Simulation of Field Theories in Wavelet Representation

The field is expanded in a wavelet series and the wavelet coefficients are varied in a simulation of the 2D $\phi^4$ field theory. The drastically reduced autocorrelations result in a substantial decrease of computing requirements, compared to those in local Metropolis simulations. A large part of the improvement is shown to be the result of an additional freedom in the choice of the allowed range of change at the Metropolis update of wavelet components, namely the range can be optimized independently for all wavelet sizes.Comment: 10 pages, LaTeX with 8 figures, Swansea preprint SWAT/3

A Parametric Modeling Approach to Measuring the Gas Masses of Circumstellar Disks

The disks that surround young stars are mostly composed of molecular gas, which is harder to detect and interpret than the accompanying dust. Disk mass measurements have therefore relied on large and uncertain extrapolations from the dust to the gas. We have developed a grid of models to study the dependencies of isotopologue CO line strengths on disk structure and temperature parameters and find that a combination of 13CO and C18O observations provides a robust measure of the gas mass. We apply this technique to Submillimeter Array observations of nine circumstellar disks and published measurements of six well studied disks. We find evidence for selective photodissociation of C18O and determine masses to within a factor of about three. The inferred masses for the nine disks in our survey range from 0.7-6 M_Jup, and all are well below the extrapolation from the interstellar medium gas-to-dust ratio of 100. This is consistent with the low masses of planets found around such stars, and may be due to accretion or photoevaporation of a dust-poor upper atmosphere. However, the masses may be underestimated if there are more efficient CO depletion pathways than those known in molecular clouds and cold cores.Comment: Accepted for publication in the ApJ. 15 pages, 11 figures, full model grid (Table 3) available in the source file

An excess of sub-millimetre sources towards z~1 clusters

Deep sub-millimetre observations using SCUBA are presented of the central regions of four high redshift clusters which have been extensively studied optically: CL0023+0423 (z=0.84), J0848+4453 (z=1.27), CL1604+4304 (z=0.90) and CL1604+4321 (z=0.92). 10 sub-millimetre sources are securely detected towards these four clusters at 850 microns, with two further tenuous detections; the raw 850 micron source counts exceed those determined from blank-field surveys by a factor of 3-4. In particular, towards CL1604+4304, 6 sources are detected with S(850) > 4 mJy making this the richest sub-mm field discovered to date. Corrections for gravitational lensing by these high redshift clusters reduce these excess sources counts, but are unlikely to account for more than about half of the excess, with the remainder presumably directly associated with cluster galaxies. The 450 to 850 micron flux density ratios of the detected sources are systematically higher (at a significance level > 98%) than those determined for blank-field selected sources, consistent with them being at the cluster redshifts. If subsequent identifications confirm cluster membership, these results will demonstrate that the optical Butcher-Oemler effect is also observed at sub-mm wavelengths.Comment: MNRAS, in consideration. 11 pages, including 6 figures. Minor typos correcte

The Search for AGN in Distant Galaxy Clusters

We are undertaking the first systematic study of the prevalence of AGN activity in a large sample of high redshift galaxy clusters. Local clusters contain mainly red elliptical galaxies, and have little or no luminous AGN activity. However, recent studies of some moderate to high redshift clusters have revealed significant numbers of luminous AGN within the cluster. This effect may parallel the Butcher-Oemler effect - the increase in the fraction of blue galaxies in distant clusters compared to local clusters. Our aim is to verify and quantify recent evidence that AGN activity in dense environments increases with redshift, and to evaluate the significance of this effect. As cluster AGN are far less prevalent than field sources, a large sample of over 120 cluster fields at z > 0.1 has been selected from the Chandra archives and is being analysed for excess point sources. The size of the excess, the radial distribution and flux of the sources and the dependence of these on cluster redshift and luminosity will reveal important information about the triggering and fueling of AGN.Comment: 2 pages, to appear in proceedings of 'Multi-wavelength AGN surveys', Cozumel, 200

The phase-space structure of the Klein-Gordon field

The formalism based on the equal-time Wigner function of the two-point correlation function for a quantized Klein--Gordon field is presented. The notion of the gauge-invariant Wigner transform is introduced and equations for the corresponding phase-space calculus are formulated. The equations of motion governing the Wigner function of the Klein--Gordon field are derived. It is shown that they lead to a relativistic transport equation with electric and magnetic forces and quantum corrections. The governing equations are much simpler than in the fermionic case which has been treated earlier. In addition the newly developed formalism is applied towards the description of spontaneous symmetry breakdown.Comment: 27 pages, LaTeX, UFTP 317/199

The triggering probability of radio-loud AGN: A comparison of high and low excitation radio galaxies in hosts of different colors

Low luminosity radio-loud active galactic nuclei (AGN) are generally found in massive red elliptical galaxies, where they are thought to be powered through gas accretion from their surrounding hot halos in a radiatively inefficient manner. These AGN are often referred to as "low-excitation" radio galaxies (LERGs). When radio-loud AGN are found in galaxies with a young stellar population and active star formation, they are usually high-power radiatively-efficient radio AGN ("high-excitation", HERG). Using a sample of low-redshift radio galaxies identified within the Sloan Digital Sky Survey (SDSS), we determine the fraction of galaxies that host a radio-loud AGN, $f_{RL}$, as a function of host galaxy stellar mass, $M_*$, star formation rate, color (defined by the 4000 \angstrom break strength), radio luminosity and excitation state (HERG/LERG). We find the following: 1. LERGs are predominantly found in red galaxies. 2. The radio-loud AGN fraction of LERGs hosted by galaxies of any color follows a $f^{LE}_{RL} \propto M^{2.5}_*$ power law. 3. The fraction of red galaxies hosting a LERG decreases strongly for increasing radio luminosity. For massive blue galaxies this is not the case. 4. The fraction of green galaxies hosting a LERG is lower than that of either red or blue galaxies, at all radio luminosities. 5. The radio-loud AGN fraction of HERGs hosted by galaxies of any color follows a $f^{HE}_{RL} \propto M^{1.5}_*$ power law. 6. HERGs have a strong preference to be hosted by green or blue galaxies. 7. The fraction of galaxies hosting a HERG shows only a weak dependence on radio luminosity cut. 8. For both HERGs and LERGs, the hosting probability of blue galaxies shows a strong dependence on star formation rate. This is not observed in galaxies of a different color.[abridged]Comment: 7 pages, 6 figure

Detoxification in rehabilitation in England: effective continuity of care or unhappy bedfellows?

There is evidence that residential detoxification alone does not provide satisfactory treatment outcomes and that outcomes are significantly enhanced when clients completing residential detoxification attend rehabilitation services (Gossop, Marsden, Stewart, & Rolfe, 1999; Ghodse, Reynolds, Baldacchino, et al., 2002). One way of increasing the likelihood of this continuity of treatment is by providing detoxification and rehabilitation within the same treatment facility to prevent drop-out, while the client awaits a rehabilitation bed or in the transition process. However, there is little research evidence available on the facilities that offer both medical detoxification and residential rehabilitation. The current study compares self-reported treatment provision in 87 residential rehabilitation services in England, 34 of whom (39.1%) reported that they offered detoxification services within their treatment programmes. Although there were no differences in self-reported treatment philosophies, residential rehabilitation services that offered detoxification were typically of shorter duration overall, had significantly more beds and reported offering more group work than residential rehabilitation services that did not offer detoxification. Outcomes were also different, with twice as many clients discharged on disciplinary grounds from residential rehabilitation services without detoxification facilities. The paper questions the UK classification of residential drug treatment services as either detoxification or rehabilitation and suggests the need for greater research focus on the aims, processes and outcomes of this group of treatment providers

Theoretical and experimental research on parameter tracking systems Final report, 15 Jul. 1964 - Aug. 1965

Parameter tracking systems based on equation error approach for mathematical model of unknown plan