Free University of Berlin

About: Free University of Berlin is a education organization based out in Berlin, Germany. It is known for research contribution in the topics: Population & Context (language use). The organization has 35195 authors who have published 66525 publications receiving 2094403 citations. The organization is also known as: FU Berlin.

Reduced density matrices and entanglement entropy in free lattice models

Abstract: We review the properties of reduced density matrices for free fermionic or bosonic many-particle systems in their ground state. Their basic feature is that they have a thermal form and thus lead to a quasi-thermodynamic problem with a certain free-particle Hamiltonian. We discuss the derivation of this result, the character of the Hamiltonian and its eigenstates, the single-particle spectra and the full spectra, the resulting entanglement and in particular the entanglement entropy. This is done for various one- and two-dimensional situations, including also the evolution after global or local quenches.

Comparative and International Corporate Governance

Abstract: In this article, we examine the state of the art in comparative and international corporate governance by identifying the key research questions, main concepts, and paradigms of explanations of cross-country diversity in corporate governance. First, we discuss the multiple definitions of corporate governance across disciplines and explore how this multi-dimensional nature of corporate governance posses challenges when making cross-national comparisons. Second, we review existing comparative research on corporate governance and highlight some of the main characteristics of comparative analysis. Third, we analyze how comparative corporate governance has been understood from four different scholarly perspectives: economics and management, culture and sociology, legal, and political paradigms. We conclude from this third section that future research should make an effort to better integrate cross-disciplinary paradigms. Fourth, we investigate what insights these four perspectives bring to better understand change and stability in two particular governance dimensions: corporate ownership and the role of labor in comparative corporate governance. Finally, we conclude the article with some forward looking suggestions regarding (1) how different perspectives of corporate governance can be more effectively integrated by adopting case-based, historical and actor-centered forms of institutional explanations and by (2) discussing the current U.S. corporate governance system, frequently seen as the "best practice" model.

Representations of odours and odour mixtures visualized in the honeybee brain

Abstract: Most animals depend on the identification of odours to locate food or to find mating partners. To accomplish this, the olfactory system must recognize relative concentrations of a large number of substances by analysing complex patterns of chemoreceptor activations1,2, but how these patterns are represented in the brain is not well understood. Previous studies indicated that odours evoke specific patterns of activity in olfactory sensory centres3–7 and led to the hypothesis that single glomeruli in the olfactory bulb of mammals respond to particular receptor types8–10. We made optical recordings in vivo in the honeybee brain to investigate neuronal population responses to odorants delivered naturally to the animal. We report here that odours evoked specific spatio–temporal excitation patterns in the antennal lobe, the structural and functional analogue of the olfactory bulb11. Specific ensembles of active glomeruli represent odours in a combinatorial manner. A comparison between different individuals shows remarkable similarities for a pheromone component, but not for general flower odours. Mixtures evoked patterns that were combinations of the single odorant responses. These combinations were not fully additive, however, indicating inhibitory effects on single glomeruli. Such interactions could be crucial for the formation of singular codes for complex odour blends.