the age distribution, the latter showing multifractal properties.Comment: 11 pages, 7 figures revtex, submitted to PRE see also: cond-mat/020920

Social Entrepreneurship and Broader Theories: Shedding New Light on the “Bigger Picture”

This article documents the results of a research workshop bringing together six perspectives on social entrepreneurship. The idea was to challenge existing concepts of the economy, the firm, and entrepreneurship in order to shed new light on social entrepreneurship and on our existing theoretical frameworks. The first two contributions use a macro-perspective and discuss the notion of adaptive societies and the tragedies of disharmonization, respectively. Taking a management perspective, the next two focus on the limits of conventional assumptions in management theory, particularly human capital theory and resource-based view. The final two contributions follow an entrepreneurship perspective highlighting the usefulness of mobilization theory and the business model lens to social entrepreneurship. Despite this diversity, all contributions share the fact that they challenge narrow definitions of the unit of analysis in social entrepreneurship; they illustrate the aspect of social embeddedness, and they argue for an open-but-disciplined diversity of theories in social entrepreneurship research

Performance configurations over time: implications for growth- and profit-oriented strategies

Strategic entrepreneurship can be described as simultaneous opportunity seeking and advantage seeking. Younger firms are generally more flexible and therefore enjoy 'discovery advantages', whereas established firms tend to be resource rich and more experienced and consequently enjoy 'exploitation advantages'. The resulting evolution of the two important performance dimensions 'growth' and 'profitability' by firm age is not well understood. In this paper we integrate several theoretical arguments concerning profit-growth relationships to develop a dynamic model of firm development which suggests different development pathways for young firms. This leads to several unidirectional, competing hypotheses that we examine by studying the profitability-growth configurations of approximately 3,500 small firms and how these configurations evolve over time. We find that for both young and old firms, a focus on achieving above-average profitability and then striving for growth is a more likely path towards achieving sustained above-average performance than is first pursuing strong growth in the hope of building profitability later. In line with our hypothesis we find that younger firms are over-represented as 'Stars' (high on both growth and profitability) and under-represented as 'Poor' (low on both growth and profitability). However, young firms in the 'Star' category are also less likely than their older counterparts to maintain that position. Furthermore, our results indicate that young firms are over-represented not only among 'Stars', but also among growth-orientated firms regardless of the level of profitability. The findings strongly caution against the blind pursuit of growth for young firms, in favor of a thoughtful analysis of how both growth and profitability might be developed by firms. The results also question whether simultaneous high performance in terms of growth and profitability among young firms usually reflects a successful entrepreneurial strategy. The results can also be interpreted as luck on the part of a sub-group of young firms who indiscriminately pursue growth opportunities with varying profit prospects, and in many cases the high growth-profit performance will be short lived