Explicit Relativistic Vortex Solutions for Cool Two-Constituent Superfluid Dynamics

We give a class of explicit solutions for the stationary and cylindrically symmetric vortex configurations for a ``cool'' two-component superfluid (i.e. superfluid with an ideal gas of phonons). Each solution is characterized only by a set of (true) constants of integration. We then compute the effective asymptotic contribution of the vortex to the stress energy tensor by comparison with a uniform reference state without vortex.Comment: 33 pages, RevTeX, no figures, to appear in Phys. Rev.

Differential rotation of relativistic superfluid in neutron stars

It is shown how to set up a mathematically elegant and fully relativistic superfluid model that can provide a realistic approximation (neglecting small anisotropies due to crust solidity, magnetic fields, et cetera, but allowing for the regions with vortex pinning) of the global structure of a rotating neutron star, in terms of just two independently moving constituents, one of which represents the differentially rotating neutron superfluid, while the other part represents the combination of all the other ingredients, including the degenerate electrons, the superfluid protons in the core, and the ions in the crust, whose electromagnetic interactions will tend to keep them locked together in a state of approximately rigid rotation. Order of magnitude estimates are provided for relevant parameters such as the resistive drag coefficient and the maximum pinning force.Comment: 35 pages, Latex, no figure, submitted to M.N.R.A.

Automatic grounding of vague geographic ontology in data

In constructing an ontological theory of a domain such as geography, it is important not only to take account of the vagueness and ambiguity which is inherent in many of the relevant concepts, but also to be able to relate the high-level definitions of the theory to actual sets of data of varying kinds. Any attempt to ignore or remove vagueness and ambiguity risks errors and conflict in the ontological theory with the knowledge of different domain experts, while an inability to ground the theory in real data limits its practical use. We present here a means of structuring such a theory to handle these issues in a principled manner, which lends itself to concrete implementation. We illustrate with reference to several examples from the domain of hydrography

Energy of Magnetic Vortices in Rotating Superconductor

We carry out a systematic analytic investigation of stationary and cylindrically symmetric vortex configurations for simple models representing an incompressible non-relativistic superconductor in a rigidly rotating background. It is shown that although the magnetic and kinetic contributions to the energy per unit length of such a vortex are separately modified by the background angular velocity, its effect on the total energy per unit length cancels out. For a type II superconductor threaded by a parallel array of such vortices, this result implies that the relevant macroscopic magnetic field strength H will not be equal to the large scale average of the local magnetic induction B (as has previously been suggested) but instead that H will simply be equal to the external London field that characterizes the value of B outside the vortices.Comment: 8 pages, uses RevTeX, submitted to Phys.Rev.

Do Small Businesses Create More Jobs? New Evidence for the United States from the National Establishment Time Series

We use a new database, the National Establishment Time Series (NETS), to revisit the debate about the role of small businesses in job creation. Birch (e.g., 1987) argued that small firms are the most important source of job creation in the U.S. economy. But Davis et al. (1996a) argued that this conclusion was flawed, and based on improved methods and using data for the manufacturing sector, they concluded that there was no relationship between establishment size and net job creation. Using the NETS data, we examine evidence for the overall economy, as well as for different sectors. The results indicate that small firms and small establishments create more jobs, on net, although the difference is much smaller than what is suggested by Birch's methods. Moreover, in the recent period we study, a negative relationship between establishment size and job creation holds for both the manufacturing and services sectors.job creation, job destruction, small businesses