3,066 research outputs found
The high energy limit of the trajectory representation of quantum mechanics
The trajectory representation in the high energy limit (Bohr correspondence
principle) manifests a residual indeterminacy. This indeterminacy is compared
to the indeterminacy found in the classical limit (Planck's constant to 0)
[Int. J. Mod. Phys. A 15, 1363 (2000)] for particles in the classically allowed
region, the classically forbiden region, and near the WKB turning point. The
differences between Bohr's and Planck's principles for the trajectory
representation are compared with the differences between these correspondence
principles for the wave representation. The trajectory representation in the
high energy limit is shown to go to neither classical nor statistical
mechanics. The residual indeterminacy is contrasted to Heisenberg uncertainty.
The relationship between indeterminacy and 't Hooft's information loss and
equivalence classes is investigated.Comment: 12 pages of LaTeX. No figures. Incorporated into the "Proceedings of
the Seventh International Wigner Symposium" (ed. M. E. Noz), 24-29 August
2001, U. of Maryland. Proceedings available at
http://www.physics.umd.edu/robo
The Clustering Of Galaxies Around Radio-Loud AGNs
We examine the hypothesis that mergers and close encounters between galaxies
can fuel AGNs by increasing the rate at which gas accretes towards the central
black hole. We compare the clustering of galaxies around radio-loud AGNs with
the clustering around a population of radio-quiet galaxies with similar masses,
colors and luminosities. Our catalog contains 2178 elliptical radio galaxies
with flux densities greater than 2.8 mJy at 1.4 GHz from the 6dFGS survey. We
find that radio AGNs with more than 200 times the median radio power have, on
average, more close (r<160 kpc) companions than their radio-quiet counterparts,
suggestive that mergers play a role in forming the most powerful radio
galaxies. For ellipticals of fixed stellar mass, the radio power is not a
function of large-scale environment nor halo mass, consistent with the radio
powers of ellipticals varying by orders of magnitude over billions of years.Comment: 12 pages, 6 figure
Ways to Clear Worthless Brush for Pasture Use
There\u27s no shortage of total permanent pasture in the state to meet current production needs. But individual farm operators sometimes wish to convert a particular area or tract of brushland to pasture. How can this be done
VLBI observations of nearby radio loud Active Galactic Nuclei
We present an update of the parsec scale properties of the Bologna Complete
Sample consisting of 95 radio sources from the B2 Catalog of Radio Sources and
the Third Cambridge Revised Catalog (3CR), with z < 0.1. Thanks to recent new
data we have now parsec scale images for 76 sources of the sample. Most of them
show a one-sided jet structure but we find a higher fraction of two-sided
sources in comparison with previous flux-limited VLBI surveys. A few peculiar
sources are presented and discussed in more detail.Comment: 6 pages, 7 figures, Proceedings for "The Universe under the
Microscope" (AHAR 2008), April 2008, to be published in Journal of Physics:
Conference Series by Institute of Physics Publishing; R. Schoedel, A. Eckart,
S. Pfalzner, and E. Ros ed
The drivers of AGN activity in galaxy clusters: AGN fraction as a function of mass and environment
We present an analysis of optical spectroscopically identified active galactic nuclei (AGN) down to a cluster magnitude of M * + 1 in a sample of six self-similar Sloan Digital Sky Survey galaxy clusters at z ~ 0.07. These clusters are specifically selected to lack significant substructure at bright limits in their central regions so that we are largely able to eliminate the local action of merging clusters on the frequency of AGN. We demonstrate that the AGN fraction increases significantly from the cluster centre to 1.5R virial , but tails off at larger radii. If only comparing the cluster core region to regions at ~2R virial , no significant variation would be found. We compute the AGN fraction by mass and show that massive galaxies (log(stellarmass) > 10.7) are host to a systematically higher fraction of AGN than lower mass galaxies at all radii from the cluster centre. We attribute this deficit of AGN in the cluster centre to the changing mix of galaxy types with radius. We use the WHAN diagnostic to separate weak AGN from 'retired' galaxies in which the main ionization mechanism comes from old stellar populations. These retired AGN are found at all radii, while the mass effect is much more pronounced: we find that massive galaxies are more likely to be in the retired class. Further, we show that our AGN have no special position inside galaxy clusters - they are neither preferentially located in the infall regions nor situated at local maxima of galaxy density as measured with ∑ 5 . However, we find that the most powerful AGN (with [O III] equivalent widths < -10 Å) reside at significant velocity offsets in the cluster, and this brings our analysis into agreement with previous work on X-ray-selected AGN. Our results suggest that if interactions with other galaxies are responsible for triggering AGN activity, the time lag between trigger and AGN enhancement must be sufficiently long to obfuscate the encounter site and wipe out the local galaxy density signal. © 2012 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society
Evidence for Intergalactic Absorption in the TeV Gamma-Ray Spectrum of Mkn 501
The recent HEGRA observations of the blazar Mkn 501 show strong curvature in
the very high energy gamma-ray spectrum. Applying the gamma-ray opacity derived
from an empirically based model of the intergalactic infrared background
radiation field (IIRF), to these observations, we find that the intrinsic
spectrum of this source is consistent with a power-law: dN/dE~ E^-alpha with
alpha=2.00 +/- 0.03 over the range 500 GeV - 20 TeV. Within current synchrotron
self-Compton scenarios, the fact that the TeV spectral energy distribution of
Mkn 501 does not vary with luminosity, combined with the correlated, spectrally
variable emission in X-rays, as observed by the BeppoSAX and RXTE instruments,
also independently implies that the intrinsic spectrum must be close to
alpha=2. Thus, the observed curvature in the spectrum is most easily understood
as resulting from intergalactic absorption.Comment: 7 pages, 1 figure, accepted in ApJ Letters 1999 April
How was it for you? Experiences of participatory design in the UK health service
Improving co-design methods implies that we need to understand those methods, paying attention to not only the effect of method choices on design outcomes, but also how methods affect the people involved in co-design. In this article, we explore participants' experiences from a year-long participatory health service design project to develop ‘Better Outpatient Services for Older People’. The project followed a defined method called experience-based design (EBD), which represented the state of the art in participatory service design within the UK National Health Service. A sample of participants in the project took part in semi-structured interviews reflecting on their involvement in and their feelings about the project. Our findings suggest that the EBD method that we employed was successful in establishing positive working relationships among the different groups of stakeholders (staff, patients, carers, advocates and design researchers), although conflicts remained throughout the project. Participants' experiences highlighted issues of wider relevance in such participatory design: cost versus benefit, sense of project momentum, locus of control, and assumptions about how change takes place in a complex environment. We propose tactics for dealing with these issues that inform the future development of techniques in user-centred healthcare design
An optical-IR jet in 3C133
We report the discovery of a new optical-IR synchrotron jet in the radio
galaxy 3C133 from our HST/NICMOS snapshot survey. The jet and eastern hotspot
are well resolved, and visible at both optical and IR wavelengths. The IR jet
follows the morphology of the inner part of the radio jet, with three distinct
knots identified with features in the radio. The radio-IR SED's of the knots
are examined, along with those of two more distant hotspots at the eastern
extreme of the radio feature. The detected emission appears to be synchrotron,
with peaks in the NIR for all except one case, which exhibits a power-law
spectrum throughout.Comment: ApJ accepted. 14 pages, 6 figure
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