Scaling Behaviour of the Maximal Growth Rate in the Rosensweig Instability

The dependence of the maximal growth rate of the modes of the Rosensweig instability on the properties of the magnetic fluid and the external magnetic induction is studied. An expansion and a fit procedure are applied in the appropriate ranges of the supercritical induction $\hat B$. With increasing $\hat B$ the scaling of the maximal growth rate changes from linear to a combination of linear and square-root-like scaling. The scaling of the corresponding wave number alternates from quadratic to primarily linear. For very small $\hat B$ the dependence of the maximal growth rate on the viscosity is given. Suggestions are made for experiments to test the predicted scaling behaviours.Comment: 8 pages, 4 figures; to appear in Europhys. Let

Editor’s Note

With this issue, Law and Contemporary Problems initiates a new practice of offering occasional mini-symposia on topics which deserve treatment, but may not fill an entire issue. The topics we have chosen certainly deserve treatment. The questions of policy posed by the prospect of additional urban growth in the eighties demand far more thoughtful attention than they have yet had. The relevance of an examination into the control of political and ideological dissent is manifest as we contemplate world events of the past year. We are pleased to offer these two brief symposia. We will introduce others from time to time in future issues. David Lang

Credit in the Body of Christ (Northern France, 1300-1600)

This paper examines a practice that is nearly imperceptible to historians because the bulk of evidence for it is to be found in the interstices of the beaten paths of legal and social history and because it mixes economic and religious matters in a strikingly unfamiliar manner. From the thirteenth to the sixteenth century, excommunication for debt offered ordinary people an economical, efficacious enforcement mechanism for small-scale, daily, unwritten credit. At the same time, the practice offered holders of ecclesiastical jurisdiction an important opportunity to round out their incomes, particularly in the difficult fifteenth century. This transitional practice reveals a level of credit below that of the letters of change, annuities secured on real property, or written obligations beloved of economic historians and historians of banking. Studying the practice casts light on the transition from the face-to-face, local economies of the high Middle Ages to the regional economies of the early modern period, on how the Reformation shaped early modern regimes of credit, and on how the disappearance of ecclesiastical civil justice facilitated the emergence of early modern juridically sovereign territories

XYZ States - Results from Experiments

Charmonium(-like) or bottomonium(-like) states, which are incompatible with predictions from a static quark anti-quark potential model, are often refered to as XYZ states. In this lecture, some peculiar properties of states such as the X(3872), the Y(4260), or the Zc(3900) are explained. Such properties are utmost proximity to a threshold, overpopulation of states, or possibly binding in the regime of string breaking. Among decays, the surprising observation of isospin violation, and using radiative decays for the observation of a D-wave state is discussed. A second part of the lecture presents recent precision measurements of masses of newly observed bottomonium states. These masses can be used for testing particular aspects of the potential, such as test of the tensor term or test of the flavor independence. At the end, an example is given, how future experiments may be able to measure widths of a charmonium(-like) state in the sub-MeV regime.Comment: Lecture given at the Helmholtz International Summer School Physics of Heavy Quarks and Hadrons, Dubna, Russia, 07/15-28/201

Reimagining the Public Domain

In a paper included among this collection of works from the Duke Law School’s Conference on the Public Domain, James Boyle kindly credits an early essay of mine, Recognizing the Public Domain, with having contributed initially to the contemporary study of the subject. Boyle quotes a passage from that essay in which I suggested that recognition of new intellectual property interests should be offset today by equally deliberate recognition of individual rights in the public domain . . . . Each [intellectual property] right ought to be marked off clearly against the public domain

Towards OpenMath Content Dictionaries as Linked Data

"The term 'Linked Data' refers to a set of best practices for publishing and connecting structured data on the web". Linked Data make the Semantic Web work practically, which means that information can be retrieved without complicated lookup mechanisms, that a lightweight semantics enables scalable reasoning, and that the decentral nature of the Web is respected. OpenMath Content Dictionaries (CDs) have the same characteristics - in principle, but not yet in practice. The Linking Open Data movement has made a considerable practical impact: Governments, broadcasting stations, scientific publishers, and many more actors are already contributing to the "Web of Data". Queries can be answered in a distributed way, and services aggregating data from different sources are replacing hard-coded mashups. However, these services are currently entirely lacking mathematical functionality. I will discuss real-world scenarios, where today's RDF-based Linked Data do not quite get their job done, but where an integration of OpenMath would help - were it not for certain conceptual and practical restrictions. I will point out conceptual shortcomings in the OpenMath 2 specification and common bad practices in publishing CDs and then propose concrete steps to overcome them and to contribute OpenMath CDs to the Web of Data.Comment: Presented at the OpenMath Workshop 2010, http://cicm2010.cnam.fr/om