63,779 research outputs found
Interaction Between Gravity Compensation Suspension System and Deployable Structure
Gravity compensation suspension systems are essential to support space structures during tests on Earth, but also impose constraints on the structures that have the effect of changing their behavior. A computational and experimental study of the interaction of a rigid panel solar array model with a manually adjustable suspension system during quasi-static deployment tests in the 1-g environment of the laboratory is presented. A methodology is established for modeling this interaction, for predicting the effects of suspension system adjustments, and for optimization of the suspension system through these adjustments. Some improvements can be achieved by manual adjustments, but further optimization requires an active system
Studying pion effects on the chiral phase transition
We investigate the chiral phase transition at finite temperatures and zero
chemical potential with Dyson-Schwinger equations. Our truncation for the
quark-gluon interaction includes mesonic degrees of freedom, which allows us to
study the impact of the pions on the nature of the phase transition. Within the
present scheme we find a five percent change of the critical temperature due to
the pion backreaction whereas the mean field character of the transition is not
changed.Comment: 2 pages, 2 figures, talk given by J.A.M. at the 30th International
School of Nuclear Physics, Erice, Sicily from 16 - 24 September 200
On critical scaling at the QCD N_f=2 chiral phase transition
We investigate the critical scaling of the quark propagator of N_f=2 QCD
close to the chiral phase transition at finite temperature. We argue that it is
mandatory to take into account the back-reaction effects of pions and the sigma
onto the quark to observe critical behavior beyond mean field. On condition of
self-consistency of the quark Dyson-Schwinger equation we extract the scaling
behavior for the quark propagator analytically. Crucial in this respect is the
correct pion dispersion relation when the critical temperature is approached
from below. Our results are consistent with the known relations for the quark
condensate and the pion decay constant from universality. We verify the
analytical findings also numerically assuming the critical dispersion relation
for the Goldstone bosons.Comment: 9 pages, 6 figure
Dynamically induced scalar quark confinement
We employ a functional approach to investigate the confinement problem in
quenched Landau gauge QCD. We demonstrate analytically that a linear rising
potential between massive quarks is generated by infrared singularities in the
dressed quark-gluon vertex. The selfconsistent mechanism that generates these
singularities is driven by the scalar Dirac amplitudes of the full vertex and
the quark propagator. These can only be present when chiral symmetry is broken.
We have thus uncovered a novel mechanism that directly links chiral symmetry
breaking with confinement.Comment: 12 pages, 2 figures; v2: clarifications added and typos corrected,
version to be published by MPL
Chiral and deconfinement phase transitions of two-flavour QCD at finite temperature and chemical potential
We present results for the chiral and deconfinement transition of two flavor
QCD at finite temperature and chemical potential. To this end we study the
quark condensate and its dual, the dressed Polyakov loop, with functional
methods using a set of Dyson-Schwinger equations. The quark-propagator is
determined self-consistently within a truncation scheme including temperature
and in-medium effects of the gluon propagator. For the chiral transition we
find a crossover turning into a first order transition at a critical endpoint
at large quark chemical potential, . For the
deconfinement transition we find a pseudo-critical temperature above the chiral
transition in the crossover region but coinciding transition temperatures close
to the critical endpoint.Comment: 4 pages, 4 figures. v2: minor changes, comments adde
How to feel in order to be satisfied at work? A differentiating view on the Affective Events Theory
Affective Events Theory (AET; Weiss & Cropanzano, 1996) states that emotions at work affect job satisfaction. We specified existing research by distinguishing
between frequency and intensity of emotional episodes at work and by varying the time frame for which emotions were reported. In a paper-pencil study employed
persons (N = 228) reported the frequency and the intensity of positive and negative work-related affective states. The time period, for which emotions were reported,
was varied between subjects (last week vs. last month).
When predicting job satisfaction, regression analyses indicated that (1) the frequency of emotions is a better predictor than their intensity and that (2) positive
emotions are a better predictor than negative emotions when reporting affective states for the last week, whereas this pattern reverses for the time frame of last
month. Thus, with an increasing time interval, negative emotions seem to have a comparatively better cognitive representation
Quark spectral properties above Tc from Dyson-Schwinger equations
We report on an analysis of the quark spectral representation at finite
temperatures based on the quark propagator determined from its Dyson-Schwinger
equation in Landau gauge. In Euclidean space we achieve nice agreement with
recent results from quenched lattice QCD. We find different analytical
properties of the quark propagator below and above the deconfinement
transition. Using a variety of ansaetze for the spectral function we then
analyze the possible quasiparticle spectrum, in particular its quark mass and
momentum dependence in the high temperature phase. This analysis is completed
by an application of the Maximum Entropy Method, in principle allowing for any
positive semi-definite spectral function. Our results motivate a more direct
determination of the spectral function in the framework of Dyson-Schwinger
equations
- âŠ