14,522 research outputs found
The Symmetry of Partner Modelling
© 2016, International Society of the Learning Sciences, Inc. Collaborative learning has often been associated with the construction of a shared understanding of the situation at hand. The psycholinguistics mechanisms at work while establishing common grounds are the object of scientific controversy. We postulate that collaborative tasks require some level of mutual modelling, i.e. that each partner needs some model of what the other partners know/want/intend at a given time. We use the term “some model” to stress the fact that this model is not necessarily detailed or complete, but that we acquire some representations of the persons we interact with. The question we address is: Does the quality of the partner model depend upon the modeler’s ability to represent his or her partner? Upon the modelee’s ability to make his state clear to the modeler? Or rather, upon the quality of their interactions? We address this question by comparing the respective accuracies of the models built by different team members. We report on 5 experiments on collaborative problem solving or collaborative learning that vary in terms of tasks (how important it is to build an accurate model) and settings (how difficult it is to build an accurate model). In 4 studies, the accuracy of the model that A built about B was correlated with the accuracy of the model that B built about A, which seems to imply that the quality of interactions matters more than individual abilities when building mutual models. However, these findings do not rule out the fact that individual abilities also contribute to the quality of modelling process
On the influence of collisional rate coefficients on the water vapour excitation
Water is a key molecule in many astrophysical studies. Its high dipole moment
makes this molecule to be subthermally populated under the typical conditions
of most astrophysical objects. This motivated the calculation of various sets
of collisional rate coefficients (CRC) for HO (with He or H) which are
necessary to model its rotational excitation and line emission. We performed
accurate non--local non--LTE radiative transfer calculations using different
sets of CRC in order to predict the line intensities from transitions that
involve the lowest energy levels of HO (E 900 K). The results obtained
from the different CRC sets are then compared using line intensity ratio
statistics. For the whole range of physical conditions considered in this work,
we obtain that the intensities based on the quantum and QCT CRC are in good
agreement. However, at relatively low H volume density ((H)
10 cm) and low water abundance ((HO) 10), these
physical conditions being relevant to describe most molecular clouds, we find
differences in the predicted line intensities of up to a factor of 3 for
the bulk of the lines. Most of the recent studies interpreting early Herschel
Space Observatory spectra used the QCT CRC. Our results show that although the
global conclusions from those studies will not be drastically changed, each
case has to be considered individually, since depending on the physical
conditions, the use of the QCT CRC may lead to a mis--estimate of the water
vapour abundance of up to a factor of 3
Top Compositeness and Precision Unification
The evolution of Standard Model gauge couplings is studied in a
non-supersymmetric scenario in which the hierarchy problem is resolved by Higgs
compositeness above the weak scale. It is argued that massiveness of the top
quark combined with precision tests of the bottom quark imply that the
right-handed top must also be composite. If, further, the Standard Model gauge
symmetry is embedded into a simple subgroup of the unbroken composite-sector
flavor symmetry, then precision coupling unification is shown to occur
at~10^{15} GeV, to a degree comparable to supersymmetric unification.Comment: v2: few extra comments added; slightly shorter version published in
PR
Statistics of layered zigzags: a two-dimensional generalization of TASEP
A novel discrete growth model in 2+1 dimensions is presented in three
equivalent formulations: i) directed motion of zigzags on a cylinder, ii)
interacting interlaced TASEP layers, and iii) growing heap over 2D substrate
with a restricted minimal local height gradient. We demonstrate that the
coarse-grained behavior of this model is described by the two-dimensional
Kardar-Parisi-Zhang equation. The coefficients of different terms in this
hydrodynamic equation can be derived from the steady state flow-density curve,
the so called `fundamental' diagram. A conjecture concerning the analytical
form of this flow-density curve is presented and is verified numerically.Comment: 5 pages, 4 figure
Density dependent strong coupling constant of QCD derived from compact star data
The present work is an endeavour to connect the properties of tiny nearly
massless objects with those of some of the most massive ones, the compact
stars.
Since 1996 there is major influx of X-ray and ray data from binary
stars, one or both of which are compact objects that are difficult to explain
as neutron stars since they contain a mass M in too small a radius R . The
suggestion has been put forward that these are strange quark stars (SS)
explainable in a simple model with chiral symmetry restoration (CSR) for the
quarks and the M, R and other properties like QPOs (quasi periodic
oscillations) in their X-ray power spectrum.
It would be nice if this astrophysical data could shed some light on
fundamental properties of quarks obeying QCD. One can relate the strong
coupling constant of QCD, to the quark mass through the
Dyson-Schwinger gap equation using the real time formalism of Dolan and Jackiw.
This enables us to obtain the density dependence of from the simple
CSR referred to above. This way fundamental physics, difficult to extract from
other models like for example lattice QCD, can be constrained from present-day
compact star data and may be put back to modelling the dense quark phase of
early universe.Comment: 7 pages, 4 figure
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