Exact Algorithm for Sampling the 2D Ising Spin Glass

A sampling algorithm is presented that generates spin glass configurations of the 2D Edwards-Anderson Ising spin glass at finite temperature, with probabilities proportional to their Boltzmann weights. Such an algorithm overcomes the slow dynamics of direct simulation and can be used to study long-range correlation functions and coarse-grained dynamics. The algorithm uses a correspondence between spin configurations on a regular lattice and dimer (edge) coverings of a related graph: Wilson's algorithm [D. B. Wilson, Proc. 8th Symp. Discrete Algorithms 258, (1997)] for sampling dimer coverings on a planar lattice is adapted to generate samplings for the dimer problem corresponding to both planar and toroidal spin glass samples. This algorithm is recursive: it computes probabilities for spins along a "separator" that divides the sample in half. Given the spins on the separator, sample configurations for the two separated halves are generated by further division and assignment. The algorithm is simplified by using Pfaffian elimination, rather than Gaussian elimination, for sampling dimer configurations. For n spins and given floating point precision, the algorithm has an asymptotic run-time of O(n^{3/2}); it is found that the required precision scales as inverse temperature and grows only slowly with system size. Sample applications and benchmarking results are presented for samples of size up to n=128^2, with fixed and periodic boundary conditions.Comment: 18 pages, 10 figures, 1 table; minor clarification

A visual programming environment for the Navier-Stokes computer

The Navier-Stokes computer is a high-performance, reconfigurable, pipelined machine designed to solve large computational fluid dynamics problems. Due to the complexity of the architecture, development of effective, high-level language compilers for the system appears to be a very difficult task. Consequently, a visual programming methodology has been developed which allows users to program the system at an architectural level by constructing diagrams of the pipeline configuration. These schematic program representations can then be checked for validity and automatically translated into machine code. The visual environment is illustrated by using a prototype graphical editor to program an example problem

Irrational mode locking in quasiperiodic systems

A model for ac-driven systems, based on the Tang-Wiesenfeld-Bak-Coppersmith-Littlewood automaton for an elastic medium, exhibits mode-locked steps with frequencies that are irrational multiples of the drive frequency, when the pinning is spatially quasiperiodic. Detailed numerical evidence is presented for the large-system-size convergence of such a mode-locked step. The irrational mode locking is stable to small thermal noise and weak disorder. Continuous time models with irrational mode locking and possible experimental realizations are discussed.Comment: 4 pages, 3 figures, 1 table; revision: 2 figures modified, reference added, minor clarification

The Effect of Mining Out Coal No. 6 Before Taking Out the Seams Above it

Item includes a discussion between A. Roy, J. L. Morris, T. Bancroft, A. Howells, E. McMillin and W. Dalrymple of Thomas Middleton's pape

The study of the fathers in the Anglican tradition 16th-19th centuries

The Anglican study of the Fathers was primarily in relation to controversies that Anglicanism had to face in the aftermath of the Reformation and the struggle for Anglican identity, rather than for their own sake. Throughout these controversies it is the Fathers who speak, not only in the defence of Anglicanism, but in defence of themselves and an improper use of their writings. In this sense there is a kinship with the Fathers and the search for Anglican identity, in that, it was the controversies of their own times that gave birth to their writings The thesis divides into three parts. The first part, The Fathers in the English Reformation, examines the way in which the Reformers used the Fathers chiefly as a means of proving what had and what had not been primitive doctrine and practice and as a valuable authority secondary to the Bible. They used the Fathers in two ways, negatively, to prove the absence of Roman doctrines, and positively, to promote a right interpretation of Scripture and demonstrate a Scriptural way of life for the Church. This is demonstrated in relation to two Reformers, Thomas Cranmer and John Jewel, and then in relation to Anglican foundation documents. The second part, Fathers and Carolines, demonstrates how the Anglican divines of the seventeenth century, building on the scriptural and patristic foundation laid by the Reformers, go farther and use the thought and piety of the Fathers within the structure of their own theological vision. Their theology finds its centre in the Incarnation, a kinship shared with the Nicene Fathers, and characterised by a vision of the Church that embraces East and West, a consequence of their immersion in Greek and Latin divinity. Again it is a theological vision that is wrought in controversy, in relation to Puritanism and Calvinism on the one side, and Roman Catholicism on the other. Part Three, Objections and Responses, examines the Anglican response to objections brought against the Fathers. The first series are Direct Objections, and came from such people as John Daille, the controversy surrounding the authenticity of the Ignatian Epistles, and John Barbeyrac. These were attempts to discredit the reputation and authority of the Fathers as having any relevance for the contemporary Church. A second series, Indirect Objections, came in the form of a new Arianism, its associations with Socinianism and its English expression in Unitarianism. It attacked the catholic doctrines of Incarnation and Trinity, some of its advocates using the Fathers to justify their attacks upon orthodoxy. An Appendix has been added to include The Tew Circle, a group of individuals, who were not so much directly attacking the Fathers, but questioning the appeal to antiquity in their search for a simplification of theological method. The presence and voice of the Fathers at the heart of Anglicanism gives to the Church of England what Dr. Jebb, the Bishop of Limerick described as The Peculiar Character of the Church of England. The Oxford Movement has been omitted, since this would need a thesis in itself. Certain nineteenth century theologians equally concerned with the renewal of patristic study, are considered. The names of such people include Henry Gary, John Collinson, J.J.Blunt, their concern being to free the Fathers from the misrepresentations of Daille and Barbeyrac, encourage young divines to read the Fathers and discover the peculiar character of the Church of England, and thereby free themselves from the ruts of modern theology. J.B.Lightfoot is included in relation to the The Ignatian Controversy

Results of aircraft open-loop tests of an experimental magnetic leader cable system for guidance during roll-out and turnoff

An experimental magnetic leader cable (MLC) system designed to measure aircraft lateral displacement from centerline and heading relative to centerline during rollout, turnoff, and taxi was tested at NASA's Wallops Flight Facility using NASA's Transport System Research Vehicle (TSRV), a modified B-737. The MLC system consisted of ground equipment that produced a magnetic field about a wire along runway centerline and airborne equipment that detected the strength and direction of this field and computed displacement and heading. Results of these tests indicate that estimates of aircraft displacement from centerline produced by the magnetic leader cable system using either of the two algorithms appear to be adequate for use by an automatic control system during rollout, turnoff, and taxi. Estimates of heading, however, are not sufficiently accurate for use, probably because of distortion of the magnetic field by the metal aircraft