41 research outputs found
Nonequilibrium time evolution of the spectral function in quantum field theory
Transport or kinetic equations are often derived assuming a quasi-particle
(on-shell) representation of the spectral function. We investigate this
assumption using a three-loop approximation of the 2PI effective action in real
time, without a gradient expansion or on-shell approximation. For a scalar
field in 1+1 dimensions the nonlinear evolution, including the integration over
memory kernels, can be solved numerically. We find that a spectral function
approximately described by a nonzero width emerges dynamically. During the
nonequilibrium time evolution the Wigner transformed spectral function is
slowly varying, even in presence of strong qualitative changes in the effective
particle distribution. These results may be used to make further analytical
progress towards a quantum Boltzmann equation including off-shell effects and a
nonzero width.Comment: 20 pages with 6 eps figures, explanation and references added; to
appear in Phys.Rev.
Transport equations for chiral fermions to order \hbar and electroweak baryogenesis: Part I
This is the first in a series of two papers. We use the Schwinger-Keldysh
formalism to derive semiclassical Boltzmann transport equations for massive
chiral fermions and scalar particles. Our considerations include complex mass
terms and mixing fermion and scalar fields, such that CP-violation is naturally
included, rendering the equations particularly suitable for studies of
baryogenesis at a first order electroweak phase transition. In part II we
discuss the collision terms.Comment: 58 pages, 5 figures; earlier version broken up into two parts, Part
II is hep-ph/0406140; accepted for publication in Annals of Physic
Controlled nonperturbative dynamics of quantum fields out of equilibrium
We compute the nonequilibrium real-time evolution of an O(N)-symmetric scalar
quantum field theory from a systematic 1/N expansion of the 2PI effective
action to next-to-leading order, which includes scattering and memory effects.
In contrast to the standard 1/N expansion of the 1PI effective action, the
next-to-leading order expansion in presence of a possible expectation value for
the composite operator leads to a bounded time evolution where the truncation
error may be controlled by higher powers in 1/N. We present a detailed
comparison with the leading-order results and determine the range of validity
of standard mean field type approximations.
We investigate ``quench'' and ``tsunami'' initial conditions frequently used
to mimic idealized far-from-equilibrium pion dynamics in the context of
heavy-ion collisions. For spatially homogeneous initial conditions we find
three generic regimes, characterized by an early-time exponential damping, a
parametrically slow (power-law) behavior at intermediate times, and a late-time
exponential approach to thermal equilibrium. The different time scales are
obtained from a numerical solution of the time-reversal invariant equations in
1+1 dimensions without further approximations. We discuss in detail the
out-of-equilibrium behavior of the nontrivial n-point correlation functions as
well as the evolution of a particle number distribution and inverse slope
parameter.Comment: 48 pages, 20 figures, Nucl.Phys.A version, minor wording changes,
reference adde
Personalized medication adherence management in asthma and COPD:a review of effective interventions and development of a practical adherence toolkit
BACKGROUND: Medication non-adherence management of patients with asthma/COPD remains challenging. Given the multitude of underlying causes, a personalized approach is required. The Test of Adherence to Inhalers (TAI) can identify reasons for non-adherence, but does not provide guidance on how to effectively act on results. OBJECTIVE: To develop a practical, evidence-based decision support toolkit for healthcare professionals managing adult patients with asthma and/or COPD, by matching TAI-identified adherence barriers to proven effective adherence enhancing interventions. METHODS: A literature review in PubMed and Embase was performed identifying interventions that enhanced medication adherence in adult patients with asthma and/or COPD. Randomised controlled trials (RCTs) published in English with full-texts available were included. Effective interventions were assessed by the Cochrane risk of bias tool, categorized, matched with specific TAI responses and developed into a practical TAI Toolkit. The Toolkit was assessed on content and usability (System Usability Scale, SUS) by a multidisciplinary group of healthcare professionals. RESULTS: Forty RCTs were included in the review. In total, seven effective interventions catergories were identified, informing the TAI Toolkit: reminders, educational interventions, motivational strategies, feedback on medication use, shared decision making, simplifying medication regimen and multiple component interventions. Healthcare professionals rated the TAI Toolkit with a mean SUS score of 71.4 (range: 57.5-80.0). CONCLUSION: Adherence can be improved using different interventions that the TAI Toolkit helps selecting. The TAI Toolkit was well received by healthcare professionals. Further research is required to test its validity, practicality and effectiveness in practice
QCD with Chemical Potential in a Small Hyperspherical Box
To leading order in perturbation theory, we solve QCD, defined on a small
three sphere in the large N and Nf limit, at finite chemical potential and map
out the phase diagram in the (mu,T) plane. The action of QCD is complex in the
presence of a non-zero quark chemical potential which results in the sign
problem for lattice simulations. In the large N theory, which at low
temperatures becomes a conventional unitary matrix model with a complex action,
we find that the dominant contribution to the functional integral comes from
complexified gauge field configurations. For this reason the eigenvalues of the
Polyakov line lie off the unit circle on a contour in the complex plane. We
find at low temperatures that as mu passes one of the quark energy levels there
is a third-order Gross-Witten transition from a confined to a deconfined phase
and back again giving rise to a rich phase structure. We compare a range of
physical observables in the large N theory to those calculated numerically in
the theory with N=3. In the latter case there are no genuine phase transitions
in a finite volume but nevertheless the observables are remarkably similar to
the large N theory.Comment: 44 pages, 18 figures, jhep3 format. Small corrections and
clarifications added in v3. Conclusions cleaned up. Published versio
Flavour-coherent propagators and Feynman rules: Covariant cQPA formulation
We present a simplified and generalized derivation of the flavour-coherent
propagators and Feynman rules for the fermionic kinetic theory based on
coherent quasiparticle approximation (cQPA). The new formulation immediately
reveals the composite nature of the cQPA Wightman function as a product of two
spectral functions and an effective two-point interaction vertex, which
contains all quantum statistical and coherence information. We extend our
previous work to the case of nonzero dispersive self-energy, which leads to a
broader range of applications. By this scheme, we derive flavoured kinetic
equations for local 2-point functions , which are
reminiscent of the equations of motion for the density matrix. We emphasize
that in our approach all the interaction terms are derived from first
principles of nonequilibrium quantum field theory.Comment: 20 pages, 3 figures. Minor modifications, version published in JHE
Phenomics for photosynthesis, growth and reflectance in Arabidopsis thaliana reveals circadian and long-term fluctuations in heritability
Calming device
A device (1), for calming down a subject, comprises a content delivering means (12,14) adapted for delivering a content in a first mode, at least one sensor (22, 24, 26, 28, 29) configured to detect an activity level of the subject and a controlling unit operatively coupled to the at least one sensor. The controlling unit receives the detected activity level and compares the detected activity level with a pre-determined threshold activity level. The controlling unit is capable of changing the delivery of the content to a second mode when the detected activity level is above the threshold activity level