Expected Anomalies in the Fossil Record

The problem of intermediates in the fossil record has been frequently discussed ever since Darwin. The extent of `gaps' (missing transitional stages) has been used to argue against gradual evolution from a common ancestor. Traditionally, gaps have often been explained by the improbability of fossilization and the discontinuous selection of found fossils. Here we take an analytical approach and demonstrate why, under certain sampling conditions, we may not expect intermediates to be found. Using a simple null model, we show mathematically that the question of whether a taxon sampled from some time in the past is likely to be morphologically intermediate to other samples (dated earlier and later) depends on the shape and dimensions of the underlying phylogenetic tree that connects the taxa, and the times from which the fossils are sampled

Isospinning Skyrmions

In the Skyrme model atomic nuclei are modelled as quantized soliton solutions in a nonlinear field theory of pions. The mass number is given by the conserved topological charge B of the solitons. Conventionally, Skyrmions are semiclassically quantized within the rigid body approach. In this approach Skyrmions are effectively treated as rigid rotors in space and isospace that is it is assumed that Skyrmions do not deform at all when they spin and isospin. This approximation resulted in qualitative and encouraging quantitative agreement with experimental nuclear physics data. In this talk, we point out that the theoretical agreement could be further improved by allowing classical Skyrmion solutions to deform as they spin and isospin. As a first step towards a better understanding of how nuclei can be approximated by classically spinning and isospinning soliton solutions, we study how classical Skyrmion solutions of topological charges B=1?4,8 deform when classical isospin is added

Children at risk of poor educational outcomes. How educational research can support early identification and improve prevention. Special issue editorial

The editorial presents the papers of this special issue regarding children at risk of poor educational outcomes. The articles “provide a cross-section of the multifaceted research carried out within this framework. This research demonstrates the various theoretical and methodological approaches that can be used to tackle the question of how to provide support for students at risk.” (DIPF/Orig.

Constitutional Talk: Exploring Institutional Scope Conditions for Effective Arguing

[From the introduction]. Arguing, understood as reason-giving, is all pervasive in international politics: Negotiating actors give reasons for their demands at almost any time, regardless of whether talks are con-ducted in public or behind closed doors. And yet, since negotiations have most often been conceived of as processes of bargaining in which actors seek to adjust their behavior through the exchange of threats and incentives, arguments have primarily been treated as rather epiphenomenal to strategic interaction. In this paper we argue that under certain circum-stances arguments affect negotiating actors’ preferences, and subsequently lead to outcomes that are not easily explained in pure bargaining terms. Arguing and bargaining as different modes of interaction, however, are not contending but rather complementing explanations. As a result, we have to ask which scope conditions are particularly conducive to enabling arguing to prevail in decentralized negotiations and, thus, to affect both process and outcome. In a structured-focused comparison of Intergovernmental Conferences (IGCs) with the European Convention we aim to unveil institutional factors that induce actors to take validity claims into account and change their preferences accordingly. At the example of negotiations on sim-plification and the single legal personality of the European Union we seek to demonstrate that the transparency of the debate in conjunction with a higher degree of uncertainty about appro-priate behavior made arguing in the Convention particularly effective