Justifications in Constraint Handling Rules for Logical Retraction in Dynamic Algorithms

We present a straightforward source-to-source transformation that introduces justifications for user-defined constraints into the CHR programming language. Then a scheme of two rules suffices to allow for logical retraction (deletion, removal) of constraints during computation. Without the need to recompute from scratch, these rules remove not only the constraint but also undo all consequences of the rule applications that involved the constraint. We prove a confluence result concerning the rule scheme and show its correctness. When algorithms are written in CHR, constraints represent both data and operations. CHR is already incremental by nature, i.e. constraints can be added at runtime. Logical retraction adds decrementality. Hence any algorithm written in CHR with justifications will become fully dynamic. Operations can be undone and data can be removed at any point in the computation without compromising the correctness of the result. We present two classical examples of dynamic algorithms, written in our prototype implementation of CHR with justifications that is available online: maintaining the minimum of a changing set of numbers and shortest paths in a graph whose edges change.Comment: Pre-proceedings paper presented at the 27th International Symposium on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur, Belgium, 10-12 October 2017 (arXiv:1708.07854

Gardner's deformations of the N=2 supersymmetric a=4-KdV equation

We prove that P.Mathieu's Open problem on constructing Gardner's deformation for the N=2 supersymmetric a=4-Korteweg-de Vries equation has no supersymmetry invariant solutions, whenever it is assumed that they retract to Gardner's deformation of the scalar KdV equation under the component reduction. At the same time, we propose a two-step scheme for the recursive production of the integrals of motion for the N=2, a=4-SKdV. First, we find a new Gardner's deformation of the Kaup-Boussinesq equation, which is contained in the bosonic limit of the super-hierarchy. This yields the recurrence relation between the Hamiltonians of the limit, whence we determine the bosonic super-Hamiltonians of the full N=2, a=4-SKdV hierarchy. Our method is applicable towards the solution of Gardner's deformation problems for other supersymmetric KdV-type systems.Comment: Extended version of the talks given by A.V.K. at 8th International conference `Symmetry in Nonlinear Mathematical Physics' (June 20-27, 2009, Kiev, Ukraine) and 9th International workshop `Supersymmetry and Quantum Symmetries' (July 29 - August 3, 2009, JINR, Dubna, Russia); 22 page

Drivers of Resident Support for Animal Care Oriented Ballot Initiatives

Recent high profile incidents and public debates in the United States have highlighted the increasing interest residents have regarding animal rearing and handling practices. This paper examines resident support for national legislation that mirrors Proposition 2, which in November 2008 passed in California. Results suggest perceptions regarding animal welfare information accuracy of livestock industry and consumer groups are particularly influential determinants of voting behavior and demand. The analysis also suggests residents may not fully appreciate price or tax implications when supporting additional animal welfare legislation. Implications for livestock industry and policy makers are provided along with suggestions for additional research.animal handling and welfare, ballot initiatives, information accuracy, legislation, Proposition 2, voting behavior, willingness to pay, Agribusiness, Agricultural and Food Policy, Farm Management, Livestock Production/Industries, Q18, Q13, Q11,

The pseudogap in Bi2212 single crystals from tunneling measurements: a possible evidence for the Cooper pairs above Tc

We present electron-tunneling spectroscopy of slightly overdoped Bi2212 single crystals with Tc = 87 - 90 K in a temperature range between 14 K and 290 K using a break-junction technique. The pseudogap which has been detected above Tc appears at T* = 280 K. The analysis of the spectra shows that there is a contribution to the pseudogap above Tc, which disappears approximately at 110 - 115 K. We associate this contribution with the presence of incoherent Cooper pairs.Comment: 12 pages including 4 figures, to be published in Europhysics Letter

Investigation of the anisotropy of dissipation processes in single crystal of Yba2Cu3O7-d system

By means of contactless mechanical method of the measurement of energy losses in superconductors, the anisotropy of dissipation processes has been studied in single crystal high-temperature layered superconductors of Yba2Cu3O7-d system, being in mixed state. The observed anisotropy of energy losses indicates the possibility of the existence of the symmetry of order parameter of dx2-y2 type in these single crystals.Comment: 4 pages, 3 figure

Collisions and drag in debris discs with eccentric parent belts

Context: High-resolution images of circumstellar debris discs reveal off-centred rings that indicate past or ongoing perturbation, possibly caused by secular gravitational interaction with unseen stellar or substellar companions. The purely dynamical aspects of this departure from radial symmetry are well understood. However, the observed dust is subject to additional forces and effects, most notably collisions and drag. Aims: To complement the studies of dynamics, we therefore aim to understand how new asymmetries are created by the addition of collisional evolution and drag forces, and existing ones strengthened or overridden. Methods: We augmented our existing numerical code "Analysis of Collisional Evolution" (ACE) by an azimuthal dimension, the longitude of periapse. A set of fiducial discs with global eccentricities ranging from 0 to 0.4 is evolved over giga-year timescales. Size distribution and spatial variation of dust are analysed and interpreted. The basic impact of belt eccentricity on spectral energy distributions (SEDs) and images is discussed. Results: We find features imposed on characteristic timescales. First, radiation pressure defines size cutoffs that differ between periapse and apoapse, resulting in an asymmetric halo. The differences in size distribution make the observable asymmetry of the halo depend on wavelength. Second, collisional equilibrium prefers smaller grains on the apastron side of the parent belt, reducing the effect of pericentre glow and the overall asymmetry. Third, Poynting-Robertson drag fills the region interior to an eccentric belt such that the apastron side is more tenuous. Interpretation and prediction of the appearance in scattered light is problematic when spatial and size distribution are coupled.Comment: Accepted for publication in A&A, 14 pages, 16 figure