723 research outputs found
Simplified models for photohadronic interactions in cosmic accelerators
We discuss simplified models for photo-meson production in cosmic
accelerators, such as Active Galactic Nuclei and Gamma-Ray Bursts. Our
self-consistent models are directly based on the underlying physics used in the
SOPHIA software, and can be easily adapted if new data are included. They allow
for the efficient computation of neutrino and photon spectra (from pi^0
decays), as a major requirement of modern time-dependent simulations of the
astrophysical sources and parameter studies. In addition, the secondaries
(pions and muons) are explicitely generated, a necessity if cooling processes
are to be included. For the neutrino production, we include the helicity
dependence of the muon decays which in fact leads to larger corrections than
the details of the interaction model. The separate computation of the pi^0,
pi^+, and pi^- fluxes allows, for instance, for flavor ratio predictions of the
neutrinos at the source, which are a requirement of many tests of neutrino
properties using astrophysical sources. We confirm that for charged pion
generation, the often used production by the Delta(1232)-resonance is typically
not the dominant process in Active Galactic Nuclei and Gamma-Ray Bursts, and we
show, for arbitrary input spectra, that the number of neutrinos are
underestimated by at least a factor of two if they are obtained from the
neutral to charged pion ratio. We compare our results for several levels of
simplification using isotropic synchrotron and thermal spectra, and we
demonstrate that they are sufficiently close to the SOPHIA software.Comment: Treatment of high energy interactions refined, additional black body
benchmark added (v2), some references corrected (v3). A Mathematica notebook
which illustrates the implementation of one model can be found at
http://theorie.physik.uni-wuerzburg.de/~winter/Resources/AstroModel/Sim-B.html
. 46 pages, 14 (color) figures, 7 tables. Final version, accepted for
publication in Ap
An Enhanced Hardware Description Language Implementation for Improved Design-Space Exploration in High-Energy Physics Hardware Design
Detectors in High-Energy Physics (HEP) have increased tremendously in accuracy, speed and integration. Consequently HEP experiments are confronted with an immense amount of data to be read out, processed and stored. Originally low-level processing has been accomplished in hardware, while more elaborate algorithms have been executed on large computing farms. Field-Programmable Gate Arrays (FPGAs) meet HEP's need for ever higher real-time processing performance by providing programmable yet fast digital logic resources. With the fast move from HEP Digital Signal Processing (DSPing) applications into the domain of FPGAs, related design tools are crucial to realise the potential performance gains. This work reviews Hardware Description Languages (HDLs) in respect to the special needs present in the HEP digital hardware design process. It is especially concerned with the question, how features outside the scope of mainstream digital hardware design can be implemented efficiently into HDLs. It will argue that functional languages are especially suitable for implementation of domain-specific languages, including HDLs. Casestudies examining the implementation complexity of HEP-specific language extensions to the functional HDCaml HDL will prove the viability of the suggested approach
Effect of malachite green in presence of surface actants
Effect of malachite green in presence of surface actant
Magnetic Phase Diagrams of Manganites-like Local-Moment Systems with Jahn-Teller distortions
We use an extended two-band Kondo lattice model (KLM) to investigate the
occurrence of different (anti-)ferromagnetic phases or phase separation
depending on several model parameters. With regard to CMR-materials like the
manganites we have added a Jahn-Teller term, direct antiferromagnetic coupling
and Coulomb interaction to the KLM. The electronic properties are
self-consistently calculated in an interpolating self-energy approach with no
restriction to classical spins and going beyond mean-field treatments. Further
on we do not have to limit the Hund's coupling to low or infinite values.
Zero-temperature phase diagrams are presented for large parameter intervals.
There are strong influences of the type of Coulomb interaction (intraband,
interband) and of the important parameters (Hund's coupling, direct
antiferromagnetic exchange, Jahn-Teller distortion), especially at intermediate
couplings.Comment: 11 pages, 9 figures. Accepted for publication in Phys. Rev.
On proton synchrotron blazar models: the case of quasar 3C 279
In the present work we propose an innovative estimation method for the
minimum Doppler factor and energy content of the gamma-ray emitting region of
quasar 3C 279, using a standard proton synchrotron blazar model and the
principles of automatic photon quenching. The latter becomes relevant for high
enough magnetic fields and results in spontaneous annihilation of gamma-rays.
The absorbed energy is then redistributed into electron-positron pairs and soft
radiation. We show that as quenching sets an upper value for the source
rest-frame gamma-ray luminosity, one has, by neccessity, to resort to Doppler
factors that lie above a certain value in order to explain the TeV
observations. The existence of this lower limit for the Doppler factor has also
implications on the energetics of the emitting region. In this aspect, the
proposed method can be regarded as an extension of the widely used one for
estimating the equipartition magnetic field using radio observations. In our
case, the leptonic synchrotron component is replaced by the proton synchrotron
emission and the radio by the VHE gamma-ray observations. We show specifically
that one can model the TeV observations by using parameter values that minimize
both the energy density and the jet power at the cost of high-values of the
Doppler factor. On the other hand, the modelling can also be done by using the
minimum possible Doppler factor; this, however, leads to a particle dominated
region and high jet power for a wide range of magnetic field values. Despite
the fact that we have focused on the case of 3C 279, our analysis can be of
relevance to all TeV blazars favoring hadronic modelling that have, moreover,
simultaneous X-ray observations.Comment: 12 pages, 11 figures, 1 Table, accepted for publication in MNRA
Temporal signatures of leptohadronic feedback mechanisms in compact sources
The hadronic model of Active Galactic Nuclei and other compact high energy
astrophysical sources assumes that ultra-relativistic protons,
electron-positron pairs and photons interact via various hadronic and
electromagnetic processes inside a magnetized volume, producing the
multiwavelength spectra observed from these sources. A less studied property of
such systems is that they can exhibit a variety of temporal behaviours due to
the operation of different feedback mechanisms. We investigate the effects of
one possible feedback loop, where \gamma-rays produced by photopion processes
are being quenched whenever their compactness increases above a critical level.
This causes a spontaneous creation of soft photons in the system that result in
further proton cooling and more production of \gamma-rays, thus making the loop
operate. We perform an analytical study of a simplified set of equations
describing the system, in order to investigate the connection of its temporal
behaviour with key physical parameters. We also perform numerical integration
of the full set of kinetic equations verifying not only our analytical results
but also those of previous numerical studies. We find that once the system
becomes `supercritical', it can exhibit either a periodic behaviour or a damped
oscillatory one leading to a steady state. We briefly point out possible
implications of such a supercriticality on the parameter values used in Active
Galactic Nuclei spectral modelling, through an indicative fitting of the VHE
emission of blazar 3C 279.Comment: 19 pages, 20 figures, accepted for publication in MNRA
Cancer-related fatigue in palliative care: a global perspective
Cancer-related fatigue (CRF) in a palliative care setting is a distressing symptom that can have a negative impact on a patient's quality of life. A range of setting- and disease-specific factors, unknown aetiology and absence of unilateral guidelines make CRF treatment a challenge for clinicians. In the absence of high-quality evidence in favour of any pharmacological and nonpharmacological measures, except exercise, cognitive behavioural therapy and psychosocial interventions, a personalised integrative oncology approach can lead to effective management. Findings suggest adoption of a severity-based symptom-stage adjusted CRF management care pathway, highlighting best practices to illustrate the lived experience of this symptom. Overcoming barriers by staff training, patient education, facilitating communication and patients' self-care, will increase CRF management effectiveness. Future CRF multisymptom or multidimensional nature investigation trials of its underlying mechanisms and new pharmacological and nonpharmacological strategies applied separately or in combination, will help reveal the best approach to CRF diagnosis, assessment and management
Reduced Order Modeling for Parameterized Time-Dependent PDEs using Spatially and Memory Aware Deep Learning
We present a novel reduced order model (ROM) approach for parameterized
time-dependent PDEs based on modern learning. The ROM is suitable for
multi-query problems and is nonintrusive. It is divided into two distinct
stages: A nonlinear dimensionality reduction stage that handles the spatially
distributed degrees of freedom based on convolutional autoencoders, and a
parameterized time-stepping stage based on memory aware neural networks (NNs),
specifically causal convolutional and long short-term memory NNs. Strategies to
ensure generalization and stability are discussed. The methodology is tested on
the heat equation, advection equation, and the incompressible Navier-Stokes
equations, to show the variety of problems the ROM can handle
Remote Entanglement between a Single Atom and a Bose-Einstein Condensate
Entanglement between stationary systems at remote locations is a key resource
for quantum networks. We report on the experimental generation of remote
entanglement between a single atom inside an optical cavity and a Bose-Einstein
condensate (BEC). To produce this, a single photon is created in the
atom-cavity system, thereby generating atom-photon entanglement. The photon is
transported to the BEC and converted into a collective excitation in the BEC,
thus establishing matter-matter entanglement. After a variable delay, this
entanglement is converted into photon-photon entanglement. The matter-matter
entanglement lifetime of 100 s exceeds the photon duration by two orders
of magnitude. The total fidelity of all concatenated operations is 95%. This
hybrid system opens up promising perspectives in the field of quantum
information
Photon-Photon Entanglement with a Single Trapped Atom
An experiment is performed where a single rubidium atom trapped within a
high-finesse optical cavity emits two independently triggered entangled
photons. The entanglement is mediated by the atom and is characterized both by
a Bell inequality violation of S=2.5, as well as full quantum-state tomography,
resulting in a fidelity exceeding F=90%. The combination of cavity-QED and
trapped atom techniques makes our protocol inherently deterministic - an
essential step for the generation of scalable entanglement between the nodes of
a distributed quantum network.Comment: 5 pages, 4 figure
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