4,608 research outputs found
Gossip at Work: Unsanctioned Evaluative Talk in Formal School Meetings
This article uses a form of linguistic ethnography to analyze videotaped recordings of gossip that took place during formal school meetings. By comparing this gossip data against existing models of gossip based on data collected in informal settings, we identify eleven new response classes, including four forms of indirectness that operate to cloak gossip under ambiguity, and seven forms of avoidance that change the trajectory of gossip. In doing so, this article makes three larger contributions. First, it opens a new front in research on organizational politics by providing an empirically grounded, conceptually rich vocabulary for analyzing gossip in formal contexts. Second, it contributes to knowledge about social interactions in organizations. By examining gossip talk embedded within a work context, this project highlights the nexus between structure, agency, and interaction. Third, it contributes to understandings of gossip in general. By examining gossip in a context previously unexamined, this project provides analytical leverage for theorizing conditions under which gossip is likely and when it will take various forms
Theory of the waterfall phenomenon in cuprate superconductors
Based on exact diagonalization and variational cluster approximation
calculations we study the relationship between charge transfer models and the
corresponding single band Hubbard models. We present an explanation for the
waterfall phenomenon observed in angle resolved photoemission spectroscopy
(ARPES) on cuprate superconductors. The phenomenon is due to the destructive
interference between the phases of the O2p orbitals belonging to a given
Zhang-Rice singlet and the Bloch phases of the photohole which occurs in
certain regions of k-space. It therefore may be viewed as a direct experimental
visualisation of the Zhang-Rice construction of an effective single band model
for the CuO2 plane.Comment: 11 pages, 9 Postscript figure
Landau mapping and Fermi liquid parameters of the 2D t-J model
We study the momentum distribution function n(k) in the 2D t-J model on small
clusters by exact diagonalization. We show that n(k) can be decomposed
systematically into two components with Bosonic and Fermionic doping
dependence. The Bosonic component originates from the incoherent motion of
holes and has no significance for the low energy physics. For the Fermionic
component we exlicitely perform the one-to-one Landau mapping between the low
lying eigenstates of the t-J model clusters and those of an equivalent system
of spin-1/2 quasiparticles. This mapping allows to extract the quasiparticle
dispersion, statistics, and Landau parameters. The results show conclusively
that the 2D t-J model for small doping is a Fermi liquid with a `small' Fermi
surface and a moderately strong attractive interaction between the
quasiparticles.Comment: Revtex file, 5 pages with 5 embedded eps-files, hardcopies of figures
(or the entire manuscript) can be obtained by e-mail request to:
[email protected]
Space Transfer Concepts and Analyses for Exploration Missions. Technical Directive 12: Beamed Power Systems Study
Parametric models were constructed for Earth-based laser powered electric orbit transfer from low Earth orbit to geosynchronous orbit. These models were used to carry out performance, cost/benefit, and sensitivity analyses of laser-powered transfer systems including end-to-end life cycle cost analyses for complete systems. Comparisons with conventional orbit transfer systems were made indicating large potential cost savings for laser-powered transfer. Approximate optimization was done to determine best parameter values for the systems. Orbit transfer flights simulations were conducted to explore effects of parameters not practical to model with a spreadsheet. The simulations considered view factors that determine when power can be transferred from ground stations to an orbit transfer vehicle and conducted sensitivity analyses for numbers of ground stations, Isp including dual-Isp transfers, and plane change profiles. Optimal steering laws were used for simultaneous altitude and plane change. Viewing geometry and low-thrust orbit raising were simultaneously simulated. A very preliminary investigation of relay mirrors was made
Spectral density for a hole in an antiferromagnetic stripe phase
Using variational trial wave function based on the string picture we study
the motion of a single mobile hole in the stripe phase of the doped
antiferromagnet. The holes within the stripes are taken to be static, the
undoped antiferromagnetic domains in between the hole stripes are assumed to
have alternating staggered magnetization, as is suggested by neutron scattering
experiments. The system is described by the t-t'-t''-J model with realistic
parameters and we compute the single particle spectral density.Comment: RevTex-file, 9 PRB pages with 15 .eps and .gif files. To appear in
PRB. Hardcopies of figures (or the entire manuscript) can be obtained by
e-mail request to: [email protected]
First Experiences Integrating PC Distributed I/O Into Argonne's ATLAS Control System
First Experiences Integrating PC Distributed I/O Into Argonne's ATLAS Control
System The roots of ATLAS (Argonne Tandem-Linac Accelerator System) date back
to the early 1960s. Located at the Argonne National Laboratory, the accelerator
has been designated a National User Facility, which focuses primarily on
heavy-ion nuclear physics. Like the accelerator it services, the control system
has been in a constant state of evolution. The present real-time portion of the
control system is based on the commercial product Vsystem [1]. While Vsystem
has always been capable of distributed I/O processing, the latest offering of
this product provides for the use of relatively inexpensive PC hardware and
software. This paper reviews the status of the ATLAS control system, and
describes first experiences with PC distributed I/O.Comment: ICALEPCS 2001 Conference, PSN WEAP027, 3 pages, 1 figur
Dynamics of an SO(5) symmetric ladder model
We discuss properties of an exactly SO(5) symmetric ladder model. In the
strong coupling limit we demonstrate how the SO(3)-symmetric description of
spin ladders in terms of bond Bosons can be upgraded to an SO(5)-symmetric
bond-Boson model, which provides a particularly simple example for the concept
of SO(5) symmetry. Based on this representation we show that antiferro-
magnetism on one hand and superconductivity on the other hand can be understood
as condensation of either magnetic or charged Bosons into an RVB vacuum. We
identify exact eigenstates of a finite cluster with general multiplets of the
SO(5) group, and present numerical results for the single particle spectra and
spin/charge correlation functions of the SO(5)-symmetric model and identify
`fingerprints' of SO(5) symmetry in these. In particluar we show that SO(5)
symmetry implies a `generalized rigid band behavior' of the photoemission
spectrum, i.e. spectra for the doped case are rigorously identical to spectra
for spin-polarized states at half-filling. We discuss the problem of adiabatic
continuity between the SO(5) symmetric ladder and the actual t-J ladder and
demonstrate the feasibility of a `Landau mapping' between the two models.Comment: Revtex-file, 16 pages with 15 eps-figures. Hardcopies of Figures (or
the entire manuscript) obtainable by e-mail request to
[email protected]
Validity of the rigid band picture for the t-J model
We present an exact diagonalization study of the doping dependence of the
single particle Green's function in 16, 18 and 20 site clusters of t-J model.
We find evidence for rigid-band behaviour starting from the half-filled case:
upon doping, the topmost states of the quasiparticle band observed in the
photoemisson spectrum at half-filling cross the chemical potential and reappear
as the lowermost states of the inverse photoemission spectrum. Features in the
inverse photoemission spectra which are inconsistent with rigid-band behaviour
are shown to originate from the nontrivial point group symmetry of the ground
state with two holes, which enforces different selection rules than at
half-filling. Deviations from rigid band behaviour which lead to the formation
of the `large Fermi surface' in the momentum distribution occur only at
energies far from the chemical potential. A Luttinger Fermi surface and a
nearest neighbor hopping band do not exist.Comment: Remarks: Revtex file + 7 figures attached as compressed postscript
files Figures can also be obtained by ordinary mail on reques
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