1,031 research outputs found
Many-electron transport in Aharonov-Bohm interferometers: Time-dependent density-functional study
We apply time-dependent density-functional theory to study many-electron
transport in Aharonov-Bohm interferometers in a non-equilibrium situation. The
conductance properties in the system are complex and depend on the enclosed
magnetic flux in the interferometer, the number of interacting particles, and
the mutual distance of the transport channels at the points of encounter.
Generally, the electron-electron interactions do not suppress the visibility of
Aharonov-Bohm oscillations if the interchannel distance -- determined by the
positioning of the incompressible strips through the external magnetic field --
is optimized. However, the interactions also impose an interesting
Aharonov-Bohm phase shift with channel distances below or above the optimal
one. This effect is combined with suppressed oscillation amplitudes. We analyze
these effects within different approximations for the exchange-correlation
potential in time-dependent density-functional theory.Comment: to appear in Eur. J. Phys. B (2013
Hadron multiplicities, pT-spectra and net-baryon number in central Pb+Pb collisions at the LHC
We compute the initial energy density and net baryon number density in 5%
most central Pb+Pb collisions at TeV from pQCD + (final state)
saturation, and describe the evolution of the produced system with
boost-invariant transversely expanding hydrodynamics. In addition to the total
multiplicity at midrapidity, we give predictions for the multiplicity of
charged hadrons, pions, kaons and (anti)protons, for the total transverse
energy and net-baryon number, as well as for the -spectrum of charged
hadrons, pions and kaons. We also predict the region of applicability of
hydrodynamics by comparing these results with high- hadron spectra
computed from pQCD and energy losses.Comment: 2 pages, 2 figures, to be presented at the workshop "Heavy Ion
Collisions at the LHC: Last Call for Predictions" at CERN 29 May - 2 Jun
The Effects of Gravitational Back-Reaction on Cosmological Perturbations
Because of the non-linearity of the Einstein equations, the cosmological
fluctuations which are generated during inflation on a wide range of
wavelengths do not evolve independently. In particular, to second order in
perturbation theory, the first order fluctuations back-react both on the
background geometry and on the perturbations themselves. I this paper, the
gravitational back-reaction of long wavelength (super-Hubble) scalar metric
fluctuations on the perturbations themselves is investigated for a large class
of inflationary models. Specifically, the equations describing the evolution of
long wavelength cosmological metric and matter perturbations in an inflationary
universe are solved to second order in both the amplitude of the perturbations
and in the slow roll expansion parameter. Assuming that the linear fluctuations
have random phases, we show that the fractional correction to the power
spectrum due to the leading infrared back-reaction terms does not change the
shape of the spectrum. The amplitude of the effect is suppressed by the product
of the inflationary slow-roll parameter and the amplitude of the linear power
spectrum. The non-gaussianity of the spectrum induced by back-reaction is
commented upon.Comment: 9 page
Possible polarisation and spin dependent aspects of quantum gravity
We argue that quantum gravity theories that carry a Lie algebraic
modification of the Poincare' and Heisenberg algebras inevitably provide
inhomogeneities that may serve as seeds for cosmological structure formation.
Furthermore, in this class of theories one must expect a strong polarisation
and spin dependence of various quantum-gravity effects.Comment: Awarded an "honourable mention" in the 2007 Gravity Research
Foundation Essay Competitio
Concealment of type 1 diabetes at work in Finland: a mixed-method study
Objectives To explore the possible reasons for concealing type 1 diabetes (T1D) at work.
Methods The main set of data came from a cross-sectional survey (response rate 49.3%), the participants of which were 688 wage earners with T1D. Concealment of T1D was measured by asking respondents have they ever during their working career hidden their diabetes from their (A) colleagues and (B) line manager. Furthermore, semistructured interviews (n=20) were conducted to obtain deeper understanding. Questionnaire data were analysed
using logistic regression analyses and qualitative interviews with inductive thematic analysis.
Results About 30% of wage earners with T1D had concealed their condition during their working career from their colleagues and almost 20% from their line manager. Individuals aged 18–44 years age were more likely to conceal
their T1D from their colleagues than older workers during their working career. Not disclosing T1D to the extended family (OR 5.24 (95% CI 2.06 to 13.35)), feeling an outsider at work (OR
2.47 (95% CI 1.58 to 3.84)), being embarrassed by receiving special attention at work (OR 1.99 (95% CI 1.33 to 2.96)) and neglecting treatment at work (OR 1.59 (95% CI 1.01 to 2.48))
were all associated with concealment of T1D from colleagues. The youngest age group of 18–24 years were more likely
to conceal their T1D from their line managers than the older age groups during their working career. Not disclosing T1D to the extended family (OR 4.41 (95% CI 1.72 to 11.32)), feeling like an outsider at work (OR 2.51 (1.52 to 4.14)) and being
embarrassed by receiving special attention at work (OR 1.81 (95% CI 1.13 to 2.91)) were associated with concealment of T1D from line managers. From the interviews, five main themes related to concealment emerged, expressing fears related to the consequences of telling: (1) being perceived as weak, (2) job discrimination, (3) unwanted attention, (4) being seen as a person who uses their T1D for seeking advantages
and (5) losing privacy.
Conclusions A considerable proportion of wage earners with T1D are concealing their diagnosis often because
of feelings associated with stigma. Both overemphasis and underestimation of T1D at work by the colleagues or line manager may lead to concealing T1D and may thus be harmful to self-management of T1D. The obstacles in disclosing T1D might be diminished by giving adequate
information at the workplace about the condition and its significance
Disclosure of type 1 diabetes at work among Finnish workers
© 2016 Diabetes UK.Aims: To determine which self-management factors and psychosocial work factors were associated with disclosing diabetes to colleagues, line managers and occupational health personnel among workers with Type 1 diabetes. Methods: A total of 767 working-aged respondents with Type 1 diabetes completed a Finnish cross-sectional survey named 'People with Type 1 Diabetes in Worklife'. Factor analysis was carried out, followed by logistic regressions to estimate the associations between self-management factors, psychosocial work factors and the likelihood of disclosure separately to colleagues, line managers and occupational health personnel. The models were adjusted for sociodemographic, diabetes-related and work-related variables. Results: A total of 52% of the respondents had disclosed their diabetes to their colleagues, 45% to occupational health personnel and 28% to their line manager. Receiving social support and having good psychosocial work ability were significantly associated with disclosure to colleagues, line managers and occupational health personnel. Relations at work were associated with disclosure to colleagues and the line manager. Furthermore, opportunity to self-manage diabetes at work was associated with disclosure to colleagues. Conclusions: Line managers and colleagues have a remarkable role to play in providing workplace support to workers with Type 1 diabetes. Disclosure of Type 1 diabetes should be encouraged as line managers can provide workers with the right support, implement work adaptations and facilitate job retention. As only half of respondents disclosed their Type 1 diabetes at work, further research is required into the reasons for and consequences of not disclosing a diagnosis
Testing the Copernican and Cosmological Principles in the local universe with galaxy surveys
Cosmological density fields are assumed to be translational and rotational
invariant, avoiding any special point or direction, thus satisfying the
Copernican Principle. A spatially inhomogeneous matter distribution can be
compatible with the Copernican Principle but not with the stronger version of
it, the Cosmological Principle which requires the additional hypothesis of
spatial homogeneity. We establish criteria for testing that a given density
field, in a finite sample at low redshifts, is statistically and/or spatially
homogeneous. The basic question to be considered is whether a distribution is,
at different spatial scales, self-averaging. This can be achieved by studying
the probability density function of conditional fluctuations. We find that
galaxy structures in the SDSS samples, the largest currently available, are
spatially inhomogeneous but statistically homogeneous and isotropic up to ~ 100
Mpc/h. Evidences for the breaking of self-averaging are found up to the largest
scales probed by the SDSS data. The comparison between the results obtained in
volumes of different size allows us to unambiguously conclude that the lack of
elf-averaging is induced by finite-size effects due to long-range correlated
fluctuations. We finally discuss the relevance of these results from the point
of view of cosmological modeling.Comment: 12 pages, 3 figures, accepted for publication in JCA
LTB solutions in Newtonian gauge: from strong to weak fields
Lemaitre-Tolman-Bondi (LTB) solutions are used frequently to describe the
collapse or expansion of spherically symmetric inhomogeneous mass distributions
in the Universe. These exact solutions are obtained in the synchronous gauge
where nonlinear dynamics (with respect to the FLRW background) induce large
deviations from the FLRW metric. In this paper we show explicitly that this is
a gauge artefact (for realistic sub-horizon inhomogeneities). We write down the
nonlinear gauge transformation from synchronous to Newtonian gauge for a
general LTB solution using the fact that the peculiar velocities are small. In
the latter gauge we recover the solution in the form of a weakly perturbed FLRW
metric that is assumed in standard cosmology. Furthermore we show how to obtain
the LTB solutions directly in Newtonian gauge and illustrate how the Newtonian
approximation remains valid in the nonlinear regime where cosmological
perturbation theory breaks down. Finally we discuss the implications of our
results for the backreaction scenario.Comment: 17 page
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