124,280 research outputs found
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 . With increasing
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 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
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