RGFGA: An efficient representation and crossover for grouping genetic algorithms

There is substantial research into genetic algorithms that are used to group large numbers of objects into mutually exclusive subsets based upon some fitness function. However, nearly all methods involve degeneracy to some degree. We introduce a new representation for grouping genetic algorithms, the restricted growth function genetic algorithm, that effectively removes all degeneracy, resulting in a more efficient search. A new crossover operator is also described that exploits a measure of similarity between chromosomes in a population. Using several synthetic datasets, we compare the performance of our representation and crossover with another well known state-of-the-art GA method, a strawman optimisation method and a well-established statistical clustering algorithm, with encouraging results

Companions of Qsos at Redshift 1.1

We discuss broad- and narrow-band imaging of 7 arcmin fields of 14 QSOs with redshift ~1.1. The narrow-band filters were chosen to detect redshifted [O II] 3727A, and the broad bands are R and I, which correspond to rest wavelengths {}~3300A and ~3800A. In 100 arcsec subfields surrounding the QSOs, we detect an excess of typically 15 detected objects over the background of 25. Several of the QSO subfields also contain an excess of blue (R-I < 1.0) galaxies compared with the other subfields. Finally, several of the QSO subfields contain an excess of galaxies with significant narrow-band flux compared with the other subfields, and many of these are also blue. Most of the QSOs are radio-quiet in a region of sky overpopulated with z=1.1 QSOs, and 3 others are radio-loud from other parts of the sky. We suggest that most of these z=1.1 QSOs are in compact groups of starbursting galaxies. In our data, there is no significant difference between radio-loud and radio-quiet QSOs. We discuss cosmic evolutionary implications.Comment: 9 pages Plain Tex, 8 figures upon request, SISSA-DAO-94-00

ICARUS: Intelligent coupon allocation for retailers using search

Many retailers run loyalty card schemes for their customers offering incentives in the form of money off coupons. The total value of the coupons depends on how much the customer has spent. This paper deals with the problem of finding the smallest set of coupons such that each possible total can be represented as the sum of a pre-defined number of coupons. A mathematical analysis of the problem leads to the development of a genetic algorithm solution. The algorithm is applied to real world data using several crossover operators and compared to well known straw-person methods. Results are promising showing that considerable time can be saved by using this method, reducing a few days worth of consultancy time to a few minutes of computation

The Gravitational Lens CFRS03.1077

An exquisite gravitational arc with a radius of 2.1" has been discovered around the z = 0.938 field elliptical galaxy CFRS03.1077 during HST observations of Canada-France Redshift Survey (CFRS) fields. Spectroscopic observations of the arc show that the redshift of the resolved lensed galaxy is z = 2.941. This gravitational lens-source system is well-fitted using the position angle and ellipticity derived from the visible matter distribution and an isothermal mass profile with a mass corresponding to sigma =387+-5 km/s. Surprisingly, given the evidence for passive evolution of elliptical galaxies, this is in good agreement with an estimate based on the fundamental plane for z = 0 ellipticals. This, perhaps, indicates that this galaxy has not shared in the significant evolution observed for average elliptical galaxies at z ~ 1. A second elliptical galaxy with similar luminosity from the CFRS survey, CFRS 14.1311 at z=0.807, is also a lens but in this case the lens model gives a much smaller mass-to-light ratio, i.e., it appears to confirm the expected evolution. This suggests that this pair of field elliptical galaxies may have very different evolutionary histories, a significant result if confirmed. Clearly, CFRS03.1077 demonstrates that these "Einstein rings" are powerful probes of high redshift galaxies.Comment: 11 pages, 5 figures, accepted by Ap.

THE CANADA-FRANCE REDSHIFT SURVEY V: Global Properties of the Sample

The photometric and spectroscopic data of the CFRS survey of objects with 17.5 < I_{AB} < 22.5 are combined and analysed. The overall completeness is 85%. The redshift histogram of the sample is presented for 591 field galaxies with secure redshifts. The median redshift is z = 0.56, and the highest redshift observed is z = 1.3; 25 galaxies have z > 1 The distributions of magnitudes and colors demonstrate that galaxies at these high redshifts have very similar colors to those observed locally. The survey thus represents a major improvement in our knowledge of field galaxies at large look-back times. Only ~1% of the galaxies are as compact as stars (on images with FWHM ~ 0.9") and comparisons of the photometric and spectroscopic data show that only one galaxy was initially incorrectly classified spectroscopically as a star, and only two stars were misclassified as galaxies. It is demonstrated that the redshift distributions in the five fields are statistically consistent with each other, once the reduction in the effective number of independent galaxies due to small-scale clustering in redshift is taken into account. The photometric properties of the spectroscopically-unidentified objects indicate that most are likely to be galaxies rather than stars. At least half of these must have the same redshift distribution as the identified galaxies, and a combination of magnitudes, colors and compactness of the remaining unidentified galaxies is used to predict their redshifts. The majority are probably ordinary galaxies at the high redshift end of our sample, including some quiescent galaxies at z > 1.0, rather than some new or unusual population.Comment: 20 uuencoded postscript pages (first part) with 12 figures (second part). Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.html and coming soon on a CFRS homepage. Accepted June 19, scheduled for Dec 10 issue of Ap

Algorithms for the workflow satisfiability problem engineered for counting constraints

The workflow satisfiability problem (WSP) asks whether there exists an assignment of authorized users to the steps in a workflow specification that satisfies the constraints in the specification. The problem is NP-hard in general, but several subclasses of the problem are known to be fixed-parameter tractable (FPT) when parameterized by the number of steps in the specification. In this paper, we consider the WSP with user-independent counting constraints, a large class of constraints for which the WSP is known to be FPT. We describe an efficient implementation of an FPT algorithm for solving this subclass of the WSP and an experimental evaluation of this algorithm. The algorithm iteratively generates all equivalence classes of possible partial solutions until, whenever possible, it finds a complete solution to the problem. We also provide a reduction from a WSP instance to a pseudo-Boolean SAT instance. We apply this reduction to the instances used in our experiments and solve the resulting PB SAT problems using SAT4J, a PB SAT solver. We compare the performance of our algorithm with that of SAT4J and discuss which of the two approaches would be more effective in practice

A VLT/FORS2 Multi-Slit Search for Lyman-alpha Emitting Galaxies at z~6.5

We present results from a deep spectroscopic search in the 9150A atmospheric window for z~6.5 Lyman-alpha emitting galaxies using the VLT/FORS2. Our multi-slit+narrow-band filter survey covers a total spatial area of 17.6 sq. arcmin in four different fields and reaches fluxes down to 5x10^(-18) erg/s/cm^2 (7 sigma detection). Our detection limit is significantly fainter than narrow-band searches at this redshift and fainter also than the unlensed brightness of Hu et al.'s HCM6A at z=6.56, and thus provides better overlap with surveys at much lower redshifts. Eighty secure emission line galaxies are detected. However, based on their clear continuum emission shortward of the line or the presence of multiple lines, none of these can be Ly-alpha emission at z~6.5. Our null result of finding no z~6.5 Ly-alpha emitters suggests that the number density of Ly-alpha emitters with L>2x10^(42) erg/s declines by ~2 between z~3 and z~6.5.Comment: accepted by ApJ Letters (originally submitted June 11, 2004

THE CANADA-FRANCE REDSHIFT SURVEY II: Spectroscopic Program; Data for the 0000-00 and 1000+25 Fields

This paper describes the methods used to obtain the spectroscopic data and construct redshift catalogs for the Canada-France deep Redshift Survey (CFRS). The full data set consists of more than one thousand spectra, of objects with 17.5 < I_{AB} < 22.5, obtained from deep multi-slit data with the MARLIN and MOS-SIS spectrographs at the CFHT. The final spectroscopic catalog contains 200 stars, 591 galaxies with secure redshifts in the range 0 < z < 1.3, 6 QSOs, and 146 objects with very uncertain or unknown redshifts, leading to an overall success rate of identification of 85%. Additionally, 67 objects affected by observational problems have been placed in a supplemental list. We describe here the instrumental set up, and the observing procedures used to efficiently gather this large data set. New optimal ways of packing spectra on the detector to significantly increase the multiplexing gain offered by multi-slit spectroscopy are described. Dedicated data reduction procedures have been developed under the IRAF environment to allow for fast and accurate processing. Very strict procedures have been followed to establish a reliable list of final spectroscopic measurements. Fully independent processing of the data has been carried out by three members of the team for each data set associated with a multi-slit mask, and final redshifts were assigned only after the careful comparison of the three independent measurements. A confidence class scheme was established. We strongly emphasize the benefits of such procedures. Finally, we present the spectroscopic data obtained for 303 objects in the 0000-00 and 1000+25 fields. The success rate in spectroscopic identification isComment: 16 uuencoded postcript pages with figures 4,5,8,9 and 12. Other (large) figures available from the authors. Large data table not yet released. Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.html and coming soon on a CFRS homepage. Accepted June 19, scheduled for the Dec 10 issue of Ap