2,067 research outputs found
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Improving decision-making and cognitive bias using innovative approaches to simulated scenario and debrief design
Description of Gluon Propagation in the Presence of an A^2 Condensate
There is a good deal of current interest in the condensate A^2 which has been
seen to play an important role in calculations which make use of the operator
product expansion. That development has led to the publication of a large
number of papers which discuss how that condensate could play a role in a
gauge-invariant formulation. In the present work we consider gluon propagation
in the presence of such a condensate which we assume to be present in the
vacuum. We show that the gluon propagator has no on-mass-shell pole and,
therefore, a gluon cannot propagate over extended distances. That is, the gluon
is a nonpropagating mode in the gluon condensate. In the present work we
discuss the properties of both the Euclidean-space and Minkowski-space gluon
propagator. In the case of the Euclidean-space propagator we can make contact
with the results of QCD lattice calculations of the propagator in the Landau
gauge. With an appropriate choice of normalization constants, we present a
unified representation of the gluon propagator that describes both the
Minkowski-space and Euclidean-space dynamics in which the A^2 condensate plays
an important role.Comment: 28 pages, 11 figure
The Nielsen Identities for the Two-Point Functions of QED and QCD
We consider the Nielsen identities for the two-point functions of full QCD
and QED in the class of Lorentz gauges. For pedagogical reasons the identities
are first derived in QED to demonstrate the gauge independence of the photon
self-energy, and of the electron mass shell. In QCD we derive the general
identity and hence the identities for the quark, gluon and ghost propagators.
The explicit contributions to the gluon and ghost identities are calculated to
one-loop order, and then we show that the quark identity requires that in
on-shell schemes the quark mass renormalisation must be gauge independent.
Furthermore, we obtain formal solutions for the gluon self-energy and ghost
propagator in terms of the gauge dependence of other, independent Green
functions.Comment: 25 pages, plain TeX, 4 figures available upon request, MZ-TH/94-0
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Non-verbal communication in meetings of psychiatrists and patients with schizophrenia
Objective
Recent evidence found that patients with schizophrenia display nonâverbal behaviour designed to avoid social engagement during the opening moments of their meetings with psychiatrists. This study aimed to replicate, and build on, this finding, assessing the nonâverbal behaviour of patients and psychiatrists during meetings, exploring changes over time and its association with patients' symptoms and the quality of the therapeutic relationship.
Method
40âvideotaped routine outâpatient consultations, involving patients with schizophrenia, were analysed. Nonâverbal behaviour of patients and psychiatrists was assessed during three fixed, 2âmin intervals using a modified Ethological Coding System for Interviews. Symptoms, satisfaction with communication and the quality of the therapeutic relationship were also measured.
Results
Over time, patients' nonâverbal behaviour remained stable, whilst psychiatrists' flight behaviour decreased. Patients formed two groups based on their nonâverbal profiles, one group (n = 25) displaying proâsocial behaviour, inviting interaction and a second (n = 15) displaying flight behaviour, avoiding interaction. Psychiatrists interacting with proâsocial patients displayed more proâsocial behaviours (P < 0.001). Patients' proâsocial profile was associated reduced symptom severity (P < 0.05), greater satisfaction with communication (P < 0.001) and positive therapeutic relationships (P < 0.05).
Conclusion
Patients' nonâverbal behaviour during routine psychiatric consultations remains unchanged, and is linked to both their psychiatrist's nonâverbal behaviour and the quality of the therapeutic relationship
Collinearity, convergence and cancelling infrared divergences
The Lee-Nauenberg theorem is a fundamental quantum mechanical result which
provides the standard theoretical response to the problem of collinear and
infrared divergences. Its argument, that the divergences due to massless
charged particles can be removed by summing over degenerate states, has been
successfully applied to systems with final state degeneracies such as LEP
processes. If there are massless particles in both the initial and final
states, as will be the case at the LHC, the theorem requires the incorporation
of disconnected diagrams which produce connected interference effects at the
level of the cross-section. However, this aspect of the theory has never been
fully tested in the calculation of a cross-section. We show through explicit
examples that in such cases the theorem introduces a divergent series of
diagrams and hence fails to cancel the infrared divergences. It is also
demonstrated that the widespread practice of treating soft infrared divergences
by the Bloch-Nordsieck method and handling collinear divergences by the
Lee-Nauenberg method is not consistent in such cases.Comment: 29 pages, 17 figure
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